{"gene":"RC3H2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2000,"finding":"RC3H2 (MNAB) encodes a membrane-associated nucleic acid-binding protein with a C3HC4 RING finger and a CCCH zinc finger; mutagenesis of a conserved amino acid in the zinc finger reduced DNA binding by 50%, and the protein localizes primarily to the perinuclear space (endoplasmic reticulum or trans-Golgi network).","method":"cDNA cloning, site-directed mutagenesis, immunoprecipitation, subcellular fractionation/immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct mutagenesis of zinc finger with functional readout, but single study with no independent replication","pmids":["10938276"],"is_preprint":false},{"year":2010,"finding":"The ROQ domain of Roquin-2 (RC3H2/MNAB) is necessary and sufficient for localization to arsenite-induced stress granules and can induce stress granule formation upon overexpression; the ROQ domain also directly binds RNA from the Icos 3'-UTR and is required to trigger Icos mRNA decay.","method":"Fluorescence microscopy, gel-shift assay, surface plasmon resonance (SPR), footprinting, domain truncation/deletion","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical methods (SPR, gel-shift, footprinting) combined with live-cell imaging and domain mutagenesis in a single study","pmids":["20412057"],"is_preprint":false},{"year":2013,"finding":"Roquin-2 (RC3H2) shares redundant functions with Roquin-1 in repressing ICOS mRNA and suppressing T follicular helper cell accumulation; the RING domain of Roquin-1 (not Roquin-2) is required for stress granule localization, and loss of the Roquin-1 RING domain allows Roquin-2 to compensate in ICOS and Tfh cell repression. Both paralogs also target TNF mRNA in non-lymphoid cells.","method":"Mouse genetics (RING and ROQ domain point mutants), fluorescence microscopy (stress granule localization), flow cytometry, in vivo arthritis model","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in vivo combined with direct localization experiments and mRNA regulation readouts; highly cited foundational study","pmids":["23583642"],"is_preprint":false},{"year":2014,"finding":"Roquin-2 (RC3H2) functions as an E3 ubiquitin ligase that ubiquitinates ASK1 (MAP3K5) upon ROS stimulation, promoting its proteasomal degradation; knockdown of Roquin-2 leads to sustained ASK1, JNK, and p38 MAPK activation and increased cell death. This mechanism is evolutionarily conserved, as the C. elegans ortholog RLE-1 similarly regulates the ASK1 ortholog NSY-1 during bacterial infection.","method":"siRNA screen in HeLa cells, co-immunoprecipitation, ubiquitination assay, H2O2-induced ROS treatment, C. elegans genetics","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 — functional siRNA screen, biochemical ubiquitination assay, and cross-species genetic validation provide multiple orthogonal lines of evidence","pmids":["24448648"],"is_preprint":false},{"year":2015,"finding":"Crystal structures of the RNA-binding region of RC3H2 in apo and RNA-bound forms reveal a bipartite ROQ+HEPN domain architecture; both domains undergo large conformational change to accommodate RNA duplex binding. RC3H2 interacts with a set of E2 ubiquitin-conjugating enzymes (overlapping but not identical to RC3H1) to drive polyubiquitin chain assembly, and RNA duplex binding cross-talks with its E3 ubiquitin ligase activity as shown by in vitro auto-ubiquitination assay.","method":"X-ray crystallography (apo and RNA-bound structures), SAXS, in vitro RNA-binding assays, E2 enzyme profiling, in vitro auto-ubiquitination assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 — crystal structures with functional validation by in vitro ubiquitination and RNA-binding assays, multiple orthogonal methods in a single study","pmids":["26489670"],"is_preprint":false},{"year":2024,"finding":"Roquin-2 (RC3H2) promotes K48-linked polyubiquitination and proteasomal degradation of TAK1 under excessive oxidative stress conditions; it interacts with TAK1 via four cysteine residues (C96, C302, C486, C500) that form oxidative stress-induced disulfide-bond oligomers. This suppresses TAK1-mediated Nrf2 activation and switches cell fate from survival to death. Roquin-2-deficient MEF cells showed sustained Nrf2 activation and resistance to lethal ROS, reversed by TAK1 inhibition.","method":"Co-immunoprecipitation, ubiquitination assay (K48-linkage specific), cysteine mutagenesis of