{"gene":"RNF220","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2010,"finding":"RNF220 is a RING domain E3 ubiquitin ligase that binds E2 enzymes, undergoes auto-ubiquitination, and targets Sin3B (a scaffold protein of the Sin3/HDAC corepressor complex) for K48-linked ubiquitination and proteasomal degradation, identified via yeast two-hybrid screen with in vitro and in vivo interaction confirmation.","method":"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation, co-expression ubiquitination assay, proteasome inhibitor experiments","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (Y2H, in vitro binding, co-IP, ubiquitination assay) in a single study","pmids":["20170641"],"is_preprint":false},{"year":2014,"finding":"RNF220 physically interacts with β-catenin and with USP7 (a deubiquitinase); the RNF220/USP7 complex deubiquitinates β-catenin to stabilize it and enhance canonical Wnt signaling. RNF220 itself is destabilized by GSK3β phosphorylation, creating a positive feedback loop upon Wnt stimulation.","method":"Co-immunoprecipitation, knockdown experiments, luciferase Wnt reporter assay, ubiquitination assay, epistasis analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, functional reporter assays, knockdown phenotype, epistasis; moderate-to-strong evidence from single lab with multiple methods","pmids":["25266658"],"is_preprint":false},{"year":2018,"finding":"RNF220 cooperates with the zinc-finger protein ZC4H2 to ubiquitinate and degrade ventral spinal cord transcription factors Dbx1, Dbx2, and Nkx2.2, thereby specifying ventral progenitor domains (including p2 domain producing V2 interneurons) during spinal cord patterning. RNF220-null mice lose the p2 domain.","method":"RNF220 knockout mouse, chick spinal cord knockdown, co-immunoprecipitation, co-expression ubiquitination assay, immunostaining of progenitor markers","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with specific domain phenotype, co-IP, biochemical ubiquitination assay, orthogonal chick model","pmids":["30177510"],"is_preprint":false},{"year":2018,"finding":"A loss-of-function RNF220 mutation (p.P19L) in humans causes small-headed sperm by reducing RNF220 protein levels, leading to elevated Sin3B and excessive chromatin condensation in sperm.","method":"Whole-exome sequencing, Western blot, clinical phenotyping of consanguineous family","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 3 — human genetics with mechanistic interpretation via Sin3B pathway, single study","pmids":["30500349"],"is_preprint":false},{"year":2020,"finding":"ZC4H2 is required for RNF220 protein stability and proper Gli ubiquitination in vivo; ZC4H2 and RNF220 knockout animals phenocopy each other in ventral spinal cord patterning defects.","method":"ZC4H2 and RNF220 knockout mouse and zebrafish, immunostaining, Western blot, ubiquitination assay","journal":"Journal of molecular cell biology","confidence":"High","confidence_rationale":"Tier 2 — parallel KO models in two species plus biochemical data; replicated epistasis","pmids":["31336385"],"is_preprint":false},{"year":2020,"finding":"RNF220 mediates K63-linked polyubiquitination of STAT1 at residue K110, which promotes the interaction between STAT1 and JAK1, enhancing STAT1 phosphorylation and activation of interferon-stimulated gene expression. RNF220 deficiency impairs IFN signaling and increases susceptibility to bacterial and viral infection.","method":"Rnf220 knockout mouse, in vitro ubiquitination assay, site-directed mutagenesis (K110R), co-immunoprecipitation, infection models (A. baumannii, HSV-1), ISG expression analysis","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro ubiquitination assay with mutagenesis, KO mouse with infection phenotype, mechanistic epistasis with JAK1","pmids":["32814877"],"is_preprint":false},{"year":2020,"finding":"The RNF220/ZC4H2 complex monoubiquitylates Phox2a and Phox2b transcription factors, and this modification is required for full transcriptional activity of Phox2a/Phox2b and proper development of locus coeruleus noradrenergic neurons.","method":"Rnf220 and Zc4h2 knockout mouse, in vitro ubiquitination assay, co-immunoprecipitation, immunostaining of LC-NA markers","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1–2 — KO mouse, in vitro ubiquitination, co-IP, functional transcriptional readout","pmids":["32094113"],"is_preprint":false},{"year":2020,"finding":"RNF220 promotes Shh target gene expression in cerebellar granule neuron progenitors by targeting the PRC2 component EED for ubiquitination, altering histone modification marks on Shh target promoters. RNF220+/−; Ptch1+/− mice show lower spontaneous medulloblastoma occurrence.","method":"Conditional knockout mouse, Daoy cell knockdown, co-immunoprecipitation, ChIP for histone marks, xenograft assay","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — KO/KD, co-IP with EED, ChIP evidence for epigenetic mechanism, in vivo tumor model","pmids":["32376680"],"is_preprint":false},{"year":2020,"finding":"RNF220 promotes the stabilization of Cyclin D1 protein (without directly ubiquitinating it) through upregulation of the deubiquitinase USP22; RNF220 cannot stabilize Cyclin D1 without USP22, promoting G1-to-S phase transition in AML cells.","method":"Overexpression/knockdown in AML cell lines, co-immunoprecipitation, Western blot, cell cycle analysis, ubiquitination assay","journal":"Blood cells, molecules & diseases","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, co-IP and KD with phenotype, mechanistic pathway proposed via USP22","pmids":["32896826"],"is_preprint":false},{"year":2021,"finding":"RNF220 interacts with TDP43 in vitro and in vivo and promotes its polyubiquitination and proteasomal degradation; RNF220+/− mice develop progressive mobility defects and ALS-like pathology including TDP43 cytoplasmic accumulation, astrocytosis, and muscle denervation in spinal motor neurons.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, RNF220 haploinsufficient mouse model, immunostaining, behavioral analysis","journal":"Journal of molecular cell biology","confidence":"High","confidence_rationale":"Tier 2 — co-IP + in vitro ubiquitination + KO mouse with specific ALS-like cellular phenotypes","pmids":["33386850"],"is_preprint":false},{"year":2021,"finding":"Mass spectrometry identified lamin B1 as an RNF220-binding protein; co-immunoprecipitation showed reduced binding of RNF220 disease mutants (R363Q, R365Q) to lamin B1. RNF220 knockdown in Drosophila disrupts lamin Dm0 localization and causes neurodegeneration; primary patient fibroblasts with RNF220 mutations show nuclear morphology abnormalities (blebs, herniations).","method":"Mass spectrometry interactome, co-immunoprecipitation, Drosophila RNAi knockdown, patient fibroblast morphological analysis","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 2 — MS identification + co-IP + in vivo Drosophila model + human patient cells; multiple orthogonal methods","pmids":["33964137"],"is_preprint":false},{"year":2021,"finding":"RNF220-mediated K63-linked polyubiquitination promotes cytoplasmic Gli protein accumulation in aggresomes in an HDAC6-dependent manner; polyubiquitinated Gli interacts with p62 and undergoes autophagy-mediated degradation. RNF220 also inhibits Gli2 and Gli3 processing both in vitro and in vivo.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, aggresome detection, HDAC6 knockdown, p62 interaction assay, mouse in vivo analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical assays in single lab; in vitro and in vivo corroboration","pmids":["33895473"],"is_preprint":false},{"year":2022,"finding":"RNF220 directly interacts with AMPA receptor subunits (AMPARs) and mediates their polyubiquitination; RNF220 knockout specifically increases AMPAR protein levels, enhances basal synaptic activity, and impairs synaptic plasticity. Neuropathology-related RNF220 variants fail to repress AMPAR-mediated excitatory responses due to attenuated AMPAR interaction.