{"gene":"EXOSC1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2000,"finding":"The SKI4 gene is identical to CSL4, which encodes a core component of the exosome. A point mutation in the putative RNA-binding domain of Csl4p (ski4-1, G253E) strongly impairs 3'-to-5' mRNA degradation without affecting exosome function in rRNA or snRNA processing, demonstrating that distinct exosome functions can be genetically separated and that the RNA-binding domain of Csl4p has a specific role in mRNA degradation.","method":"Genetic epistasis, allele identification, mRNA half-life assays, RNA processing assays in S. cerevisiae","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal functional assays (mRNA decay, rRNA processing, snRNA processing) with defined point mutations, replicated across alleles in a single rigorous study","pmids":["11027292"],"is_preprint":false},{"year":2001,"finding":"The human protein hCsl4p is a component of the human exosome (PM/Scl complex), as evidenced by autoantibodies in patients with idiopathic inflammatory myopathy and PM/Scl overlap syndrome targeting hCsl4p along with other exosome subunits.","method":"ELISA and Western blotting with affinity-purified recombinant hCsl4p using patient sera","journal":"Arthritis research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — detection of autoantibody binding to recombinant hCsl4p establishes it as an exosome component in human cells, single lab but two orthogonal methods (ELISA + Western blot)","pmids":["11879549"],"is_preprint":false},{"year":2002,"finding":"Human hCsl4p directly interacts with exosome subunits hRrp42p and hRrp46p, and these protein-protein interactions are required for hCsl4p's association with the exosome complex in vivo. Mutants of hCsl4p that fail to interact with either hRrp42p or hRrp46p cannot associate with the exosome.","method":"Mammalian two-hybrid assay, GST pull-down, co-immunoprecipitation from cell lysates","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal binding established by multiple orthogonal methods (two-hybrid + GST pulldown + in vivo co-IP), with loss-of-function mutant validation in a single lab","pmids":["11812149"],"is_preprint":false},{"year":2005,"finding":"Crystal structures of archaeal exosome isoforms revealed that Csl4 (along with Rrp4) forms a trimeric cap on top of the hexameric RNase-PH domain ring. The S1 domains of this cap and a 'neck' region of the RNase-PH ring form an RNA entry pore that restricts access to unstructured RNA, explaining processive degradation of unstructured RNA and the requirement for cofactors to degrade structured RNA.","method":"X-ray crystallography of archaeal exosome, tungstate soaks, structural and mutational analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with active-site identification and mutational validation; foundational structural paper replicated by subsequent studies","pmids":["16285927"],"is_preprint":false},{"year":2007,"finding":"Crystal structure of the Sulfolobus solfataricus nine-subunit exosome with bound RNA substrate shows that RNA binds both at the active site and at the opposite side in the narrowest constriction of the central channel, establishing that Csl4 contributes to the RNA-binding cap that channels substrate through the central pore for processive degradation.","method":"X-ray crystallography at 1.6 Å and 2.3 Å resolution with RNA-bound complex","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with substrate-bound form, mechanistically rationalizes processive degradation and RNA stalling","pmids":["17380186"],"is_preprint":false},{"year":2008,"finding":"In yeast (Csl4/Ski4p), the zinc-ribbon domain of Csl4 is required for exosome-mediated mRNA decay but none of its domains are individually required for viability, indicating that specific structural domains contribute to specific exosome functions.","method":"Domain deletion analysis in S. cerevisiae with mRNA decay assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — domain deletion with defined functional readout (mRNA decay vs. viability), multiple domain constructs tested in a single rigorous study","pmids":["19060898"],"is_preprint":false},{"year":2008,"finding":"Archaeal Csl4, when incorporated into the nine-subunit exosome (Csl4-exosome), enhances efficient degradation of structured RNA substrates (tRNA, heteropolymeric transcripts) by the catalytic Rrp41-Rrp42 hexamer. Csl4 