DNAJB6

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005737 cytoplasm	IBA GO_REF:0000033	ACCEPT	Summary: DNAJB6 localizes to the cytoplasm, particularly the DNAJB6b isoform which is predominantly cytosolic. This is well supported by multiple lines of evidence including immunostaining in PMID:10954706, subcellular fractionation in PMID:21231916, and the observation in PMID:22366786 that LGMD1D mutations exert their pathogenic effect specifically through the cytoplasmic isoform DNAJB6b. The IBA annotation is appropriately broad and well supported by phylogenetic conservation. Reason: Cytoplasmic localization is a well-established core feature of DNAJB6, especially the DNAJB6b isoform. PMID:10954706 showed colocalization with K8/18 filaments in HeLa cells. PMID:21231916 demonstrated cytosolic localization by IDA. PMID:22366786 showed LGMD1D mutations exert effects through the cytoplasmic isoform specifically. The IBA annotation is correct and represents a core localization. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells. PMID:22366786 Strikingly, these phenotypes were generated exclusively upon injection of mutant DNAJB6b; neither mutation, when engineered into DNAJB6a, had any impact (Fig. 2).
GO:0006457 protein folding	IBA GO_REF:0000033	ACCEPT	Summary: DNAJB6 is a DnaJ co-chaperone that participates in the Hsp70 chaperone network, which broadly functions in protein folding and quality control. However, DNAJB6 specifically acts as a holdase rather than a foldase -- it suppresses aggregation but cannot stimulate refolding of denatured substrates (PMID:21231916). The IBA annotation to GO:0006457 (protein folding) captures the general chaperone pathway context but is somewhat misleading for DNAJB6 specifically, since the protein prevents aggregation rather than promoting productive folding. However, protein folding as a GO BP term encompasses the broader process including aggregation prevention, so the term is acceptable if understood in this context. Reason: While DNAJB6 is specifically a holdase rather than foldase (PMID:21231916), GO:0006457 (protein folding) as a biological process broadly encompasses protein quality control activities including aggregation prevention. DNAJB6 participates in the Hsp70-dependent protein folding/quality control pathway via its J-domain, and as an IBA annotation this represents a reasonable phylogenetically inferred function for the DnaJ family. The term is not wrong, though it should be understood that DNAJB6 contributes specifically to the anti-aggregation arm of protein quality control. Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. PMID:11896048 overexpressed MRJ effectively suppressed polyglutamine-dependent protein aggregation, caspase activity, and cellular toxicity file:human/DNAJB6/DNAJB6-deep-research-falcon.md In neuronal cells, the DNAJB6b isoform is required and sufficient to reduce tau aggregation; its J-domain is necessary, consistent with Hsp70-dependent anti-aggregation.
GO:0005634 nucleus	IBA GO_REF:0000033	ACCEPT	Summary: DNAJB6 localizes to the nucleus, particularly the DNAJB6a isoform which is predominantly nuclear (PMID:10954706, PMID:22366786). PMID:10954706 showed nuclear localization by immunostaining. The deep research review also confirms nuclear localization for isoform A. The IBA annotation is well supported and phylogenetically appropriate for the DnaJ family. Reason: Nuclear localization is well established for DNAJB6, particularly isoform A. PMID:10954706 demonstrated nuclear staining. This is a core localization for the protein, consistent with phylogenetic inference. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells. Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70.
GO:0051087 protein-folding chaperone binding	IBA GO_REF:0000033	ACCEPT	Summary: DNAJB6 binds Hsp70/HSPA family chaperones through its J-domain. PMID:10954706 demonstrated that Mrj (DNAJB6) immunoprecipitated with Hsp/c70 and that the N-terminal J-domain region mediates Hsp70 interaction. PMID:22366786 confirmed interaction with HSPA8 (Hsc70). The IBA annotation correctly reflects this core co-chaperone binding activity. Reason: Binding to Hsp70 chaperones is the defining molecular function of J-domain proteins. DNAJB6 interacts with Hsp/c70 via its J-domain (PMID:10954706), and this interaction is essential for the protein's co-chaperone function. The IBA annotation is a core function well supported by phylogenetic conservation across the DnaJ family. Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70. Mrj bound to K18 through its C terminus and interacted with Hsp/c70 via its N terminus, which contains the J domain.
GO:0044183 protein folding chaperone	IBA GO_REF:0000033	ACCEPT	Summary: GO:0044183 (protein folding chaperone) is an MF term describing proteins that bind other proteins to assist the protein folding process. DNAJB6 acts as a co-chaperone within the Hsp70 network, functioning specifically as a holdase that prevents aggregation rather than assisting productive folding. The IBA annotation is phylogenetically appropriate for the DnaJ family and represents the closest available GO molecular function term for DNAJB6 chaperone activity, even though a holdase-specific term would be more precise. Reason: GO:0044183 is the best available MF term for DNAJB6 chaperone activity. While DNAJB6 specifically acts as a holdase rather than foldase (PMID:21231916), there is no dedicated holdase term in GO. The IBA annotation is phylogenetically sound for the DnaJ family. This is already being used as the replacement term for the obsoleting GO:0051082, making it a core annotation. Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation. file:human/DNAJB6/DNAJB6-deep-research-falcon.md DNAJB6 is a human class B Hsp40/JDP co-chaperone that deploys an autoinhibited, J-domain-controlled mechanism to engage Hsp70 and prevent pathological protein aggregation.