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, forebrain-specific RNF220 KO mouse, electrophysiology (mEPSC recordings), surface biotinylation assay, behavioral tests (learning/memory), RING domain mutant analysis","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1–2 — reconstitution-level in vitro ubiquitination, KO mouse with electrophysiology and behavioral phenotypes, mutant validation","pmids":["36179027"],"is_preprint":false},{"year":2022,"finding":"RLIM ubiquitin E3 ligase directly ubiquitinates and stabilizes ZC4H2, which in turn stabilizes RNF220, forming an RLIM–ZC4H2–RNF220 cascade required for full Shh signaling activation in cerebellar granule neuron progenitors and medulloblastoma progression.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, RLIM knockdown/KO, cerebellar CGNP proliferation assays, clinical MB sample correlation","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP, in vitro ubiquitination, KD functional assay; single lab","pmids":["35040952"],"is_preprint":false},{"year":2023,"finding":"Smurf1 and Smurf2 E3 ubiquitin ligases interact with RNF220 and target it for polyubiquitination and proteasomal degradation, negatively regulating RNF220 protein levels and Shh signaling in medulloblastoma cells.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, Smurf1/2 knockdown/overexpression, xenograft assay, clinical MB sample protein correlation","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP, in vitro ubiquitination, functional KD/OE with xenograft; single lab","pmids":["37537194"],"is_preprint":false},{"year":2023,"finding":"RNF220 interacts with USP22 in gastric cancer cells; RNF220-mediated stabilization of the Wnt/β-catenin axis requires USP22, promoting cancer cell growth and stemness.","method":"Co-immunoprecipitation, Western blot, knockdown/overexpression, xenograft mouse model","journal":"Tissue & cell","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP and functional KD/OE, mechanistic pathway via USP22, single lab","pmids":["37295272"],"is_preprint":false},{"year":2024,"finding":"RNF220 mediates K63-linked polyubiquitination and stabilization of Olig1 and Olig2 transcription factors in oligodendroglial cells; RNF220 depletion in oligodendrocyte lineage impedes OPC proliferation, differentiation, and myelination, causing learning and memory defects. A leukodystrophy-associated RNF220R365Q knock-in mouse shows deregulated Olig ubiquitination and pathomimetic myelination defects.","method":"Conditional RNF220 KO in oligodendrocyte lineage, in vitro ubiquitination assay, K63-linkage-specific antibody, RNF220R365Q knock-in mouse, MBP immunostaining, behavioral tests","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro ubiquitination with linkage specificity, lineage-specific KO, disease knock-in model, multiple functional readouts","pmids":["38324685"],"is_preprint":false},{"year":2024,"finding":"RNF220 polyubiquitinates and degrades WDR5 (a key component of the TrxG/MLL complex); loss of RNF220 leads to WDR5 accumulation, de-repression of Hox gene expression in the pons, and disrupted pontine neural circuits. Genetic ablation of Wdr5 or pharmacological WDR5 inhibition rescues Hox de-repression in Rnf220-deficient mice.","method":"Rnf220 conditional KO mouse, single-nucleus RNA-seq, co-immunoprecipitation, in vitro ubiquitination assay, intrauterine WDR5 inhibitor injection, Wdr5 conditional ablation rescue experiment","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro ubiquitination, co-IP, KO mouse, genetic rescue; multiple orthogonal methods","pmids":["39526890"],"is_preprint":false},{"year":2025,"finding":"RNF220 directly binds the SH2 and TAD domains of STAT3 via its N-terminal domain and mediates K63-linked polyubiquitination at K615, K626, K631, and K642 of STAT3, stabilizing STAT3 protein and driving pro-hypertrophic transcriptional responses in cardiomyocytes.","method":"RNF220 KO and overexpression mouse, primary cardiomyocytes, proteomic mass spectrometry, co-immunoprecipitation, in vitro ubiquitination assay with site-directed mutagenesis, Ang II cardiac hypertrophy model, STAT3 inhibitor rescue","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1–2 — MS interactome, co-IP, in vitro ubiquitination with mutagenesis, KO/OE mouse models, pharmacological rescue","pmids":["41219491"],"is_preprint":false},{"year":2025,"finding":"RNF220 directly interacts with PDE10A and facilitates its K48-linked ubiquitination and proteasomal degradation; elevated RNF220 (stabilized by METTL3-mediated m6A modification of RNF220 mRNA via IGF2BP2) reduces PDE10A to drive cisplatin resistance and promote PD-L1 expression for immune evasion in bladder cancer.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, RNF220 overexpression/KD, m6A methylation assay, RNA pulldown, in vivo xenograft","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP + in vitro ubiquitination + functional KD/OE + in vivo model; single lab","pmids":["40158470"],"is_preprint":false},{"year":2025,"finding":"The N-terminally truncated RNF220 isoform 4 (ΔN-RNF220, 308 aa) is the predominant isoform in most non-brain tissues; isoform 4b displays distinct subcellular localization and subnuclear structures and interacts with WDR5. ΔN-RNF220 is the sole isoform expressed in murine myoblasts and is required for MyoD and myogenin expression and muscle differentiation.","method":"ChIP-seq (H3K4me3 ENCODE), Western blot isoform profiling, subcellular fractionation/immunofluorescence, co-immunoprecipitation with WDR5, siRNA knockdown in myoblasts, differentiation assays","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiments, co-IP, KD with functional differentiation phenotype; single lab","pmids":["40609864"],"is_preprint":false}],"current_model":"RNF220 is an evolutionarily conserved RING-type E3 ubiquitin ligase that modifies diverse substrates (Sin3B, Gli1/2/3, EED, Phox2a/b, STAT1, STAT3, TDP43, AMPA receptors, WDR5, Olig1/2, PDE10A) with K48- or K63-linked polyubiquitin chains or monoubiquitin, thereby regulating their stability, subcellular localization, or activity; it frequently acts in a complex with ZC4H2 (itself stabilized by RLIM), is itself degraded by Smurf1/2 and GSK3β, and controls multiple developmental and disease-relevant signaling pathways including Shh/Gli, Wnt/β-catenin, IFN-JAK-STAT1, and STAT3-mediated cardiac hypertrophy, as well as synaptic AMPAR levels, oligodendrocyte myelination, and Hox gene patterning in the hindbrain."},"narrative":{"teleology":[{"year":2010,"claim":"Establishing that RNF220 is an active E3 ubiquitin ligase answered the fundamental question of its molecular function: it binds E2 enzymes, auto-ubiquitinates, and targets Sin3B for K48-linked ubiquitination and proteasomal degradation, linking it to transcriptional corepressor regulation.","evidence":"Yeast two-hybrid, in vitro binding, co-IP, and ubiquitination assays in mammalian cells","pmids":["20170641"],"confidence":"High","gaps":["No in vivo phenotype from Sin3B degradation was shown","Substrate specificity beyond Sin3B was unknown","RING domain catalytic residue requirements not mapped"]},{"year":2014,"claim":"Revealing that RNF220 acts as a scaffold for the deubiquitinase USP7 to stabilize β-catenin showed that RNF220 can activate signaling pathways non-catalytically, expanding its functional repertoire beyond direct substrate ubiquitination.","evidence":"Co-IP, Wnt luciferase reporter, knockdown, ubiquitination assay, GSK3β epistasis in mammalian cells","pmids":["25266658"],"confidence":"High","gaps":["Whether RNF220 E3 ligase activity is required for USP7 recruitment was not resolved","In vivo developmental relevance