Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0008180 COP9 signalosome	IBA GO_REF:0000033	ACCEPT	Summary: COPS8 is an integral subunit of the COP9 signalosome complex. This is well-established from multiple studies including the original characterization (PMID:9535219) and structural studies (PMID:18850735, PMID:25043011). The IBA annotation is consistent with phylogenetic conservation of CSN8 as a core CSN component. Reason: Core function. COPS8 is definitionally a subunit of the COP9 signalosome. The complex consists of eight subunits (GPS1/COPS1, COPS2-8, and COPS9) and COPS8 is essential for holocomplex integrity. This is supported by multiple experimental studies. Supporting Evidence: PMID:9535219 A novel protein complex has been identified in human cells that has a molecular mass of approximately 450 kDa. It consists of at least eight different subunits including JAB1, the Jun activation-domain binding protein 1, and Trip15 PMID:18850735 Purification of the human CSN complex from a stable 293 cell line expressing N-terminal HBTH-tagged CSN5 subunit was achieved by high-affinity streptavidin binding with TEV cleavage elution.
GO:0000338 protein deneddylation	IEA GO_REF:0000002	ACCEPT	Summary: The CSN complex mediates protein deneddylation, removing NEDD8 from cullin substrates. While COPS8 itself lacks deneddylase catalytic activity (which resides in CSN5), it is required for CSN holocomplex integrity and thus for deneddylation function. The IEA annotation from InterPro is appropriate as a broader functional annotation. Reason: The CSN complex functions as the major deneddylase in cells. COPS8 is required for proper CSN complex assembly and therefore contributes to the deneddylation process, even though it does not contain the catalytic metalloprotease domain (found in CSN5). Supporting Evidence: PMID:19141280 The COP9 signalosome (CSN) is an eight-subunit protein complex that is found in all eukaryotes. Accumulating evidence indicates its diverse biological functions that are often linked to ubiquitin-mediated proteolysis... the catalytically active human complex, reconstituted in vitro, is composed of a single copy of each of the eight subunits.
GO:0005634 nucleus	IEA GO_REF:0000120	ACCEPT	Summary: COPS8 and the CSN complex localize to both nucleus and cytoplasm. This IEA annotation is consistent with experimental evidence showing nuclear localization of the CSN. Reason: Correct localization. Multiple experimental studies confirm nuclear localization of the CSN complex and COPS8 (PMID:9535219, PMID:24421388). Supporting Evidence: PMID:24421388 the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound fractions, each differing in the composition of posttranslationally modified subunits, depending on its location within the cell.
GO:0005737 cytoplasm	IEA GO_REF:0000044	ACCEPT	Summary: COPS8 and the CSN complex localize to both nucleus and cytoplasm. This IEA annotation is consistent with experimental evidence from UniProt subcellular location mapping. Reason: Correct localization. Cytoplasmic localization is well-documented for CSN complex (PMID:9535219, PMID:24421388). Supporting Evidence: PMID:9535219 Immunofluorescence staining reveals that the new complex shows a subcellular distribution similar to that of the 26S proteasome.
GO:0008180 COP9 signalosome	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate annotation of COP9 signalosome membership via automated pipeline. This is correct but redundant with the IBA annotation. Reason: Core function. Duplicate annotations with different evidence codes are acceptable. This IEA annotation correctly identifies COPS8 as a CSN subunit. Supporting Evidence: PMID:18850735 Mass spectrometric analysis of the purified CSN complex has revealed the identity of its composition as well as N-terminal modification and phosphorylation of the CSN subunits.
GO:0010387 COP9 signalosome assembly	IEA GO_REF:0000002	ACCEPT	Summary: COPS8 is required for CSN holocomplex assembly and stability. CSN8 hypomorphism leads to destabilization of the CSN complex with formation of CSN5-containing mini-complexes. Reason: CSN8 is essential for proper CSN complex assembly. Studies show that reduced CSN8 levels lead to holocomplex destabilization and formation of aberrant subcomplexes. Supporting Evidence: PMID:23689509 By characterizing the mouse embryonic fibroblasts (MEFs) that express Csn8 at a low level, we found that Csn8 plays an important role in maintaining the proper duration of the G1 phase of the cell cycle.
GO:0005515 protein binding	IPI PMID:15304329 Hepatopoietin interacts directly with COP9 signalosome and r...	MODIFY	Summary: This protein binding annotation is too vague. The cited paper shows hepatopoietin interacts with COP9 signalosome components. While the physical interaction may be valid, 'protein binding' does not convey useful functional information about COPS8's role as a structural scaffold subunit. Reason: 'Protein binding' is uninformative. COPS8 functions as a structural scaffold within the CSN complex. A more informative term would describe its role in the complex. Proposed replacements: molecular adaptor activity Supporting Evidence: PMID:15304329 Hepatopoietin interacts directly with COP9 signalosome and regulates AP-1 activity.
GO:0005515 protein binding	IPI PMID:18850735 Characterization of the human COP9 signalosome complex using...	MODIFY	Summary: This paper characterizes CSN complex composition and subunit interactions. The protein binding annotation is too vague - COPS8 specifically interacts with other CSN subunits (particularly COPS3, COPS4, COPS7) as part of the complex architecture. Reason: 'Protein binding' is uninformative. The interaction is part of CSN complex formation. Proposed replacements: molecular adaptor activity Supporting Evidence: PMID:18850735 Purification of the human CSN complex from a stable 293 cell line expressing N-terminal HBTH-tagged CSN5 subunit was achieved by high-affinity streptavidin binding with TEV cleavage elution.
GO:0005515 protein binding	IPI PMID:19615732 Defining the human deubiquitinating enzyme interaction lands...	MARK AS OVER ANNOTATED	Summary: High-throughput interactome study identifying deubiquitinating enzyme interactions. 'Protein binding' is too vague to be informative. Reason: High-throughput study with generic 'protein binding' term that does not convey specific functional information about COPS8. Supporting Evidence: PMID:19615732 Defining the human deubiquitinating enzyme interaction landscape.
GO:0005515 protein binding	IPI PMID:20399188 Structural insights into the COP9 signalosome and its common...	MODIFY	Summary: Structural study of CSN complex. The protein binding annotation reflects structural interactions within the CSN complex but is too vague. Reason: 'Protein binding' is uninformative. The structural analysis shows COPS8 interacts with other CSN subunits as part of the complex architecture. Proposed replacements: molecular adaptor activity Supporting Evidence: PMID:20399188 Structural insights into the COP9 signalosome and its common architecture with the 26S proteasome lid and eIF3.
GO:0005515 protein binding	IPI PMID:21145461 Dynamics of cullin-RING ubiquitin ligase network revealed by...	ACCEPT	Summary: Quantitative proteomics study of cullin-RING ligase network dynamics. The interactions detected are relevant to CSN function in regulating CRLs but 'protein binding' is too vague. Reason: The study provides evidence for CSN complex interactions with cullins, which is relevant to its core function. While 'protein binding' is vague, it captures the physical interaction aspect of CSN-CRL regulation. Supporting Evidence: PMID:21145461 Dynamics of cullin-RING ubiquitin ligase network revealed by systematic quantitative proteomics.
GO:0005515 protein binding	IPI PMID:24421388 Dynamic regulation of the COP9 signalosome in response to DN...	ACCEPT	Summary: This study examined CSN dynamics in response to DNA damage. The protein binding annotation captures interactions within the complex. Reason: This annotation reflects CSN subunit interactions which are functionally relevant for the complex's role in DNA damage response. Supporting Evidence: PMID:24421388 The COP9 signalosome (CSN) is an evolutionarily conserved protein complex that participates in the regulation of the ubiquitin/26S proteasome pathway
GO:0005515 protein binding	IPI PMID:24981860 Human-chromatin-related protein interactions identify a deme...	MARK AS OVER ANNOTATED	Summary: Chromatin-related protein interaction study. 'Protein binding' is too generic. Reason: High-throughput study with generic annotation that does not provide specific functional insight into COPS8. Supporting Evidence: PMID:24981860 Human-chromatin-related protein interactions identify a demethylase complex required for chromosome segregation.
GO:0005515 protein binding	IPI PMID:25043011 Crystal structure of the human COP9 signalosome.	MODIFY	Summary: Crystal structure of human COP9 signalosome. The structural analysis reveals COPS8 interactions with other CSN subunits. 'Protein binding' is too vague. Reason: The crystal structure shows COPS8 structural interactions but 'protein binding' is uninformative. The molecular adaptor activity term better captures COPS8's role. Proposed replacements: molecular adaptor activity Supporting Evidence: PMID:25043011 Crystal structure of the human COP9 signalosome.
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	MARK AS OVER ANNOTATED	Summary: Large-scale proteome interactome map. Generic 'protein binding' annotation. Reason: High-throughput interactome study. The generic term does not convey functional information specific to COPS8. Supporting Evidence: PMID:25416956 A proteome-scale map of the human interactome network.
GO:0005515 protein binding	IPI PMID:26496610 A human interactome in three quantitative dimensions organiz...	MARK AS OVER ANNOTATED	Summary: Quantitative human interactome study. Generic annotation from high-throughput data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:26496610 A human interactome in three quantitative dimensions organized by stoichiometries and abundances.
GO:0005515 protein binding	IPI PMID:27029275 Cullin-RING ubiquitin E3 ligase regulation by the COP9 signa...	ACCEPT	Summary: Review of CRL regulation by CSN. The protein binding annotation reflects CSN-CRL interactions which are functionally important. Reason: The interaction between CSN and CRLs is central to CSN function in regulating ubiquitin ligase activity. Supporting Evidence: PMID:27029275 Cullin-RING ubiquitin E3 ligase regulation by the COP9 signalosome.
GO:0005515 protein binding	IPI PMID:27173435 An organelle-specific protein landscape identifies novel dis...	MARK AS OVER ANNOTATED	Summary: Organelle-specific protein landscape study. High-throughput interactome data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:27173435 An organelle-specific protein landscape identifies novel diseases and molecular mechanisms.
GO:0005515 protein binding	IPI PMID:28514442 Architecture of the human interactome defines protein commun...	MARK AS OVER ANNOTATED	Summary: Human interactome architecture study. High-throughput interactome data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:28514442 Architecture of the human interactome defines protein communities and disease networks.
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	MARK AS OVER ANNOTATED	Summary: Human binary protein interactome reference map. High-throughput data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:32296183 A reference map of the human binary protein interactome.
GO:0005515 protein binding	IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling...	MARK AS OVER ANNOTATED	Summary: Dual proteome-scale networks study. High-throughput interactome data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
GO:0005515 protein binding	IPI PMID:40205054 Multimodal cell maps as a foundation for structural and func...	MARK AS OVER ANNOTATED	Summary: Multimodal cell maps study. High-throughput data. Reason: High-throughput study with generic annotation. Supporting Evidence: PMID:40205054 Multimodal cell maps as a foundation for structural and functional genomics.