GO:0051082 unfolded protein binding	IBA GO_REF:0000033	MODIFY	Summary: GO:0051082 (unfolded protein binding) is now formally obsolete (go-ontology#30962). DNAJB6 does bind unfolded/misfolded proteins as a co-chaperone, but crucially it does NOT refold them. PMID:21231916 demonstrated that DNAJB6 suppresses polyQ aggregation but cannot stimulate luciferase refolding, indicating holdase-like rather than foldase activity. The IBA annotation propagated from phylogenetic inference is broadly correct in that DNAJB6 engages unfolded clients, but the term itself is now formally obsolete. GO:0044183 (protein folding chaperone) is the closest available replacement, though its definition ("Binding to a protein or a protein-containing complex to assist the protein folding process") is not ideal for a holdase. A dedicated holdase activity term would be more appropriate for DNAJB6 but does not currently exist in GO. Reason: GO:0051082 is now formally obsolete per go-ontology#30962. DNAJB6 does interact with unfolded/aggregation-prone proteins, but its mechanism is holdase-like (preventing aggregation) rather than foldase-like (promoting refolding). PMID:21231916 showed that DNAJB6 overexpression suppressed polyQ aggregation but did not stimulate luciferase refolding. GO:0044183 (protein folding chaperone) is proposed as an interim replacement since it is the parent term already assigned by IBA, but a more specific holdase-type term would better capture DNAJB6 function if one existed in GO. Proposed replacements: protein folding chaperone Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation.
GO:0005634 nucleus	IEA GO_REF:0000120	ACCEPT	Summary: This IEA annotation from Ensembl Compara ortholog transfer is consistent with the well-established nuclear localization of DNAJB6, particularly isoform A. Multiple experimental studies confirm nuclear localization (PMID:10954706, PMID:21231916, PMID:21630459). The IEA is broader than the IBA and IDA annotations but is not incorrect. Reason: Nuclear localization is well supported experimentally. The IEA annotation is redundant with stronger IBA and IDA evidence but is not wrong. Accepted as a valid additional annotation. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells.
GO:0030018 Z disc	IEA GO_REF:0000044	ACCEPT	Summary: This IEA annotation from UniProtKB subcellular location mapping is supported by direct experimental evidence in PMID:22366786, which demonstrated by immunofluorescence that DNAJB6 localizes primarily to Z-disks in skeletal muscle. This localization is functionally relevant as LGMDD1 mutations cause Z-disk myofibrillar disintegration. Reason: Z disc localization is directly demonstrated by IDA in PMID:22366786. The IEA annotation is consistent with this experimental evidence and correctly maps the UniProt subcellular location annotation. Supporting Evidence: PMID:22366786 Immunofluorescence (IF) microscopy showed DNAJB6 primarily in Z-disks in both control (not shown) and LGMD1D muscle samples (Fig. 1a).
GO:0030544 Hsp70 protein binding	IEA GO_REF:0000002	ACCEPT	Summary: This IEA annotation from InterPro domain mapping correctly identifies DNAJB6 as an Hsp70-binding protein. DNAJB6 interacts with Hsp70/Hsc70 through its J-domain, as demonstrated experimentally in PMID:10954706 (co-immunoprecipitation with Hsp/c70) and confirmed by the Reactome pathway annotations (R-HSA-5251955, R-HSA-5251959). This is a core molecular function. Reason: Hsp70 binding is the fundamental co-chaperone activity of all J-domain proteins. DNAJB6 binds Hsp/c70 via its N-terminal J-domain (PMID:10954706). The InterPro mapping is accurate. While GO:0051087 (protein-folding chaperone binding) is a parent term also annotated, GO:0030544 is more specific to the Hsp70 interaction and is a valid annotation. Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70. Mrj bound to K18 through its C terminus and interacted with Hsp/c70 via its N terminus, which contains the J domain.
GO:0048471 perinuclear region of cytoplasm	IEA GO_REF:0000044	ACCEPT	Summary: This IEA annotation from UniProtKB subcellular location mapping is consistent with the experimentally determined perinuclear localization of DNAJB6. PMID:10954706 demonstrated perinuclear staining by IDA, and the UniProt entry explicitly states perinuclear region localization (ECO:0000269\|PubMed:10954706). Reason: Perinuclear localization is experimentally supported by PMID:10954706 with IDA evidence. The IEA mapping from UniProt subcellular location vocabulary is correct and consistent with the direct experimental observation. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells.
GO:0051082 unfolded protein binding	IEA GO_REF:0000002	MODIFY	Summary: This IEA annotation was inferred from InterPro domain mapping (IPR043183, DNJB2/6-like). GO:0051082 is now formally obsolete (go-ontology#30962). While the InterPro domain is correctly identified, the mapped term does not accurately capture DNAJB6 function. DNAJB6 has holdase-like activity (suppressing aggregation) rather than foldase activity (refolding proteins), as demonstrated in PMID:21231916. GO:0044183 (protein folding chaperone) is the closest available replacement term, though a holdase-specific term would be more appropriate. Reason: GO:0051082 is now formally obsolete per go-ontology#30962. The IEA mapping from InterPro IPR043183 correctly identifies DNAJB6 as a J-domain protein that interacts with unfolded clients, but the term itself is being retired. DNAJB6 functions as a holdase rather than a foldase (PMID:21231916), so GO:0044183 (protein folding chaperone) is proposed as an interim replacement, acknowledging that a holdase-specific term would better represent the actual molecular activity. Proposed replacements: protein folding chaperone Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation.
