CGRRF1 (cell growth regulator with RING finger domain protein 1; also known as CGR19 and RNF197) is a 332-residue endoplasmic reticulum (ER) membrane-anchored protein with an N-terminal hydrophobic/transmembrane region and a C-terminal cytosolic RING-type zinc finger (residues ~274-309; NMR structure PDB 2EA5). Its domain architecture (a canonical C3HC4/C3H2C3 RING coupled to a transmembrane membrane anchor) is the hallmark of ER-resident RING-type E3 ubiquitin ligases that act in ER-associated degradation (ERAD), where they cooperate with E2 conjugating enzymes to ubiquitinate substrates destined for proteasomal degradation. CGRRF1 localizes to the ER and partially to the nucleus, is transcriptionally up-regulated by ER stress (thapsigargin, tunicamycin) downstream of the ATF6 branch of the unfolded protein response, and is ubiquitously expressed with highest levels in testis and cerebellum. It was originally discovered as CGR19, a p53-induced transcript whose overexpression inhibits growth of several cell lines, the basis of its historical description as a cell growth/cell cycle regulator. An early genome-wide screen reported a negative in vitro autoubiquitination result when CGRRF1 was paired with the promiscuous E2 UbcH5c/UBE2D3, but subsequent substrate-focused work established CGRRF1 as a functional ER E3 ligase acting in regulatory ERAD: together with the cognate E2 UBE2J2 it ubiquitinates Evi/Wntless (WLS/GPR177), the dedicated cargo receptor for Wnt secretion, targeting it for VCP/p97-dependent extraction and proteasomal degradation when Wnt ligand is unavailable and thereby tuning the cell's Wnt secretory capacity. Its broader physiological substrate repertoire and high-resolution catalytic mechanism remain incompletely defined.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0030308
negative regulation of cell growth
|
IBA
GO_REF:0000033 |
KEEP AS NON CORE |
Summary: Phylogenetically inferred (IBA) negative regulation of cell growth, transferred across the CGRRF1 ortholog group (PANTHER:PTN002310361, including rat ortholog RGD:620803). This trace is rooted in the original observation that CGR19/CGRRF1 overexpression inhibits cell growth.
Reason: The growth-inhibitory phenotype derives from overexpression assays (PMID:8968090) and reflects a downstream cellular consequence rather than the molecular core function of the protein, which structurally is an ER-membrane RING-domain protein. No mechanism links CGRRF1 directly to a growth-control pathway. Retained as a non-core biological-process annotation.
Supporting Evidence:
PMID:8968090
Both CGR11 and CGR19 are able to inhibit the growth of several cell lines.
|
|
GO:0005634
nucleus
|
IEA
GO_REF:0000044 |
KEEP AS NON CORE |
Summary: Nucleus localization mapped electronically (IEA) from the UniProt subcellular-location vocabulary (UniProtKB-SubCell:SL-0191). The underlying experimental basis is the antibody-based localization in PubMed:22361696.
Reason: A transmembrane-anchored ER-membrane RING protein localizing to the nucleus is biologically unexpected and the support is antibody-based immunolocalization that may overlap with a nucleoplasmic signal. Retained as non-core; the ER localization is the better-supported and mechanistically relevant compartment.
Supporting Evidence:
file:human/CGRRF1/CGRRF1-uniprot.txt
SUBCELLULAR LOCATION: Nucleus {ECO:0000269|PubMed:22361696}.
|
|
GO:0005783
endoplasmic reticulum
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: Endoplasmic reticulum localization mapped electronically (IEA) from the UniProt subcellular-location vocabulary (UniProtKB-SubCell:SL-0095), corroborating the experimentally supported ER annotation (IDA, PMID:27485036).
Reason: Correct compartment and consistent with the protein's membrane-anchored RING architecture. This IEA entry is concordant with the experimental IDA annotation to the same term and the well-supported ER localization, so it is accepted.
Supporting Evidence:
file:human/CGRRF1/CGRRF1-uniprot.txt
Endoplasmic reticulum {ECO:0000269|PubMed:27485036}.
|
|
GO:0005515
protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
MARK AS OVER ANNOTATED |
Summary: Generic protein binding annotation derived entirely from the HuRI high-throughput binary (yeast two-hybrid) interactome screen, supported by individual interactors such as CDIPT (UniProtKB:O14735) and ~30 additional systematic Y2H hits listed in UniProt (mostly other single- or multi-pass membrane and ER/Golgi proteins).
Reason: Bare "protein binding" is uninformative per curation guidelines and conveys no specific molecular function. The interactions come from a single large-scale binary interactome map without validation or functional context, and no specific informative molecular-function term can be justified from these HuRI hits alone. Note that the functionally meaningful protein-protein contacts of CGRRF1 established in focused studies - its cognate E2 UBE2J2 and its substrate Evi/WLS - are captured separately by the E3-ligase molecular-function and ERAD process annotations rather than by this generic HuRI-derived term.
Supporting Evidence:
PMID:32296183
Here we present a human 'all-by-all' reference interactome map of human binary protein interactions, or 'HuRI'.
file:human/CGRRF1/CGRRF1-deep-research-falcon.md
CGRRF1 works in conjunction with the **E2 ubiquitin-conjugating enzyme UBE2J2** to ubiquitinate substrates
|
|
GO:0005654
nucleoplasm
|
IDA
GO_REF:0000052 |
KEEP AS NON CORE |
Summary: Nucleoplasm localization from Human Protein Atlas immunofluorescence (IDA, HPA).
Reason: HPA immunofluorescence reports a nucleoplasmic signal, but this is not consistent with the protein's primary identity as a transmembrane ER-membrane RING protein, and antibody-based localization of this poorly characterized (Tdark) protein should be treated cautiously. Retained as observed but non-core.
Supporting Evidence:
file:human/CGRRF1/CGRRF1-uniprot.txt
Nucleus {ECO:0000269|PubMed:22361696}.
|
|
GO:0005783
endoplasmic reticulum
|
IDA
PMID:27485036 Genome-wide identification and gene expression profiling of ... |
ACCEPT |
Summary: Experimentally supported (IDA) ER localization: V5-tagged CGRRF1 stably overexpressed in COS-1 cells partially colocalized with endogenous PDI, an ER-resident chaperone, indicating ER localization. Consistent with the protein's N-terminal transmembrane anchor.
Reason: This is the best-supported and mechanistically relevant subcellular localization, directly observed by immunocytochemistry and consistent with the membrane-anchored RING-domain architecture expected of an ER-resident E3 ligase. A more specific term (GO:0005789 endoplasmic reticulum membrane) is biologically appropriate given the transmembrane anchor, but the IDA colocalization with PDI supports the parent ER term directly.
Supporting Evidence:
PMID:27485036
RNFT1, RNF185, CGRRF1 and RNF19B partially colocalised with endogenous PDI, an ER-resident chaperone, indicating their localisation to the ER
|
|
GO:0008285
negative regulation of cell population proliferation
|
TAS
PMID:8968090 Induction of cell growth regulatory genes by p53. |
KEEP AS NON CORE |
Summary: Author statement (TAS) that CGR19/CGRRF1, a p53-induced gene, inhibits the growth of several cell lines when overexpressed, the original functional description of the gene.
Reason: This reflects an overexpression growth-inhibition phenotype rather than a defined molecular mechanism. It is a descriptive, downstream biological observation and is retained as non-core rather than as the central function of an ER-membrane RING-domain protein.
Supporting Evidence:
PMID:8968090
Both CGR11 and CGR19 are able to inhibit the growth of several cell lines.
|
|
GO:0061630
ubiquitin protein ligase activity
|
TAS
PMID:32614325 Interaction mapping of endoplasmic reticulum ubiquitin ligas... |
NEW |
Summary: Not present in the current GOA set, but added (NEW) on the basis of substrate-focused work (Glaeser et al., 2018, EMBO J) showing CGRRF1 is a functional ER RING-type E3 ubiquitin ligase that, with the cognate E2 UBE2J2, ubiquitinates the Wnt cargo receptor Evi/WLS and targets it for ERAD. CGRRF1 depletion increases Evi steady-state levels and reduces Evi poly-ubiquitination (TUBE2 pulldown), CGRRF1 co-immunoprecipitates with Evi, and catalytic RING-domain (C2/C4A) mutants stabilise Evi - together establishing E2- and substrate-specific E3 activity. This reconciles the earlier negative in vitro autoubiquitination result (PMID:27485036), which used only the promiscuous non-cognate E2 UbcH5c/UBE2D3.