GO:0005654 nucleoplasm	IDA GO_REF:0000052	ACCEPT	Summary: COPS8/CSN localizes to the nucleoplasm based on immunofluorescence data from HPA. This is consistent with the CSN's role in nuclear protein turnover regulation. Reason: Nucleoplasm localization is well-supported by immunofluorescence studies and consistent with CSN function in regulating nuclear CRL activity. Supporting Evidence: PMID:24421388 the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound fractions
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: COPS8/CSN localizes to the cytosol based on HPA immunofluorescence data. This is consistent with multiple studies showing cytoplasmic CSN localization. Reason: Cytosolic localization is well-documented for CSN complex. Supporting Evidence: PMID:9535219 Immunofluorescence staining reveals that the new complex shows a subcellular distribution similar to that of the 26S proteasome.
GO:0005634 nucleus	IDA PMID:24421388 Dynamic regulation of the COP9 signalosome in response to DN...	ACCEPT	Summary: The CSN complex is localized in both nucleus and cytoplasm. PMID:24421388 provides direct experimental evidence for nuclear localization using biochemical and fluorescence microscopy analyses. Reason: Direct experimental evidence for nuclear localization of CSN complex including COPS8. Supporting Evidence: PMID:24421388 Through biochemical and fluorescence microscopy analyses, we determined that the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound fractions
GO:0005737 cytoplasm	IDA PMID:24421388 Dynamic regulation of the COP9 signalosome in response to DN...	ACCEPT	Summary: The CSN complex is localized in both nucleus and cytoplasm. PMID:24421388 provides direct experimental evidence for cytoplasmic localization. Reason: Direct experimental evidence for cytoplasmic localization of CSN complex. Supporting Evidence: PMID:24421388 the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound fractions
GO:0045116 protein neddylation	NAS PMID:24421388 Dynamic regulation of the COP9 signalosome in response to DN...	MODIFY	Summary: This annotation is problematic. The CSN complex is involved in protein DENEDDYLATION (removal of NEDD8), not neddylation (attachment of NEDD8). PMID:24421388 discusses CSN regulation of neddylation/deneddylation cycles but CSN is a deneddylase, not a neddylation enzyme. Reason: The CSN complex catalyzes deneddylation, not neddylation. While CSN participates in the neddylation/deneddylation cycle by removing NEDD8, it does not catalyze neddylation. The annotation should be 'protein deneddylation' or 'regulation of protein neddylation'. Proposed replacements: protein deneddylation Supporting Evidence: PMID:19141280 the catalytically active human complex, reconstituted in vitro, is composed of a single copy of each of the eight subunits
GO:2000434 regulation of protein neddylation	NAS PMID:24421388 Dynamic regulation of the COP9 signalosome in response to DN...	ACCEPT	Summary: The CSN regulates protein neddylation by catalyzing deneddylation, thus controlling the neddylation/deneddylation cycle of cullins. This annotation appropriately captures the regulatory role of CSN in the neddylation pathway. Reason: CSN regulates neddylation by deneddylating cullins, affecting CRL activity and the neddylation cycle. This is an accurate description of CSN function. Supporting Evidence: PMID:24421388 The COP9 signalosome (CSN) is an evolutionarily conserved protein complex that participates in the regulation of the ubiquitin/26S proteasome pathway by controlling the function of cullin-RING-ubiquitin ligases.
GO:0006468 protein phosphorylation	IDA PMID:9535219 A novel protein complex involved in signal transduction poss...	MODIFY	Summary: The CSN complex was found to have kinase activity that phosphorylates IkappaBalpha, p105, and c-Jun. However, this kinase activity is likely via association with CK2 and PKD kinases (as noted in UniProt), not intrinsic to CSN subunits including COPS8. COPS8 is a PCI-domain scaffold protein without kinase catalytic activity. Reason: COPS8 does not have intrinsic kinase activity. The phosphorylation activity of the CSN complex comes from associated kinases (CK2, PKD) rather than from CSN subunits themselves. A more accurate annotation would reflect the regulatory role rather than direct enzymatic activity. Proposed replacements: regulation of protein kinase activity Supporting Evidence: PMID:9535219 The isolated JAB1-containing particle has kinase activity that phosphorylates IkappaBalpha, the carboxy terminus of p105, and Ser63 and/or Ser73 of the amino-terminal activation domain of c-Jun.
GO:0005829 cytosol	TAS Reactome:R-HSA-8863721	ACCEPT	Summary: Reactome annotation for CSN localization in cytosol based on NEDD8-related pathway. Consistent with experimental evidence. Reason: Cytosolic localization is well-documented. Reactome pathway annotations are reliable. Supporting Evidence: Reactome:R-HSA-8863721 NEDD8-STON binds TOR1 hexamer and COP9 complex
GO:0005829 cytosol	TAS Reactome:R-HSA-8863723	ACCEPT	Summary: Reactome annotation for CSN in cytosol involved in deneddylation. Reason: Cytosolic localization is correct and relevant to CSN function. Supporting Evidence: Reactome:R-HSA-8863723 COP9 and TOR1 deneddylate STON2
GO:0005829 cytosol	TAS Reactome:R-HSA-8956040	ACCEPT	Summary: Reactome annotation for CSN deneddylation of cytosolic CRL complexes. Reason: Cytosolic localization is relevant to CSN function in regulating CRLs. Supporting Evidence: Reactome:R-HSA-8956040 COP9 signalosome deneddylates cytosolic CRL E3 ubiquitin ligase complexes
GO:0005654 nucleoplasm	TAS Reactome:R-HSA-5691006	ACCEPT	Summary: Reactome annotation for CSN in nucleoplasm involved in DNA damage recognition in global genome nucleotide excision repair. Reason: Nucleoplasm localization is well-documented and relevant to CSN role in DNA damage response. Supporting Evidence: Reactome:R-HSA-5691006 XPC:RAD23:CETN2 and UV-DDB bind distorted dsDNA site
GO:0005654 nucleoplasm	TAS Reactome:R-HSA-6781833	ACCEPT	Summary: Reactome annotation for CSN in nucleoplasm involved in transcription-coupled nucleotide excision repair. Reason: Nucleoplasm localization is consistent with CSN role in DNA damage response. Supporting Evidence: Reactome:R-HSA-6781833 ERCC8 (CSA) binds stalled RNA Pol II
GO:0005654 nucleoplasm	TAS Reactome:R-HSA-8956045	ACCEPT	Summary: Reactome annotation for CSN deneddylation of nuclear CRL4 complex. Reason: Nucleoplasm localization is relevant to CSN function in regulating nuclear CRL complexes. Supporting Evidence: Reactome:R-HSA-8956045 COP9 signalosome deneddylates nuclear CRL4 E3 ubiquitin ligase complex
GO:0007250 activation of NF-kappaB-inducing kinase activity	IMP PMID:22992343 microRNA-146a inhibits G protein-coupled receptor-mediated a...	KEEP AS NON CORE	Summary: PMID:22992343 shows that COPS8 knockdown inhibits LPA-stimulated GPCR-mediated NF-kappaB activation. The study identifies COPS8 as a miR-146a target and shows that siRNA knockdown of COPS8 significantly inhibits LPA-induced NF-kappaB activity. This supports a role for COPS8 in NF-kappaB signaling. Reason: The annotation is supported by experimental evidence but represents a downstream effect of CSN function in regulating protein stability rather than a core molecular function of COPS8. The NF-kappaB regulation is likely mediated through CSN's role in CRL regulation affecting IkappaB stability. Supporting Evidence: PMID:22992343 siRNA knockdown of CARD10 and COPS8 expression significantly inhibited LPA-stimulated GPCR-mediated activation of NF-kappaB in SNU638 cells
GO:0008180 COP9 signalosome	IDA PMID:9535219 A novel protein complex involved in signal transduction poss...	ACCEPT	Summary: The original study identifying the human COP9 signalosome. COPS8 is identified as a subunit of the 450 kDa complex by mass spectrometry and biochemical analysis. Reason: Core function - fundamental paper establishing COPS8 as a CSN subunit. Supporting Evidence: PMID:9535219 A novel protein complex has been identified in human cells that has a molecular mass of approximately 450 kDa. It consists of at least eight different subunits
GO:0008285 negative regulation of cell population proliferation	IMP PMID:23689509 COP9 signalosome subunit Csn8 is involved in maintaining pro...	ACCEPT	Summary: PMID:23689509 shows that Csn8 hypomorphism (reduced CSN8 levels) leads to ACCELERATED cell growth, not negative regulation. The paper demonstrates that decreased CSN8 levels shorten G1 phase and increase proliferation. This annotation appears to be inverted - CSN8 normally restrains proliferation, so the annotation is technically correct but requires clarification. Reason: The study shows that normal CSN8 levels maintain proper G1 phase duration and prevent accelerated proliferation. Thus COPS8 does participate in negative regulation of proliferation under normal conditions. Supporting Evidence: PMID:23689509 A decreased level of Csn8, either in Csn8 hypomorphic MEFs or following siRNA-mediated knockdown in HeLa cells, accelerated cell growth rate. Csn8 hypomorphic MEFs exhibited a shortened G1 duration
GO:0048471 perinuclear region of cytoplasm	IDA PMID:9535219 A novel protein complex involved in signal transduction poss...	ACCEPT	Summary: The original CSN paper shows perinuclear localization by immunofluorescence, similar to the 26S proteasome distribution. Reason: Direct experimental evidence for perinuclear localization of the CSN complex. Supporting Evidence: PMID:9535219 Immunofluorescence staining reveals that the new complex shows a subcellular distribution similar to that of the 26S proteasome.
GO:0070062 extracellular exosome	HDA PMID:19056867 Large-scale proteomics and phosphoproteomics of urinary exos...	KEEP AS NON CORE	Summary: High-throughput proteomics study detecting COPS8 in urinary exosomes. This is likely a minor localization not representing core function. Reason: While COPS8 may be present in exosomes based on proteomics data, this does not represent a core functional localization. The primary sites of CSN function are nucleus and cytoplasm. Supporting Evidence: PMID:19056867 Large-scale proteomics and phosphoproteomics of urinary exosomes.
GO:0000338 protein deneddylation	IDA PMID:19141280 Symmetrical modularity of the COP9 signalosome complex sugge...	ACCEPT	Summary: The reconstituted CSN complex shows deneddylase activity. COPS8 is required for proper complex assembly and thus for deneddylation function, though the catalytic activity resides in CSN5. Reason: Core function. While COPS8 is not the catalytic subunit, it is essential for CSN holocomplex integrity and therefore for deneddylation activity. Supporting Evidence: PMID:19141280 the catalytically active human complex, reconstituted in vitro, is composed of a single copy of each of the eight subunits. By forming a total of 35 subcomplexes, we are able to build a comprehensive interaction map that shows two symmetrical modules, Csn1/2/3/8 and Csn4/5/6/7
GO:0008180 COP9 signalosome	IDA PMID:18850735 Characterization of the human COP9 signalosome complex using...	ACCEPT	Summary: Affinity purification and mass spectrometry characterization confirming COPS8 as a CSN subunit with identification of post-translational modifications. Reason: Core function. Direct experimental evidence for COPS8 as a CSN complex subunit. Supporting Evidence: PMID:18850735 Mass spectrometric analysis of the purified CSN complex has revealed the identity of its composition as well as N-terminal modification and phosphorylation of the CSN subunits.
GO:0005634 nucleus	TAS PMID:8689678 The COP9 complex, a novel multisubunit nuclear regulator inv...	ACCEPT	Summary: Original study in Arabidopsis showing nuclear localization of the COP9 complex. Human CSN shows similar localization pattern. Reason: Nuclear localization is conserved for CSN complex across species. Supporting Evidence: PMID:8689678 The complex is acidic, binds heparin, and is localized within the nucleus.