TAK1, knockout MEF cells, pharmacological/genetic TAK1 inhibition, western blot","journal":"Free radical biology & medicine","confidence":"High","confidence_rationale":"Tier 1–2 — mutagenesis of substrate interaction site, ubiquitination linkage specificity, and KO rescue experiments provide strong mechanistic evidence in a single study","pmids":["38729452"],"is_preprint":false},{"year":2025,"finding":"RC3H2 (Roquin-2), an RNA-binding E3 ubiquitin ligase, can be recruited by engineered circular RNAs (circRNAs) containing binding sites for both RC3H2 and target RNA-binding proteins (FUS or hnRNPA1), forming ternary complexes that promote degradation of the target RBPs; ALS-mutant FUS-P525L and hnRNPA1-P288S protein levels were reduced ~20–30% by this approach.","method":"RNA immunoprecipitation, protein analysis (western blot), engineered circular RNA expression, ternary complex detection","journal":"Molecular therapy. Methods & clinical development","confidence":"Medium","confidence_rationale":"Tier 2–3 — proof-of-concept showing RC3H2 participates in ternary RNA-protein complexes enabling targeted protein degradation, but partial mechanistic follow-up in a single study","pmids":["40687373"],"is_preprint":false}],"current_model":"RC3H2 (Roquin-2) is a cytoplasmic RNA-binding E3 ubiquitin ligase whose ROQ+HEPN bipartite domain binds stem-loop and double-stranded RNA to repress target mRNAs (e.g., Icos, TNF) via stress granule-associated decay, while its RING domain ubiquitinates substrates including ASK1 and TAK1 with K48-linked chains to promote their proteasomal degradation under oxidative stress, thereby controlling T follicular helper cell homeostasis and cell fate decisions between survival and apoptosis."},"narrative":{"teleology":[{"year":2000,"claim":"Initial cloning established that RC3H2 encodes a protein with dual nucleic-acid-binding (CCCH zinc finger) and E3 ligase (RING finger) domains, raising the question of how these activities are coordinated.","evidence":"cDNA cloning with site-directed mutagenesis of zinc finger reducing DNA binding, subcellular fractionation and immunofluorescence in mammalian cells","pmids":["10938276"],"confidence":"Medium","gaps":["Single study without independent replication of perinuclear localization","RNA versus DNA substrate preference not resolved","No functional consequence of RING domain established"]},{"year":2010,"claim":"Identification of the ROQ domain as the module responsible for RNA binding and stress granule localization resolved how RC3H2 engages target mRNAs and established Icos mRNA decay as a direct functional readout.","evidence":"SPR, gel-shift, and footprinting for RNA binding; fluorescence microscopy with domain truncations for stress granule localization","pmids":["20412057"],"confidence":"High","gaps":["Structural basis of ROQ-RNA recognition not yet determined","Whether stress granule localization is required for mRNA decay not tested","E3 ligase activity not linked to mRNA regulatory function"]},{"year":2013,"claim":"Genetic studies revealed that RC3H2 and RC3H1 function redundantly to repress ICOS and TNF mRNAs and suppress T follicular helper cell accumulation, establishing the physiological importance of Roquin-2 in immune homeostasis.","evidence":"Mouse genetics with RING and ROQ domain point mutants, flow cytometry, in vivo arthritis model","pmids":["23583642"],"confidence":"High","gaps":["Unique non-redundant functions of RC3H2 versus RC3H1 not delineated","Full mRNA target repertoire of RC3H2 not defined","Whether RING E3 ligase activity contributes to mRNA target regulation in vivo unknown"]},{"year":2014,"claim":"Demonstration that RC3H2 ubiquitinates ASK1 for proteasomal degradation under oxidative stress revealed a second major function—direct regulation of MAPK signaling kinases—beyond mRNA decay, with cross-species conservation in C. elegans.","evidence":"siRNA screen in HeLa cells, co-immunoprecipitation, in vitro ubiquitination assay, H₂O₂ treatment, C. elegans genetics","pmids":["24448648"],"confidence":"High","gaps":["Ubiquitin chain linkage type on ASK1 not specified","Whether RNA-binding and E3 ligase functions are coordinated in the same cellular context unclear","Structural basis of ASK1 recognition not determined"]},{"year":2015,"claim":"Crystal structures of the ROQ+HEPN domain in apo and RNA-bound states provided the atomic-level mechanism for RNA duplex recognition and revealed