of RNF220–Wnt axis not yet tested"]},{"year":2018,"claim":"Demonstrating that the RNF220/ZC4H2 complex degrades ventral spinal cord transcription factors (Dbx1/2, Nkx2.2) established RNF220 as a key patterning enzyme in neural tube development, with RNF220-null mice losing the p2 progenitor domain.","evidence":"RNF220 knockout mouse and chick spinal cord knockdown with co-IP and ubiquitination assays","pmids":["30177510"],"confidence":"High","gaps":["The precise ubiquitin chain type on these substrates was not determined","How ZC4H2 activates or directs RNF220 activity was mechanistically unclear"]},{"year":2020,"claim":"A cluster of studies in 2020 revealed that RNF220 employs distinct ubiquitin chain types to regulate diverse substrates—K63-linked chains on STAT1 to promote JAK1 interaction and IFN signaling, monoubiquitin on Phox2a/b to activate transcription in noradrenergic neurons, and ubiquitination of EED to modulate Shh-responsive histone marks—establishing RNF220 as a versatile ubiquitin writer with substrate-specific chain-type selectivity.","evidence":"Multiple KO mouse models, in vitro ubiquitination with K110R mutagenesis (STAT1), infection models, ChIP for histone marks (EED), LC-NA marker immunostaining (Phox2a/b)","pmids":["32896877","32094113","32376680"],"confidence":"High","gaps":["How chain-type specificity is determined for each substrate was not resolved","Whether these functions require ZC4H2 was not systematically tested for all substrates","The E2 partners conferring K63 versus K48 or monoubiquitin specificity were not identified"]},{"year":2020,"claim":"Parallel work showed ZC4H2 is required for RNF220 protein stability in vivo and that ZC4H2 and RNF220 KO animals phenocopy each other, solidifying the ZC4H2–RNF220 obligate complex as the functional unit for ventral neural patterning and Gli regulation.","evidence":"ZC4H2 and RNF220 KO in mouse and zebrafish with biochemical and immunostaining readouts","pmids":["31336385"],"confidence":"High","gaps":["Structural basis of ZC4H2-mediated RNF220 stabilization was unknown","Whether ZC4H2 also participates in non-Gli substrate ubiquitination remained untested"]},{"year":2021,"claim":"Identifying RNF220 as an E3 ligase for TDP43 proteasomal degradation, with haploinsufficient mice developing ALS-like pathology, directly implicated RNF220 in motor neuron disease mechanisms through TDP43 proteostasis failure.","evidence":"Co-IP, in vitro ubiquitination, RNF220+/− mouse with progressive motor deficits, TDP43 cytoplasmic accumulation, and muscle denervation","pmids":["33386850"],"confidence":"High","gaps":["Whether TDP43 ubiquitination is K48-linked was not explicitly shown","Human genetic association between RNF220 and ALS had not been established"]},{"year":2021,"claim":"Mass spectrometry identification of lamin B1 as an RNF220 interactor, combined with disease-mutant disruption of this interaction and nuclear envelope defects in patient fibroblasts, provided the first mechanistic link between RNF220 mutations and human neurodegeneration via nuclear lamina dysfunction.","evidence":"MS interactome, co-IP with disease mutants, Drosophila RNAi, patient fibroblast nuclear morphology","pmids":["33964137"],"confidence":"High","gaps":["Whether RNF220 ubiquitinates lamin B1 was not tested","The precise disease alleles' effect on other known substrates was not comprehensively assessed"]},{"year":2022,"claim":"Showing that RNF220 directly ubiquitinates AMPA receptor subunits to control their synaptic levels, with forebrain-specific KO mice exhibiting enhanced basal transmission and impaired plasticity, established RNF220 as a post-synaptic E3 ligase governing excitatory neurotransmission.","evidence":"Forebrain-specific RNF220 KO mouse, electrophysiology (mEPSC), surface biotinylation, in vitro ubiquitination, behavioral tests","pmids":["36179027"],"confidence":"High","gaps":["Which specific AMPAR subunit lysine residues are ubiquitinated was not mapped","Whether AMPAR ubiquitination is K48- or K63-linked was not determined"]},{"year":2022,"claim":"Delineation of the upstream RLIM–ZC4H2–RNF220 stabilization cascade showed that RLIM ubiquitinates ZC4H2 to prevent its degradation, thereby maintaining RNF220 levels required for Shh signaling in cerebellar granule neuron progenitors and medulloblastoma.","evidence":"Co-IP, in vitro ubiquitination, RLIM KO/KD, CGNP proliferation assay, clinical medulloblastoma samples","pmids":["35040952"],"confidence":"Medium","gaps":["The ubiquitin chain type on ZC4H2 was not determined","Whether RLIM regulation of the cascade operates outside the cerebellum was not tested","Single-lab finding"]},{"year":2023,"claim":"Identification of Smurf1/2 as E3 ligases that degrade RNF220 revealed a negative regulatory circuit controlling RNF220 protein levels and Shh signaling output in medulloblastoma cells.","evidence":"Co-IP, in vitro ubiquitination, Smurf1/2 KD/OE, xenograft tumor model, clinical sample correlation","pmids":["37537194"],"confidence":"Medium","gaps":["The degron motifs on RNF220 recognized by Smurf1/2 were not identified","Interplay with GSK3β-mediated destabilization was not integrated"]},{"year":2024,"claim":"Demonstrating that RNF220 K63-ubiquitinates and stabilizes Olig1/2 to drive oligodendrocyte differentiation and myelination, and that a leukodystrophy knock-in (R365Q) mouse recapitulates myelination defects, provided direct evidence that RNF220 mutations cause human leukodystrophy through defective oligodendrocyte function.","evidence":"Oligodendrocyte-lineage conditional KO, K63-linkage-specific ubiquitination, RNF220-R365Q knock-in mouse, MBP immunostaining, behavioral tests","pmids":["38324685"],"confidence":"High","gaps":["Whether other myelin-associated substrates are RNF220 targets was not explored","The structural basis for R365Q disrupting Olig ubiquitination is unknown"]},{"year":2024,"claim":"Showing that RNF220 ubiquitinates and degrades the TrxG/MLL component WDR5, with loss of RNF220 causing WDR5 accumulation and Hox gene de-repression in the pons, established RNF220 as an epigenetic regulator of hindbrain anteroposterior identity; genetic and pharmacological WDR5 rescue confirmed the epistatic relationship.","evidence":"Conditional KO mouse, snRNA-seq, co-IP, in vitro ubiquitination, WDR5 inhibitor rescue, Wdr5 conditional ablation","pmids":["39526890"],"confidence":"High","gaps":["The ubiquitin chain type on WDR5 was not specified","Whether RNF220–WDR5 regulation operates outside the hindbrain is unknown"]},{"year":2025,"claim":"Identification of STAT3 as a direct RNF220 substrate with K63-linked polyubiquitination at four mapped lysines, driving STAT3 stabilization and pro-hypertrophic gene programs, extended RNF220's role beyond the nervous system into cardiac pathophysiology.","evidence":"RNF220 KO/OE mouse, mass spectrometry, co-IP, site-directed mutagenesis of K615/K626/K631/K642, Ang II cardiac hypertrophy model, STAT3 inhibitor rescue","pmids":["41219491"],"confidence":"High","gaps":["Whether cardiomyocyte RNF220 operates with ZC4H2 was not tested","Therapeutic potential of targeting RNF220 in cardiac hypertrophy was not addressed"]},{"year":2025,"claim":"Discovery that a truncated ΔN-RNF220 isoform (isoform 4) is the predominant form in non-brain tissues, with distinct localization and a requirement for myoblast differentiation via MyoD/myogenin expression, revealed that tissue-specific isoform usage determines RNF220 function.","evidence":"Isoform-specific Western blot profiling, subcellular fractionation, co-IP with WDR5, siRNA KD in myoblasts with differentiation assay","pmids":["40609864"],"confidence":"Medium","gaps":["Whether ΔN-RNF220 has different substrate specificity than full-length was not determined","The isoform responsible for each known substrate interaction has not been systematically assigned"]},{"year":null,"claim":"Major unresolved questions include: how RNF220 achieves substrate-specific ubiquitin chain-type selectivity (K48 vs K63 vs mono), the structural basis of the ZC4H2–RNF220 complex and how ZC4H2 directs substrate recognition, the identity of cognate E2 enzymes for each chain type, and whether tissue-specific isoforms confer distinct substrate repertoires.