itself has no hydrolytic RNase activity alone or in context of the complex, but strong substrate binding mediated by Csl4 is important for phosphorolysis.","method":"In vitro reconstitution of archaeal exosome complexes with different subunit compositions, RNase activity assays under varied conditions","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with defined subunit combinations, multiple substrates and conditions tested, single lab","pmids":["19053279"],"is_preprint":false},{"year":2010,"finding":"Archaeal Csl4 confers different substrate specificity to the exosome compared with Rrp4: the Csl4-exosome degrades RNA with an A-poor 3'-end with higher efficiency, while the Rrp4-exosome strongly prefers poly(A) RNA. This establishes that Csl4 and Rrp4 have distinct functional roles in substrate selection.","method":"In vitro RNA degradation assays with reconstituted archaeal exosome complexes containing defined Rrp4 or Csl4 caps","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with comparative substrate specificity assays across multiple RNA substrates, single lab","pmids":["20488184"],"is_preprint":false},{"year":2010,"finding":"The Csl4-exosome (archaeal) interacts with the archaea-specific DnaG subunit, which binds to the Csl4-exosome but not to the Rrp4-exosome, showing that Csl4 mediates DnaG recruitment to the exosome complex.","method":"In vitro binding assays with reconstituted complexes; co-purification","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — interaction demonstrated in vitro with reconstituted complexes, single lab, single method","pmids":["20488184"],"is_preprint":false},{"year":2011,"finding":"Human hCsl4p functionally rescues the null phenotype of yeast ski4Δ cells and partially complements the superkiller phenotype of ski4-1 mutation. The equivalent point mutation G152E in hCsl4p (corresponding to yeast ski4-1 G253E) impairs hCsl4p activity. hCsl4p physically interacts with the Dis3p exonuclease of the yeast exosome despite lacking the N-terminal third of Ski4p. This N-terminal third of Ski4p is dispensable for RNA degradation function.","method":"Yeast complementation assays, superkiller phenotype analysis, co-immunoprecipitation with Dis3p, site-directed mutagenesis","journal":"Yeast","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional rescue, physical interaction by co-IP, and point mutation analysis all in one study; multiple orthogonal methods confirming the same conclusion","pmids":["22068837"],"is_preprint":false},{"year":2013,"finding":"The archaeal DnaG protein binds to the Csl4-exosome but not to the Rrp4-exosome of Sulfolobus solfataricus. DnaG is a poly(A)-binding protein that enhances degradation of adenine-rich transcripts specifically in the context of the Csl4-exosome, functioning as a second poly(A)-binding subunit in the heteromeric RNA-binding cap.","method":"In vitro binding assays, RNA degradation assays with reconstituted exosome complexes, poly(A)-binding assays","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal in vitro assays (binding + degradation), mechanistic specificity shown by comparing Csl4- vs Rrp4-exosomes, single lab","pmids":["23324612"],"is_preprint":false},{"year":2014,"finding":"Archaeal Csl4 is involved in the interaction with the archaea-specific DnaG subunit of the exosome complex. In the archaeal exosome, Rrp4 confers poly(A) specificity while Csl4 mediates DnaG association. Both Rrp4 and Csl4 form a variable RNA-binding trimeric cap on the hexameric ring.","method":"Biochemical reconstitution, subunit interaction analysis, in vitro RNA degradation assays","journal":"Wiley interdisciplinary reviews. RNA","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — review synthesizing multiple experimental findings from same lab, citing reconstitution experiments; moderate confidence as it is a review rather than original data paper","pmids":["24789718"],"is_preprint":false},{"year":2021,"finding":"A homozygous missense variant p.Ser35Leu in EXOSC1 reduces EXOSC1 protein levels and reduces the EXO9 (nine-subunit exosome) complex abundance in patient cells, establishing that EXOSC1 is required for stable EXO9 complex formation in human cells and that loss of EXOSC1 function causes pontocerebellar hypoplasia type 1.","method":"Immunoblotting, blue native PAGE, exome sequencing, in silico mutagenesis of protein structure","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — two orthogonal biochemical methods (immunoblotting + BN-PAGE) showing loss of protein and complex, single lab, patient-derived material","pmids":["33463720"],"is_preprint":false},{"year":2021,"finding":"EXOSC1 cleaves single-stranded DNA preferentially at C sites in vitro, acts as an endogenous source of mutations via C>A transversions in human kidney renal clear cell carcinoma cells, and sensitizes these cells to PARP inhibitors.","method":"In vitro ssDNA cleavage assays, statistical correlation of EXOSC1 expression with mutation spectra in KIRC, cell sensitivity assays with PARP inhibitors","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — in vitro enzymatic activity on ssDNA combined with cellular mutation pattern analysis; novel claimed activity (ssDNA cleavage) not independently replicated","pmids":["34159897"],"is_preprint":false},{"year":2023,"finding":"The EXOSC1 variant p.Arg183Trp causes a slow-growth phenotype in yeast when expressed as the human variant, while EXOSC1-Ser35Leu is lethal in the same model, demonstrating impaired exosome function. Protein levels of both EXOSC1 variants are reduced compared with wild-type when expressed in budding yeast, confirming pathogenicity through reduced protein stability.","method":"Yeast complementation and growth assays, Western blotting for protein levels in yeast","journal":"American journal of medical genetics. Part A","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional growth assay and protein quantification, two independent EXOSC1 variants tested, yeast model system","pmids":["37024942"],"is_preprint":false},{"year":2023,"finding":"Exosc1 null mouse embryos implant and form an egg cylinder but are developmentally delayed and fail to initiate gastrulation by embryonic day 7.5, demonstrating that EXOSC1 is essential for early mammalian development at the gastrulation stage.","method":"Homozygous knockout mouse embryo analysis, embryo recovery at defined developmental stages, morphological and lineage-specification analysis","journal":"Gene expression patterns","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean knockout with defined developmental phenotype, single study, no molecular rescue performed","pmids":["37940010"],"is_preprint":false},{"year":2025,"finding":"CARM1 methylates arginine 6 of EXOSC1, protecting it from proteasome-mediated degradation. This post-translational methylation event enhances RNA exosome activity, attenuates nuclear export of retroelement transcripts by the mRNA export pathway, and thereby suppresses the viral mimicry response and antitumor immunity.","method":"Mass spectrometry identification of methylation site, proteasome inhibitor assays, RNAseq, functional pathway analysis in tumor cell lines","journal":"Science translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry identification of specific PTM site combined with functional consequences, single lab, novel finding","pmids":["40203080"],"is_preprint":false},{"year":2025,"finding":"Using inducible CRISPR/Cas9 knockouts in mouse embryonic stem cells, Exosc1 is identified as the terminally incorporated cap subunit in a sequential RNA exosome assembly pathway (initiated by Exosc2, Exosc4, and Exosc7). Unlike other structural subunits, Exosc1 is dispensable for cell viability, revealing that the RNA exosome has a modular, functionally resilient architecture. Orphan exosome subunits are degraded by the ubiquitin-proteasome system.","method":"Inducible dual-guide CRISPR/Cas9 knockout system in mESCs, proteomics, assembly hierarchy analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic genetic perturbation with proteomics readout, multiple subunits tested, preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.03.14.643291"],"is_preprint":true}],"current_model":"EXOSC1 (hCsl4p/Csl4p) is a structural cap subunit of the RNA exosome that is terminally incorporated into the complex during a sequential assembly process, where it directly interacts with exosome subunits EXOSC6 (hRrp46p) and EXOSC7 (hRrp42p) to anchor into the nine-subunit ring; its zinc-ribbon and S1 RNA-binding domains contribute to substrate-specific mRNA degradation (but not to rRNA/snRNA processing or viability), it channels structured RNA substrates to the catalytic core, it is stabilized by CARM1-mediated arginine-6 methylation that prevents proteasomal degradation, and loss of EXOSC1 disrupts EXO9 complex integrity and causes pontocerebellar hypoplasia in humans and failure of gastrulation in mice."