Core Functions

COPS8 is an integral structural subunit of the COP9 signalosome, essential for holocomplex integrity and stability.

Molecular Function:

molecular adaptor activity

Cellular Locations:

cytosol nucleoplasm

In Complex:

COP9 signalosome

Through its role in maintaining CSN complex integrity, COPS8 is required for the deneddylation activity of the CSN complex on cullin substrates.

Molecular Function:

molecular adaptor activity

Directly Involved In:

protein deneddylation

In Complex:

COP9 signalosome

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000052

Gene Ontology annotation based on curation of immunofluorescence data

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:8689678

The COP9 complex, a novel multisubunit nuclear regulator involved in light control of a plant developmental switch.

Original identification of COP9 complex in Arabidopsis showing nuclear localization

PMID:9535219

A novel protein complex involved in signal transduction possessing similarities to 26S proteasome subunits.

Original characterization of human COP9 signalosome
Identification of eight subunits including COPS8
Detection of associated kinase activity
Perinuclear localization similar to 26S proteasome

PMID:15304329

Hepatopoietin interacts directly with COP9 signalosome and regulates AP-1 activity.

PMID:18850735

Characterization of the human COP9 signalosome complex using affinity purification and mass spectrometry.

Confirmed CSN composition
Identified COPS8 phosphorylation at Ser-175
Showed COPS8 N-terminal methionine removal

PMID:19056867

Large-scale proteomics and phosphoproteomics of urinary exosomes.

PMID:19141280

Symmetrical modularity of the COP9 signalosome complex suggests its multifunctionality.

Reconstituted catalytically active CSN complex
Showed COPS8 in Csn1/2/3/8 module
Demonstrated deneddylase activity requires intact complex

PMID:19615732

Defining the human deubiquitinating enzyme interaction landscape.

PMID:20399188

Structural insights into the COP9 signalosome and its common architecture with the 26S proteasome lid and eIF3.

PMID:21145461

Dynamics of cullin-RING ubiquitin ligase network revealed by systematic quantitative proteomics.

PMID:22992343

microRNA-146a inhibits G protein-coupled receptor-mediated activation of NF-κB by targeting CARD10 and COPS8 in gastric cancer.

COPS8 identified as miR-146a target
COPS8 knockdown inhibits LPA-induced NF-kappaB activation
COPS8 involved in GPCR-mediated NF-kappaB signaling

PMID:23689509

COP9 signalosome subunit Csn8 is involved in maintaining proper duration of the G1 phase.

Csn8 hypomorphism accelerates cell proliferation
Csn8 maintains proper G1 phase duration
Reduced Csn8 leads to increased free Csn5

PMID:24421388

Dynamic regulation of the COP9 signalosome in response to DNA damage.

CSN localized to cytoplasm, nucleoplasm, and chromatin
UV damage causes CSN shuttling to nucleus
Phosphorylation of CSN8 regulated by DNA damage

PMID:24981860

Human-chromatin-related protein interactions identify a demethylase complex required for chromosome segregation.

PMID:25043011

Crystal structure of the human COP9 signalosome.

High-resolution structure of CSN complex
COPS8 structural interactions with other subunits

PMID:25416956

A proteome-scale map of the human interactome network.

PMID:26496610

A human interactome in three quantitative dimensions organized by stoichiometries and abundances.

PMID:27029275

Cullin-RING ubiquitin E3 ligase regulation by the COP9 signalosome.

PMID:27173435

An organelle-specific protein landscape identifies novel diseases and molecular mechanisms.

PMID:28514442

Architecture of the human interactome defines protein communities and disease networks.

PMID:32296183

A reference map of the human binary protein interactome.

PMID:33961781

Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.

PMID:40205054

Multimodal cell maps as a foundation for structural and functional genomics.

Reactome:R-HSA-5691006

XPC:RAD23:CETN2 and UV-DDB bind distorted dsDNA site

Reactome:R-HSA-6781833

ERCC8 (CSA) binds stalled RNA Pol II

Reactome:R-HSA-8863721

NEDD8-STON binds TOR1 hexamer and COP9 complex

Reactome:R-HSA-8863723

COP9 and TOR1 deneddylate STON2

Reactome:R-HSA-8956040

COP9 signalosome deneddylates cytosolic CRL E3 ubiquitin ligase complexes

Reactome:R-HSA-8956045

COP9 signalosome deneddylates nuclear CRL4 E3 ubiquitin ligase complex

file:human/COPS8/COPS8-deep-research-falcon.md

Deep research synthesis on COPS8/CSN8 function

COPS8 is a PCI-domain scaffold subunit of the COP9 signalosome
CSN8 is essential for holocomplex integrity
Deneddylase catalytic activity resides in CSN5, not COPS8

Suggested Experiments

Experiment: Structural studies to define COPS8's specific contributions to CSN-CRL interactions

Experiment: Systematic analysis of CSN8 mutations on complex assembly and deneddylase activity

Experiment: Investigation of COPS8 phosphorylation (Ser-175) on CSN function

📚 Additional Documentation

Deep Research Falcon

(COPS8-deep-research-falcon.md)

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organism: human
gene_id: COPS8
gene_symbol: COPS8
uniprot_accession: Q99627
protein_description: 'RecName: Full=COP9 signalosome complex subunit 8; Short=SGN8;
Short=Signalosome subunit 8; AltName: Full=COP9 homolog; Short=hCOP9; AltName:
Full=JAB1-containing signalosome subunit 8;'
gene_info: Name=COPS8; Synonyms=CSN8;
organism_full: Homo sapiens (Human).
protein_family: Belongs to the CSN8 family. .
protein_domains: COP9_CSN8. (IPR033205); CSN8_PSD8_EIF3K. (IPR033464); PCI_dom.
(IPR000717); CSN8_PSD8_EIF3K (PF10075)
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: Q99627
Protein Description: RecName: Full=COP9 signalosome complex subunit 8; Short=SGN8; Short=Signalosome subunit 8; AltName: Full=COP9 homolog; Short=hCOP9; AltName: Full=JAB1-containing signalosome subunit 8;
Gene Information: Name=COPS8; Synonyms=CSN8;
Organism (full): Homo sapiens (Human).
Protein Family: Belongs to the CSN8 family. .
Key Domains: COP9_CSN8. (IPR033205); CSN8_PSD8_EIF3K. (IPR033464); PCI_dom. (IPR000717); CSN8_PSD8_EIF3K (PF10075)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "COPS8" matches the protein description above
Verify the organism is correct: Homo sapiens (Human).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'COPS8' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene COPS8 (gene ID: COPS8, UniProt: Q99627) in human.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: Q99627
Protein Description: RecName: Full=COP9 signalosome complex subunit 8; Short=SGN8; Short=Signalosome subunit 8; AltName: Full=COP9 homolog; Short=hCOP9; AltName: Full=JAB1-containing signalosome subunit 8;
Gene Information: Name=COPS8; Synonyms=CSN8;
Organism (full): Homo sapiens (Human).
Protein Family: Belongs to the CSN8 family. .
Key Domains: COP9_CSN8. (IPR033205); CSN8_PSD8_EIF3K. (IPR033464); PCI_dom. (IPR000717); CSN8_PSD8_EIF3K (PF10075)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "COPS8" matches the protein description above
Verify the organism is correct: Homo sapiens (Human).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Please provide a comprehensive research report on the gene COPS8 (gene ID: COPS8, UniProt: Q99627) in human.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Plan overview
Objectives were defined to: verify identity for human COPS8 (CSN8; UniProt Q99627), gather recent literature (prioritizing 2023–2024), extract mechanistic and localization evidence, compile recent disease/translation findings, and synthesize a concise artifact and full report with citations.

Verification of target identity and domains
- Gene/protein identity: COPS8 (synonym CSN8) encodes the eighth canonical subunit of the human COP9 signalosome (CSN), an evolutionarily conserved eight-subunit complex. This aligns with UniProt Q99627 and the target description. Contemporary reviews reaffirm the eight-subunit architecture and subfamily composition (PCI-domain subunits and MPN-domain subunits) for the human CSN, with CSN8 falling within the PCI-domain cohort (review synthesis). (dubiel2024comparisonoftwo pages 4-5)
- Organism: Homo sapiens (human) studies and reviews cited herein examine the human CSN and its subunits, including COPS8/CSN8. (liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5)
- Domain/family: CSN8 is one of the PCI-domain subunits of the CSN; the complex contains six PCI-domain subunits (including CSN8) and two MPN subunits (CSN5/CSN6), consistent with the PCI_dom annotation provided. (dubiel2024comparisonoftwo pages 4-5)
- No symbol ambiguity detected for human COPS8/CSN8 in the cited sources; research specifically refers to the human COP9 signalosome subunit 8.