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural data exist for RNF220 or ZC4H2–RNF220 complex","E2 partners are entirely uncharacterized","Isoform-substrate specificity mapping has not been performed"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,5,6,7,9,11,12,16,17,18,19]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,2,5,6,9,12,16,17,18,19]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[10,20]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,5,7,11,15,18]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,4,6,7,16,17]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,2,5,9,12,16,17,18,19]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[12]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,9,10,16]}],"complexes":["ZC4H2–RNF220 E3 ligase complex","RLIM–ZC4H2–RNF220 stabilization cascade"],"partners":["ZC4H2","USP7","LMNB1","WDR5","STAT1","STAT3","CTNNB1","TDP43"],"other_free_text":[]},"mechanistic_narrative":"RNF220 is a RING-type E3 ubiquitin ligase that modifies a broad repertoire of substrates with K48-linked, K63-linked, or monoubiquitin chains, thereby controlling protein stability, localization, or transcriptional activity across neural development, synaptic function, myelination, immune signaling, and cardiac hypertrophy. It ubiquitinates Sin3B, ventral spinal cord transcription factors (Dbx1/2, Nkx2.2), Gli proteins, Phox2a/b, EED, TDP43, AMPA receptors, WDR5, Olig1/2, STAT1, STAT3, and PDE10A, and frequently operates in a complex with ZC4H2, whose stability is maintained by RLIM [PMID:20170641, PMID:30177510, PMID:32094113, PMID:36179027, PMID:38324685, PMID:39526890, PMID:32896826, PMID:41219491, PMID:31336385, PMID:35040952]. RNF220 additionally scaffolds the deubiquitinase USP7 to stabilize β-catenin, amplifying Wnt signaling, and is itself targeted for degradation by Smurf1/2 and destabilized by GSK3β phosphorylation [PMID:25266658, PMID:37537194]. Loss-of-function mutations in RNF220 cause a leukodystrophy-spectrum neurodegenerative disorder in humans, with disease-associated variants disrupting lamin B1 interaction, nuclear envelope integrity, AMPA receptor regulation, and oligodendrocyte myelination [PMID:33964137, PMID:36179027, PMID:38324685]."},"prefetch_data":{"uniprot":{"accession":"Q5VTB9","full_name":"E3 ubiquitin-protein ligase RNF220","aliases":["RING finger protein 220","RING-type E3 ubiquitin transferase RNF220"],"length_aa":566,"mass_kda":62.8,"function":"E3 ubiquitin-protein ligase that promotes the ubiquitination and proteasomal degradation of SIN3B (By similarity). Independently of its E3 ligase activity, acts as a CTNNB1 stabilizer through USP7-mediated deubiquitination of CTNNB1 promoting Wnt signaling (PubMed:25266658, PubMed:33964137). Plays a critical role in the regulation of nuclear lamina (PubMed:33964137)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q5VTB9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RNF220","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RNF220","total_profiled":1310},"omim":[{"mim_id":"619688","title":"LEUKODYSTROPHY, HYPOMYELINATING, 23, WITH ATAXIA, DEAFNESS, LIVER DYSFUNCTION, AND DILATED CARDIOMYOPATHY; HLD23","url":"https://www.omim.org/entry/619688"},{"mim_id":"616136","title":"RING FINGER PROTEIN 220; RNF220","url":"https://www.omim.org/entry/616136"},{"mim_id":"312080","title":"PELIZAEUS-MERZBACHER DISEASE; PMD","url":"https://www.omim.org/entry/312080"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":85.5},{"tissue":"skeletal muscle","ntpm":22.8}],"url":"https://www.proteinatlas.org/search/RNF220"},"hgnc":{"alias_symbol":["FLJ10597"],"prev_symbol":["C1orf164"]},"alphafold":{"accession":"Q5VTB9","domains":[{"cath_id":"3.30.40.10","chopping":"402-418_490-566","consensus_level":"medium","plddt":91.1816,"start":402,"end":566}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VTB9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VTB9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VTB9-F1-predicted_aligned_error_v6.png","plddt_mean":58.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RNF220","jax_strain_url":"https://www.jax.org/strain/search?query=RNF220"},"sequence":{"accession":"Q5VTB9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5VTB9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5VTB9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VTB9"}},"corpus_meta":[{"pmid":"25266658","id":"PMC_25266658","title":"The ubiquitin ligase RNF220 enhances canonical Wnt signaling through USP7-mediated deubiquitination of β-catenin.","date":"2014","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/25266658","citation_count":81,"is_preprint":false},{"pmid":"34702297","id":"PMC_34702297","title":"CircRNF220, not its linear cognate gene RNF220, regulates cell growth and is associated with relapse in pediatric acute myeloid leukemia.","date":"2021","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34702297","citation_count":44,"is_preprint":false},{"pmid":"20170641","id":"PMC_20170641","title":"RNF220, an E3 ubiquitin ligase that targets Sin3B for ubiquitination.","date":"2010","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/20170641","citation_count":39,"is_preprint":false},{"pmid":"30177510","id":"PMC_30177510","title":"Rnf220 cooperates with Zc4h2 to specify spinal progenitor 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neurology","url":"https://pubmed.ncbi.nlm.nih.gov/33964137","citation_count":19,"is_preprint":false},{"pmid":"33386850","id":"PMC_33386850","title":"Haploinsufficiency of the TDP43 ubiquitin E3 ligase RNF220 leads to ALS-like motor neuron defects in the mouse.","date":"2021","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/33386850","citation_count":19,"is_preprint":false},{"pmid":"34716995","id":"PMC_34716995","title":"The many faces of the E3 ubiquitin ligase, RNF220, in neural development and beyond.","date":"2021","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/34716995","citation_count":17,"is_preprint":false},{"pmid":"32896826","id":"PMC_32896826","title":"RNF220 promotes the proliferation of leukaemic cells and reduces the degradation of the Cyclin D1 protein through USP22.","date":"2020","source":"Blood cells, molecules & diseases","url":"https://pubmed.ncbi.nlm.nih.gov/32896826","citation_count":17,"is_preprint":false},{"pmid":"32630355","id":"PMC_32630355","title":"Loss of ZC4H2 and RNF220 Inhibits Neural Stem Cell Proliferation and Promotes Neuronal Differentiation.","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/32630355","citation_count":16,"is_preprint":false},{"pmid":"37295272","id":"PMC_37295272","title":"RNF220 promotes gastric cancer growth and stemness via modulating the USP22/wnt/β-catenin pathway.","date":"2023","source":"Tissue & cell","url":"https://pubmed.ncbi.nlm.nih.gov/37295272","citation_count":13,"is_preprint":false},{"pmid":"30500349","id":"PMC_30500349","title":"A homozygous RNF220 mutation leads to male infertility with small-headed sperm.","date":"2018","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/30500349","citation_count":12,"is_preprint":false},{"pmid":"35040952","id":"PMC_35040952","title":"Sequential stabilization of RNF220 by RLIM and ZC4H2 during cerebellum development and Shh-group medulloblastoma progression.","date":"2022","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/35040952","citation_count":10,"is_preprint":false},{"pmid":"38324685","id":"PMC_38324685","title":"RNF220-mediated