},"narrative":{"mechanistic_narrative":"EXOSC1 (hCsl4p/Csl4p) is a structural cap subunit of the RNA exosome, the conserved 3'-to-5' RNA-degradation machine, where it sits atop the hexameric RNase-PH ring and helps form the RNA-binding cap that channels substrate through the central pore for processive degradation [PMID:16285927, PMID:17380186]. In human cells it incorporates into the exosome through direct protein-protein interactions with the EXOSC6 (hRrp42p) and EXOSC7 (hRrp46p) subunits, and mutants unable to bind these partners fail to associate with the complex [PMID:11812149]; EXOSC1 is required for stable assembly of the nine-subunit EXO9 complex [PMID:33463720]. EXOSC1 is itself catalytically inert but contributes substrate specificity and binding: its zinc-ribbon and S1 RNA-binding domains are required for exosome-mediated mRNA decay yet are dispensable for rRNA/snRNA processing and viability, genetically separating distinct exosome functions, and cap-conferred substrate binding promotes degradation of structured RNAs and transcripts with particular 3'-end composition [PMID:11027292, PMID:19060898, PMID:19053279, PMID:20488184]. Human EXOSC1 functionally substitutes for yeast Csl4p and physically interacts with the catalytic Dis3p exonuclease [PMID:22068837]. CARM1-mediated methylation of arginine 6 protects EXOSC1 from proteasomal degradation, thereby enhancing exosome activity and suppressing the viral-mimicry response by limiting nuclear export of retroelement transcripts [PMID:40203080]. Loss-of-function variants cause pontocerebellar hypoplasia type 1 by reducing EXOSC1 protein and EXO9 complex abundance [PMID:33463720, PMID:37024942], and Exosc1-null mouse embryos fail to initiate gastrulation, establishing an essential developmental role [PMID:37940010]. A reported in vitro single-stranded DNA cleavage activity links EXOSC1 to C>A mutational signatures in renal carcinoma cells [PMID:34159897].","teleology":[{"year":2000,"claim":"Established that the exosome cap subunit Csl4p carries a function-specific RNA-binding domain, separating mRNA degradation from rRNA/snRNA processing.","evidence":"Genetic epistasis and a point mutation (ski4-1, G253E) with mRNA half-life and RNA processing assays in S. cerevisiae","pmids":["11027292"],"confidence":"High","gaps":["Did not define the structural basis of the RNA-binding domain","Human ortholog not yet characterized"]},{"year":2001,"claim":"Identified the human ortholog hCsl4p as a bona fide component of the human exosome (PM/Scl complex).","evidence":"ELISA and Western blotting of recombinant hCsl4p with patient autoimmune sera","pmids":["11879549"],"confidence":"Medium","gaps":["Autoantibody recognition does not define molecular function","No interaction map within the complex"]},{"year":2002,"claim":"Defined how EXOSC1 anchors into the exosome, showing direct interactions with EXOSC6 (hRrp42p) and EXOSC7 (hRrp46p) are required for incorporation.","evidence":"Mammalian two-hybrid, GST pull-down, and co-IP with loss-of-function mutants","pmids":["11812149"],"confidence":"High","gaps":["Did not resolve assembly order relative to other subunits","No structural model of the human interface"]},{"year":2007,"claim":"Resolved the structural role of Csl4 as part of a trimeric cap forming an RNA entry pore that channels substrate to the catalytic core for processive degradation.","evidence":"X-ray crystallography of archaeal exosome with and without bound RNA","pmids":["16285927","17380186"],"confidence":"High","gaps":["Archaeal system; human-specific contacts not directly resolved","Does not address cofactor-dependent structured-RNA handling in vivo"]},{"year":2010,"claim":"Demonstrated that Csl4 confers distinct substrate selectivity and recruits the archaea-specific DnaG, showing the cap is a modular determinant of specificity rather than a passive scaffold.","evidence":"In vitro reconstitution of archaeal exosomes with defined caps, comparative RNA degradation and binding assays","pmids":["19053279","20488184","23324612","24789718"],"confidence":"High","gaps":["DnaG is archaea-specific; no human cap-specific cofactor identified","Csl4 itself has no catalytic activity"]},{"year":2011,"claim":"Confirmed functional conservation by showing human hCsl4p rescues yeast ski4 loss