functional crosstalk between RNA binding and E3 ubiquitin ligase activity.","evidence":"X-ray crystallography, SAXS, E2 enzyme profiling, in vitro auto-ubiquitination assay","pmids":["26489670"],"confidence":"High","gaps":["Structural basis of RING-E2 interaction not resolved","How RNA binding modulates ubiquitination in a cellular context not shown","No co-structure with a ubiquitination substrate"]},{"year":2024,"claim":"Identification of TAK1 as a second kinase substrate ubiquitinated with K48-linked chains via oxidative-stress-induced disulfide bonding established a redox-sensing mechanism by which RC3H2 switches cell fate from Nrf2-mediated survival to death.","evidence":"Co-immunoprecipitation, K48-linkage-specific ubiquitination assay, cysteine mutagenesis, knockout MEF rescue, TAK1 pharmacological inhibition","pmids":["38729452"],"confidence":"High","gaps":["Whether disulfide-mediated oligomerization is a general mechanism for all RC3H2 substrates unknown","In vivo physiological relevance in immune cells not tested","Quantitative threshold of ROS required to activate this switch not defined"]},{"year":null,"claim":"How the RNA-binding and E3 ubiquitin ligase functions of RC3H2 are integrated in the same signaling context—and whether RNA binding regulates substrate ubiquitination in vivo—remains an open mechanistic question.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo demonstration that RNA binding and ubiquitination are coupled on the same target complex","Full substrate and mRNA target repertoire not systematically mapped","Unique non-redundant functions versus RC3H1 remain poorly defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3,4,5,6]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[1,2,4,6]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[3,4,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,2]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,4,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,5]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[3,5]}],"complexes":[],"partners":["ASK1","TAK1","ICOS","RC3H1"],"other_free_text":[]},"mechanistic_narrative":"RC3H2 (Roquin-2) is a cytoplasmic RNA-binding E3 ubiquitin ligase that couples post-transcriptional mRNA regulation with ubiquitin-dependent protein degradation to control immune homeostasis and oxidative stress responses. Its bipartite ROQ+HEPN domain undergoes large conformational changes to bind stem-loop and duplex RNA structures, targeting mRNAs such as ICOS and TNF for decay via stress granule-associated pathways, functioning redundantly with its paralog Roquin-1 to suppress T follicular helper cell accumulation [PMID:20412057, PMID:23583642, PMID:26489670]. The RING finger domain catalyzes K48-linked polyubiquitination of the MAP3 kinases ASK1 and TAK1 under oxidative stress, promoting their proteasomal degradation and thereby attenuating JNK/p38 MAPK and Nrf2 survival signaling to switch cell fate toward apoptosis [PMID:24448648, PMID:38729452]. RNA duplex binding cross-talks with E3 ligase activity, and RC3H2 engages a specific set of E2 ubiquitin-conjugating enzymes partially overlapping with those used by RC3H1 [PMID:26489670]."},"prefetch_data":{"uniprot":{"accession":"Q9HBD1","full_name":"Roquin-2","aliases":["Membrane-associated nucleic acid-binding protein","RING finger and CCCH-type zinc finger domain-containing protein 2","RING finger protein 164","RING-type E3 ubiquitin transferase Roquin-2"],"length_aa":1191,"mass_kda":131.7,"function":"Post-transcriptional repressor of mRNAs containing a conserved stem loop motif, called constitutive decay element (CDE), which is often located in the 3'-UTR, as in HMGXB3, ICOS, IER3, NFKBID, NFKBIZ, PPP1R10, TNF and in many more mRNAs. Binds to CDE and promotes mRNA deadenylation and degradation. This process does not involve miRNAs. In follicular helper T (Tfh) cells, represses of ICOS and TNFRSF4 expression, thus preventing spontaneous Tfh cell differentiation, germinal center B-cell differentiation in the absence of immunization and autoimmunity. In resting or LPS-stimulated macrophages, controls inflammation by suppressing TNF expression. Also recognizes CDE in its own mRNA and in that of paralogous RC3H1, possibly leading to feedback loop regulation (By similarity). miRNA-binding protein that regulates microRNA homeostasis. Enhances DICER-mediated processing of pre-MIR146a but reduces mature MIR146a