K63-linked polyubiquitination stabilizes Olig proteins during oligodendroglial development and myelination.","date":"2024","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/38324685","citation_count":7,"is_preprint":false},{"pmid":"37537194","id":"PMC_37537194","title":"Smurf1 and Smurf2 mediated polyubiquitination and degradation of RNF220 suppresses Shh-group medulloblastoma.","date":"2023","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/37537194","citation_count":6,"is_preprint":false},{"pmid":"40158470","id":"PMC_40158470","title":"N6-methyladenosine-modified RNF220 induces cisplatin resistance and immune escape via regulating PDE10A K48-linked ubiquitination in bladder cancer.","date":"2025","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40158470","citation_count":5,"is_preprint":false},{"pmid":"35399523","id":"PMC_35399523","title":"Rnf220 is Implicated in the Dorsoventral Patterning of the Hindbrain Neural Tube in Mice.","date":"2022","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/35399523","citation_count":5,"is_preprint":false},{"pmid":"33895473","id":"PMC_33895473","title":"RNF220-mediated ubiquitination promotes aggresomal accumulation and autophagic degradation of cytoplasmic Gli via HDAC6.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/33895473","citation_count":3,"is_preprint":false},{"pmid":"39526890","id":"PMC_39526890","title":"The E3 ubiquitin ligase RNF220 maintains hindbrain Hox expression patterns through regulation of WDR5 stability.","date":"2024","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/39526890","citation_count":2,"is_preprint":false},{"pmid":"37642089","id":"PMC_37642089","title":"The RNF220 domain nuclear factor Teyrha-Meyrha (Tey) regulates the migration and differentiation of specific visceral and somatic muscles in Drosophila.","date":"2023","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/37642089","citation_count":1,"is_preprint":false},{"pmid":"41219491","id":"PMC_41219491","title":"RNF220 mediates K63-linked polyubiquitination of STAT3 and aggravates pathological cardiac hypertrophy.","date":"2025","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/41219491","citation_count":0,"is_preprint":false},{"pmid":"40609864","id":"PMC_40609864","title":"N-Terminal deleted isoforms of E3 ligase RNF220 are ubiquitously expressed and required for mouse muscle differentiation.","date":"2025","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/40609864","citation_count":0,"is_preprint":false},{"pmid":"41244923","id":"PMC_41244923","title":"Dual oncogenic role of RNF220 in AML: linking metabolic rewiring to cell proliferation and immune evasion.","date":"2025","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41244923","citation_count":0,"is_preprint":false},{"pmid":"40938201","id":"PMC_40938201","title":"RNF220 enhances USP22 to promote cell growth, metastasis and stemness in hepatocellular carcinoma by activating the Akt pathway.","date":"2025","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/40938201","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.07.647521","title":"N-Terminal Deleted Isoforms of E3 Ligase RNF220 (Isoform 4) Are Ubiquitously Expressed and Required for Mouse Muscle Differentiation","date":"2025-04-09","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.07.647521","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.10.13.681987","title":"Distinct 5′ and 3′ Coverage Biases Shape Transcriptome Interpretation in Nanopore Direct RNA versus PCR-cDNA Sequencing","date":"2025-10-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.13.681987","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15510,"output_tokens":5353,"usd":0.063412},"stage2":{"model":"claude-opus-4-6","input_tokens":8916,"output_tokens":4249,"usd":0.226208},"total_usd":0.28962,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"RNF220 is a RING domain E3 ubiquitin ligase that binds E2 enzymes, undergoes auto-ubiquitination, and targets Sin3B (a scaffold protein of the Sin3/HDAC corepressor complex) for K48-linked ubiquitination and proteasomal degradation, identified via yeast two-hybrid screen with in vitro and in vivo interaction confirmation.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation, co-expression ubiquitination assay, proteasome inhibitor experiments\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (Y2H, in vitro binding, co-IP, ubiquitination assay) in a single study\",\n      \"pmids\": [\"20170641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNF220 physically interacts with β-catenin and with USP7 (a deubiquitinase); the RNF220/USP7 complex deubiquitinates β-catenin to stabilize it and enhance canonical Wnt signaling. RNF220 itself is destabilized by GSK3β phosphorylation, creating a positive feedback loop upon Wnt stimulation.\",\n      \"method\": \"Co-immunoprecipitation, knockdown experiments, luciferase Wnt reporter assay, ubiquitination assay, epistasis analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, functional reporter assays, knockdown phenotype, epistasis; moderate-to-strong evidence from single lab with multiple methods\",\n      \"pmids\": [\"25266658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RNF220 cooperates with the zinc-finger protein ZC4H2 to ubiquitinate and degrade ventral spinal cord transcription factors Dbx1, Dbx2, and Nkx2.2, thereby specifying ventral progenitor domains (including p2 domain producing V2 interneurons) during spinal cord patterning. RNF220-null mice lose the p2 domain.\",\n      \"method\": \"RNF220 knockout mouse, chick spinal cord knockdown, co-immunoprecipitation, co-expression ubiquitination assay, immunostaining of progenitor markers\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with specific domain phenotype, co-IP, biochemical ubiquitination assay, orthogonal chick model\",\n      \"pmids\": [\"30177510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A loss-of-function RNF220 mutation (p.P19L) in humans causes small-headed sperm by reducing RNF220 protein levels, leading to elevated Sin3B and excessive chromatin condensation in sperm.\",\n      \"method\": \"Whole-exome sequencing, Western blot, clinical phenotyping of consanguineous family\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — human genetics with mechanistic interpretation via Sin3B pathway, single study\",\n      \"pmids\": [\"30500349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ZC4H2 is required for RNF220 protein stability and proper Gli ubiquitination in vivo; ZC4H2 and RNF220 knockout animals phenocopy each other in ventral spinal cord patterning defects.\",\n      \"method\": \"ZC4H2 and RNF220 knockout mouse and zebrafish, immunostaining, Western blot, ubiquitination assay\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — parallel KO models in two species plus biochemical data; replicated epistasis\",\n      \"pmids\": [\"31336385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNF220 mediates K63-linked polyubiquitination of STAT1 at residue K110, which promotes the interaction between STAT1 and JAK1, enhancing STAT1 phosphorylation and activation of interferon-stimulated gene expression. RNF220 deficiency impairs IFN signaling and increases susceptibility to bacterial and viral infection.\",\n      \"method\": \"Rnf220 knockout mouse, in vitro ubiquitination assay, site-directed mutagenesis (K110R), co-immunoprecipitation, infection models (A. baumannii, HSV-1), ISG expression analysis\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination assay with mutagenesis, KO mouse with infection phenotype, mechanistic epistasis with JAK1\",\n      \"pmids\": [\"32814877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The RNF220/ZC4H2 complex monoubiquitylates Phox2a and Phox2b transcription factors, and this modification is required for full transcriptional activity of Phox2a/Phox2b and proper development of locus coeruleus noradrenergic neurons.