Reason: The E3-ligase molecular function is now supported by independent experimental work and is corroborated in a cached full-text review (Fenech et al., 2020, eLife), which states that Evi/WLS/GPR177 "was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)". This is the mechanistically central function of the protein and was previously only inferred from RING+TM structure; it should be represented explicitly. Evidence is treated as TAS (Traceable Author Statement): the primary experiments (siRNA depletion, TUBE2 pulldown, co-IP, RING C2/C4A mutant stabilisation of Evi) are reported in Glaeser et al. 2018 (EMBO J, doi:10.15252/embj.201797311), which is not yet cached as a PMID in this repository; the `original_reference_id` PMID:32614325 (Fenech et al. 2020) traceably attributes the function to that primary source. The annotation should be re-evidenced as IMP against the Glaeser 2018 PMID once it is fetched.
Supporting Evidence:
PMID:32614325
Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)
file:human/CGRRF1/CGRRF1-deep-research-falcon.md
**RING domain mutants** of CGRRF1 stabilized Evi protein levels, confirming the requirement of an intact catalytic domain for substrate turnover
|
|
GO:0036503
ERAD pathway
|
TAS
PMID:32614325 Interaction mapping of endoplasmic reticulum ubiquitin ligas... |
NEW |
Summary: Not present in the current GOA set, but added (NEW). CGRRF1 acts in ER-associated degradation (ERAD): it is an ER-membrane RING E3 whose best-characterised role is the regulated ERAD of the Wnt cargo receptor Evi/WLS, working with the E2 UBE2J2 and the VCP/p97 dislocation machinery to route Evi to proteasomal degradation when Wnt ligand is absent. This is "regulatory ERAD" of a mature, properly folded secretory factor rather than classical disposal of misfolded protein.
Reason: Independent experimental work (Glaeser et al., 2018) and a cached full-text review (Fenech et al., 2020, eLife) place CGRRF1 in the ERAD pathway as the E3 ligase for the Evi/WLS substrate. The ER localization (IDA, PMID:27485036), ER-stress/ATF6 transcriptional induction, and RING+TM architecture already in the review are all consistent with this process annotation, which makes the gene's core biological role explicit. Evidence is treated as TAS (Traceable Author Statement): the primary experiments are reported in Glaeser et al. 2018 (EMBO J, doi:10.15252/embj.201797311, not yet cached as a PMID); the `original_reference_id` PMID:32614325 (Fenech et al. 2020) traceably attributes the ERAD-pathway role to that primary source. Re-evidence as IMP once the Glaeser 2018 PMID is fetched.
Supporting Evidence:
PMID:32614325
Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)
file:human/CGRRF1/CGRRF1-deep-research-falcon.md
CGRRF1 functions primarily as an **E3 ubiquitin ligase** embedded in the endoplasmic reticulum (ER) membrane, where it participates in **ER-associated degradation (ERAD)** pathways
|
Q: Does CGRRF1 possess ubiquitin-protein ligase activity with an E2 other than UbcH5c/UBE2D3, given that the only published in vitro autoubiquitination assay (using UbcH5c) was negative?
Q: What are the physiological ERAD substrates of CGRRF1, and does it function within or parallel to the canonical HRD1/SYVN1 ERAD machinery?
Q: How are the reported ER-membrane and nucleoplasmic localizations reconciled, and is the nuclear signal a genuine localization or an antibody artifact for this Tdark protein?
Experiment: Perform in vitro autoubiquitination and substrate-ubiquitination assays across a panel of E2 conjugating enzymes (beyond UbcH5c/UBE2D3) using recombinant CGRRF1 RING domain, with RING point mutants as negative controls, to determine whether CGRRF1 has E3 ligase activity with a cognate E2.
Hypothesis: CGRRF1 is a bona fide RING E3 ubiquitin ligase whose activity requires a specific E2 not tested in the original in vitro screen.
Type: biochemical assay
Experiment: Identify CGRRF1 interaction partners and candidate substrates by proximity labeling (BioID/TurboID) or affinity purification-mass spectrometry from ER membranes, followed by ubiquitination and stability assays of candidate substrates upon CGRRF1 depletion or RING mutation.
Hypothesis: CGRRF1 ubiquitinates one or more ER-membrane or ER-luminal client proteins, targeting them for ERAD-mediated proteasomal degradation.
Type: proteomics / interactomics
Experiment: Knock out or deplete CGRRF1 in cells challenged with ER stressors and measure accumulation of model ERAD substrates, UPR marker induction, and ER-stress-induced apoptosis, with rescue by WT versus RING-dead CGRRF1.
Hypothesis: Loss of CGRRF1 impairs ERAD of specific substrates and alters sensitivity to ER stress in a RING-domain-dependent manner.
Type: genetic manipulation / cell biology
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CGRRF1 (UniProt: Q99675), also known as CGR19 or RNF197, encodes a cell growth regulator with RING finger domain protein 1 in humans (kaneko2016genomewideidentificationand pages 1-2, glaeser2018erad‐dependentcontrolof pages 1-2). The gene symbol is unambiguous in the literature, with all sources referring to the same human ER-associated RING finger protein. The protein belongs to the family of ER-resident E3 ubiquitin ligases and contains characteristic RING finger and transmembrane domains (kaneko2016genomewideidentificationand pages 1-2, fenech2020interactionmappingof pages 1-2).
CGRRF1 functions primarily as an E3 ubiquitin ligase embedded in the endoplasmic reticulum (ER) membrane, where it participates in ER-associated degradation (ERAD) pathways (glaeser2018erad‐dependentcontrolof pages 1-2, wolf2021eviwlsfunctionis pages 1-2). The protein catalyzes the transfer of ubiquitin to specific substrate proteins, marking them for proteasomal degradation. CGRRF1's role extends beyond conventional protein quality control of misfolded proteins to include regulatory ERAD, which controls the abundance of properly folded, functional proteins in response to physiological conditions (glaeser2018erad‐dependentcontrolof pages 1-2, christianson2023mechanismsofsubstrate pages 50-53).
The E3 ligase activity of CGRRF1 appears to be substrate- and E2-specific. While one genome-wide screening study reported that CGRRF1 did not possess detectable in vitro autoubiquitination activity when paired with the promiscuous E2 enzyme UbcH5a (kaneko2016genomewideidentificationand pages 1-2), subsequent focused investigations demonstrated that CGRRF1 is functionally active when paired with its cognate E2 enzyme, UBE2J2, and specific substrates such as Evi/WLS (glaeser2018erad‐dependentcontrolof pages 10-12, glaeser2018erad‐dependentcontrolof pages 13-14). This substrate and E2 specificity is consistent with the specialized regulatory functions of CGRRF1 rather than a broad protein quality control role.
The best-characterized and experimentally validated substrate of CGRRF1 is Evi (also known as Wntless or WLS/GPR177), the dedicated cargo receptor for Wnt protein secretion (glaeser2018erad‐dependentcontrolof pages 1-2, wolf2021eviwlsfunctionis pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12). Multiple lines of experimental evidence support this substrate relationship:
Beyond Evi/WLS, proximity labeling studies have identified CGRRF1 in the neighborhood of nuclear envelope proteins such as lamin B receptor (LBR) and emerin, suggesting potential roles in regulating inner nuclear membrane protein homeostasis (cheng2022sharedanddistinctivea pages 6-7, cheng2022sharedanddistinctivea pages 3-4). However, this remains preliminary evidence requiring further validation.
CGRRF1 is a single-pass transmembrane protein with a predicted transmembrane domain spanning approximately amino acids 15-37 (kaneko2016genomewideidentificationand pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12). The protein's topology positions the N-terminal region within the ER lumen while the C-terminal portion, containing the catalytic machinery, faces the cytosol (glaeser2018erad‐dependentcontrolof pages 10-12).