Key concepts and definitions (current understanding)
- COP9 signalosome (CSN) function: The CSN is a master regulator of cullin–RING E3 ligases (CRLs). Its core enzymatic activity is deneddylation—the removal of the ubiquitin-like modifier NEDD8 from cullin scaffolds—which turns over CRL activation cycles and thereby tunes substrate ubiquitination rates. CSN5 (JAB1) harbors the JAMM/MPN metalloprotease activity responsible for deneddylation within the assembled complex. (Review and cancer-focused analysis, with URLs and dates: Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862; Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (dubiel2024comparisonoftwo pages 4-5, liu2024cop9signalosomecomplex pages 12-16)
- COPS8 (CSN8) role within CSN: CSN8 is a structural PCI-domain subunit required for holocomplex integrity. Perturbation (hypomorphism) of CSN8 destabilizes the CSN holocomplex, with consequences for CRL regulation and additional CSN5-dependent functions (see Recent developments and Vascular remodeling sections). (bioRxiv preprint, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

Recent developments and latest research (2023–2024 priority)
- Systems/comparative review: A 2024 review compared the CSN with the 26S proteasome lid, summarizing up-to-date mechanistic understanding of deneddylation, CSN–proteasome/SCF interactions, and variant CSN assemblies with roles in DNA damage response. It consolidates the placement of CSN5 as the deneddylase and highlights CSN’s regulatory reach across CRLs and stress pathways. (Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862) (dubiel2024comparisonoftwo pages 4-5)
- Cancer transcriptomic/prognostic update: In hepatocellular carcinoma (HCC), the CSN subunits are broadly upregulated with associations to poorer overall survival; functional assays reported that overexpression of certain subunits, including COPS8, enhanced proliferation, EMT, and vascular invasion. Multivariate analyses identified COPS5, COPS7B, and COPS9 as independent prognostic biomarkers. This work integrates TCGA, HPA, and immunohistochemistry, and explores immune infiltration correlations. (Aging, Mar 2024, 16:5264–5287, https://doi.org/10.18632/aging.205646) (liu2024cop9signalosomecomplex pages 12-16)
- Vascular remodeling mechanism implicating CSN8: A 2023 mechanistic preprint demonstrated that CSN8 hypomorphism leads to CSN holocomplex destabilization and accumulation of cytoplasmic CSN5 “mini-complexes.” In vascular smooth muscle cells (VSMCs), this state drives hyperproliferation and neointimal hyperplasia via a deneddylation-independent mechanism centered on CSN5-mediated nuclear export of p27; conversely, smooth muscle-specific deletion of CSN5 suppresses proliferation and neointimal growth. Pharmacologic CSN5 inhibition (CSN5i-3) blunted neointima formation in wild-type settings but did not rescue the CSN8-hypomorphic phenotype and showed moderate cardiotoxicity, prompting suggestions for local delivery strategies. (bioRxiv, posted Apr 12, 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

Primary function, mechanism, and pathway context
- Biochemical role: COPS8 is a PCI-domain scaffold subunit of the CSN holocomplex; by maintaining complex integrity, it enables CSN5-dependent deneddylation of cullins and the associated turnover of active CRLs. This positions COPS8 upstream of broad ubiquitin-mediated proteostasis and signaling flux. (Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862; Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (dubiel2024comparisonoftwo pages 4-5, liu2024cop9signalosomecomplex pages 12-16)
- Pathways and signaling: CSN-regulated CRL activity interfaces with p53, c-Jun/AP‑1, and NF‑κB/IκBα signaling axes, influencing cell cycle, stress, and inflammatory responses. Bioinformatic protein–protein interaction analysis in HCC highlighted strong CSN links to p53 and multiple cullins. (Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (liu2024cop9signalosomecomplex pages 12-16)
- DNA damage response: Variant CSN assemblies and CSN functions contribute to DNA damage signaling and repair pathways, as summarized by the 2024 review, underscoring CSN’s integration with stress responses beyond proteostasis. (Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862) (dubiel2024comparisonoftwo pages 4-5)

Subcellular localization and site of action
- The CSN operates in both cytoplasm and nucleus to control CRL activity and related signaling. In CSN8-hypomorphic cells and injured vessels, cytoplasmic CSN5-containing mini-complexes accumulate and promote nuclear export of p27, providing direct evidence of nucleo‑cytoplasmic functional interplay when CSN8 is compromised. (bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

Current applications and real-world implementations
- Biomarkers in oncology: CSN subunits, including COPS8, are candidate prognostic biomarkers in HCC; integrative clinical modeling (Kaplan–Meier, Cox regression, ROC, nomograms) supports the prognostic utility of a CSN signature, including immune infiltration correlations with COPS expression. (Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (liu2024cop9signalosomecomplex pages 12-16)
- Therapeutic concepts in vascular disease: Preclinical inhibition of CSN5 (CSN5i-3) reduced neointimal hyperplasia, supporting CSN5/CSN targeting to modulate VSMC proliferation and restenosis risk; toxicity observations and lack of rescue in CSN8 hypomorphism suggest context-dependent strategies and potential for local delivery (e.g., drug-eluting stents). (bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

Expert opinions and analysis from authoritative sources
- Comparative 2024 review perspective: The CSN is framed as a central UPS regulator akin to the proteasome lid, with a “neddylation–deneddylation cycle” driving substrate processing by CRLs. The review emphasizes therapeutic targeting possibilities while cautioning on the complexity of CSN variants and pathway crosstalk in DNA damage and cancer. (Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862) (dubiel2024comparisonoftwo pages 4-5)
- Cancer bioinformatics/functional synthesis (2024): The HCC study’s multilevel integration posits a practical route to clinical adoption of CSN-based prognostic signatures and motivates mechanistic follow-up on specific subunits, including COPS8, that enhance EMT and invasiveness when overexpressed. (Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (liu2024cop9signalosomecomplex pages 12-16)

Relevant statistics and recent data points
- HCC cohort analytics: The HCC analysis incorporated multi-omics databases and immunohistochemistry; expression of multiple CSN subunits was significantly upregulated in HCC and associated with shorter overall survival; COPS5, COPS7B, COPS9 were independent prognostic biomarkers in multivariate Cox models. The study included paired tumor/adjacent tissues and immune infiltration analyses (TIMER/TISIDB/ssGSEA/ESTIMATE). (Aging, Mar 2024, https://doi.org/10.18632/aging.205646) (liu2024cop9signalosomecomplex pages 12-16)
- Vascular remodeling models: In mouse left common carotid artery ligation, CSN subunit expression rose in injured vessels; smooth-muscle CSN5 knockout inhibited proliferation and neointima, while CSN8 hypomorphism exacerbated both. CSN5 pharmacologic inhibition (CSN5i-3) reduced neointima in wild-type but not in CSN8-hypomorphic conditions; toxicity signals were noted with systemic dosing. (bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)
- Melanoma: Elevated COPS8 expression correlated with poor survival; knockdown reduced proliferation, migration, and invasion and reversed EMT marker trends, supporting an oncogenic role. (Bioscience, Biotechnology, and Biochemistry, Feb 2021, https://doi.org/10.1093/bbb/zbaa017) (sun2021cops8incutaneous pages 6-8)

Embedded summary artifact
| Aspect | Summary | Key Evidence/Notes | Source (with URL and date) |
|---|---|---|---|
| Identity | COPS8 encodes CSN8, the eighth subunit of the eight-member COP9 signalosome (PCI-domain family), a conserved multisubunit complex. | CSN composition and PCI-family assignment are described in recent CSN reviews. (dubiel2024comparisonoftwo pages 4-5) | https://doi.org/10.3389/fcell.2024.1496862 (Nov 2024) (dubiel2024comparisonoftwo pages 4-5) |
| Core function | The COP9 signalosome regulates cullin-RING E3 ligases by removing NEDD8 (deneddylation); CSN5 contains the catalytic JAMM/MPN metalloprotease activity. | Deneddylation of cullins by CSN controls CRL activity and downstream ubiquitination. (liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) | https://doi.org/10.18632/aging.205646 (Mar 2024); https://doi.org/10.3389/fcell.2024.1496862 (Nov 2024) (liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) |
| COPS8-specific roles | CSN8 hypomorphism destabilizes the CSN holocomplex, promotes formation of cytoplasmic CSN5 "mini-complexes," and is linked to altered cell-cycle control and increased proliferation in vascular smooth muscle cells. | Functional preclinical data show CSN8-hypo increases VSMC proliferation and neointimal hyperplasia via a CSN5-mediated, nuclear-export mechanism. (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20) | https://doi.org/10.1101/2023.04.11.536468 (Apr 2023) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20) |
| Localization | The CSN functions in both nucleus and cytoplasm; CSN5-containing mini-complexes were observed in the cytoplasm, and CSN activity affects nucleo-cytoplasmic trafficking (e.g., p27 nuclear export). | Subcellular shifts of CSN subunits (CSN5 nuclear export / cytoplasmic mini-complexes) linked to altered cell-cycle regulator localization. (giri2023cop9signalosomepromotes pages 1-5) | https://doi.org/10.1101/2023.04.11.536468 (Apr 2023) (giri2023cop9signalosomepromotes pages 1-5) |
| Disease associations — cancer | Multiple COPS subunits are upregulated in cancers; COPS8 overexpression associates with poorer prognosis in HCC and functions as an oncogene in cutaneous melanoma promoting EMT. | Transcriptomic/prognostic analyses in HCC and a functional study in melanoma report COPS8 upregulation, proliferation/EMT effects, and survival associations. (liu2024cop9signalosomecomplex pages 12-16, sun2021cops8incutaneous pages 6-8) | https://doi.org/10.18632/aging.205646 (Mar 2024); https://doi.org/10.1093/bbb/zbaa017 (Feb 2021) (liu2024cop9signalosomecomplex pages 12-16, sun2021cops8incutaneous pages 6-8) |
| Inflammation / neurological | The CSN modulates inflammatory signaling and has been implicated in neuroinflammation and ischemic neuronal stress models via effects on CRL-regulated pathways (e.g., NF-κB, Akt). | Functional studies and reviews indicate CSN-dependent deneddylation alters microglial/endothelial inflammatory responses and neuronal survival. (liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) | https://doi.org/10.18632/aging.205646 (Mar 2024); https://doi.org/10.3389/fcell.2024.1496862 (Nov 2024) (liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) |
| Vascular remodeling | CSN influences neointimal hyperplasia: CSN5 knockout in smooth muscle reduces VSMC proliferation, whereas CSN8-hypomorphism exacerbates neointima formation; increased CSN5 observed in human PAH neointima. | Preclinical ligation and VSMC studies report CSN5/CSN8-dependent effects on p27 localization, proliferation, and neointimal growth. (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20) | https://doi.org/10.1101/2023.04.11.536468 (Apr 2023) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20) |
| Applications | COP9 subunits (including COPS8) have biomarker potential in HCC; pharmacologic CSN5 inhibition (CSN5i-3) suppresses VSMC proliferation and neointima in models but has toxicity considerations. | Biomarker analyses and preclinical inhibitor studies show translational potential and caution on toxicity/delivery. (liu2024cop9signalosomecomplex pages 12-16, giri2023cop9signalosomepromotes pages 1-5) | https://doi.org/10.18632/aging.205646 (Mar 2024); https://doi.org/10.1101/2023.04.11.536468 (Apr 2023) (liu2024cop9signalosomecomplex pages 12-16, giri2023cop9signalosomepromotes pages 1-5) |
| 2023–2024 highlights | Key recent findings: 2023 preprint links CSN8 hypomorphism to vascular disease mechanisms; 2024 study identifies COP9 subunits as prognostic in HCC; 2024 review synthesizes CSN roles versus the proteasome lid. | These items capture recent mechanistic, translational, and review-level updates on CSN/COPS8 biology. (giri2023cop9signalosomepromotes pages 1-5, liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) | https://doi.org/10.1101/2023.04.11.536468 (Apr 2023); https://doi.org/10.18632/aging.205646 (Mar 2024); https://doi.org/10.3389/fcell.2024.1496862 (Nov 2024) (giri2023cop9signalosomepromotes pages 1-5, liu2024cop9signalosomecomplex pages 12-16, dubiel2024comparisonoftwo pages 4-5) |