\",\n      \"method\": \"Rnf220 and Zc4h2 knockout mouse, in vitro ubiquitination assay, co-immunoprecipitation, immunostaining of LC-NA markers\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — KO mouse, in vitro ubiquitination, co-IP, functional transcriptional readout\",\n      \"pmids\": [\"32094113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNF220 promotes Shh target gene expression in cerebellar granule neuron progenitors by targeting the PRC2 component EED for ubiquitination, altering histone modification marks on Shh target promoters. RNF220+/−; Ptch1+/− mice show lower spontaneous medulloblastoma occurrence.\",\n      \"method\": \"Conditional knockout mouse, Daoy cell knockdown, co-immunoprecipitation, ChIP for histone marks, xenograft assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO/KD, co-IP with EED, ChIP evidence for epigenetic mechanism, in vivo tumor model\",\n      \"pmids\": [\"32376680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNF220 promotes the stabilization of Cyclin D1 protein (without directly ubiquitinating it) through upregulation of the deubiquitinase USP22; RNF220 cannot stabilize Cyclin D1 without USP22, promoting G1-to-S phase transition in AML cells.\",\n      \"method\": \"Overexpression/knockdown in AML cell lines, co-immunoprecipitation, Western blot, cell cycle analysis, ubiquitination assay\",\n      \"journal\": \"Blood cells, molecules & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, co-IP and KD with phenotype, mechanistic pathway proposed via USP22\",\n      \"pmids\": [\"32896826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF220 interacts with TDP43 in vitro and in vivo and promotes its polyubiquitination and proteasomal degradation; RNF220+/− mice develop progressive mobility defects and ALS-like pathology including TDP43 cytoplasmic accumulation, astrocytosis, and muscle denervation in spinal motor neurons.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, RNF220 haploinsufficient mouse model, immunostaining, behavioral analysis\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP + in vitro ubiquitination + KO mouse with specific ALS-like cellular phenotypes\",\n      \"pmids\": [\"33386850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mass spectrometry identified lamin B1 as an RNF220-binding protein; co-immunoprecipitation showed reduced binding of RNF220 disease mutants (R363Q, R365Q) to lamin B1. RNF220 knockdown in Drosophila disrupts lamin Dm0 localization and causes neurodegeneration; primary patient fibroblasts with RNF220 mutations show nuclear morphology abnormalities (blebs, herniations).\",\n      \"method\": \"Mass spectrometry interactome, co-immunoprecipitation, Drosophila RNAi knockdown, patient fibroblast morphological analysis\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — MS identification + co-IP + in vivo Drosophila model + human patient cells; multiple orthogonal methods\",\n      \"pmids\": [\"33964137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF220-mediated K63-linked polyubiquitination promotes cytoplasmic Gli protein accumulation in aggresomes in an HDAC6-dependent manner; polyubiquitinated Gli interacts with p62 and undergoes autophagy-mediated degradation. RNF220 also inhibits Gli2 and Gli3 processing both in vitro and in vivo.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, aggresome detection, HDAC6 knockdown, p62 interaction assay, mouse in vivo analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical assays in single lab; in vitro and in vivo corroboration\",\n      \"pmids\": [\"33895473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RNF220 directly interacts with AMPA receptor subunits (AMPARs) and mediates their polyubiquitination; RNF220 knockout specifically increases AMPAR protein levels, enhances basal synaptic activity, and impairs synaptic plasticity. Neuropathology-related RNF220 variants fail to repress AMPAR-mediated excitatory responses due to attenuated AMPAR interaction.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, forebrain-specific RNF220 KO mouse, electrophysiology (mEPSC recordings), surface biotinylation assay, behavioral tests (learning/memory), RING domain mutant analysis\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstitution-level in vitro ubiquitination, KO mouse with electrophysiology and behavioral phenotypes, mutant validation\",\n      \"pmids\": [\"36179027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RLIM ubiquitin E3 ligase directly ubiquitinates and stabilizes ZC4H2, which in turn stabilizes RNF220, forming an RLIM–ZC4H2–RNF220 cascade required for full Shh signaling activation in cerebellar granule neuron progenitors and medulloblastoma progression.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, RLIM knockdown/KO, cerebellar CGNP proliferation assays, clinical MB sample correlation\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP, in vitro ubiquitination, KD functional assay; single lab\",\n      \"pmids\": [\"35040952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Smurf1 and Smurf2 E3 ubiquitin ligases interact with RNF220 and target it for polyubiquitination and proteasomal degradation, negatively regulating RNF220 protein levels and Shh signaling in medulloblastoma cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, Smurf1/2 knockdown/overexpression, xenograft assay, clinical MB sample protein correlation\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP, in vitro ubiquitination, functional KD/OE with xenograft; single lab\",\n      \"pmids\": [\"37537194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RNF220 interacts with USP22 in gastric cancer cells; RNF220-mediated stabilization of the Wnt/β-catenin axis requires USP22, promoting cancer cell growth and stemness.\",\n      \"method\": \"Co-immunoprecipitation, Western blot, knockdown/overexpression, xenograft mouse model\",\n      \"journal\": \"Tissue & cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP and functional KD/OE, mechanistic pathway via USP22, single lab\",\n      \"pmids\": [\"37295272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF220 mediates K63-linked polyubiquitination and stabilization of Olig1 and Olig2 transcription factors in oligodendroglial cells; RNF220 depletion in oligodendrocyte lineage impedes OPC proliferation, differentiation, and myelination, causing learning and memory defects. A leukodystrophy-associated RNF220R365Q knock-in mouse shows deregulated Olig ubiquitination and pathomimetic myelination defects.\",\n      \"method\": \"Conditional RNF220 KO in oligodendrocyte lineage, in vitro ubiquitination assay, K63-linkage-specific antibody, RNF220R365Q knock-in mouse, MBP immunostaining, behavioral tests\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination with linkage specificity, lineage-specific KO, disease knock-in model, multiple functional readouts\",\n      \"pmids\": [\"38324685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF220 polyubiquitinates and degrades WDR5 (a key component of the TrxG/MLL complex); loss of RNF220 leads to WDR5 accumulation, de-repression of Hox gene expression in the pons, and disrupted pontine neural circuits. Genetic ablation of Wdr5 or pharmacological WDR5 inhibition rescues Hox de-repression in Rnf220-deficient mice.\",\n      \"method\": \"Rnf220 conditional KO mouse, single-nucleus RNA-seq, co-immunoprecipitation, in vitro ubiquitination assay, intrauterine WDR5 inhibitor injection, Wdr5 conditional ablation rescue experiment\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination, co-IP, KO mouse, genetic rescue; multiple orthogonal methods\",\n      \"pmids\": [\"39526890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RNF220 directly binds the SH2 and TAD domains of STAT3 via its N-terminal domain and mediates K63-linked polyubiquitination at K615, K626, K631, and K642 of STAT3, stabilizing STAT3 protein and driving pro-hypertrophic transcriptional responses in cardiomyocytes.