The catalytic core consists of a C3HC4 RING-type zinc finger domain located at amino acids 274-315 (glaeser2018erad‐dependentcontrolof pages 10-12). This RING domain contains the canonical arrangement of cysteine and histidine residues (CVVCQNGTVNWVLLPCRHTCLCDGCVKYFQQCPMCR) that coordinate two zinc ions, which are essential for the structural integrity and catalytic function of the E3 ligase (glaeser2018erad‐dependentcontrolof pages 10-12). Site-directed mutagenesis of conserved cysteine residues (C2/C4A) within the RING domain abolished CGRRF1's ability to promote substrate degradation, confirming the functional importance of this domain (glaeser2018erad‐dependentcontrolof pages 10-12).
The transmembrane architecture is critical for CGRRF1's function, as it allows the protein to access both ER lumenal and membrane-embedded substrates while presenting the ubiquitin conjugation machinery to the cytosolic proteasomal degradation system (christianson2023mechanismsofsubstrate pages 50-53, fenech2020interactionmappingof pages 1-2).
CGRRF1 is localized to the endoplasmic reticulum membrane, where it carries out its E3 ubiquitin ligase functions (kaneko2016genomewideidentificationand pages 1-2, fenech2020interactionmappingof pages 1-2). Genome-wide profiling of ER-localized E3 ligases confirmed that CGRRF1 is partially localized to the ER, consistent with its role in ERAD (kaneko2016genomewideidentificationand pages 1-2). The protein's membrane topology places the catalytic RING domain on the cytosolic side of the ER membrane, enabling access to cytosolic E2 enzymes and the ubiquitin-proteasome system (glaeser2018erad‐dependentcontrolof pages 10-12, christianson2023mechanismsofsubstrate pages 50-53).
Recent proximity labeling studies using TurboID fusions to nuclear envelope proteins identified CGRRF1 in the neighborhoods of emerin and lamin B receptor (LBR), suggesting that CGRRF1 may also function at the inner nuclear membrane (INM), which is continuous with the ER (cheng2022sharedanddistinctivea pages 6-7, cheng2022sharedanddistinctivea pages 3-4). This dual localization would be consistent with CGRRF1's potential roles in regulating both ER and nuclear envelope proteostasis.
CGRRF1 works in conjunction with the E2 ubiquitin-conjugating enzyme UBE2J2 to ubiquitinate substrates (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12, glaeser2018erad‐dependentcontrolof pages 13-14). UBE2J2 is an ER-associated E2 enzyme that contains a catalytic ubiquitin-conjugating core domain (UBCc) spanning amino acids 14-127, with an active site cysteine residue critical for thioester bond formation with ubiquitin (glaeser2018erad‐dependentcontrolof pages 10-12). The E2 also possesses a C-terminal transmembrane domain that anchors it to the ER membrane (glaeser2018erad‐dependentcontrolof pages 10-12).
Experimental evidence for the CGRRF1-UBE2J2 partnership includes:
- Functional complementation: Knockdown of either CGRRF1 or UBE2J2 produces similar phenotypes, including stabilization of Evi protein and reduced Evi ubiquitination (glaeser2018erad‐dependentcontrolof pages 10-12, glaeser2018erad‐dependentcontrolof pages 1-2)
- Biochemical interaction: The RING domain of CGRRF1 interacts with the catalytic domain of UBE2J2 to facilitate ubiquitin transfer to substrates (glaeser2018erad‐dependentcontrolof pages 10-12)
The ubiquitin chains formed on Evi substrates include K11-, K48-, and K63-linkages, as detected by mass spectrometry and linkage-specific antibodies (wolf2021eviwlsfunctionis pages 1-2). K48-linked polyubiquitin chains are the canonical signal for proteasomal degradation, while K11 and K63 linkages may contribute to substrate recognition and processing through the ERAD pathway.
CGRRF1 plays a critical regulatory role in the Wnt signaling pathway by controlling the availability of the Wnt cargo receptor Evi/WLS, which is essential for secretion of lipidated Wnt proteins (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7, glaeser2018erad‐dependentcontrolof pages 13-14). The mechanism operates as a feedback loop that adjusts cellular secretory capacity to match Wnt ligand availability:
In the absence of Wnt ligands: Evi is continuously ubiquitinated by the CGRRF1-UBE2J2 complex and targeted for ERAD. The AAA-ATPase VCP/p97 extracts ubiquitinated Evi from the ER membrane and delivers it to the proteasome for degradation (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7). This prevents accumulation of unused cargo receptor and maintains appropriate ER homeostasis.
In the presence of palmitoylated Wnt proteins: Wnt ligands bind to Evi following palmitoleic acid modification by the acyltransferase Porcupine (Porcn). This Wnt-Evi interaction stabilizes Evi by preventing its CGRRF1-mediated ubiquitination and degradation (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 3-4). The stabilized Evi accumulates and increases the cell's capacity to transport Wnt proteins to the cell surface for secretion. Inhibition of Porcn with the small molecule LGK974 blocks Wnt palmitoylation and results in rapid CGRRF1-dependent degradation of Evi (glaeser2018erad‐dependentcontrolof pages 3-4).
This regulatory mechanism ensures that Wnt-producing cells maintain an optimal level of cargo receptor that matches the demand for Wnt secretion. The pathway represents an elegant example of regulatory ERAD, where degradation of a functional protein is controlled by the availability of its cargo (glaeser2018erad‐dependentcontrolof pages 1-2, christianson2023mechanismsofsubstrate pages 50-53).
A triaging complex involving Porcupine (Porcn) and VCP appears to determine whether Evi enters the secretory pathway or the ERAD pathway (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14). Porcn acts as both a Wnt-modifying enzyme and a sensor of Wnt availability, helping coordinate the decision between Evi stabilization (for secretion) and Evi degradation (via ERAD).
As an ER-resident E3 ubiquitin ligase, CGRRF1 is a component of the broader ERAD machinery that maintains ER protein homeostasis (kaneko2016genomewideidentificationand pages 1-2, christianson2023mechanismsofsubstrate pages 50-53, fenech2020interactionmappingof pages 1-2). ERAD is a specialized ubiquitin-proteasome system pathway that prevents the secretion and aggregation of proteins that have failed to fold properly or are no longer needed (christianson2023mechanismsofsubstrate pages 50-53).
The ERAD pathway involving CGRRF1 includes several key components:
- Recognition: ERLIN2 links Evi/WLS to the ubiquitination machinery, potentially serving as an adapter or recognition factor (wolf2021eviwlsfunctionis pages 1-2, christianson2023mechanismsofsubstrate pages 50-53)
- Ubiquitination: CGRRF1 (E3 ligase) and UBE2J2 (E2 enzyme) catalyze polyubiquitin chain formation on substrates (glaeser2018erad‐dependentcontrolof pages 10-12, glaeser2018erad‐dependentcontrolof pages 1-2)
- Extraction/Dislocation: VCP/p97 (also known as Cdc48 in yeast) uses ATP hydrolysis to extract ubiquitinated substrates from the ER membrane (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7)
- Degradation: Extracted substrates are delivered to the 26S proteasome for proteolysis (glaeser2018erad‐dependentcontrolof pages 1-2)
Recent comprehensive reviews of ERAD mechanisms in mammals cite CGRRF1 as a specialized ER-E3 ligase that extends beyond traditional protein quality control to regulate signaling pathway components (christianson2023mechanismsofsubstrate pages 50-53, wang2025sel1lhrd1mediatederadin pages 6-8, christianson2023mechanismsofsubstrate pages 26-30).
CGRRF1 expression is transcriptionally upregulated in response to ER stress (kaneko2016genomewideidentificationand pages 1-2). In a genome-wide screen of 37 candidate RING finger-containing, transmembrane protein-encoding genes, CGRRF1 was identified as one of four genes (along with RNFT1, RNF185, and RNF19B) whose expression was significantly increased following ER stress induction (kaneko2016genomewideidentificationand pages 1-2). This stress-responsive expression pattern suggests that CGRRF1 contributes to the cellular adaptive response to ER proteotoxic stress, potentially by enhancing the capacity for ERAD of accumulated or misfolded proteins.