GO:0005515 protein binding	IPI PMID:10954706 Identification of Mrj, a DnaJ/Hsp40 family protein, as a ker...	MODIFY	Summary: PMID:10954706 demonstrated that DNAJB6 (Mrj) binds to K18 (keratin 18) and Hsp/c70 by yeast two-hybrid and co-immunoprecipitation. These are specific, functionally relevant interactions. However, GO:0005515 (protein binding) is an uninformative term that does not capture the nature of the interaction. More specific terms like GO:0030544 (Hsp70 protein binding) and GO:0019215 (intermediate filament binding) would better describe the interactions demonstrated. Reason: GO:0005515 (protein binding) is too vague and uninformative. The interactions demonstrated in PMID:10954706 -- with K18 and Hsp/c70 -- are specific and functionally relevant. These are better captured by GO:0030544 (Hsp70 protein binding) for the Hsp70 interaction and GO:0019215 (intermediate filament binding) for the K18 interaction. Proposed replacements: Hsp70 protein binding intermediate filament binding Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70. Mrj bound to K18 through its C terminus and interacted with Hsp/c70 via its N terminus, which contains the J domain.
GO:0005515 protein binding	IPI PMID:16919237 Breast cancer metastasis suppressor 1 (BRMS1) is stabilized ...	MARK AS OVER ANNOTATED	Summary: PMID:16919237 concerns the stabilization of BRMS1 by the Hsp90 chaperone system. DNAJB6 is listed as a binding partner from co-immunoprecipitation. The UniProt interaction data confirms BRMS1 (Q9HCU9) interacts with DNAJB6 (NbExp=2). This is likely a client or co-chaperone network interaction. GO:0005515 (protein binding) is uninformative. Reason: While the interaction with BRMS1 may be genuine from co-immunoprecipitation data, GO:0005515 (protein binding) is an uninformative term. The interaction with BRMS1 is likely part of DNAJB6's general chaperone client handling rather than a specific functional interaction. This does not add meaningful information beyond what is already captured by more specific chaperone-related MF terms.
GO:0005515 protein binding	IPI PMID:23414517 A human skeletal muscle interactome centered on proteins inv...	MARK AS OVER ANNOTATED	Summary: PMID:23414517 describes a human skeletal muscle interactome centered on proteins involved in muscular dystrophies. This is a large-scale interaction study. GO:0005515 (protein binding) from a high-throughput interactome study is uninformative. Reason: GO:0005515 (protein binding) from a large-scale interactome mapping study adds no specific functional information. The interactions detected in PMID:23414517 may be biologically relevant but the GO term itself is too general to be useful.
GO:0005515 protein binding	IPI PMID:25036637 A quantitative chaperone interaction network reveals the arc...	MARK AS OVER ANNOTATED	Summary: PMID:25036637 describes a quantitative chaperone interaction network. This is a systematic chaperone interactome study. GO:0005515 (protein binding) from this study is uninformative, though the underlying data about chaperone network interactions is valuable. Reason: GO:0005515 (protein binding) from a systematic chaperone network study is too general. The chaperone-specific interactions are better captured by terms like GO:0051087 (protein-folding chaperone binding) and GO:0030544 (Hsp70 protein binding), which are already annotated.
GO:0005515 protein binding	IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ...	MARK AS OVER ANNOTATED	Summary: PMID:32814053 describes interactome mapping of neurodegenerative disease proteins. This is a high-throughput study. GO:0005515 (protein binding) is uninformative. Reason: GO:0005515 (protein binding) from a large-scale neurodegenerative disease interactome mapping study is too general to be informative. The chaperone-client interactions are better represented by more specific functional terms.
GO:0005515 protein binding	IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling...	MARK AS OVER ANNOTATED	Summary: PMID:33961781 describes dual proteome-scale networks revealing cell-specific remodeling of the human interactome. This is a high-throughput study. GO:0005515 (protein binding) is uninformative. Reason: GO:0005515 (protein binding) from a large-scale proteomics interactome study is too general to be informative for understanding DNAJB6 function.
GO:0005515 protein binding	IPI PMID:40205054 Multimodal cell maps as a foundation for structural and func...	MARK AS OVER ANNOTATED	Summary: PMID:40205054 describes multimodal cell maps as a foundation for structural and functional genomics. This is a high-throughput study. GO:0005515 (protein binding) is uninformative. Reason: GO:0005515 (protein binding) from a large-scale cell map study is too general to be informative for DNAJB6 functional annotation.
GO:0003677 DNA binding	IEA GO_REF:0000107	REMOVE	Summary: This IEA annotation from Ensembl Compara ortholog transfer suggests DNA binding activity. There is no direct experimental evidence for DNAJB6 binding DNA. DNAJB6 is a DnaJ co-chaperone with well-characterized protein-binding activities (Hsp70, keratin, aggregation-prone substrates) but no known nucleic acid binding activity. The J-domain and G/F-rich regions are protein interaction domains. While DNAJB6a localizes to the nucleus, this reflects its role in nuclear proteostasis rather than DNA binding. This annotation likely results from incorrect ortholog transfer. Reason: There is no experimental evidence for DNAJB6 DNA binding activity. DNAJB6 is a protein chaperone that interacts with Hsp70, keratins, and aggregation-prone substrates. Its nuclear localization (isoform A) relates to proteostasis functions, not DNA binding. This IEA annotation likely results from erroneous ortholog transfer and is not supported by any published literature or UniProt functional annotation. The UniProt entry describes only protein-protein interactions and chaperone activity, with no mention of DNA binding.