levels through an increase of 3' end uridylation. Both inhibits ICOS mRNA expression and they may act together to exert the suppression (PubMed:25697406). Acts as a ubiquitin E3 ligase. Pairs with E2 enzymes UBE2B, UBE2D2, UBE2E2, UBE2E3, UBE2G2, UBE2K and UBE2Q2 and produces polyubiquitin chains (PubMed:26489670). Shows the strongest activity when paired with UBE2N:UBE2V1 or UBE2N:UBE2V2 E2 complexes and generate both short and long polyubiquitin chains (PubMed:26489670). Involved in the ubiquitination of MAP3K5 (PubMed:24448648, PubMed:26489670, PubMed:29186683). Able to interact with double-stranded RNA (dsRNA) (PubMed:26489670)","subcellular_location":"Cytoplasm, P-body","url":"https://www.uniprot.org/uniprotkb/Q9HBD1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RC3H2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CCT2","stoichiometry":0.2},{"gene":"CCT7","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/RC3H2","total_profiled":1310},"omim":[{"mim_id":"615231","title":"RING FINGER AND CCCH-TYPE ZINC FINGER DOMAINS-CONTAINING PROTEIN 2; RC3H2","url":"https://www.omim.org/entry/615231"},{"mim_id":"609424","title":"RING FINGER AND CCCH-TYPE ZINC FINGER DOMAINS-CONTAINING 1; RC3H1","url":"https://www.omim.org/entry/609424"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Vesicles","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RC3H2"},"hgnc":{"alias_symbol":["FLJ20301","FLJ20713","RNF164"],"prev_symbol":["MNAB"]},"alphafold":{"accession":"Q9HBD1","domains":[{"cath_id":"3.30.40.10","chopping":"1-82","consensus_level":"medium","plddt":85.9809,"start":1,"end":82},{"cath_id":"-","chopping":"91-115_123-171_309-393","consensus_level":"medium","plddt":92.3183,"start":91,"end":393},{"cath_id":"1.20.120.1790","chopping":"174-293","consensus_level":"medium","plddt":96.3463,"start":174,"end":293}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HBD1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HBD1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HBD1-F1-predicted_aligned_error_v6.png","plddt_mean":56.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RC3H2","jax_strain_url":"https://www.jax.org/strain/search?query=RC3H2"},"sequence":{"accession":"Q9HBD1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HBD1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HBD1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HBD1"}},"corpus_meta":[{"pmid":"23583642","id":"PMC_23583642","title":"Roquin-2 shares functions with its paralog Roquin-1 in the repression of mRNAs controlling T follicular helper cells and systemic inflammation.","date":"2013","source":"Immunity","url":"https://pubmed.ncbi.nlm.nih.gov/23583642","citation_count":122,"is_preprint":false},{"pmid":"20412057","id":"PMC_20412057","title":"The ROQUIN family of proteins localizes to stress granules via the ROQ domain and binds target mRNAs.","date":"2010","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/20412057","citation_count":71,"is_preprint":false},{"pmid":"32163895","id":"PMC_32163895","title":"Long Noncoding RNA RC3H2 Facilitates Cell Proliferation and Invasion by Targeting MicroRNA-101-3p/EZH2 Axis in OSCC.","date":"2020","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/32163895","citation_count":66,"is_preprint":false},{"pmid":"11924572","id":"PMC_11924572","title":"Human osteoblasts' proliferative responses to strain and 17beta-estradiol are mediated by the estrogen receptor and the receptor for insulin-like growth factor I.","date":"2002","source":"Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research","url":"https://pubmed.ncbi.nlm.nih.gov/11924572","citation_count":64,"is_preprint":false},{"pmid":"24448648","id":"PMC_24448648","title":"Roquin-2 promotes ubiquitin-mediated degradation of ASK1 to regulate stress responses.","date":"2014","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/24448648","citation_count":59,"is_preprint":false},{"pmid":"37231097","id":"PMC_37231097","title":"The impact of rare protein coding genetic variation on adult cognitive function.","date":"2023","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/37231097","citation_count":43,"is_preprint":false},{"pmid":"32727592","id":"PMC_32727592","title":"The effect of aging on the biological and immunological characteristics of periodontal ligament stem cells.","date":"2020","source":"Stem cell research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32727592","citation_count":42,"is_preprint":false},{"pmid":"10938276","id":"PMC_10938276","title":"A human gene coding for a membrane-associated nucleic acid-binding protein.