However, unlike RNFT1 and RNF185, CGRRF1 overexpression did not confer significant resistance to ER stressor treatment in the initial screening study (kaneko2016genomewideidentificationand pages 1-2), suggesting that its primary role may be in regulatory ERAD rather than broad cytoprotection against ER stress.
The functional characterization of CGRRF1 is based on multiple complementary experimental approaches:
CGRRF1 has potential relevance to cancer biology through its regulation of Wnt signaling. Analysis of The Cancer Genome Atlas (TCGA) data revealed that CGRRF1 mRNA levels are reduced in several cancers, including endometrial and colon adenocarcinomas (glaeser2018erad‐dependentcontrolof pages 13-14). This downregulation could contribute to the aberrantly elevated Evi protein levels observed in cancer tissues, even in the absence of increased Evi transcription (glaeser2018erad‐dependentcontrolof pages 13-14).
Since Wnt signaling is frequently dysregulated in cancer and drives tumor progression, the loss of CGRRF1-mediated control over Evi/WLS abundance could enhance Wnt secretory capacity and promote autocrine/paracrine Wnt signaling in tumors (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14). This mechanism represents a potential indirect route to Wnt pathway activation that is distinct from mutations in downstream Wnt pathway components like β-catenin or APC.
The therapeutic implications are noteworthy: targeting CGRRF1 or the ERAD pathway components that regulate Evi/WLS could provide an alternative approach to blocking Wnt secretion in Wnt-driven malignancies (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14). Current clinical trials are exploring Porcupine inhibitors like LGK974 to block Wnt secretion, but modulation of the CGRRF1-mediated ERAD pathway represents an unexplored therapeutic avenue.
Given CGRRF1's role in ER protein quality control and its stress-responsive expression, the protein may have relevance to diseases involving ER proteostasis dysfunction. Recent work has highlighted the importance of ER-resident E3 ligases in maintaining cellular protein homeostasis and responding to metabolic challenges (christianson2023mechanismsofsubstrate pages 50-53, wang2025sel1lhrd1mediatederadin pages 6-8). However, no direct genetic associations between CGRRF1 mutations and human disease have been reported to date, unlike other ERAD components such as SEL1L and HRD1, which are linked to neurodevelopmental disorders (wang2025sel1lhrd1mediatederadin pages 6-8).
Despite significant advances in understanding CGRRF1's role in Evi/WLS regulation and Wnt secretion, several important questions remain:
Substrate repertoire: Beyond Evi/WLS, the full spectrum of CGRRF1 substrates is unknown. Proximity labeling studies suggest potential involvement in nuclear envelope protein regulation, but these remain to be validated (cheng2022sharedanddistinctivea pages 6-7, cheng2022sharedanddistinctivea pages 3-4).
Structural mechanism: High-resolution structural information for CGRRF1 is not available. The mechanistic details of how CGRRF1 recognizes substrates, engages UBE2J2, and coordinates with other ERAD factors remain to be elucidated at the atomic level.
Tissue-specific roles: The physiological importance of CGRRF1 in different tissues and developmental stages is poorly characterized. Generation of tissue-specific knockout mouse models would help address this gap.
Regulation: The mechanisms controlling CGRRF1 expression beyond ER stress, as well as potential post-translational modifications that regulate its activity, are not well understood.
Clinical validation: While CGRRF1 expression correlates with cancer outcomes in database analyses, direct experimental evidence linking CGRRF1 loss to tumor progression or therapeutic response is limited (glaeser2018erad‐dependentcontrolof pages 13-14).
Recent comprehensive reviews of ERAD mechanisms acknowledge CGRRF1 as an important but incompletely characterized member of the ER-resident E3 ligase family (christianson2023mechanismsofsubstrate pages 50-53, christianson2023mechanismsofsubstrate pages 26-30).
| Feature | Summary for human CGRRF1 | Key evidence/citation |
|---|---|---|
| Protein identity | CGRRF1 = cell growth regulator with RING finger domain protein 1; aliases include CGR19 and RNF197. Literature on ERAD/Wnt regulation refers to the same human ER-associated RING finger protein. | (glaeser2018erad‐dependentcontrolof pages 1-2, kaneko2016genomewideidentificationand pages 1-2) |
| Primary molecular function | Best-supported function is an ER-resident RING-type E3 ubiquitin ligase involved in ER-associated degradation (ERAD) and regulatory control of membrane protein abundance, especially the Wnt cargo receptor Evi/WLS. | (glaeser2018erad‐dependentcontrolof pages 1-2, wolf2021eviwlsfunctionis pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14) |
| Enzymatic activity status | CGRRF1 was reported in one screen to lack detectable in vitro autoubiquitination activity when tested with a promiscuous E2 (UbcH5a), but later substrate-focused work showed that CGRRF1 is required for Evi ubiquitination and degradation, consistent with E2- and substrate-specific E3 activity. | (kaneko2016genomewideidentificationand pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14, glaeser2018erad‐dependentcontrolof pages 10-12) |
| Structural features | CGRRF1 is a single-pass membrane protein with a predicted transmembrane segment near aa 15-37 and a cytosolic C3HC4 RING domain at aa 274-315. The RING contains conserved cysteine/histidine residues required for catalytic function. | (glaeser2018erad‐dependentcontrolof pages 10-12, kaneko2016genomewideidentificationand pages 1-2) |
| Catalytic importance of RING domain | Mutation of conserved cysteines in the CGRRF1 RING domain stabilized interaction with endogenous Evi and increased Evi steady-state levels, indicating that the intact RING domain is required for substrate turnover. | (glaeser2018erad‐dependentcontrolof pages 10-12) |
| Subcellular localization | CGRRF1 is partially localized to the endoplasmic reticulum and is considered one of the ER membrane-embedded ubiquitin ligases. Its topology places the catalytic RING domain on the cytosolic side of the ER membrane. | (kaneko2016genomewideidentificationand pages 1-2, fenech2020interactionmappingof pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12) |
| Additional localization inference | Proximity-labeling studies of nuclear-envelope proteins identified CGRRF1 in the emerin/LBR neighborhood, suggesting presence in the ER–nuclear envelope continuum and possible access to the inner nuclear membrane proteostasis environment. | (cheng2022sharedanddistinctivea pages 6-7, cheng2022sharedanddistinctivea pages 3-4) |
| Known substrate: Evi/WLS | The strongest experimentally supported substrate is Evi/WLS (GPR177), the Wnt cargo receptor. In the absence of Wnt ligands, Evi is ubiquitinated and degraded by ERAD, requiring CGRRF1. | (glaeser2018erad‐dependentcontrolof pages 1-2, wolf2021eviwlsfunctionis pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12) |
| Evidence for Evi substrate assignment | siRNA knockdown of CGRRF1 increased Evi abundance; TUBE pulldown showed reduced ubiquitinated Evi after CGRRF1 knockdown; CGRRF1 co-immunoprecipitated with Evi. | (glaeser2018erad‐dependentcontrolof pages 10-12, wolf2021eviwlsfunctionis pages 1-2) |
| Other candidate substrates | A proteomics study suggested that CGRRF1 may influence lamin B receptor (LBR) abundance, but this remains preliminary/candidate-level evidence, not yet a firmly established direct substrate relationship. | (cheng2022sharedanddistinctivea pages 6-7) |
| E2 enzyme partner(s) | The best-supported cognate E2 is UBE2J2, which works with CGRRF1 in Evi ubiquitination. UBE2J2 and CGRRF1 depletion produce similar stabilization of Evi and reduced Evi ubiquitination. | (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12, glaeser2018erad‐dependentcontrolof pages 13-14) |