GO:0005737 cytoplasm	IEA GO_REF:0000107	ACCEPT	Summary: This IEA annotation from Ensembl Compara ortholog transfer is consistent with the well-established cytoplasmic localization of DNAJB6, particularly isoform B. Redundant with the IBA annotation but not incorrect. Reason: Cytoplasmic localization is well established for DNAJB6, especially isoform B. The IEA from ortholog transfer is consistent with direct experimental evidence and IBA annotation.
GO:0005654 nucleoplasm	IDA GO_REF:0000052	ACCEPT	Summary: This IDA annotation from immunofluorescence curation (HPA) indicates nucleoplasm localization. DNAJB6a is predominantly nuclear. The Human Protein Atlas immunofluorescence data provides direct observation of nucleoplasmic localization, consistent with isoform A distribution and the Reactome pathway annotation R-HSA-5251955 (HSP40s activate HSP70 ATPase in nucleoplasm). Reason: Nucleoplasm localization is consistent with the known nuclear distribution of DNAJB6a. HPA immunofluorescence data provides direct visualization. This is supported by the Reactome pathway R-HSA-5251955 which places DNAJB6 in the nucleoplasm for HSP70 ATPase activation.
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: This IDA annotation from immunofluorescence curation (HPA) indicates cytosol localization. DNAJB6b is predominantly cytosolic. The Human Protein Atlas data is consistent with multiple studies showing cytosolic localization of DNAJB6b (PMID:21231916, PMID:22366786). Reason: Cytosol localization is well established for DNAJB6b. HPA immunofluorescence provides direct evidence. Consistent with PMID:21231916 and PMID:22366786 which demonstrate cytosolic DNAJB6b function.
GO:1900034 regulation of cellular response to heat	TAS Reactome:R-HSA-3371453	KEEP AS NON CORE	Summary: This TAS annotation from Reactome (R-HSA-3371453, Regulation of HSF1-mediated heat shock response) places DNAJB6 in the heat shock response pathway. As a DnaJ/Hsp40 co-chaperone, DNAJB6 participates in the Hsp70 chaperone network that is central to the cellular heat shock response. The Reactome pathway describes how chaperones regulate HSF1 activity. This is a legitimate biological process for DNAJB6 but represents a broader pathway context rather than a core specific function. Reason: DNAJB6 participates in the Hsp70 chaperone network that regulates the heat shock response, but this represents a general pathway context rather than the specific anti-aggregation holdase activity that is DNAJB6's primary function. The Reactome pathway annotation is valid but non-core.
GO:0050877 nervous system process	IDA PMID:11896048 Characterization of a brain-enriched chaperone, MRJ, that in...	MARK AS OVER ANNOTATED	Summary: PMID:11896048 (Chuang et al. 2002) characterized DNAJB6/MRJ as a brain-enriched chaperone that inhibits Huntingtin aggregation. The paper showed that MRJ is highly enriched in the central nervous system and suppressed polyglutamine-dependent aggregation and toxicity in neuronal cell models. However, the annotation to GO:0050877 (nervous system process) is overly broad and not directly demonstrated. The paper shows DNAJB6 has chaperone activity that is relevant in neurons, but it does not demonstrate involvement in a specific nervous system process. The enrichment in brain and activity in neuronal cells does not constitute evidence for involvement in nervous system processes per se -- the chaperone activity is a general proteostasis function that happens to be important in neurons. Reason: PMID:11896048 demonstrates that DNAJB6 is brain-enriched and suppresses polyglutamine aggregation in neuronal cells, but this does not constitute direct evidence for involvement in nervous system processes. The chaperone/anti-aggregation activity is a general proteostasis function, not a nervous system-specific process. Being enriched in brain tissue does not make a protein's function a "nervous system process." The anti-aggregation activity is better captured by GO:0090084 (negative regulation of inclusion body assembly) and GO:0006457 (protein folding). Supporting Evidence: PMID:11896048 Tissue distribution studies showed that MRJ is highly enriched in the central nervous system. In an in vitro cell model of HD, overexpressed MRJ effectively suppressed polyglutamine-dependent protein aggregation, caspase activity, and cellular toxicity.
GO:0001671 ATPase activator activity	TAS Reactome:R-HSA-5251955	ACCEPT	Summary: This TAS annotation from Reactome (R-HSA-5251955, HSP40s activate intrinsic ATPase activity of HSP70s in the nucleoplasm) correctly identifies DNAJB6 as an activator of HSP70 ATPase activity. The Reactome pathway summary explicitly lists DNAJB6 (as DNAJB6) among the HSP40s that stimulate HSP70 ATPase activity, citing Izawa et al. 2000 (PMID:10954706) and Hanai & Mashima 2003. This is a core molecular function of all J-domain proteins. Reason: ATPase activator activity toward Hsp70 is the defining molecular function of J-domain proteins including DNAJB6. The Reactome pathway correctly identifies DNAJB6 as stimulating HSP70 ATPase activity in the nucleoplasm. PMID:10954706 and UniProt both confirm this function. This is a core annotation. Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70.