and interacts with the Dis3p catalytic exonuclease.","evidence":"Yeast complementation, superkiller phenotype analysis, co-IP with Dis3p, site-directed mutagenesis","pmids":["22068837"],"confidence":"High","gaps":["N-terminal third dispensable but its native role unclear","Human in-cell substrate specificity not mapped"]},{"year":2021,"claim":"Linked EXOSC1 to human disease by showing a missense variant reduces EXOSC1 and EXO9 complex abundance and causes pontocerebellar hypoplasia type 1.","evidence":"Exome sequencing, immunoblotting, blue native PAGE on patient cells","pmids":["33463720"],"confidence":"Medium","gaps":["Tissue-specific basis of neurodegeneration not explained","No rescue experiment in patient cells"]},{"year":2021,"claim":"Reported a non-canonical activity, proposing EXOSC1 cleaves ssDNA at C sites and contributes to C>A mutagenesis and PARP-inhibitor sensitivity in renal carcinoma.","evidence":"In vitro ssDNA cleavage assays plus mutation-spectrum correlation and cell sensitivity assays in KIRC","pmids":["34159897"],"confidence":"Medium","gaps":["Novel ssDNA-cleavage activity not independently replicated","Mechanistic link between exosome role and DNA cleavage unresolved"]},{"year":2023,"claim":"Validated pathogenicity of EXOSC1 variants and tied disease to reduced protein stability and impaired exosome function.","evidence":"Yeast complementation/growth assays and Western blotting of human variants in budding yeast; knockout mouse embryo phenotyping","pmids":["37024942","37940010"],"confidence":"Medium","gaps":["Cross-species variant modeling may not capture human-specific effects","Molecular cause of gastrulation failure not defined; no rescue performed"]},{"year":2025,"claim":"Identified CARM1-mediated arginine-6 methylation as a stabilizing post-translational switch controlling EXOSC1 abundance, exosome activity, and the viral-mimicry/antitumor immune response.","evidence":"Mass spectrometry, proteasome inhibitor assays, RNAseq and pathway analysis in tumor cell lines","pmids":["40203080"],"confidence":"Medium","gaps":["Single lab; physiological generality beyond tumor cells unclear","How methylation alters complex stability mechanistically not resolved"]},{"year":2025,"claim":"Placed EXOSC1 as the terminally incorporated cap subunit in a sequential exosome assembly hierarchy and showed it is dispensable for viability, revealing modular, resilient architecture.","evidence":"Inducible dual-guide CRISPR/Cas9 knockouts and proteomics in mouse embryonic stem cells (preprint)","pmids":["bio_10.1101_2025.03.14.643291"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Dispensability for viability contrasts with embryonic lethality in vivo; reconciliation needed"]},{"year":null,"claim":"How EXOSC1's cap-mediated substrate selectivity and its proposed ssDNA-cleavage activity are integrated, regulated, and deployed across tissues to produce the human disease and developmental phenotypes remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human-cell structural model of the assembled cap with EXOSC1","Substrate repertoire degraded via EXOSC1 in human cells undefined","Reconciliation of in vitro dispensability with embryonic essentiality"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,3,4,6,7]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,3,12,17]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[6,7]}],"localization":[],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,3,4,6]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[15]}],"complexes":["RNA exosome (EXO9 / PM-Scl complex)"],"partners":["EXOSC6","EXOSC7","DIS3","CARM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y3B2","full_name":"Exosome complex component CSL4","aliases":["Exosome component 1"],"length_aa":195,"mass_kda":21.5,"function":"Non-catalytic component of the RNA exosome complex which has 3'->5' exoribonuclease activity and participates in a multitude of cellular RNA processing and degradation events. In the nucleus, the RNA exosome complex is involved in proper maturation of stable RNA species such as rRNA, snRNA and snoRNA, in the elimination of RNA processing by-products and non-coding 'pervasive' transcripts, such as antisense RNA species and promoter-upstream transcripts (PROMPTs), and of mRNAs with processing defects, thereby limiting or excluding their export to the cytoplasm. The RNA exosome may be involved in Ig class