| Interacting proteins/cofactors | Factors linked to the same Evi ERAD route include VCP/p97 for extraction/dislocation, Porcn as a triage factor coupling cargo loading versus degradation, and ERLIN2, which links EVI/WLS to the ubiquitination machinery. | (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7, wolf2021eviwlsfunctionis pages 1-2) |
| ERAD role | CGRRF1 participates in regulatory ERAD rather than only disposal of misfolded proteins, helping tune the abundance of a mature secretory-pathway factor (Evi/WLS) according to cellular need. | (glaeser2018erad‐dependentcontrolof pages 1-2, wolf2021eviwlsfunctionis pages 1-2, christianson2023mechanismsofsubstrate pages 50-53) |
| Wnt pathway role | By limiting or permitting Evi/WLS abundance, CGRRF1 indirectly regulates the capacity for Wnt ligand secretion. Thus, CGRRF1 functions upstream of extracellular Wnt signaling by controlling cargo-receptor availability in Wnt-producing cells. | (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7, glaeser2018erad‐dependentcontrolof pages 13-14) |
| Mechanistic model in Wnt-producing cells | Without palmitoleated Wnt, Evi is polyubiquitinated and sent to ERAD via CGRRF1/UBE2J2/VCP. With Wnt present, Evi is stabilized, increasing secretory capacity for Wnt export. | (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 6-7, glaeser2018erad‐dependentcontrolof pages 3-4) |
| Ubiquitin chain context | EVI/WLS was reported to carry K11, K48, and K63-linked ubiquitin modifications in the broader pathway analysis; CGRRF1 is specifically implicated in the Evi ubiquitination step together with UBE2J2. | (wolf2021eviwlsfunctionis pages 1-2, glaeser2018erad‐dependentcontrolof pages 10-12) |
| ER stress regulation | CGRRF1 transcript levels were identified as significantly upregulated by ER stress in a genome-wide survey of candidate ERAD E3 ligases, supporting a role in ER proteostasis. | (kaneko2016genomewideidentificationand pages 1-2) |
| Broader ER-E3 classification | Reviews of ERAD place CGRRF1 among the set of ER-resident transmembrane E3 ligases whose functions extend beyond classic quality control to regulated control of signaling and metabolic proteins. | (fenech2020interactionmappingof pages 1-2, christianson2023mechanismsofsubstrate pages 50-53, wang2025sel1lhrd1mediatederadin pages 6-8) |
| Disease/cancer relevance | The most direct disease relevance from available evidence is indirect: CGRRF1 mRNA is reduced in some cancers (including endometrial and colon adenocarcinomas in TCGA-based analysis discussed by Glaeser et al.), which could contribute to elevated Evi/Wnt secretory activity. | (glaeser2018erad‐dependentcontrolof pages 13-14) |
| Functional implication in cancer biology | Because Evi/WLS and Wnt secretion are frequently dysregulated in cancer, CGRRF1 is proposed as a potential modulator of Wnt-driven malignancy, though this remains a mechanistic inference rather than a clinically validated biomarker/target. | (glaeser2018erad‐dependentcontrolof pages 1-2, glaeser2018erad‐dependentcontrolof pages 13-14) |
| Current limitations of knowledge | CGRRF1 remains poorly characterized outside the Evi/WLS pathway: substrate scope, structural mechanism, tissue-specific roles, and disease causality are still incompletely defined. Recent ERAD reviews cite CGRRF1 mainly as an example of a specialized ER-E3 in Wnt cargo-receptor control. | (christianson2023mechanismsofsubstrate pages 50-53, wang2025sel1lhrd1mediatederadin pages 6-8) |
Table: This table compiles the main experimentally supported features of human CGRRF1, including its identity, structure, localization, enzymatic role, pathway context, and disease relevance. It is useful as a concise evidence-based reference for functional annotation of this relatively understudied ER-associated RING finger protein.
CGRRF1 (Cell Growth Regulator with RING Finger Domain Protein 1, also known as CGR19 or RNF197) is an ER membrane-embedded E3 ubiquitin ligase that plays a specialized role in regulatory ER-associated degradation (ERAD). The protein functions primarily to control the abundance of the Wnt cargo receptor Evi/WLS, thereby regulating cellular capacity for Wnt ligand secretion. CGRRF1 works in partnership with the E2 enzyme UBE2J2 to ubiquitinate substrates marked for proteasomal degradation. The protein's activity is regulated by Wnt ligand availability, creating a feedback mechanism that adjusts Evi levels to match secretory demand. CGRRF1 is transcriptionally upregulated by ER stress and may have broader roles in ER and nuclear envelope proteostasis. Reduced CGRRF1 expression in certain cancers suggests potential involvement in Wnt-driven malignancies, though the clinical significance requires further validation. While CGRRF1's role in Evi/WLS regulation is well-established through multiple experimental approaches, the full substrate repertoire, structural mechanism, and physiological importance in different tissues remain areas for future investigation.
References
(kaneko2016genomewideidentificationand pages 1-2): Masayuki Kaneko, Ikuko Iwase, Yuki Yamasaki, Tomoko Takai, Yan Wu, Soshi Kanemoto, Koji Matsuhisa, Rie Asada, Yasunobu Okuma, Takeshi Watanabe, Kazunori Imaizumi, and Yausyuki Nomura. Genome-wide identification and gene expression profiling of ubiquitin ligases for endoplasmic reticulum protein degradation. Scientific Reports, Aug 2016. URL: https://doi.org/10.1038/srep30955, doi:10.1038/srep30955. This article has 92 citations and is from a peer-reviewed journal.
(glaeser2018erad‐dependentcontrolof pages 1-2): Kathrin Glaeser, Manuela Urban, Emma Fenech, Oksana Voloshanenko, Dominique Kranz, Federica Lari, John C Christianson, and Michael Boutros. Erad‐dependent control of the wnt secretory factor evi. The EMBO Journal, Jan 2018. URL: https://doi.org/10.15252/embj.201797311, doi:10.15252/embj.201797311. This article has 71 citations.
(fenech2020interactionmappingof pages 1-2): Emma J Fenech, Federica Lari, Philip D Charles, Roman Fischer, Marie Laétitia-Thézénas, Katrin Bagola, Adrienne W Paton, James C Paton, Mads Gyrd-Hansen, Benedikt M Kessler, and John C Christianson. Interaction mapping of endoplasmic reticulum ubiquitin ligases identifies modulators of innate immune signalling. eLife, Jul 2020. URL: https://doi.org/10.7554/elife.57306, doi:10.7554/elife.57306. This article has 107 citations and is from a domain leading peer-reviewed journal.
(wolf2021eviwlsfunctionis pages 1-2): Lucie M. Wolf, Annika M. Lambert, Julie Haenlin, and Michael Boutros. Evi/wls function is regulated by ubiquitylation and is linked to er-associated degradation by erlin2. Journal of Cell Science, Aug 2021. URL: https://doi.org/10.1242/jcs.257790, doi:10.1242/jcs.257790. This article has 31 citations and is from a domain leading peer-reviewed journal.
(christianson2023mechanismsofsubstrate pages 50-53): John C. Christianson, Ernst Jarosch, and Thomas Sommer. Mechanisms of substrate processing during er-associated protein degradation. Nature Reviews Molecular Cell Biology, 24:777-796, Aug 2023. URL: https://doi.org/10.1038/s41580-023-00633-8, doi:10.1038/s41580-023-00633-8. This article has 193 citations and is from a domain leading peer-reviewed journal.
(glaeser2018erad‐dependentcontrolof pages 10-12): Kathrin Glaeser, Manuela Urban, Emma Fenech, Oksana Voloshanenko, Dominique Kranz, Federica Lari, John C Christianson, and Michael Boutros. Erad‐dependent control of the wnt secretory factor evi. The EMBO Journal, Jan 2018. URL: https://doi.org/10.15252/embj.201797311, doi:10.15252/embj.201797311. This article has 71 citations.
(glaeser2018erad‐dependentcontrolof pages 13-14): Kathrin Glaeser, Manuela Urban, Emma Fenech, Oksana Voloshanenko, Dominique Kranz, Federica Lari, John C Christianson, and Michael Boutros. Erad‐dependent control of the wnt secretory factor evi. The EMBO Journal, Jan 2018. URL: https://doi.org/10.15252/embj.201797311, doi:10.15252/embj.201797311. This article has 71 citations.