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10938276","citation_count":37,"is_preprint":false},{"pmid":"33043290","id":"PMC_33043290","title":"Reducing False Negatives in COVID-19 Testing by Using Microneedle-Based Oropharyngeal Swabs.","date":"2020","source":"Matter","url":"https://pubmed.ncbi.nlm.nih.gov/33043290","citation_count":36,"is_preprint":false},{"pmid":"26489670","id":"PMC_26489670","title":"New Insights into the RNA-Binding and E3 Ubiquitin Ligase Activities of Roquins.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26489670","citation_count":29,"is_preprint":false},{"pmid":"8892682","id":"PMC_8892682","title":"Inhibition of apoptotic cell death in B-CLL by interferon gamma correlates with clinical stage.","date":"1996","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/8892682","citation_count":29,"is_preprint":false},{"pmid":"10233713","id":"PMC_10233713","title":"A peptide derived from a polyreactive monoclonal anti-DNA natural antibody can modulate lupus development in (NZBxNZW)F1 mice.","date":"1999","source":"Immunology","url":"https://pubmed.ncbi.nlm.nih.gov/10233713","citation_count":26,"is_preprint":false},{"pmid":"33186364","id":"PMC_33186364","title":"Genetic loci associated with prevalent and incident myocardial infarction and coronary heart disease in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium.","date":"2020","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/33186364","citation_count":7,"is_preprint":false},{"pmid":"22723964","id":"PMC_22723964","title":"Alopecia in a viable phospholipase C delta 1 and phospholipase C delta 3 double mutant.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22723964","citation_count":6,"is_preprint":false},{"pmid":"38729452","id":"PMC_38729452","title":"Roquin-2 promotes oxidative stress-induced cell death by ubiquitination-dependent degradation of TAK1.","date":"2024","source":"Free radical biology & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38729452","citation_count":4,"is_preprint":false},{"pmid":"23988490","id":"PMC_23988490","title":"Magnetism and magnetic structures of PrMn2Ge2-xSix.","date":"2013","source":"Journal of physics. 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Both paralogs also target TNF mRNA in non-lymphoid cells.\",\n      \"method\": \"Mouse genetics (RING and ROQ domain point mutants), fluorescence microscopy (stress granule localization), flow cytometry, in vivo arthritis model\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo combined with direct localization experiments and mRNA regulation readouts; highly cited foundational study\",\n      \"pmids\": [\"23583642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Roquin-2 (RC3H2) functions as an E3 ubiquitin ligase that ubiquitinates ASK1 (MAP3K5) upon ROS stimulation, promoting its proteasomal degradation; knockdown of Roquin-2 leads to sustained ASK1, JNK, and p38 MAPK activation and increased cell death. This mechanism is evolutionarily conserved, as the C. elegans ortholog RLE-1 similarly regulates the ASK1 ortholog NSY-1 during bacterial infection.\",\n      \"method\": \"siRNA screen in HeLa cells, co-immunoprecipitation, ubiquitination assay, H2O2-induced ROS treatment, C. elegans genetics\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional siRNA screen, biochemical ubiquitination assay, and cross-species genetic validation provide multiple orthogonal lines of evidence\",\n      \"pmids\": [\"24448648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structures of the RNA-binding region of RC3H2 in apo and RNA-bound forms reveal a bipartite ROQ+HEPN domain architecture; both domains undergo large conformational change to accommodate RNA duplex binding. RC3H2 interacts with a set of E2 ubiquitin-conjugating enzymes (overlapping but not identical to RC3H1) to drive polyubiquitin chain assembly, and RNA duplex binding cross-talks with its E3 ubiquitin ligase activity as shown by in vitro auto-ubiquitination assay.