Table: A concise, cited table summarizing COPS8/CSN8 identity, core function, localization, disease links, recent 2023–2024 findings, and translational notes, with sources (context IDs and DOIs) for rapid reference.

Synthesis: precise role of COPS8
- Structural and regulatory role: COPS8 (CSN8) is a PCI-domain subunit essential for CSN holocomplex integrity, enabling the CSN’s deneddylase function to control CRL activity. Its disruption (hypomorphism) reveals an additional layer of CSN biology—CSN5 mini-complex formation and altered nucleo‑cytoplasmic trafficking of p27—linking COPS8 status to cell-cycle progression in vascular smooth muscle. (Frontiers in Cell and Developmental Biology, Nov 2024, https://doi.org/10.3389/fcell.2024.1496862; bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (dubiel2024comparisonoftwo pages 4-5, giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)
- Pathways and disease: Through the CSN, COPS8 influences CRL-dependent turnover of key regulators across p53, AP‑1, and NF‑κB axes, contributing to cancer biology (HCC prognostic value; EMT/invasion) and vascular remodeling (neointimal hyperplasia; CSN5 nuclear export of p27). The 2024 HCC study underscores translational potential for CSN subunit signatures, while the 2023 vascular work highlights opportunities and caveats for CSN5-targeted therapeutics. (Aging, Mar 2024, https://doi.org/10.18632/aging.205646; bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (liu2024cop9signalosomecomplex pages 12-16, giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

Limitations and open questions
- CSN8-specific enzymology: Unlike CSN5, CSN8 does not harbor catalytic deneddylase activity; its precise structural contributions to substrate selection and complex dynamics in human cells remain active areas of research.
- Context dependence: CSN5 inhibition phenotypes differ when CSN8 is hypomorphic, suggesting that COPS8 status may stratify responses to CSN-directed interventions and favor local over systemic delivery in vascular indications. (bioRxiv, Apr 2023, https://doi.org/10.1101/2023.04.11.536468) (giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20)

References (URLs and dates included above; citations by context IDs): (dubiel2024comparisonoftwo pages 4-5, liu2024cop9signalosomecomplex pages 12-16, giri2023cop9signalosomepromotes pages 1-5, giri2023cop9signalosomepromotes pages 17-20, sun2021cops8incutaneous pages 6-8, liu2024cop9signalosomecomplex pages 20-21)

References

(dubiel2024comparisonoftwo pages 4-5): Dawadschargal Dubiel and Wolfgang Dubiel. Comparison of two ups regulators: the 26s proteasome lid and the cop9 signalosome. Frontiers in Cell and Developmental Biology, Nov 2024. URL: https://doi.org/10.3389/fcell.2024.1496862, doi:10.3389/fcell.2024.1496862. This article has 1 citations and is from a poor quality or predatory journal.
(liu2024cop9signalosomecomplex pages 12-16): Jiahui Liu, Dexing Han, Junfeng Xuan, Jinye Xie, Weijia Wang, Quan Zhou, and Kang Chen. Cop9 signalosome complex is a prognostic biomarker and corresponds with immune infiltration in hepatocellular carcinoma. Aging (Albany NY), 16:5264-5287, Mar 2024. URL: https://doi.org/10.18632/aging.205646, doi:10.18632/aging.205646. This article has 3 citations.
(giri2023cop9signalosomepromotes pages 1-5): Samiksha Giri, Chao Suo, Ruggero Pardi, Gregory A. Fishbein, Khosrow Rezvani, Yabing Chen, and Xuejun Wang. Cop9 signalosome promotes neointimal hyperplasia via deneddylation and csn5-mediated nuclear export. BioRxiv, Apr 2023. URL: https://doi.org/10.1101/2023.04.11.536468, doi:10.1101/2023.04.11.536468. This article has 0 citations and is from a poor quality or predatory journal.
(giri2023cop9signalosomepromotes pages 17-20): Samiksha Giri, Chao Suo, Ruggero Pardi, Gregory A. Fishbein, Khosrow Rezvani, Yabing Chen, and Xuejun Wang. Cop9 signalosome promotes neointimal hyperplasia via deneddylation and csn5-mediated nuclear export. BioRxiv, Apr 2023. URL: https://doi.org/10.1101/2023.04.11.536468, doi:10.1101/2023.04.11.536468. This article has 0 citations and is from a poor quality or predatory journal.
(sun2021cops8incutaneous pages 6-8): Liangliang Sun. Cops8 in cutaneous melanoma: an oncogene that accelerates the malignant development of tumor cells and predicts poor prognosis. Bioscience, biotechnology, and biochemistry, 85 2:242-250, Feb 2021. URL: https://doi.org/10.1093/bbb/zbaa017, doi:10.1093/bbb/zbaa017. This article has 4 citations.
(liu2024cop9signalosomecomplex pages 20-21): Jiahui Liu, Dexing Han, Junfeng Xuan, Jinye Xie, Weijia Wang, Quan Zhou, and Kang Chen. Cop9 signalosome complex is a prognostic biomarker and corresponds with immune infiltration in hepatocellular carcinoma. Aging (Albany NY), 16:5264-5287, Mar 2024. URL: https://doi.org/10.18632/aging.205646, doi:10.18632/aging.205646. This article has 3 citations.

Citations

dubiel2024comparisonoftwo pages 4-5
https://doi.org/10.3389/fcell.2024.1496862;
https://doi.org/10.18632/aging.205646
https://doi.org/10.1101/2023.04.11.536468
https://doi.org/10.3389/fcell.2024.1496862
https://doi.org/10.1093/bbb/zbaa017
https://doi.org/10.18632/aging.205646;
https://doi.org/10.3389/fcell.2024.1496862,
https://doi.org/10.18632/aging.205646,
https://doi.org/10.1101/2023.04.11.536468,
https://doi.org/10.1093/bbb/zbaa017,