(cheng2022sharedanddistinctivea pages 6-7): Li-Chun Cheng, Xi Zhang, Kanishk Abhinav, Julie A Nguyen, Sabyasachi Baboo, Salvador Martinez-Bartolomé, Tess C Branon, Alice Y Ting, Esther Loose, John R Yates, and Larry Gerace. Shared and distinctive neighborhoods of emerin and lamin b receptor revealed by proximity labeling and quantitative proteomics. Journal of Proteome Research, 21:2197-2210, Aug 2022. URL: https://doi.org/10.1021/acs.jproteome.2c00281, doi:10.1021/acs.jproteome.2c00281. This article has 14 citations and is from a peer-reviewed journal.
(cheng2022sharedanddistinctivea pages 3-4): Li-Chun Cheng, Xi Zhang, Kanishk Abhinav, Julie A Nguyen, Sabyasachi Baboo, Salvador Martinez-Bartolomé, Tess C Branon, Alice Y Ting, Esther Loose, John R Yates, and Larry Gerace. Shared and distinctive neighborhoods of emerin and lamin b receptor revealed by proximity labeling and quantitative proteomics. Journal of Proteome Research, 21:2197-2210, Aug 2022. URL: https://doi.org/10.1021/acs.jproteome.2c00281, doi:10.1021/acs.jproteome.2c00281. This article has 14 citations and is from a peer-reviewed journal.
(glaeser2018erad‐dependentcontrolof pages 6-7): Kathrin Glaeser, Manuela Urban, Emma Fenech, Oksana Voloshanenko, Dominique Kranz, Federica Lari, John C Christianson, and Michael Boutros. Erad‐dependent control of the wnt secretory factor evi. The EMBO Journal, Jan 2018. URL: https://doi.org/10.15252/embj.201797311, doi:10.15252/embj.201797311. This article has 71 citations.
(glaeser2018erad‐dependentcontrolof pages 3-4): Kathrin Glaeser, Manuela Urban, Emma Fenech, Oksana Voloshanenko, Dominique Kranz, Federica Lari, John C Christianson, and Michael Boutros. Erad‐dependent control of the wnt secretory factor evi. The EMBO Journal, Jan 2018. URL: https://doi.org/10.15252/embj.201797311, doi:10.15252/embj.201797311. This article has 71 citations.
(wang2025sel1lhrd1mediatederadin pages 6-8): Huilun Helen Wang, Ida Biunno, Shengyi Sun, and Ling Qi. Sel1l-hrd1-mediated erad in mammals. Nature cell biology, 27:1063-1073, Jun 2025. URL: https://doi.org/10.1038/s41556-025-01690-1, doi:10.1038/s41556-025-01690-1. This article has 24 citations and is from a highest quality peer-reviewed journal.
(christianson2023mechanismsofsubstrate pages 26-30): John C. Christianson, Ernst Jarosch, and Thomas Sommer. Mechanisms of substrate processing during er-associated protein degradation. Nature Reviews Molecular Cell Biology, 24:777-796, Aug 2023. URL: https://doi.org/10.1038/s41580-023-00633-8, doi:10.1038/s41580-023-00633-8. This article has 193 citations and is from a domain leading peer-reviewed journal.
*-deep-research*.md file found in this gene directory.UPS|E3 ubiquitin and UBL ligases|RING|other|other ; PN-node mapping: RING/other subtype+type no_mapping; RING group mapped → GO:0061630 ubiquitin protein ligase activity (ok_for_propagation, new_to_goa); class context_only (GO:0061630, too_broad).This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.
id: Q99675
gene_symbol: CGRRF1
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: >-
CGRRF1 (cell growth regulator with RING finger domain protein 1; also known as CGR19 and
RNF197) is a 332-residue endoplasmic reticulum (ER) membrane-anchored protein with an
N-terminal hydrophobic/transmembrane region and a C-terminal cytosolic RING-type zinc
finger (residues ~274-309; NMR structure PDB 2EA5). Its domain architecture (a canonical
C3HC4/C3H2C3 RING coupled to a transmembrane membrane anchor) is the hallmark of ER-resident
RING-type E3 ubiquitin ligases that act in ER-associated degradation (ERAD), where they
cooperate with E2 conjugating enzymes to ubiquitinate substrates destined for proteasomal
degradation. CGRRF1 localizes to the ER and partially to the nucleus, is transcriptionally
up-regulated by ER stress (thapsigargin, tunicamycin) downstream of the ATF6 branch of the
unfolded protein response, and is ubiquitously expressed with highest levels in testis and
cerebellum. It was originally discovered as CGR19, a p53-induced transcript whose
overexpression inhibits growth of several cell lines, the basis of its historical
description as a cell growth/cell cycle regulator. An early genome-wide screen reported a
negative in vitro autoubiquitination result when CGRRF1 was paired with the promiscuous E2
UbcH5c/UBE2D3, but subsequent substrate-focused work established CGRRF1 as a functional ER
E3 ligase acting in regulatory ERAD: together with the cognate E2 UBE2J2 it ubiquitinates
Evi/Wntless (WLS/GPR177), the dedicated cargo receptor for Wnt secretion, targeting it for
VCP/p97-dependent extraction and proteasomal degradation when Wnt ligand is unavailable and
thereby tuning the cell's Wnt secretory capacity. Its broader physiological substrate
repertoire and high-resolution catalytic mechanism remain incompletely defined.
aliases:
- CGR19
- RNF197
existing_annotations:
- term:
id: GO:0030308
label: negative regulation of cell growth
evidence_type: IBA
original_reference_id: GO_REF:0000033
qualifier: involved_in
review:
summary: >-
Phylogenetically inferred (IBA) negative regulation of cell growth, transferred across the
CGRRF1 ortholog group (PANTHER:PTN002310361, including rat ortholog RGD:620803). This trace
is rooted in the original observation that CGR19/CGRRF1 overexpression inhibits cell growth.
action: KEEP_AS_NON_CORE
reason: >-
The growth-inhibitory phenotype derives from overexpression assays (PMID:8968090) and reflects
a downstream cellular consequence rather than the molecular core function of the protein, which
structurally is an ER-membrane RING-domain protein. No mechanism links CGRRF1 directly to a
growth-control pathway. Retained as a non-core biological-process annotation.
supported_by:
- reference_id: PMID:8968090
supporting_text: Both CGR11 and CGR19 are able to inhibit the growth of several cell lines.
- term:
id: GO:0005634
label: nucleus
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: >-
Nucleus localization mapped electronically (IEA) from the UniProt subcellular-location
vocabulary (UniProtKB-SubCell:SL-0191). The underlying experimental basis is the antibody-based
localization in PubMed:22361696.
action: KEEP_AS_NON_CORE
reason: >-
A transmembrane-anchored ER-membrane RING protein localizing to the nucleus is biologically
unexpected and the support is antibody-based immunolocalization that may overlap with a
nucleoplasmic signal. Retained as non-core; the ER localization is the better-supported and
mechanistically relevant compartment.
supported_by:
- reference_id: file:human/CGRRF1/CGRRF1-uniprot.txt
supporting_text: "SUBCELLULAR LOCATION: Nucleus {ECO:0000269|PubMed:22361696}."
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: >-
Endoplasmic reticulum localization mapped electronically (IEA) from the UniProt
subcellular-location vocabulary (UniProtKB-SubCell:SL-0095), corroborating the experimentally
supported ER annotation (IDA, PMID:27485036).
action: ACCEPT
reason: >-
Correct compartment and consistent with the protein's membrane-anchored RING architecture. This
IEA entry is concordant with the experimental IDA annotation to the same term and the
well-supported ER localization, so it is accepted.
supported_by:
- reference_id: file:human/CGRRF1/CGRRF1-uniprot.txt
supporting_text: "Endoplasmic reticulum {ECO:0000269|PubMed:27485036}."