switch recombination (CSR) and/or Ig variable region somatic hypermutation (SHM) by targeting AICDA deamination activity to transcribed dsDNA substrates. In the cytoplasm, the RNA exosome complex is involved in general mRNA turnover and specifically degrades inherently unstable mRNAs containing AU-rich elements (AREs) within their 3' untranslated regions, and in RNA surveillance pathways, preventing translation of aberrant mRNAs. It seems to be involved in degradation of histone mRNA. The catalytic inactive RNA exosome core complex of 9 subunits (Exo-9) is proposed to play a pivotal role in the binding and presentation of RNA for ribonucleolysis, and to serve as a scaffold for the association with catalytic subunits and accessory proteins or complexes. EXOSC1 as peripheral part of the Exo-9 complex stabilizes the hexameric ring of RNase PH-domain subunits through contacts with EXOSC6 and EXOSC8","subcellular_location":"Nucleus, nucleolus; Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9Y3B2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/EXOSC1","classification":"Common Essential","n_dependent_lines":828,"n_total_lines":1208,"dependency_fraction":0.6854304635761589},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RPS16","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/EXOSC1","total_profiled":1310},"omim":[{"mim_id":"619304","title":"PONTOCEREBELLAR HYPOPLASIA, TYPE 1F; PCH1F","url":"https://www.omim.org/entry/619304"},{"mim_id":"613974","title":"DExD/H-BOX HELICASE 60; DDX60","url":"https://www.omim.org/entry/613974"},{"mim_id":"607596","title":"PONTOCEREBELLAR HYPOPLASIA, TYPE 1A; PCH1A","url":"https://www.omim.org/entry/607596"},{"mim_id":"606493","title":"EXOSOME COMPONENT 1; EXOSC1","url":"https://www.omim.org/entry/606493"},{"mim_id":"158373","title":"MUCIN 5, SUBTYPES A AND C, TRACHEOBRONCHIAL; MUC5AC","url":"https://www.omim.org/entry/158373"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear bodies","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EXOSC1"},"hgnc":{"alias_symbol":["hCsl4p","Csl4p","CSL4","Ski4p","SKI4","CGI-108","p13"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y3B2","domains":[{"cath_id":"2.40.50.100","chopping":"5-55","consensus_level":"high","plddt":82.711,"start":5,"end":55},{"cath_id":"2.40.50.140","chopping":"68-153","consensus_level":"high","plddt":80.4541,"start":68,"end":153}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3B2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3B2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3B2-F1-predicted_aligned_error_v6.png","plddt_mean":78.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EXOSC1","jax_strain_url":"https://www.jax.org/strain/search?query=EXOSC1"},"sequence":{"accession":"Q9Y3B2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y3B2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y3B2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3B2"}},"corpus_meta":[{"pmid":"19060898","id":"PMC_19060898","title":"The exosome contains domains with specific endoribonuclease, exoribonuclease and cytoplasmic mRNA decay activities.","date":"2008","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19060898","citation_count":241,"is_preprint":false},{"pmid":"23000172","id":"PMC_23000172","title":"Transcriptome-wide analysis of exosome targets.","date":"2012","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/23000172","citation_count":164,"is_preprint":false},{"pmid":"11027292","id":"PMC_11027292","title":"Function of the ski4p (Csl4p) and Ski7p proteins in 3'-to-5' degradation of mRNA.","date":"2000","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11027292","citation_count":154,"is_preprint":false},{"pmid":"10744028","id":"PMC_10744028","title":"The yeast antiviral proteins Ski2p, Ski3p, and Ski8p exist as a complex in vivo.","date":"2000","source":"RNA (New York, 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A point mutation in the putative RNA-binding domain of Csl4p (ski4-1, G253E) strongly impairs 3'-to-5' mRNA degradation without affecting exosome function in rRNA or snRNA processing, demonstrating that distinct exosome functions can be genetically separated and that the RNA-binding domain of Csl4p has a specific role in mRNA degradation.