📄 View Raw YAML

id: Q99627
gene_symbol: COPS8
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  COPS8 (CSN8) encodes the eighth subunit of the COP9 signalosome (CSN), an evolutionarily
  conserved eight-subunit protein complex. COPS8 is a PCI-domain scaffold subunit essential
  for CSN holocomplex integrity and stability. The CSN complex functions as a master regulator
  of cullin-RING E3 ligases (CRLs) through its deneddylation activity, removing the
  ubiquitin-like modifier NEDD8 from cullin scaffolds. While COPS8 itself does not possess
  catalytic activity (the deneddylase activity resides in CSN5/JAB1), it is required for
  proper complex assembly and function. CSN8 hypomorphism destabilizes the CSN holocomplex
  and leads to formation of cytoplasmic CSN5 mini-complexes. The protein localizes to both
  cytoplasm and nucleus where the CSN complex regulates CRL-dependent protein turnover
  affecting signaling pathways including p53, c-Jun/AP-1, and NF-kappaB/IkappaBalpha.
alternative_products:
  - id: Q99627-1
    name: '1'
  - id: Q99627-2
    name: '2'
existing_annotations:
  - term:
      id: GO:0008180
      label: COP9 signalosome
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: >-
        COPS8 is an integral subunit of the COP9 signalosome complex. This is well-established
        from multiple studies including the original characterization (PMID:9535219) and
        structural studies (PMID:18850735, PMID:25043011). The IBA annotation is consistent
        with phylogenetic conservation of CSN8 as a core CSN component.
      action: ACCEPT
      reason: >-
        Core function. COPS8 is definitionally a subunit of the COP9 signalosome. The complex
        consists of eight subunits (GPS1/COPS1, COPS2-8, and COPS9) and COPS8 is essential
        for holocomplex integrity. This is supported by multiple experimental studies.
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            A novel protein complex has been identified in human cells that has a molecular
            mass of approximately 450 kDa. It consists of at least eight different subunits
            including JAB1, the Jun activation-domain binding protein 1, and Trip15
        - reference_id: PMID:18850735
          supporting_text: >-
            Purification of the human CSN complex from a stable 293 cell line expressing
            N-terminal HBTH-tagged CSN5 subunit was achieved by high-affinity streptavidin
            binding with TEV cleavage elution.
  - term:
      id: GO:0000338
      label: protein deneddylation
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: >-
        The CSN complex mediates protein deneddylation, removing NEDD8 from cullin substrates.
        While COPS8 itself lacks deneddylase catalytic activity (which resides in CSN5), it is
        required for CSN holocomplex integrity and thus for deneddylation function. The IEA
        annotation from InterPro is appropriate as a broader functional annotation.
      action: ACCEPT
      reason: >-
        The CSN complex functions as the major deneddylase in cells. COPS8 is required for
        proper CSN complex assembly and therefore contributes to the deneddylation process,
        even though it does not contain the catalytic metalloprotease domain (found in CSN5).
      supported_by:
        - reference_id: PMID:19141280
          supporting_text: >-
            The COP9 signalosome (CSN) is an eight-subunit protein complex that is found in
            all eukaryotes. Accumulating evidence indicates its diverse biological functions
            that are often linked to ubiquitin-mediated proteolysis... the catalytically active
            human complex, reconstituted in vitro, is composed of a single copy of each of the
            eight subunits.
  - term:
      id: GO:0005634
      label: nucleus
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: >-
        COPS8 and the CSN complex localize to both nucleus and cytoplasm. This IEA annotation
        is consistent with experimental evidence showing nuclear localization of the CSN.
      action: ACCEPT
      reason: >-
        Correct localization. Multiple experimental studies confirm nuclear localization of
        the CSN complex and COPS8 (PMID:9535219, PMID:24421388).
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound
            fractions, each differing in the composition of posttranslationally modified
            subunits, depending on its location within the cell.
  - term:
      id: GO:0005737
      label: cytoplasm
    evidence_type: IEA
    original_reference_id: GO_REF:0000044
    review:
      summary: >-
        COPS8 and the CSN complex localize to both nucleus and cytoplasm. This IEA annotation
        is consistent with experimental evidence from UniProt subcellular location mapping.
      action: ACCEPT
      reason: >-
        Correct localization. Cytoplasmic localization is well-documented for CSN complex
        (PMID:9535219, PMID:24421388).
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            Immunofluorescence staining reveals that the new complex shows a subcellular
            distribution similar to that of the 26S proteasome.
  - term:
      id: GO:0008180
      label: COP9 signalosome
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: >-
        Duplicate annotation of COP9 signalosome membership via automated pipeline. This is
        correct but redundant with the IBA annotation.
      action: ACCEPT
      reason: >-
        Core function. Duplicate annotations with different evidence codes are acceptable.
        This IEA annotation correctly identifies COPS8 as a CSN subunit.
      supported_by:
        - reference_id: PMID:18850735
          supporting_text: >-
            Mass spectrometric analysis of the purified CSN complex has revealed the identity
            of its composition as well as N-terminal modification and phosphorylation of the
            CSN subunits.
  - term:
      id: GO:0010387
      label: COP9 signalosome assembly
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: >-
        COPS8 is required for CSN holocomplex assembly and stability. CSN8 hypomorphism leads
        to destabilization of the CSN complex with formation of CSN5-containing mini-complexes.
      action: ACCEPT
      reason: >-
        CSN8 is essential for proper CSN complex assembly. Studies show that reduced CSN8
        levels lead to holocomplex destabilization and formation of aberrant subcomplexes.
      supported_by:
        - reference_id: PMID:23689509
          supporting_text: >-
            By characterizing the mouse embryonic fibroblasts (MEFs) that express Csn8 at a low
            level, we found that Csn8 plays an important role in maintaining the proper
            duration of the G1 phase of the cell cycle.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:15304329
    review:
      summary: >-
        This protein binding annotation is too vague. The cited paper shows hepatopoietin
        interacts with COP9 signalosome components. While the physical interaction may be
        valid, 'protein binding' does not convey useful functional information about COPS8's
        role as a structural scaffold subunit.
      action: MODIFY
      reason: >-
        'Protein binding' is uninformative. COPS8 functions as a structural scaffold within
        the CSN complex. A more informative term would describe its role in the complex.
      proposed_replacement_terms:
        - id: GO:0060090
          label: molecular adaptor activity
      supported_by:
        - reference_id: PMID:15304329
          supporting_text: >-
            Hepatopoietin interacts directly with COP9 signalosome and regulates AP-1 activity.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:18850735
    review:
      summary: >-
        This paper characterizes CSN complex composition and subunit interactions. The protein
        binding annotation is too vague - COPS8 specifically interacts with other CSN subunits
        (particularly COPS3, COPS4, COPS7) as part of the complex architecture.
      action: MODIFY
      reason: >-
        'Protein binding' is uninformative. The interaction is part of CSN complex formation.
      proposed_replacement_terms:
        - id: GO:0060090
          label: molecular adaptor activity
      supported_by:
        - reference_id: PMID:18850735
          supporting_text: >-
            Purification of the human CSN complex from a stable 293 cell line expressing
            N-terminal HBTH-tagged CSN5 subunit was achieved by high-affinity streptavidin
            binding with TEV cleavage elution.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:19615732
    review:
      summary: >-
        High-throughput interactome study identifying deubiquitinating enzyme interactions.
        'Protein binding' is too vague to be informative.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic 'protein binding' term that does not convey
        specific functional information about COPS8.
      supported_by:
        - reference_id: PMID:19615732
          supporting_text: >-
            Defining the human deubiquitinating enzyme interaction landscape.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:20399188
    review:
      summary: >-
        Structural study of CSN complex. The protein binding annotation reflects structural
        interactions within the CSN complex but is too vague.
      action: MODIFY
      reason: >-
        'Protein binding' is uninformative. The structural analysis shows COPS8 interacts
        with other CSN subunits as part of the complex architecture.
      proposed_replacement_terms:
        - id: GO:0060090
          label: molecular adaptor activity
      supported_by:
        - reference_id: PMID:20399188
          supporting_text: >-
            Structural insights into the COP9 signalosome and its common architecture with
            the 26S proteasome lid and eIF3.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:21145461
    review:
      summary: >-
        Quantitative proteomics study of cullin-RING ligase network dynamics. The interactions
        detected are relevant to CSN function in regulating CRLs but 'protein binding' is
        too vague.
      action: ACCEPT
      reason: >-
        The study provides evidence for CSN complex interactions with cullins, which is
        relevant to its core function. While 'protein binding' is vague, it captures
        the physical interaction aspect of CSN-CRL regulation.
      supported_by:
        - reference_id: PMID:21145461
          supporting_text: >-
            Dynamics of cullin-RING ubiquitin ligase network revealed by systematic
            quantitative proteomics.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:24421388
    review:
      summary: >-
        This study examined CSN dynamics in response to DNA damage. The protein binding
        annotation captures interactions within the complex.
      action: ACCEPT
      reason: >-
        This annotation reflects CSN subunit interactions which are functionally relevant
        for the complex's role in DNA damage response.
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            The COP9 signalosome (CSN) is an evolutionarily conserved protein complex that
            participates in the regulation of the ubiquitin/26S proteasome pathway
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:24981860
    review:
      summary: >-
        Chromatin-related protein interaction study. 'Protein binding' is too generic.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation that does not provide specific
        functional insight into COPS8.
      supported_by:
        - reference_id: PMID:24981860
          supporting_text: >-
            Human-chromatin-related protein interactions identify a demethylase complex
            required for chromosome segregation.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:25043011
    review:
      summary: >-
        Crystal structure of human COP9 signalosome. The structural analysis reveals
        COPS8 interactions with other CSN subunits. 'Protein binding' is too vague.
      action: MODIFY
      reason: >-
        The crystal structure shows COPS8 structural interactions but 'protein binding'
        is uninformative. The molecular adaptor activity term better captures COPS8's role.
      proposed_replacement_terms:
        - id: GO:0060090
          label: molecular adaptor activity
      supported_by:
        - reference_id: PMID:25043011
          supporting_text: >-
            Crystal structure of the human COP9 signalosome.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:25416956
    review:
      summary: >-
        Large-scale proteome interactome map. Generic 'protein binding' annotation.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput interactome study. The generic term does not convey functional
        information specific to COPS8.
      supported_by:
        - reference_id: PMID:25416956
          supporting_text: >-
            A proteome-scale map of the human interactome network.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:26496610
    review:
      summary: >-
        Quantitative human interactome study. Generic annotation from high-throughput data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:26496610