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
qualifier: enables
review:
summary: >-
Generic protein binding annotation derived entirely from the HuRI high-throughput binary
(yeast two-hybrid) interactome screen, supported by individual interactors such as CDIPT
(UniProtKB:O14735) and ~30 additional systematic Y2H hits listed in UniProt (mostly other
single- or multi-pass membrane and ER/Golgi proteins).
action: MARK_AS_OVER_ANNOTATED
reason: >-
Bare "protein binding" is uninformative per curation guidelines and conveys no specific molecular
function. The interactions come from a single large-scale binary interactome map without
validation or functional context, and no specific informative molecular-function term can be
justified from these HuRI hits alone. Note that the functionally meaningful protein-protein
contacts of CGRRF1 established in focused studies - its cognate E2 UBE2J2 and its substrate
Evi/WLS - are captured separately by the E3-ligase molecular-function and ERAD process
annotations rather than by this generic HuRI-derived term.
supported_by:
- reference_id: PMID:32296183
supporting_text: "Here we present a human 'all-by-all' reference interactome map of human binary protein interactions, or 'HuRI'."
- reference_id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
supporting_text: "CGRRF1 works in conjunction with the **E2 ubiquitin-conjugating enzyme UBE2J2** to ubiquitinate substrates"
- term:
id: GO:0005654
label: nucleoplasm
evidence_type: IDA
original_reference_id: GO_REF:0000052
qualifier: located_in
review:
summary: >-
Nucleoplasm localization from Human Protein Atlas immunofluorescence (IDA, HPA).
action: KEEP_AS_NON_CORE
reason: >-
HPA immunofluorescence reports a nucleoplasmic signal, but this is not consistent with the
protein's primary identity as a transmembrane ER-membrane RING protein, and antibody-based
localization of this poorly characterized (Tdark) protein should be treated cautiously.
Retained as observed but non-core.
supported_by:
- reference_id: file:human/CGRRF1/CGRRF1-uniprot.txt
supporting_text: "Nucleus {ECO:0000269|PubMed:22361696}."
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: IDA
original_reference_id: PMID:27485036
qualifier: located_in
review:
summary: >-
Experimentally supported (IDA) ER localization: V5-tagged CGRRF1 stably overexpressed in COS-1
cells partially colocalized with endogenous PDI, an ER-resident chaperone, indicating ER
localization. Consistent with the protein's N-terminal transmembrane anchor.
action: ACCEPT
reason: >-
This is the best-supported and mechanistically relevant subcellular localization, directly
observed by immunocytochemistry and consistent with the membrane-anchored RING-domain
architecture expected of an ER-resident E3 ligase. A more specific term (GO:0005789 endoplasmic
reticulum membrane) is biologically appropriate given the transmembrane anchor, but the IDA
colocalization with PDI supports the parent ER term directly.
supported_by:
- reference_id: PMID:27485036
supporting_text: RNFT1, RNF185, CGRRF1 and RNF19B partially colocalised with endogenous PDI, an ER-resident chaperone, indicating their localisation to the ER
- term:
id: GO:0008285
label: negative regulation of cell population proliferation
evidence_type: TAS
original_reference_id: PMID:8968090
qualifier: involved_in
review:
summary: >-
Author statement (TAS) that CGR19/CGRRF1, a p53-induced gene, inhibits the growth of several
cell lines when overexpressed, the original functional description of the gene.
action: KEEP_AS_NON_CORE
reason: >-
This reflects an overexpression growth-inhibition phenotype rather than a defined molecular
mechanism. It is a descriptive, downstream biological observation and is retained as non-core
rather than as the central function of an ER-membrane RING-domain protein.
supported_by:
- reference_id: PMID:8968090
supporting_text: Both CGR11 and CGR19 are able to inhibit the growth of several cell lines.
- term:
id: GO:0061630
label: ubiquitin protein ligase activity
evidence_type: TAS
original_reference_id: PMID:32614325
qualifier: enables
review:
summary: >-
Not present in the current GOA set, but added (NEW) on the basis of substrate-focused work
(Glaeser et al., 2018, EMBO J) showing CGRRF1 is a functional ER RING-type E3 ubiquitin ligase
that, with the cognate E2 UBE2J2, ubiquitinates the Wnt cargo receptor Evi/WLS and targets it
for ERAD. CGRRF1 depletion increases Evi steady-state levels and reduces Evi poly-ubiquitination
(TUBE2 pulldown), CGRRF1 co-immunoprecipitates with Evi, and catalytic RING-domain (C2/C4A)
mutants stabilise Evi - together establishing E2- and substrate-specific E3 activity. This
reconciles the earlier negative in vitro autoubiquitination result (PMID:27485036), which used
only the promiscuous non-cognate E2 UbcH5c/UBE2D3.
action: NEW
reason: >-
The E3-ligase molecular function is now supported by independent experimental work and is
corroborated in a cached full-text review (Fenech et al., 2020, eLife), which states that
Evi/WLS/GPR177 "was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al.,
2018)". This is the mechanistically central function of the protein and was previously only
inferred from RING+TM structure; it should be represented explicitly. Evidence is treated as
TAS (Traceable Author Statement): the primary experiments (siRNA depletion, TUBE2 pulldown,
co-IP, RING C2/C4A mutant stabilisation of Evi) are reported in Glaeser et al. 2018 (EMBO J,
doi:10.15252/embj.201797311), which is not yet cached as a PMID in this repository; the
`original_reference_id` PMID:32614325 (Fenech et al. 2020) traceably attributes the function to
that primary source. The annotation should be re-evidenced as IMP against the Glaeser 2018 PMID
once it is fetched.
supported_by:
- reference_id: PMID:32614325
supporting_text: "Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)"
- reference_id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
supporting_text: "**RING domain mutants** of CGRRF1 stabilized Evi protein levels, confirming the requirement of an intact catalytic domain for substrate turnover"
- term:
id: GO:0036503
label: ERAD pathway
evidence_type: TAS
original_reference_id: PMID:32614325
qualifier: involved_in
review:
summary: >-
Not present in the current GOA set, but added (NEW). CGRRF1 acts in ER-associated degradation
(ERAD): it is an ER-membrane RING E3 whose best-characterised role is the regulated ERAD of the
Wnt cargo receptor Evi/WLS, working with the E2 UBE2J2 and the VCP/p97 dislocation machinery to
route Evi to proteasomal degradation when Wnt ligand is absent. This is "regulatory ERAD" of a
mature, properly folded secretory factor rather than classical disposal of misfolded protein.
action: NEW
reason: >-
Independent experimental work (Glaeser et al., 2018) and a cached full-text review (Fenech et al.,
2020, eLife) place CGRRF1 in the ERAD pathway as the E3 ligase for the Evi/WLS substrate. The ER
localization (IDA, PMID:27485036), ER-stress/ATF6 transcriptional induction, and RING+TM
architecture already in the review are all consistent with this process annotation, which makes
the gene's core biological role explicit. Evidence is treated as TAS (Traceable Author Statement):
the primary experiments are reported in Glaeser et al. 2018 (EMBO J, doi:10.15252/embj.201797311,
not yet cached as a PMID); the `original_reference_id` PMID:32614325 (Fenech et al. 2020)
traceably attributes the ERAD-pathway role to that primary source. Re-evidence as IMP once the
Glaeser 2018 PMID is fetched.
supported_by:
- reference_id: PMID:32614325
supporting_text: "Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)"
- reference_id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
supporting_text: "CGRRF1 functions primarily as an **E3 ubiquitin ligase** embedded in the endoplasmic reticulum (ER) membrane, where it participates in **ER-associated degradation (ERAD)** pathways"
core_functions:
- description: >-
ER membrane-anchored RING-type E3 ubiquitin ligase. The C-terminal cytosolic RING domain
recruits the cognate ubiquitin-charged E2 enzyme UBE2J2 and transfers ubiquitin onto substrate,
while the N-terminal transmembrane segment anchors the protein in the ER membrane. E3 activity is
E2- and substrate-specific (and so was not detected in an early in vitro screen using the
promiscuous non-cognate E2 UbcH5c); catalytic RING-domain mutants fail to promote substrate
turnover.