\",\n      \"method\": \"Genetic epistasis, allele identification, mRNA half-life assays, RNA processing assays in S. cerevisiae\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal functional assays (mRNA decay, rRNA processing, snRNA processing) with defined point mutations, replicated across alleles in a single rigorous study\",\n      \"pmids\": [\"11027292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The human protein hCsl4p is a component of the human exosome (PM/Scl complex), as evidenced by autoantibodies in patients with idiopathic inflammatory myopathy and PM/Scl overlap syndrome targeting hCsl4p along with other exosome subunits.\",\n      \"method\": \"ELISA and Western blotting with affinity-purified recombinant hCsl4p using patient sera\",\n      \"journal\": \"Arthritis research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — detection of autoantibody binding to recombinant hCsl4p establishes it as an exosome component in human cells, single lab but two orthogonal methods (ELISA + Western blot)\",\n      \"pmids\": [\"11879549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Human hCsl4p directly interacts with exosome subunits hRrp42p and hRrp46p, and these protein-protein interactions are required for hCsl4p's association with the exosome complex in vivo. Mutants of hCsl4p that fail to interact with either hRrp42p or hRrp46p cannot associate with the exosome.\",\n      \"method\": \"Mammalian two-hybrid assay, GST pull-down, co-immunoprecipitation from cell lysates\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding established by multiple orthogonal methods (two-hybrid + GST pulldown + in vivo co-IP), with loss-of-function mutant validation in a single lab\",\n      \"pmids\": [\"11812149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structures of archaeal exosome isoforms revealed that Csl4 (along with Rrp4) forms a trimeric cap on top of the hexameric RNase-PH domain ring. The S1 domains of this cap and a 'neck' region of the RNase-PH ring form an RNA entry pore that restricts access to unstructured RNA, explaining processive degradation of unstructured RNA and the requirement for cofactors to degrade structured RNA.\",\n      \"method\": \"X-ray crystallography of archaeal exosome, tungstate soaks, structural and mutational analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with active-site identification and mutational validation; foundational structural paper replicated by subsequent studies\",\n      \"pmids\": [\"16285927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structure of the Sulfolobus solfataricus nine-subunit exosome with bound RNA substrate shows that RNA binds both at the active site and at the opposite side in the narrowest constriction of the central channel, establishing that Csl4 contributes to the RNA-binding cap that channels substrate through the central pore for processive degradation.\",\n      \"method\": \"X-ray crystallography at 1.6 Å and 2.3 Å resolution with RNA-bound complex\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with substrate-bound form, mechanistically rationalizes processive degradation and RNA stalling\",\n      \"pmids\": [\"17380186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In yeast (Csl4/Ski4p), the zinc-ribbon domain of Csl4 is required for exosome-mediated mRNA decay but none of its domains are individually required for viability, indicating that specific structural domains contribute to specific exosome functions.\",\n      \"method\": \"Domain deletion analysis in S. cerevisiae with mRNA decay assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — domain deletion with defined functional readout (mRNA decay vs. viability), multiple domain constructs tested in a single rigorous study\",\n      \"pmids\": [\"19060898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Archaeal Csl4, when incorporated into the nine-subunit exosome (Csl4-exosome), enhances efficient degradation of structured RNA substrates (tRNA, heteropolymeric transcripts) by the catalytic Rrp41-Rrp42 hexamer. Csl4 itself has no hydrolytic RNase activity alone or in context of the complex, but strong substrate binding mediated by Csl4 is important for phosphorolysis.