          supporting_text: >-
            A human interactome in three quantitative dimensions organized by
            stoichiometries and abundances.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:27029275
    review:
      summary: >-
        Review of CRL regulation by CSN. The protein binding annotation reflects
        CSN-CRL interactions which are functionally important.
      action: ACCEPT
      reason: >-
        The interaction between CSN and CRLs is central to CSN function in regulating
        ubiquitin ligase activity.
      supported_by:
        - reference_id: PMID:27029275
          supporting_text: >-
            Cullin-RING ubiquitin E3 ligase regulation by the COP9 signalosome.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:27173435
    review:
      summary: >-
        Organelle-specific protein landscape study. High-throughput interactome data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:27173435
          supporting_text: >-
            An organelle-specific protein landscape identifies novel diseases and
            molecular mechanisms.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:28514442
    review:
      summary: >-
        Human interactome architecture study. High-throughput interactome data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:28514442
          supporting_text: >-
            Architecture of the human interactome defines protein communities and
            disease networks.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:32296183
    review:
      summary: >-
        Human binary protein interactome reference map. High-throughput data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:32296183
          supporting_text: >-
            A reference map of the human binary protein interactome.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:33961781
    review:
      summary: >-
        Dual proteome-scale networks study. High-throughput interactome data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:33961781
          supporting_text: >-
            Dual proteome-scale networks reveal cell-specific remodeling of the
            human interactome.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:40205054
    review:
      summary: >-
        Multimodal cell maps study. High-throughput data.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput study with generic annotation.
      supported_by:
        - reference_id: PMID:40205054
          supporting_text: >-
            Multimodal cell maps as a foundation for structural and functional genomics.
  - term:
      id: GO:0005654
      label: nucleoplasm
    evidence_type: IDA
    original_reference_id: GO_REF:0000052
    review:
      summary: >-
        COPS8/CSN localizes to the nucleoplasm based on immunofluorescence data from HPA.
        This is consistent with the CSN's role in nuclear protein turnover regulation.
      action: ACCEPT
      reason: >-
        Nucleoplasm localization is well-supported by immunofluorescence studies and
        consistent with CSN function in regulating nuclear CRL activity.
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound
            fractions
  - term:
      id: GO:0005829
      label: cytosol
    evidence_type: IDA
    original_reference_id: GO_REF:0000052
    review:
      summary: >-
        COPS8/CSN localizes to the cytosol based on HPA immunofluorescence data.
        This is consistent with multiple studies showing cytoplasmic CSN localization.
      action: ACCEPT
      reason: >-
        Cytosolic localization is well-documented for CSN complex.
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            Immunofluorescence staining reveals that the new complex shows a subcellular
            distribution similar to that of the 26S proteasome.
  - term:
      id: GO:0005634
      label: nucleus
    evidence_type: IDA
    original_reference_id: PMID:24421388
    review:
      summary: >-
        The CSN complex is localized in both nucleus and cytoplasm. PMID:24421388 provides
        direct experimental evidence for nuclear localization using biochemical and
        fluorescence microscopy analyses.
      action: ACCEPT
      reason: >-
        Direct experimental evidence for nuclear localization of CSN complex including
        COPS8.
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            Through biochemical and fluorescence microscopy analyses, we determined that
            the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound
            fractions
  - term:
      id: GO:0005737
      label: cytoplasm
    evidence_type: IDA
    original_reference_id: PMID:24421388
    review:
      summary: >-
        The CSN complex is localized in both nucleus and cytoplasm. PMID:24421388 provides
        direct experimental evidence for cytoplasmic localization.
      action: ACCEPT
      reason: >-
        Direct experimental evidence for cytoplasmic localization of CSN complex.
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            the complex is localized in the cytoplasm, nucleoplasm, and chromatin-bound
            fractions
  - term:
      id: GO:0045116
      label: protein neddylation
    evidence_type: NAS
    original_reference_id: PMID:24421388
    review:
      summary: >-
        This annotation is problematic. The CSN complex is involved in protein DENEDDYLATION
        (removal of NEDD8), not neddylation (attachment of NEDD8). PMID:24421388 discusses
        CSN regulation of neddylation/deneddylation cycles but CSN is a deneddylase, not
        a neddylation enzyme.
      action: MODIFY
      reason: >-
        The CSN complex catalyzes deneddylation, not neddylation. While CSN participates
        in the neddylation/deneddylation cycle by removing NEDD8, it does not catalyze
        neddylation. The annotation should be 'protein deneddylation' or 'regulation of
        protein neddylation'.
      proposed_replacement_terms:
        - id: GO:0000338
          label: protein deneddylation
      supported_by:
        - reference_id: PMID:19141280
          supporting_text: >-
            the catalytically active human complex, reconstituted in vitro, is composed of
            a single copy of each of the eight subunits
  - term:
      id: GO:2000434
      label: regulation of protein neddylation
    evidence_type: NAS
    original_reference_id: PMID:24421388
    review:
      summary: >-
        The CSN regulates protein neddylation by catalyzing deneddylation, thus controlling
        the neddylation/deneddylation cycle of cullins. This annotation appropriately
        captures the regulatory role of CSN in the neddylation pathway.
      action: ACCEPT
      reason: >-
        CSN regulates neddylation by deneddylating cullins, affecting CRL activity and
        the neddylation cycle. This is an accurate description of CSN function.
      supported_by:
        - reference_id: PMID:24421388
          supporting_text: >-
            The COP9 signalosome (CSN) is an evolutionarily conserved protein complex that
            participates in the regulation of the ubiquitin/26S proteasome pathway by
            controlling the function of cullin-RING-ubiquitin ligases.
  - term:
      id: GO:0006468
      label: protein phosphorylation
    evidence_type: IDA
    original_reference_id: PMID:9535219
    review:
      summary: >-
        The CSN complex was found to have kinase activity that phosphorylates IkappaBalpha,
        p105, and c-Jun. However, this kinase activity is likely via association with CK2
        and PKD kinases (as noted in UniProt), not intrinsic to CSN subunits including COPS8.
        COPS8 is a PCI-domain scaffold protein without kinase catalytic activity.
      action: MODIFY
      reason: >-
        COPS8 does not have intrinsic kinase activity. The phosphorylation activity of
        the CSN complex comes from associated kinases (CK2, PKD) rather than from CSN
        subunits themselves. A more accurate annotation would reflect the regulatory
        role rather than direct enzymatic activity.
      proposed_replacement_terms:
        - id: GO:0045859
          label: regulation of protein kinase activity
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            The isolated JAB1-containing particle has kinase activity that phosphorylates
            IkappaBalpha, the carboxy terminus of p105, and Ser63 and/or Ser73 of the
            amino-terminal activation domain of c-Jun.
  - term:
      id: GO:0005829
      label: cytosol
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-8863721
    review:
      summary: >-
        Reactome annotation for CSN localization in cytosol based on NEDD8-related pathway.
        Consistent with experimental evidence.
      action: ACCEPT
      reason: >-
        Cytosolic localization is well-documented. Reactome pathway annotations are
        reliable.
      supported_by:
        - reference_id: Reactome:R-HSA-8863721
          supporting_text: >-
            NEDD8-STON binds TOR1 hexamer and COP9 complex
  - term:
      id: GO:0005829
      label: cytosol
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-8863723
    review:
      summary: >-
        Reactome annotation for CSN in cytosol involved in deneddylation.
      action: ACCEPT
      reason: >-
        Cytosolic localization is correct and relevant to CSN function.
      supported_by:
        - reference_id: Reactome:R-HSA-8863723
          supporting_text: >-
            COP9 and TOR1 deneddylate STON2
  - term:
      id: GO:0005829
      label: cytosol
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-8956040
    review:
      summary: >-
        Reactome annotation for CSN deneddylation of cytosolic CRL complexes.
      action: ACCEPT
      reason: >-
        Cytosolic localization is relevant to CSN function in regulating CRLs.
      supported_by:
        - reference_id: Reactome:R-HSA-8956040
          supporting_text: >-
            COP9 signalosome deneddylates cytosolic CRL E3 ubiquitin ligase complexes
  - term:
      id: GO:0005654
      label: nucleoplasm
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-5691006
    review:
      summary: >-
        Reactome annotation for CSN in nucleoplasm involved in DNA damage recognition
        in global genome nucleotide excision repair.
      action: ACCEPT
      reason: >-
        Nucleoplasm localization is well-documented and relevant to CSN role in DNA
        damage response.
      supported_by:
        - reference_id: Reactome:R-HSA-5691006
          supporting_text: >-
            XPC:RAD23:CETN2 and UV-DDB bind distorted dsDNA site
  - term:
      id: GO:0005654
      label: nucleoplasm
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-6781833
    review:
      summary: >-
        Reactome annotation for CSN in nucleoplasm involved in transcription-coupled
        nucleotide excision repair.
      action: ACCEPT
      reason: >-
        Nucleoplasm localization is consistent with CSN role in DNA damage response.
      supported_by:
        - reference_id: Reactome:R-HSA-6781833
          supporting_text: >-
            ERCC8 (CSA) binds stalled RNA Pol II
  - term:
      id: GO:0005654
      label: nucleoplasm
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-8956045
    review:
      summary: >-
        Reactome annotation for CSN deneddylation of nuclear CRL4 complex.
      action: ACCEPT
      reason: >-
        Nucleoplasm localization is relevant to CSN function in regulating nuclear
        CRL complexes.
      supported_by:
        - reference_id: Reactome:R-HSA-8956045
          supporting_text: >-
            COP9 signalosome deneddylates nuclear CRL4 E3 ubiquitin ligase complex
  - term:
      id: GO:0007250
      label: activation of NF-kappaB-inducing kinase activity
    evidence_type: IMP
    original_reference_id: PMID:22992343
    review:
      summary: >-
        PMID:22992343 shows that COPS8 knockdown inhibits LPA-stimulated GPCR-mediated
        NF-kappaB activation. The study identifies COPS8 as a miR-146a target and shows
        that siRNA knockdown of COPS8 significantly inhibits LPA-induced NF-kappaB
        activity. This supports a role for COPS8 in NF-kappaB signaling.
      action: KEEP_AS_NON_CORE
      reason: >-
        The annotation is supported by experimental evidence but represents a downstream
        effect of CSN function in regulating protein stability rather than a core
        molecular function of COPS8. The NF-kappaB regulation is likely mediated through
        CSN's role in CRL regulation affecting IkappaB stability.
      supported_by:
        - reference_id: PMID:22992343
          supporting_text: >-
            siRNA knockdown of CARD10 and COPS8 expression significantly inhibited
            LPA-stimulated GPCR-mediated activation of NF-kappaB in SNU638 cells
  - term:
      id: GO:0008180
      label: COP9 signalosome
    evidence_type: IDA
    original_reference_id: PMID:9535219
    review:
      summary: >-
        The original study identifying the human COP9 signalosome. COPS8 is identified
        as a subunit of the 450 kDa complex by mass spectrometry and biochemical analysis.
      action: ACCEPT
      reason: >-
        Core function - fundamental paper establishing COPS8 as a CSN subunit.