GO:0001671 ATPase activator activity	TAS Reactome:R-HSA-5251959	ACCEPT	Summary: This TAS annotation from Reactome (R-HSA-5251959, HSP40s activate intrinsic ATPase activity of HSP70s in the cytosol) correctly identifies DNAJB6 as an activator of HSP70 ATPase activity in the cytosol. The Reactome pathway explicitly mentions DNAJB6 (as DNAJB6) among the HSP40s that dramatically increase HSP70 ATPase activity, citing Izawa et al. 2000 (PMID:10954706). Duplicate of the nucleoplasm-specific annotation above but refers to the cytosolic context (isoform B). Reason: Same core function as the nucleoplasm annotation above, but in the cytosolic compartment context. Both are valid as DNAJB6 isoforms function in both compartments. This is a core molecular function. The Reactome entry explicitly names DNAJB6 as an Hsp70 ATPase stimulator. Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70.
GO:0051087 protein-folding chaperone binding	IPI PMID:21231916 The diverse members of the mammalian HSP70 machine show dist...	ACCEPT	Summary: PMID:21231916 (Hageman et al. 2011) systematically assessed Hsp70 and Hsp40 family members for chaperone activities and demonstrated functional interactions between DNAJB6 and HSP70s. The study showed that J-proteins including DNAJB6 stimulate Hsp70 ATPase activity, confirming the co-chaperone binding interaction. The IPI evidence from this study directly supports DNAJB6 binding to protein-folding chaperones (Hsp70s). Reason: PMID:21231916 provides direct experimental evidence for DNAJB6 interacting with Hsp70 family chaperones in functional assays. This is a core molecular function of J-domain proteins and is well supported by the experimental data in this publication. Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation. This was not related to client specificity itself, as the polyQ aggregation inhibitors often also suppressed heat-induced aggregation of luciferase.
GO:0032880 regulation of protein localization	IMP PMID:20889486 Molecular chaperone-mediated rescue of mitophagy by a Parkin...	KEEP AS NON CORE	Summary: PMID:20889486 (Rose et al. 2011) demonstrated that DNAJB6 can rescue the relocation of misfolded Parkin (C289G mutant) to depolarized mitochondria, thereby restoring mitophagy. DNAJB6 co-expression rescued Parkin(C289G) redistribution to mitochondria in 16% of cells (comparable to HSJ1a ΔUIM mutant). This represents regulation of protein localization through chaperone-mediated refolding/stabilization of a misfolded client. However, this is a non-core function -- it reflects DNAJB6's general anti-aggregation chaperone activity applied to a specific client (misfolded Parkin) rather than a primary regulatory role in protein localization. Reason: The ability of DNAJB6 to rescue localization of misfolded Parkin to mitochondria (PMID:20889486) is a secondary consequence of its chaperone/anti-aggregation activity, not a primary role in regulating protein localization. DNAJB6 helps misfolded Parkin achieve its correct conformation, allowing it to relocate to mitochondria -- this is chaperone activity applied to a specific client rather than a core protein localization regulatory function. Supporting Evidence: PMID:20889486 HSJ1a and DNAJB6 also restored mitophagy by promoting the relocation of Parkin(C289G) and the autophagy marker LC3 to depolarized mitochondria.
GO:0090084 negative regulation of inclusion body assembly	IMP PMID:20889486 Molecular chaperone-mediated rescue of mitophagy by a Parkin...	ACCEPT	Summary: PMID:20889486 (Rose et al. 2011) demonstrated that DNAJB6 suppresses Parkin(C289G) inclusion formation. HSJ1a and DNAJB6 both reduced aggregation of the misfolded Parkin RING1 domain mutant. This is consistent with DNAJB6's well-characterized anti-aggregation/holdase activity. The term GO:0090084 (negative regulation of inclusion body assembly) accurately captures this activity. Reason: Suppression of inclusion body formation is a core function of DNAJB6. PMID:20889486 demonstrated this specifically for misfolded Parkin, consistent with the broader anti-aggregation activity shown for polyglutamine proteins (PMID:11896048, PMID:20159555, PMID:21231916, PMID:22366786). This is a well-supported core annotation. Supporting Evidence: PMID:20889486 Parkin(C289G) aggregation and inclusion formation were suppressed by the neuronal DnaJ/Hsp40 chaperone HSJ1a(DNAJB2a). Importantly, HSJ1a and DNAJB6 also restored mitophagy by promoting the relocation of Parkin(C289G) and the autophagy marker LC3 to depolarized mitochondria.
GO:0016020 membrane	HDA PMID:19946888 Defining the membrane proteome of NK cells.	REMOVE	Summary: PMID:19946888 is a membrane proteome study of NK cells that identified 1843 proteins from isolated membrane fractions. DNAJB6 was detected in this high-throughput proteomic analysis. However, DNAJB6 has no transmembrane domains and is not known to be a membrane protein. The detection likely reflects association with membrane-proximal complexes or contamination of membrane fractions with cytoplasmic proteins. The study itself notes that approximately 60% of identified proteins were not predicted membrane proteins but were "largely involved in cellular processes and molecular functions that could be predicted to be transiently associated with membranes." Reason: DNAJB6 is a soluble cytoplasmic/nuclear protein with no transmembrane domains. Detection in a membrane proteome study (PMID:19946888) likely reflects cytoplasmic contamination of membrane fractions or transient association. The study itself acknowledges that ~60% of identified proteins are not integral membrane proteins. No other evidence supports membrane localization for DNAJB6. UniProt lists cytoplasm and nucleus as subcellular locations, not membrane. Supporting Evidence: PMID:19946888 approximately 40% of the identified proteins were predicted as plausible membrane proteins. The remaining species were largely involved in cellular processes and molecular functions that could be predicted to be transiently associated with membranes.