\",\n      \"method\": \"RNF220 KO and overexpression mouse, primary cardiomyocytes, proteomic mass spectrometry, co-immunoprecipitation, in vitro ubiquitination assay with site-directed mutagenesis, Ang II cardiac hypertrophy model, STAT3 inhibitor rescue\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — MS interactome, co-IP, in vitro ubiquitination with mutagenesis, KO/OE mouse models, pharmacological rescue\",\n      \"pmids\": [\"41219491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RNF220 directly interacts with PDE10A and facilitates its K48-linked ubiquitination and proteasomal degradation; elevated RNF220 (stabilized by METTL3-mediated m6A modification of RNF220 mRNA via IGF2BP2) reduces PDE10A to drive cisplatin resistance and promote PD-L1 expression for immune evasion in bladder cancer.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, RNF220 overexpression/KD, m6A methylation assay, RNA pulldown, in vivo xenograft\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP + in vitro ubiquitination + functional KD/OE + in vivo model; single lab\",\n      \"pmids\": [\"40158470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The N-terminally truncated RNF220 isoform 4 (ΔN-RNF220, 308 aa) is the predominant isoform in most non-brain tissues; isoform 4b displays distinct subcellular localization and subnuclear structures and interacts with WDR5. ΔN-RNF220 is the sole isoform expressed in murine myoblasts and is required for MyoD and myogenin expression and muscle differentiation.\",\n      \"method\": \"ChIP-seq (H3K4me3 ENCODE), Western blot isoform profiling, subcellular fractionation/immunofluorescence, co-immunoprecipitation with WDR5, siRNA knockdown in myoblasts, differentiation assays\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiments, co-IP, KD with functional differentiation phenotype; single lab\",\n      \"pmids\": [\"40609864\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RNF220 is an evolutionarily conserved RING-type E3 ubiquitin ligase that modifies diverse substrates (Sin3B, Gli1/2/3, EED, Phox2a/b, STAT1, STAT3, TDP43, AMPA receptors, WDR5, Olig1/2, PDE10A) with K48- or K63-linked polyubiquitin chains or monoubiquitin, thereby regulating their stability, subcellular localization, or activity; it frequently acts in a complex with ZC4H2 (itself stabilized by RLIM), is itself degraded by Smurf1/2 and GSK3β, and controls multiple developmental and disease-relevant signaling pathways including Shh/Gli, Wnt/β-catenin, IFN-JAK-STAT1, and STAT3-mediated cardiac hypertrophy, as well as synaptic AMPAR levels, oligodendrocyte myelination, and Hox gene patterning in the hindbrain.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RNF220 is a RING-type E3 ubiquitin ligase that modifies a broad repertoire of substrates with K48-linked, K63-linked, or monoubiquitin chains, thereby controlling protein stability, localization, or transcriptional activity across neural development, synaptic function, myelination, immune signaling, and cardiac hypertrophy. It ubiquitinates Sin3B, ventral spinal cord transcription factors (Dbx1/2, Nkx2.2), Gli proteins, Phox2a/b, EED, TDP43, AMPA receptors, WDR5, Olig1/2, STAT1, STAT3, and PDE10A, and frequently operates in a complex with ZC4H2, whose stability is maintained by RLIM [PMID:20170641, PMID:30177510, PMID:32094113, PMID:36179027, PMID:38324685, PMID:39526890, PMID:32896826, PMID:41219491, PMID:31336385, PMID:35040952]. RNF220 additionally scaffolds the deubiquitinase USP7 to stabilize β-catenin, amplifying Wnt signaling, and is itself targeted for degradation by Smurf1/2 and destabilized by GSK3β phosphorylation [PMID:25266658, PMID:37537194]. Loss-of-function mutations in RNF220 cause a leukodystrophy-spectrum neurodegenerative disorder in humans, with disease-associated variants disrupting lamin B1 interaction, nuclear envelope integrity, AMPA receptor regulation, and oligodendrocyte myelination [PMID:33964137, PMID:36179027, PMID:38324685].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Establishing that RNF220 is an active E3 ubiquitin ligase answered the fundamental question of its molecular function: it binds E2 enzymes, auto-ubiquitinates, and targets Sin3B for K48-linked ubiquitination and proteasomal degradation, linking it to transcriptional corepressor regulation.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, co-IP, and ubiquitination assays in mammalian cells\",\n      \"pmids\": [\"20170641\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo phenotype from Sin3B degradation was shown\", \"Substrate specificity beyond Sin3B was unknown\", \"RING domain catalytic residue requirements not mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealing that RNF220 acts as a scaffold for the deubiquitinase USP7 to stabilize β-catenin showed that RNF220 can activate signaling pathways non-catalytically, expanding its functional repertoire beyond direct substrate ubiquitination.\",\n      \"evidence\": \"Co-IP, Wnt luciferase reporter, knockdown, ubiquitination assay, GSK3β epistasis in mammalian cells\",\n      \"pmids\": [\"25266658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RNF220 E3 ligase activity is required for USP7 recruitment was not resolved\", \"In vivo developmental relevance of RNF220–Wnt axis not yet tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that the RNF220/ZC4H2 complex degrades ventral spinal cord transcription factors (Dbx1/2, Nkx2.2) established RNF220 as a key patterning enzyme in neural tube development, with RNF220-null mice losing the p2 progenitor domain.\",\n      \"evidence\": \"RNF220 knockout mouse and chick spinal cord knockdown with co-IP and ubiquitination assays\",\n      \"pmids\": [\"30177510\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The precise ubiquitin chain type on these substrates was not determined\", \"How ZC4H2 activates or directs RNF220 activity was mechanistically unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A cluster of studies in 2020 revealed that RNF220 employs distinct ubiquitin chain types to regulate diverse substrates—K63-linked chains on STAT1 to promote JAK1 interaction and IFN signaling, monoubiquitin on Phox2a/b to activate transcription in noradrenergic neurons, and ubiquitination of EED to modulate Shh-responsive histone marks—establishing RNF220 as a versatile ubiquitin writer with substrate-specific chain-type selectivity.\",\n      \"evidence\": \"Multiple KO mouse models, in vitro ubiquitination with K110R mutagenesis (STAT1), infection models, ChIP for histone marks (EED), LC-NA marker immunostaining (Phox2a/b)\",\n      \"pmids\": [\"32896877\", \"32094113\", \"32376680\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How chain-type specificity is determined for each substrate was not resolved\", \"Whether these functions require ZC4H2 was not systematically tested for all substrates\", \"The E2 partners conferring K63 versus K48 or monoubiquitin specificity were not identified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Parallel work showed ZC4H2 is required for RNF220 protein stability in vivo and that ZC4H2 and RNF220 KO animals phenocopy each other, solidifying the ZC4H2–RNF220 obligate complex as the functional unit for ventral neural patterning and Gli regulation.