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 |
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Download this section (compressed HTML)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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