GO:0005634 nucleus	IDA PMID:21231916 The diverse members of the mammalian HSP70 machine show dist...	ACCEPT	Summary: PMID:21231916 (Hageman et al. 2011) demonstrated nuclear localization of DNAJB6 by direct assay (IDA). This is consistent with the well-established nuclear distribution of the DNAJB6a isoform and supported by multiple other studies. Reason: Nuclear localization is well established for DNAJB6, particularly isoform A. The IDA evidence from PMID:21231916 adds direct experimental support to the IBA and other IDA annotations.
GO:0005829 cytosol	IDA PMID:21231916 The diverse members of the mammalian HSP70 machine show dist...	ACCEPT	Summary: PMID:21231916 (Hageman et al. 2011) demonstrated cytosol localization of DNAJB6 by direct assay (IDA). This is consistent with the well-established cytosolic distribution of the DNAJB6b isoform. Reason: Cytosol localization is well established for DNAJB6b. The IDA evidence from PMID:21231916 provides direct experimental support.
GO:0051082 unfolded protein binding	IDA PMID:21231916 The diverse members of the mammalian HSP70 machine show dist...	MODIFY	Summary: This IDA annotation from PMID:21231916 (Hageman et al., 2011) attributed unfolded protein binding to DNAJB6 based on its ability to suppress aggregation of polyQ-expanded huntingtin and heat-denatured luciferase. However, the same study critically demonstrated that DNAJB6 could NOT stimulate refolding of heat-denatured luciferase, despite being a potent suppressor of aggregation. This dissociation between aggregation suppression and refolding indicates holdase-like rather than foldase activity. GO:0051082 is now formally obsolete (go-ontology#30962). GO:0044183 (protein folding chaperone) is proposed as an interim replacement, but its definition ("Binding to a protein or a protein-containing complex to assist the protein folding process") is imprecise for DNAJB6 since the protein prevents aggregation rather than assists folding per se. A holdase activity term would be the ideal annotation but does not yet exist in GO. Reason: GO:0051082 is now formally obsolete per go-ontology#30962. The IDA evidence from PMID:21231916 actually demonstrates that DNAJB6 is a holdase rather than a foldase: it suppresses polyQ aggregation and heat-induced luciferase aggregation, but cannot stimulate luciferase refolding. This is a key functional distinction. GO:0044183 (protein folding chaperone) is proposed as the closest interim replacement, with the caveat that DNAJB6 prevents aggregation (holdase activity) rather than assisting in productive folding. The polyQ aggregation inhibitors in this study "often also suppressed heat-induced aggregation of luciferase" confirming that DNAJB6 binds and stabilizes unfolded substrates, but channels them toward aggregation prevention rather than refolding. Proposed replacements: protein folding chaperone Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation. This was not related to client specificity itself, as the polyQ aggregation inhibitors often also suppressed heat-induced aggregation of luciferase. PMID:11896048 overexpressed MRJ effectively suppressed polyglutamine-dependent protein aggregation, caspase activity, and cellular toxicity
GO:0090084 negative regulation of inclusion body assembly	IDA PMID:21231916 The diverse members of the mammalian HSP70 machine show dist...	ACCEPT	Summary: PMID:21231916 (Hageman et al. 2011) demonstrated that DNAJB6 is among the most potent suppressors of polyQ aggregation and inclusion body formation in the HSP70/HSP40 chaperone network. The study systematically tested all mammalian HSP70 and HSP40 members and found DNAJB6b to be a superior suppressor of polyQ inclusion body assembly. This is a core function of DNAJB6. Reason: Suppression of inclusion body assembly is one of the most well-characterized functions of DNAJB6. PMID:21231916 provides direct experimental evidence (IDA) that DNAJB6 is a potent suppressor of polyQ aggregation. This is further supported by PMID:11896048, PMID:20159555, and PMID:22366786. Supporting Evidence: PMID:21231916 Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation.
GO:0005634 nucleus	HDA PMID:21630459 Proteomic characterization of the human sperm nucleus.	ACCEPT	Summary: PMID:21630459 is a proteomic characterization of the human sperm nucleus that identified 403 proteins. DNAJB6 was detected in isolated sperm nuclei by mass spectrometry. This HDA (high-throughput direct assay) provides additional evidence for nuclear localization, though in a specialized cell type (sperm). Nuclear localization of DNAJB6a is well established from other studies. Reason: Detection of DNAJB6 in sperm nuclei by mass spectrometry (PMID:21630459) provides additional proteomic evidence for nuclear localization, consistent with the well-established nuclear distribution of DNAJB6a from multiple other studies.
GO:0005654 nucleoplasm	TAS Reactome:R-HSA-5251955	ACCEPT	Summary: This TAS annotation from Reactome (R-HSA-5251955, HSP40s activate intrinsic ATPase activity of HSP70s in the nucleoplasm) places DNAJB6 in the nucleoplasm as the site where it stimulates HSP70 ATPase activity. This is consistent with the nuclear localization of DNAJB6a and the HPA immunofluorescence data showing nucleoplasm localization. Reason: Nucleoplasm localization is supported by the Reactome pathway placing DNAJB6 as an HSP70 ATPase activator in the nucleoplasm, consistent with IDA evidence from HPA and the known nuclear distribution of DNAJB6a.