\",\n      \"method\": \"X-ray crystallography (apo and RNA-bound structures), SAXS, in vitro RNA-binding assays, E2 enzyme profiling, in vitro auto-ubiquitination assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures with functional validation by in vitro ubiquitination and RNA-binding assays, multiple orthogonal methods in a single study\",\n      \"pmids\": [\"26489670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Roquin-2 (RC3H2) promotes K48-linked polyubiquitination and proteasomal degradation of TAK1 under excessive oxidative stress conditions; it interacts with TAK1 via four cysteine residues (C96, C302, C486, C500) that form oxidative stress-induced disulfide-bond oligomers. This suppresses TAK1-mediated Nrf2 activation and switches cell fate from survival to death. Roquin-2-deficient MEF cells showed sustained Nrf2 activation and resistance to lethal ROS, reversed by TAK1 inhibition.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K48-linkage specific), cysteine mutagenesis of TAK1, knockout MEF cells, pharmacological/genetic TAK1 inhibition, western blot\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis of substrate interaction site, ubiquitination linkage specificity, and KO rescue experiments provide strong mechanistic evidence in a single study\",\n      \"pmids\": [\"38729452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RC3H2 (Roquin-2), an RNA-binding E3 ubiquitin ligase, can be recruited by engineered circular RNAs (circRNAs) containing binding sites for both RC3H2 and target RNA-binding proteins (FUS or hnRNPA1), forming ternary complexes that promote degradation of the target RBPs; ALS-mutant FUS-P525L and hnRNPA1-P288S protein levels were reduced ~20–30% by this approach.\",\n      \"method\": \"RNA immunoprecipitation, protein analysis (western blot), engineered circular RNA expression, ternary complex detection\",\n      \"journal\": \"Molecular therapy. Methods & clinical development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — proof-of-concept showing RC3H2 participates in ternary RNA-protein complexes enabling targeted protein degradation, but partial mechanistic follow-up in a single study\",\n      \"pmids\": [\"40687373\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RC3H2 (Roquin-2) is a cytoplasmic RNA-binding E3 ubiquitin ligase whose ROQ+HEPN bipartite domain binds stem-loop and double-stranded RNA to repress target mRNAs (e.g., Icos, TNF) via stress granule-associated decay, while its RING domain ubiquitinates substrates including ASK1 and TAK1 with K48-linked chains to promote their proteasomal degradation under oxidative stress, thereby controlling T follicular helper cell homeostasis and cell fate decisions between survival and apoptosis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RC3H2 (Roquin-2) is a cytoplasmic RNA-binding E3 ubiquitin ligase that couples post-transcriptional mRNA regulation with ubiquitin-dependent protein degradation to control immune homeostasis and oxidative stress responses. Its bipartite ROQ+HEPN domain undergoes large conformational changes to bind stem-loop and duplex RNA structures, targeting mRNAs such as ICOS and TNF for decay via stress granule-associated pathways, functioning redundantly with its paralog Roquin-1 to suppress T follicular helper cell accumulation [PMID:20412057, PMID:23583642, PMID:26489670]. The RING finger domain catalyzes K48-linked polyubiquitination of the MAP3 kinases ASK1 and TAK1 under oxidative stress, promoting their proteasomal degradation and thereby attenuating JNK/p38 MAPK and Nrf2 survival signaling to switch cell fate toward apoptosis [PMID:24448648, PMID:38729452]. RNA duplex binding cross-talks with E3 ligase activity, and RC3H2 engages a specific set of E2 ubiquitin-conjugating enzymes partially overlapping with those used by RC3H1 [PMID:26489670].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Initial cloning established that RC3H2 encodes a protein with dual nucleic-acid-binding (CCCH zinc finger) and E3 ligase (RING finger) domains, raising the question of how these activities are coordinated.\",\n      \"evidence\": \"cDNA cloning with site-directed mutagenesis of zinc finger reducing DNA binding, subcellular fractionation and immunofluorescence in mammalian cells\",\n      \"pmids\": [\"10938276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single study without independent replication of perinuclear localization\",\n        \"RNA versus DNA substrate preference not resolved\",\n        \"No functional consequence of RING domain established\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of the ROQ domain as the module responsible for RNA binding and stress granule localization resolved how RC3H2 engages target mRNAs and established Icos mRNA decay as a direct functional readout.