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            A novel protein complex has been identified in human cells that has a molecular
            mass of approximately 450 kDa. It consists of at least eight different subunits
  - term:
      id: GO:0008285
      label: negative regulation of cell population proliferation
    evidence_type: IMP
    original_reference_id: PMID:23689509
    review:
      summary: >-
        PMID:23689509 shows that Csn8 hypomorphism (reduced CSN8 levels) leads to
        ACCELERATED cell growth, not negative regulation. The paper demonstrates that
        decreased CSN8 levels shorten G1 phase and increase proliferation. This annotation
        appears to be inverted - CSN8 normally restrains proliferation, so the annotation
        is technically correct but requires clarification.
      action: ACCEPT
      reason: >-
        The study shows that normal CSN8 levels maintain proper G1 phase duration and
        prevent accelerated proliferation. Thus COPS8 does participate in negative
        regulation of proliferation under normal conditions.
      supported_by:
        - reference_id: PMID:23689509
          supporting_text: >-
            A decreased level of Csn8, either in Csn8 hypomorphic MEFs or following
            siRNA-mediated knockdown in HeLa cells, accelerated cell growth rate. Csn8
            hypomorphic MEFs exhibited a shortened G1 duration
  - term:
      id: GO:0048471
      label: perinuclear region of cytoplasm
    evidence_type: IDA
    original_reference_id: PMID:9535219
    review:
      summary: >-
        The original CSN paper shows perinuclear localization by immunofluorescence,
        similar to the 26S proteasome distribution.
      action: ACCEPT
      reason: >-
        Direct experimental evidence for perinuclear localization of the CSN complex.
      supported_by:
        - reference_id: PMID:9535219
          supporting_text: >-
            Immunofluorescence staining reveals that the new complex shows a subcellular
            distribution similar to that of the 26S proteasome.
  - term:
      id: GO:0070062
      label: extracellular exosome
    evidence_type: HDA
    original_reference_id: PMID:19056867
    review:
      summary: >-
        High-throughput proteomics study detecting COPS8 in urinary exosomes. This is
        likely a minor localization not representing core function.
      action: KEEP_AS_NON_CORE
      reason: >-
        While COPS8 may be present in exosomes based on proteomics data, this does not
        represent a core functional localization. The primary sites of CSN function are
        nucleus and cytoplasm.
      supported_by:
        - reference_id: PMID:19056867
          supporting_text: >-
            Large-scale proteomics and phosphoproteomics of urinary exosomes.
  - term:
      id: GO:0000338
      label: protein deneddylation
    evidence_type: IDA
    original_reference_id: PMID:19141280
    review:
      summary: >-
        The reconstituted CSN complex shows deneddylase activity. COPS8 is required for
        proper complex assembly and thus for deneddylation function, though the catalytic
        activity resides in CSN5.
      action: ACCEPT
      reason: >-
        Core function. While COPS8 is not the catalytic subunit, it is essential for
        CSN holocomplex integrity and therefore for deneddylation activity.
      supported_by:
        - reference_id: PMID:19141280
          supporting_text: >-
            the catalytically active human complex, reconstituted in vitro, is composed of
            a single copy of each of the eight subunits. By forming a total of 35
            subcomplexes, we are able to build a comprehensive interaction map that shows
            two symmetrical modules, Csn1/2/3/8 and Csn4/5/6/7
  - term:
      id: GO:0008180
      label: COP9 signalosome
    evidence_type: IDA
    original_reference_id: PMID:18850735
    review:
      summary: >-
        Affinity purification and mass spectrometry characterization confirming COPS8
        as a CSN subunit with identification of post-translational modifications.
      action: ACCEPT
      reason: >-
        Core function. Direct experimental evidence for COPS8 as a CSN complex subunit.
      supported_by:
        - reference_id: PMID:18850735
          supporting_text: >-
            Mass spectrometric analysis of the purified CSN complex has revealed the identity
            of its composition as well as N-terminal modification and phosphorylation of the
            CSN subunits.
  - term:
      id: GO:0005634
      label: nucleus
    evidence_type: TAS
    original_reference_id: PMID:8689678
    review:
      summary: >-
        Original study in Arabidopsis showing nuclear localization of the COP9 complex.
        Human CSN shows similar localization pattern.
      action: ACCEPT
      reason: >-
        Nuclear localization is conserved for CSN complex across species.
      supported_by:
        - reference_id: PMID:8689678
          supporting_text: >-
            The complex is acidic, binds heparin, and is localized within the nucleus.
references:
  - id: GO_REF:0000002
    title: Gene Ontology annotation through association of InterPro records with GO terms
    findings: []
  - id: GO_REF:0000033
    title: Annotation inferences using phylogenetic trees
    findings: []
  - id: GO_REF:0000044
    title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
      vocabulary mapping, accompanied by conservative changes to GO terms applied by
      UniProt
    findings: []
  - id: GO_REF:0000052
    title: Gene Ontology annotation based on curation of immunofluorescence data
    findings: []
  - id: GO_REF:0000120
    title: Combined Automated Annotation using Multiple IEA Methods
    findings: []
  - id: PMID:8689678
    title: The COP9 complex, a novel multisubunit nuclear regulator involved in light
      control of a plant developmental switch.
    findings:
      - statement: Original identification of COP9 complex in Arabidopsis showing nuclear localization
  - id: PMID:9535219
    title: A novel protein complex involved in signal transduction possessing similarities
      to 26S proteasome subunits.
    findings:
      - statement: Original characterization of human COP9 signalosome
      - statement: Identification of eight subunits including COPS8
      - statement: Detection of associated kinase activity
      - statement: Perinuclear localization similar to 26S proteasome
  - id: PMID:15304329
    title: Hepatopoietin interacts directly with COP9 signalosome and regulates AP-1
      activity.
    findings: []
  - id: PMID:18850735
    title: Characterization of the human COP9 signalosome complex using affinity purification
      and mass spectrometry.
    findings:
      - statement: Confirmed CSN composition
      - statement: Identified COPS8 phosphorylation at Ser-175
      - statement: Showed COPS8 N-terminal methionine removal
  - id: PMID:19056867
    title: Large-scale proteomics and phosphoproteomics of urinary exosomes.
    findings: []
  - id: PMID:19141280
    title: Symmetrical modularity of the COP9 signalosome complex suggests its multifunctionality.
    findings:
      - statement: Reconstituted catalytically active CSN complex
      - statement: Showed COPS8 in Csn1/2/3/8 module
      - statement: Demonstrated deneddylase activity requires intact complex
  - id: PMID:19615732
    title: Defining the human deubiquitinating enzyme interaction landscape.
    findings: []
  - id: PMID:20399188
    title: Structural insights into the COP9 signalosome and its common architecture
      with the 26S proteasome lid and eIF3.
    findings: []
  - id: PMID:21145461
    title: Dynamics of cullin-RING ubiquitin ligase network revealed by systematic
      quantitative proteomics.
    findings: []
  - id: PMID:22992343
    title: microRNA-146a inhibits G protein-coupled receptor-mediated activation of
      NF-κB by targeting CARD10 and COPS8 in gastric cancer.
    findings:
      - statement: COPS8 identified as miR-146a target
      - statement: COPS8 knockdown inhibits LPA-induced NF-kappaB activation
      - statement: COPS8 involved in GPCR-mediated NF-kappaB signaling
  - id: PMID:23689509
    title: COP9 signalosome subunit Csn8 is involved in maintaining proper duration
      of the G1 phase.
    findings:
      - statement: Csn8 hypomorphism accelerates cell proliferation
      - statement: Csn8 maintains proper G1 phase duration
      - statement: Reduced Csn8 leads to increased free Csn5
  - id: PMID:24421388
    title: Dynamic regulation of the COP9 signalosome in response to DNA damage.
    findings:
      - statement: CSN localized to cytoplasm, nucleoplasm, and chromatin
      - statement: UV damage causes CSN shuttling to nucleus
      - statement: Phosphorylation of CSN8 regulated by DNA damage
  - id: PMID:24981860
    title: Human-chromatin-related protein interactions identify a demethylase complex
      required for chromosome segregation.
    findings: []
  - id: PMID:25043011
    title: Crystal structure of the human COP9 signalosome.
    findings:
      - statement: High-resolution structure of CSN complex
      - statement: COPS8 structural interactions with other subunits
  - id: PMID:25416956
    title: A proteome-scale map of the human interactome network.
    findings: []
  - id: PMID:26496610
    title: A human interactome in three quantitative dimensions organized by stoichiometries
      and abundances.
    findings: []
  - id: PMID:27029275
    title: Cullin-RING ubiquitin E3 ligase regulation by the COP9 signalosome.
    findings: []
  - id: PMID:27173435
    title: An organelle-specific protein landscape identifies novel diseases and molecular
      mechanisms.
    findings: []
  - id: PMID:28514442
    title: Architecture of the human interactome defines protein communities and disease
      networks.
    findings: []
  - id: PMID:32296183
    title: A reference map of the human binary protein interactome.
    findings: []
  - id: PMID:33961781
    title: Dual proteome-scale networks reveal cell-specific remodeling of the human
      interactome.
    findings: []
  - id: PMID:40205054
    title: Multimodal cell maps as a foundation for structural and functional genomics.
    findings: []
  - id: Reactome:R-HSA-5691006
    title: XPC:RAD23:CETN2 and UV-DDB bind distorted dsDNA site
    findings: []
  - id: Reactome:R-HSA-6781833
    title: ERCC8 (CSA) binds stalled RNA Pol II
    findings: []
  - id: Reactome:R-HSA-8863721
    title: NEDD8-STON binds TOR1 hexamer and COP9 complex
    findings: []
  - id: Reactome:R-HSA-8863723
    title: COP9 and TOR1 deneddylate STON2
    findings: []
  - id: Reactome:R-HSA-8956040
    title: COP9 signalosome deneddylates cytosolic CRL E3 ubiquitin ligase complexes
    findings: []
  - id: Reactome:R-HSA-8956045
    title: COP9 signalosome deneddylates nuclear CRL4 E3 ubiquitin ligase complex
    findings: []
  - id: file:human/COPS8/COPS8-deep-research-falcon.md
    title: Deep research synthesis on COPS8/CSN8 function
    findings:
      - statement: COPS8 is a PCI-domain scaffold subunit of the COP9 signalosome
      - statement: CSN8 is essential for holocomplex integrity
      - statement: Deneddylase catalytic activity resides in CSN5, not COPS8
core_functions:
  - description: >-
      COPS8 is an integral structural subunit of the COP9 signalosome, essential for
      holocomplex integrity and stability.
    molecular_function:
      id: GO:0060090
      label: molecular adaptor activity
    in_complex:
      id: GO:0008180
      label: COP9 signalosome
    locations:
      - id: GO:0005829
        label: cytosol
      - id: GO:0005654
        label: nucleoplasm
  - description: >-
      Through its role in maintaining CSN complex integrity, COPS8 is required for the
      deneddylation activity of the CSN complex on cullin substrates.
    molecular_function:
      id: GO:0060090
      label: molecular adaptor activity
    directly_involved_in:
      - id: GO:0000338
        label: protein deneddylation
    in_complex:
      id: GO:0008180
      label: COP9 signalosome
suggested_questions:
  - question: Does COPS8 have any function independent of the CSN complex?
  - question: What are the specific structural contributions of COPS8 to CSN-substrate recognition?
  - question: Are there tissue-specific or developmental-stage-specific roles for COPS8?
suggested_experiments:
  - description: Structural studies to define COPS8's specific contributions to CSN-CRL interactions
  - description: Systematic analysis of CSN8 mutations on complex assembly and deneddylase activity
  - description: Investigation of COPS8 phosphorylation (Ser-175) on CSN function

COPS8

Gene Description

Existing Annotations Review

Core Functions

COPS8 is an integral structural subunit of the COP9 signalosome, essential for holocomplex integrity and stability.

Through its role in maintaining CSN complex integrity, COPS8 is required for the deneddylation activity of the CSN complex on cullin substrates.

References

Suggested Questions for Experts

Suggested Experiments

📚 Additional Documentation

Deep Research Falcon

Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Output

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Citations

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