GO:0005829 cytosol	TAS Reactome:R-HSA-5251959	ACCEPT	Summary: This TAS annotation from Reactome (R-HSA-5251959, HSP40s activate intrinsic ATPase activity of HSP70s in the cytosol) places DNAJB6 in the cytosol where it stimulates HSP70 ATPase activity. The Reactome entry explicitly names DNAJB6 among the HSP40s with this function. Consistent with the well-established cytosolic localization of DNAJB6b. Reason: Cytosol localization is well supported by the Reactome pathway placing DNAJB6 as an HSP70 ATPase activator in the cytosol, consistent with IDA evidence and the known cytosolic distribution of DNAJB6b.
GO:0005515 protein binding	IPI PMID:22366786 Mutations affecting the cytoplasmic functions of the co-chap...	MODIFY	Summary: PMID:22366786 (Sarparanta et al. 2012) demonstrated specific interactions of DNAJB6 with BAG3, HSPB8, and STUB1 (CHIP) -- members of the CASA (chaperone-assisted selective autophagy) complex -- by co-immunoprecipitation. These are functionally significant interactions linking DNAJB6 to Z-disk maintenance in muscle. However, GO:0005515 (protein binding) is uninformative. The interactions with CASA complex members are better described by GO:0051087 (protein-folding chaperone binding) for the chaperone interactions. Reason: PMID:22366786 demonstrates specific, functionally important interactions with BAG3, HSPB8, and STUB1 by co-immunoprecipitation. GO:0005515 (protein binding) is too general. The interactions with these CASA complex chaperone components are better captured by GO:0051087 (protein-folding chaperone binding), which is already annotated. Proposed replacements: protein-folding chaperone binding Supporting Evidence: PMID:22366786 we show that DNAJB6 interacts with members of the CASA complex, including the myofibrillar myopathy-causing protein BAG3
GO:0030018 Z disc	IDA PMID:22366786 Mutations affecting the cytoplasmic functions of the co-chap...	ACCEPT	Summary: PMID:22366786 (Sarparanta et al. 2012) demonstrated by immunofluorescence microscopy that DNAJB6 localizes primarily to Z-disks in skeletal muscle. Electron microscopy of LGMD1D patient muscle revealed Z-disk myofibrillar disintegration, and DNAJB6 was found in protein accumulations at these sites. This localization is functionally relevant for the CASA complex-mediated Z-disk maintenance function. Reason: Z disc localization is directly demonstrated by immunofluorescence in PMID:22366786 and is functionally significant for DNAJB6's role in muscle sarcomere maintenance via the CASA complex. LGMD1D mutations cause Z-disk disintegration, underscoring the importance of this localization. This is a core localization in skeletal muscle. Supporting Evidence: PMID:22366786 Immunofluorescence (IF) microscopy showed DNAJB6 primarily in Z-disks in both control (not shown) and LGMD1D muscle samples (Fig. 1a). Electron microscopy (EM) of LGMD1D patient muscle revealed Z-disk myofibrillar disintegration (Fig. 1b).
GO:0031072 heat shock protein binding	IDA PMID:10954706 Identification of Mrj, a DnaJ/Hsp40 family protein, as a ker...	ACCEPT	Summary: PMID:10954706 (Izawa et al. 2000) demonstrated by co-immunoprecipitation that DNAJB6 (Mrj) binds to Hsp/c70 (heat shock protein 70). The N-terminal J-domain region mediates this interaction. This is a core molecular function of all J-domain proteins. GO:0031072 (heat shock protein binding) is appropriate as it encompasses the Hsp70 binding activity and is consistent with the more specific GO:0030544 (Hsp70 protein binding). Reason: Heat shock protein binding (specifically Hsp70) is the defining interaction for J-domain proteins. PMID:10954706 provides direct co-immunoprecipitation evidence. This is a core molecular function annotation. Supporting Evidence: PMID:10954706 Mrj was immunoprecipitated not only with K18, but also with the stress-induced and constitutively expressed heat shock protein Hsp/c70. Mrj bound to K18 through its C terminus and interacted with Hsp/c70 via its N terminus, which contains the J domain.
GO:0005634 nucleus	IDA GO_REF:0000054	ACCEPT	Summary: This IDA annotation from curation of intracellular localizations of expressed fusion proteins in living cells confirms nuclear localization. Consistent with multiple other studies showing DNAJB6a nuclear localization. Reason: Nuclear localization is thoroughly supported for DNAJB6a by multiple independent methods. This IDA from fusion protein localization adds further direct evidence.
GO:0001671 ATPase activator activity	IDA PMID:11896048 Characterization of a brain-enriched chaperone, MRJ, that in...	UNDECIDED	Summary: PMID:11896048 (Chuang et al. 2002) characterized DNAJB6 (MRJ) chaperone activity and showed it functions as a co-chaperone. The UniProt entry states "Has a stimulatory effect on the ATPase activity of HSP70 in a dose-dependent and time-dependent manner" citing PMID:10954706 and PMID:28233300. While PMID:11896048 focuses on the anti-aggregation activity rather than directly measuring ATPase stimulation. The co-chaperone function is consistent with J-domain biology, but the PMID:11896048 cached evidence does not directly support ATPase activation. Reason: ATPase activator activity toward Hsp70 is a core molecular function of DNAJB6 as a J-domain co-chaperone. UniProt confirms dose-dependent and time-dependent stimulation of HSP70 ATPase activity, but this particular PMID:11896048 IDA annotation cannot be accepted because the cited source supports anti-aggregation/chaperone activity rather than direct ATPase activation. Supporting Evidence: PMID:11896048 we describe the isolation of a DnaJ-like protein MRJ and the characterization of its chaperone activity
GO:0005634 nucleus	IDA PMID:10954706 Identification of Mrj, a DnaJ/Hsp40 family protein, as a ker...	ACCEPT	Summary: PMID:10954706 (Izawa et al. 2000) showed nuclear localization of DNAJB6 (Mrj) by immunostaining. The UniProt subcellular location annotation cites this study as evidence for nuclear localization. This is consistent with the predominantly nuclear distribution of DNAJB6a. Reason: Nuclear localization is directly demonstrated by immunostaining in PMID:10954706 and confirmed by UniProt annotation. This is a core localization for DNAJB6a. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells.