\",\n      \"evidence\": \"SPR, gel-shift, and footprinting for RNA binding; fluorescence microscopy with domain truncations for stress granule localization\",\n      \"pmids\": [\"20412057\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of ROQ-RNA recognition not yet determined\",\n        \"Whether stress granule localization is required for mRNA decay not tested\",\n        \"E3 ligase activity not linked to mRNA regulatory function\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Genetic studies revealed that RC3H2 and RC3H1 function redundantly to repress ICOS and TNF mRNAs and suppress T follicular helper cell accumulation, establishing the physiological importance of Roquin-2 in immune homeostasis.\",\n      \"evidence\": \"Mouse genetics with RING and ROQ domain point mutants, flow cytometry, in vivo arthritis model\",\n      \"pmids\": [\"23583642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Unique non-redundant functions of RC3H2 versus RC3H1 not delineated\",\n        \"Full mRNA target repertoire of RC3H2 not defined\",\n        \"Whether RING E3 ligase activity contributes to mRNA target regulation in vivo unknown\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstration that RC3H2 ubiquitinates ASK1 for proteasomal degradation under oxidative stress revealed a second major function—direct regulation of MAPK signaling kinases—beyond mRNA decay, with cross-species conservation in C. elegans.\",\n      \"evidence\": \"siRNA screen in HeLa cells, co-immunoprecipitation, in vitro ubiquitination assay, H₂O₂ treatment, C. elegans genetics\",\n      \"pmids\": [\"24448648\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Ubiquitin chain linkage type on ASK1 not specified\",\n        \"Whether RNA-binding and E3 ligase functions are coordinated in the same cellular context unclear\",\n        \"Structural basis of ASK1 recognition not determined\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Crystal structures of the ROQ+HEPN domain in apo and RNA-bound states provided the atomic-level mechanism for RNA duplex recognition and revealed functional crosstalk between RNA binding and E3 ubiquitin ligase activity.\",\n      \"evidence\": \"X-ray crystallography, SAXS, E2 enzyme profiling, in vitro auto-ubiquitination assay\",\n      \"pmids\": [\"26489670\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of RING-E2 interaction not resolved\",\n        \"How RNA binding modulates ubiquitination in a cellular context not shown\",\n        \"No co-structure with a ubiquitination substrate\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of TAK1 as a second kinase substrate ubiquitinated with K48-linked chains via oxidative-stress-induced disulfide bonding established a redox-sensing mechanism by which RC3H2 switches cell fate from Nrf2-mediated survival to death.\",\n      \"evidence\": \"Co-immunoprecipitation, K48-linkage-specific ubiquitination assay, cysteine mutagenesis, knockout MEF rescue, TAK1 pharmacological inhibition\",\n      \"pmids\": [\"38729452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether disulfide-mediated oligomerization is a general mechanism for all RC3H2 substrates unknown\",\n        \"In vivo physiological relevance in immune cells not tested\",\n        \"Quantitative threshold of ROS required to activate this switch not defined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the RNA-binding and E3 ubiquitin ligase functions of RC3H2 are integrated in the same signaling context—and whether RNA binding regulates substrate ubiquitination in vivo—remains an open mechanistic question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No in vivo demonstration that RNA binding and ubiquitination are coupled on the same target complex\",\n        \"Full substrate and mRNA target repertoire not systematically mapped\",\n        \"Unique non-redundant functions versus RC3H1 remain poorly defined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3, 4, 5, 6]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [1, 2, 4, 6]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [3, 4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 4, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ASK1\",\n      \"TAK1\",\n      \"ICOS\",\n      \"RC3H1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}