\",\n      \"evidence\": \"ZC4H2 and RNF220 KO in mouse and zebrafish with biochemical and immunostaining readouts\",\n      \"pmids\": [\"31336385\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ZC4H2-mediated RNF220 stabilization was unknown\", \"Whether ZC4H2 also participates in non-Gli substrate ubiquitination remained untested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identifying RNF220 as an E3 ligase for TDP43 proteasomal degradation, with haploinsufficient mice developing ALS-like pathology, directly implicated RNF220 in motor neuron disease mechanisms through TDP43 proteostasis failure.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitination, RNF220+/− mouse with progressive motor deficits, TDP43 cytoplasmic accumulation, and muscle denervation\",\n      \"pmids\": [\"33386850\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TDP43 ubiquitination is K48-linked was not explicitly shown\", \"Human genetic association between RNF220 and ALS had not been established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Mass spectrometry identification of lamin B1 as an RNF220 interactor, combined with disease-mutant disruption of this interaction and nuclear envelope defects in patient fibroblasts, provided the first mechanistic link between RNF220 mutations and human neurodegeneration via nuclear lamina dysfunction.\",\n      \"evidence\": \"MS interactome, co-IP with disease mutants, Drosophila RNAi, patient fibroblast nuclear morphology\",\n      \"pmids\": [\"33964137\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RNF220 ubiquitinates lamin B1 was not tested\", \"The precise disease alleles' effect on other known substrates was not comprehensively assessed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showing that RNF220 directly ubiquitinates AMPA receptor subunits to control their synaptic levels, with forebrain-specific KO mice exhibiting enhanced basal transmission and impaired plasticity, established RNF220 as a post-synaptic E3 ligase governing excitatory neurotransmission.\",\n      \"evidence\": \"Forebrain-specific RNF220 KO mouse, electrophysiology (mEPSC), surface biotinylation, in vitro ubiquitination, behavioral tests\",\n      \"pmids\": [\"36179027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific AMPAR subunit lysine residues are ubiquitinated was not mapped\", \"Whether AMPAR ubiquitination is K48- or K63-linked was not determined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Delineation of the upstream RLIM–ZC4H2–RNF220 stabilization cascade showed that RLIM ubiquitinates ZC4H2 to prevent its degradation, thereby maintaining RNF220 levels required for Shh signaling in cerebellar granule neuron progenitors and medulloblastoma.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitination, RLIM KO/KD, CGNP proliferation assay, clinical medulloblastoma samples\",\n      \"pmids\": [\"35040952\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The ubiquitin chain type on ZC4H2 was not determined\", \"Whether RLIM regulation of the cascade operates outside the cerebellum was not tested\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of Smurf1/2 as E3 ligases that degrade RNF220 revealed a negative regulatory circuit controlling RNF220 protein levels and Shh signaling output in medulloblastoma cells.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitination, Smurf1/2 KD/OE, xenograft tumor model, clinical sample correlation\",\n      \"pmids\": [\"37537194\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The degron motifs on RNF220 recognized by Smurf1/2 were not identified\", \"Interplay with GSK3β-mediated destabilization was not integrated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrating that RNF220 K63-ubiquitinates and stabilizes Olig1/2 to drive oligodendrocyte differentiation and myelination, and that a leukodystrophy knock-in (R365Q) mouse recapitulates myelination defects, provided direct evidence that RNF220 mutations cause human leukodystrophy through defective oligodendrocyte function.\",\n      \"evidence\": \"Oligodendrocyte-lineage conditional KO, K63-linkage-specific ubiquitination, RNF220-R365Q knock-in mouse, MBP immunostaining, behavioral tests\",\n      \"pmids\": [\"38324685\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other myelin-associated substrates are RNF220 targets was not explored\", \"The structural basis for R365Q disrupting Olig ubiquitination is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showing that RNF220 ubiquitinates and degrades the TrxG/MLL component WDR5, with loss of RNF220 causing WDR5 accumulation and Hox gene de-repression in the pons, established RNF220 as an epigenetic regulator of hindbrain anteroposterior identity; genetic and pharmacological WDR5 rescue confirmed the epistatic relationship.\",\n      \"evidence\": \"Conditional KO mouse, snRNA-seq, co-IP, in vitro ubiquitination, WDR5 inhibitor rescue, Wdr5 conditional ablation\",\n      \"pmids\": [\"39526890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The ubiquitin chain type on WDR5 was not specified\", \"Whether RNF220–WDR5 regulation operates outside the hindbrain is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of STAT3 as a direct RNF220 substrate with K63-linked polyubiquitination at four mapped lysines, driving STAT3 stabilization and pro-hypertrophic gene programs, extended RNF220's role beyond the nervous system into cardiac pathophysiology.\",\n      \"evidence\": \"RNF220 KO/OE mouse, mass spectrometry, co-IP, site-directed mutagenesis of K615/K626/K631/K642, Ang II cardiac hypertrophy model, STAT3 inhibitor rescue\",\n      \"pmids\": [\"41219491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cardiomyocyte RNF220 operates with ZC4H2 was not tested\", \"Therapeutic potential of targeting RNF220 in cardiac hypertrophy was not addressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that a truncated ΔN-RNF220 isoform (isoform 4) is the predominant form in non-brain tissues, with distinct localization and a requirement for myoblast differentiation via MyoD/myogenin expression, revealed that tissue-specific isoform usage determines RNF220 function.\",\n      \"evidence\": \"Isoform-specific Western blot profiling, subcellular fractionation, co-IP with WDR5, siRNA KD in myoblasts with differentiation assay\",\n      \"pmids\": [\"40609864\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ΔN-RNF220 has different substrate specificity than full-length was not determined\", \"The isoform responsible for each known substrate interaction has not been systematically assigned\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include: how RNF220 achieves substrate-specific ubiquitin chain-type selectivity (K48 vs K63 vs mono), the structural basis of the ZC4H2–RNF220 complex and how ZC4H2 directs substrate recognition, the identity of cognate E2 enzymes for each chain type, and whether tissue-specific isoforms confer distinct substrate repertoires.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural data exist for RNF220 or ZC4H2–RNF220 complex\", \"E2 partners are entirely uncharacterized\", \"Isoform-substrate specificity mapping has not been performed\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 5, 6, 7, 9, 11, 12, 16, 17, 18, 19]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 2, 5, 6, 9, 12, 16, 17, 18, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [10, 20]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 5, 7, 11, 15, 18]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 4, 6, 7, 16, 17]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 2, 5, 9, 12, 16, 17, 18, 19]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 9, 10, 16]}\n    ],\n    \"complexes\": [\n      \"ZC4H2–RNF220 E3 ligase complex\",\n      \"RLIM–ZC4H2–RNF220 stabilization cascade\"\n    ],\n    \"partners\": [\n      \"ZC4H2\",\n      \"USP7\",\n      \"LMNB1\",\n      \"WDR5\",\n      \"STAT1\",\n      \"STAT3\",\n      \"CTNNB1\",\n      \"TDP43\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}