GO:0006457 protein folding	IDA PMID:11896048 Characterization of a brain-enriched chaperone, MRJ, that in...	ACCEPT	Summary: PMID:11896048 (Chuang et al. 2002) demonstrated DNAJB6 chaperone activity in suppressing polyglutamine aggregation. As discussed above for the IBA annotation of this same term, DNAJB6 specifically acts as a holdase (preventing aggregation) rather than a foldase (refolding denatured proteins). GO:0006457 (protein folding) as a biological process encompasses the broader protein quality control pathway. The IDA evidence from PMID:11896048 demonstrates chaperone activity that contributes to the protein folding/quality control pathway, even though the specific mechanism is anti-aggregation rather than productive refolding. Reason: GO:0006457 (protein folding) as a BP is broadly appropriate for DNAJB6's participation in the Hsp70-dependent protein quality control pathway. PMID:11896048 provides direct evidence of chaperone activity. While DNAJB6 specifically prevents aggregation rather than promoting refolding, the protein folding BP encompass quality control. Supporting Evidence: PMID:11896048 overexpressed MRJ effectively suppressed polyglutamine-dependent protein aggregation, caspase activity, and cellular toxicity
GO:0045109 intermediate filament organization	IDA PMID:10954706 Identification of Mrj, a DnaJ/Hsp40 family protein, as a ker...	ACCEPT	Summary: PMID:10954706 (Izawa et al. 2000) demonstrated that DNAJB6 (Mrj) plays an essential role in K8/18 intermediate filament organization. Microinjection of anti-Mrj antibody resulted in disorganization of K8/18 filaments without affecting actin filaments or microtubules. DNAJB6 bound to K18 through its C-terminus and functioned as a K18-specific co-chaperone with Hsp/c70. This is a well-supported core function directly demonstrated by loss-of-function (antibody microinjection) experiments. Reason: Intermediate filament organization is a directly demonstrated function of DNAJB6, supported by both gain-of-function (co-immunoprecipitation with K18, colocalization with K8/18 filaments) and loss-of-function (anti-Mrj antibody microinjection causing filament disorganization) experiments in PMID:10954706. This is a core biological process function. The UniProt entry also states DNAJB6 "Plays an indispensable role in the organization of KRT8/KRT18 filaments." Supporting Evidence: PMID:10954706 Microinjection of anti-Mrj antibody resulted in the disorganization of K8/18 filaments, without effects on the organization of actin filaments and microtubules. Taken together, these results suggest that Mrj may play an important role in the regulation of K8/18 filament organization as a K18-specific co-chaperone working together with Hsp/c70.
GO:0048471 perinuclear region of cytoplasm	IDA PMID:10954706 Identification of Mrj, a DnaJ/Hsp40 family protein, as a ker...	ACCEPT	Summary: PMID:10954706 (Izawa et al. 2000) demonstrated perinuclear localization of DNAJB6 (Mrj) by immunostaining. The UniProt subcellular location explicitly states "Cytoplasm, perinuclear region" with ECO:0000269\|PubMed:10954706 evidence. This is a well-supported localization. Reason: Perinuclear localization is directly demonstrated by immunostaining in PMID:10954706 and annotated in UniProt subcellular location. This is a core localization. Supporting Evidence: PMID:10954706 Immunostaining with anti-Mrj antibody showed that Mrj colocalized with K8/18 filaments in HeLa cells.
GO:0051087 protein-folding chaperone binding	IDA PMID:11896048 Characterization of a brain-enriched chaperone, MRJ, that in...	ACCEPT	Summary: PMID:11896048 (Chuang et al. 2002) characterized DNAJB6 (MRJ) as a co-chaperone that interacts with the Hsp70 chaperone network. As a J-domain protein, DNAJB6 binds and stimulates Hsp70 family chaperones. The IDA evidence supports the protein-folding chaperone binding annotation, consistent with the established co-chaperone function. Reason: Protein-folding chaperone binding (Hsp70 interaction) is a core molecular function of DNAJB6 as a J-domain co-chaperone. PMID:11896048 provides evidence for this co-chaperone function, and it is consistent with the more detailed binding data from PMID:10954706. Supporting Evidence: PMID:11896048 we describe the isolation of a DnaJ-like protein MRJ and the characterization of its chaperone activity

Gene Description

Existing Annotations Review

Core Functions

DNAJB6 binds to keratin 18 (K18) via its C-terminus and functions as a K18-specific co-chaperone with Hsp70/Hsc70 to regulate intermediate filament organization. Anti-Mrj antibody microinjection causes K8/18 filament disorganization, establishing DNAJB6 as essential for keratin filament maintenance.

References

Deep Research

Falcon

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