molecular_function:
id: GO:0061630
label: ubiquitin protein ligase activity
supported_by:
- reference_id: PMID:32614325
supporting_text: "Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)"
- reference_id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
supporting_text: "CGRRF1 works in conjunction with the **E2 ubiquitin-conjugating enzyme UBE2J2** to ubiquitinate substrates"
- reference_id: file:human/CGRRF1/CGRRF1-uniprot.txt
supporting_text: 'ZN_FING 274..309 /note="RING-type"'
- description: >-
Localizes to the endoplasmic reticulum and is transcriptionally induced as part of the ER
stress / unfolded protein response (ATF6 branch), consistent with a role in ER protein
quality control.
locations:
- id: GO:0005783
label: endoplasmic reticulum
supported_by:
- reference_id: PMID:27485036
supporting_text: RNFT1, RNF185, CGRRF1 and RNF19B partially colocalised with endogenous PDI, an ER-resident chaperone, indicating their localisation to the ER
- reference_id: PMID:27485036
supporting_text: ATF6 (N-terminal domain) significantly upregulated CGRRF1 and RNF19B expression
- description: >-
Mediates regulated ER-associated degradation (ERAD) of the Wnt cargo receptor Evi/Wntless
(WLS/GPR177): with the E2 UBE2J2 it ubiquitinates Evi and, via VCP/p97-dependent extraction,
routes it to the proteasome when Wnt ligand is unavailable, thereby tuning the cell's capacity
for Wnt ligand secretion. This is regulatory ERAD of a properly folded secretory factor rather
than disposal of misfolded protein.
locations:
- id: GO:0005783
label: endoplasmic reticulum
supported_by:
- reference_id: PMID:32614325
supporting_text: "Substrates are typified by the Wnt receptor Evi/WLS/GPR177, which after being identified early in this study was established as novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018)"
- reference_id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
supporting_text: "The best-characterized and experimentally validated substrate of CGRRF1 is **Evi (also known as Wntless or WLS/GPR177)**, the dedicated cargo receptor for Wnt protein secretion"
proposed_new_terms: []
suggested_questions:
- question: >-
Does CGRRF1 possess ubiquitin-protein ligase activity with an E2 other than UbcH5c/UBE2D3, given
that the only published in vitro autoubiquitination assay (using UbcH5c) was negative?
- question: >-
What are the physiological ERAD substrates of CGRRF1, and does it function within or parallel to
the canonical HRD1/SYVN1 ERAD machinery?
- question: >-
How are the reported ER-membrane and nucleoplasmic localizations reconciled, and is the nuclear
signal a genuine localization or an antibody artifact for this Tdark protein?
suggested_experiments:
- description: >-
Perform in vitro autoubiquitination and substrate-ubiquitination assays across a panel of E2
conjugating enzymes (beyond UbcH5c/UBE2D3) using recombinant CGRRF1 RING domain, with RING
point mutants as negative controls, to determine whether CGRRF1 has E3 ligase activity with a
cognate E2.
experiment_type: biochemical assay
hypothesis: >-
CGRRF1 is a bona fide RING E3 ubiquitin ligase whose activity requires a specific E2 not tested
in the original in vitro screen.
- description: >-
Identify CGRRF1 interaction partners and candidate substrates by proximity labeling (BioID/TurboID)
or affinity purification-mass spectrometry from ER membranes, followed by ubiquitination and
stability assays of candidate substrates upon CGRRF1 depletion or RING mutation.
experiment_type: proteomics / interactomics
hypothesis: >-
CGRRF1 ubiquitinates one or more ER-membrane or ER-luminal client proteins, targeting them for
ERAD-mediated proteasomal degradation.
- description: >-
Knock out or deplete CGRRF1 in cells challenged with ER stressors and measure accumulation of
model ERAD substrates, UPR marker induction, and ER-stress-induced apoptosis, with rescue by WT
versus RING-dead CGRRF1.
experiment_type: genetic manipulation / cell biology
hypothesis: >-
Loss of CGRRF1 impairs ERAD of specific substrates and alters sensitivity to ER stress in a
RING-domain-dependent manner.
references:
- 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: PMID:27485036
title: Genome-wide identification and gene expression profiling of ubiquitin ligases
for endoplasmic reticulum protein degradation.
findings:
- statement: >-
CGRRF1 is one of 37 human RING-finger + transmembrane proteins computationally selected as
candidate ERAD E3 ligases; it localizes to the ER (colocalization with PDI) and its expression
is up-regulated by ER stress and by ATF6.
reference_section_type: RESULTS
- statement: >-
In an in vitro autoubiquitination assay with the E2 UbcH5c/UBE2D3, CGRRF1 did NOT exhibit E3
activity, and it conferred no resistance to ER stress, unlike RNFT1 and RNF185.
reference_section_type: RESULTS
- id: PMID:32296183
title: A reference map of the human binary protein interactome.
findings:
- statement: >-
CGRRF1 protein interactions in GOA derive from the HuRI high-throughput binary (Y2H)
interactome map; interactors are mostly other membrane/ER-Golgi proteins and are not
individually validated.
reference_section_type: RESULTS
- id: PMID:32614325
title: Interaction mapping of endoplasmic reticulum ubiquitin ligases identifies modulators
of innate immune signalling.
findings:
- statement: >-
CGRRF1 is treated as one of ~25 ER-resident transmembrane RING E3 ligases; its transcript
is induced by acute ER stress, and Evi/WLS/GPR177 is stated to have been established as a
novel target for regulated ERAD by CGRRF1 (Glaeser et al., 2018), independently corroborating
the E3-ligase/ERAD/Evi-substrate role.
reference_section_type: RESULTS
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
Cached full text (full_text_available). Directly names CGRRF1 among ER-resident E3 ligases and
independently corroborates the Glaeser 2018 finding that Evi/WLS is a regulated-ERAD substrate
of CGRRF1. Provides a peer-reviewed verbatim anchor for the new E3-ligase and ERAD annotations.
- id: file:human/CGRRF1/CGRRF1-deep-research-falcon.md
title: Falcon deep research report for CGRRF1
findings:
- statement: >-
LLM-synthesized deep research report. Its CGRRF1-specific core finding - that CGRRF1 is a
functional ER E3 ligase that, with the cognate E2 UBE2J2, ubiquitinates the Wnt cargo
receptor Evi/WLS for regulated ERAD (siRNA depletion raises Evi, TUBE2 pulldown shows reduced
Evi ubiquitination, co-IP, RING-mutant stabilisation) - traces to Glaeser et al. 2018 (EMBO J)
and is independently corroborated by the cached Fenech et al. 2020 (PMID:32614325).
reference_section_type: OTHER
- statement: >-
Family/inference-level statements in the report (general ERAD machinery roles drawn from
Christianson 2023 and Wang 2025 reviews, the candidate inner-nuclear-membrane localization near
emerin/LBR from Cheng et al. 2022 proximity labeling, K11/K48/K63 chain linkages, and the
cancer/TCGA Wnt-secretion speculation) are broader inferences and should not be asserted as
CGRRF1-specific molecular function without primary verification.
reference_section_type: OTHER
reference_review:
relevance: HIGH
correctness: UNVERIFIED
review_notes: >-
LLM-generated synthesis; not independently verified for every claim. The central CGRRF1-specific
claim (active E3 ligase; cognate E2 UBE2J2; substrate Evi/WLS; regulated ERAD) is strong because
it is corroborated by a cached, peer-reviewed full-text source (Fenech 2020, PMID:32614325) and
reconciles the earlier negative in vitro autoubiquitination result (PMID:27485036, non-cognate E2
UbcH5c). Treated cautiously: candidate/inner-nuclear-membrane localization (Cheng 2022 proximity
labeling), specific ubiquitin chain linkages, and cancer/TCGA implications are family- or
inference-level and are NOT used to drive existing-annotation actions. Marked UNVERIFIED by
default for LLM synthesis pending primary-source confirmation of the Glaeser 2018 details.
- id: PMID:8968090
title: Induction of cell growth regulatory genes by p53.
findings:
- statement: >-
CGRRF1 was originally isolated as CGR19, a p53-induced cell growth regulatory gene encoding a
RING-finger protein whose overexpression inhibits growth of several cell lines.
reference_section_type: ABSTRACT