\",\n      \"method\": \"In vitro reconstitution of archaeal exosome complexes with different subunit compositions, RNase activity assays under varied conditions\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with defined subunit combinations, multiple substrates and conditions tested, single lab\",\n      \"pmids\": [\"19053279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Archaeal Csl4 confers different substrate specificity to the exosome compared with Rrp4: the Csl4-exosome degrades RNA with an A-poor 3'-end with higher efficiency, while the Rrp4-exosome strongly prefers poly(A) RNA. This establishes that Csl4 and Rrp4 have distinct functional roles in substrate selection.\",\n      \"method\": \"In vitro RNA degradation assays with reconstituted archaeal exosome complexes containing defined Rrp4 or Csl4 caps\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with comparative substrate specificity assays across multiple RNA substrates, single lab\",\n      \"pmids\": [\"20488184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The Csl4-exosome (archaeal) interacts with the archaea-specific DnaG subunit, which binds to the Csl4-exosome but not to the Rrp4-exosome, showing that Csl4 mediates DnaG recruitment to the exosome complex.\",\n      \"method\": \"In vitro binding assays with reconstituted complexes; co-purification\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — interaction demonstrated in vitro with reconstituted complexes, single lab, single method\",\n      \"pmids\": [\"20488184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Human hCsl4p functionally rescues the null phenotype of yeast ski4Δ cells and partially complements the superkiller phenotype of ski4-1 mutation. The equivalent point mutation G152E in hCsl4p (corresponding to yeast ski4-1 G253E) impairs hCsl4p activity. hCsl4p physically interacts with the Dis3p exonuclease of the yeast exosome despite lacking the N-terminal third of Ski4p. This N-terminal third of Ski4p is dispensable for RNA degradation function.\",\n      \"method\": \"Yeast complementation assays, superkiller phenotype analysis, co-immunoprecipitation with Dis3p, site-directed mutagenesis\",\n      \"journal\": \"Yeast\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue, physical interaction by co-IP, and point mutation analysis all in one study; multiple orthogonal methods confirming the same conclusion\",\n      \"pmids\": [\"22068837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The archaeal DnaG protein binds to the Csl4-exosome but not to the Rrp4-exosome of Sulfolobus solfataricus. DnaG is a poly(A)-binding protein that enhances degradation of adenine-rich transcripts specifically in the context of the Csl4-exosome, functioning as a second poly(A)-binding subunit in the heteromeric RNA-binding cap.\",\n      \"method\": \"In vitro binding assays, RNA degradation assays with reconstituted exosome complexes, poly(A)-binding assays\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal in vitro assays (binding + degradation), mechanistic specificity shown by comparing Csl4- vs Rrp4-exosomes, single lab\",\n      \"pmids\": [\"23324612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Archaeal Csl4 is involved in the interaction with the archaea-specific DnaG subunit of the exosome complex. In the archaeal exosome, Rrp4 confers poly(A) specificity while Csl4 mediates DnaG association. Both Rrp4 and Csl4 form a variable RNA-binding trimeric cap on the hexameric ring.\",\n      \"method\": \"Biochemical reconstitution, subunit interaction analysis, in vitro RNA degradation assays\",\n      \"journal\": \"Wiley interdisciplinary reviews. RNA\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — review synthesizing multiple experimental findings from same lab, citing reconstitution experiments; moderate confidence as it is a review rather than original data paper\",\n      \"pmids\": [\"24789718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A homozygous missense variant p.Ser35Leu in EXOSC1 reduces EXOSC1 protein levels and reduces the EXO9 (nine-subunit exosome) complex abundance in patient cells, establishing that EXOSC1 is required for stable EXO9 complex formation in human cells and that loss of EXOSC1 function causes pontocerebellar hypoplasia type 1.\",\n      \"method\": \"Immunoblotting, blue native PAGE, exome sequencing, in silico mutagenesis of protein structure\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — two orthogonal biochemical methods (immunoblotting + BN-PAGE) showing loss of protein and complex, single lab, patient-derived material\",\n      \"pmids\": [\"33463720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"EXOSC1 cleaves single-stranded DNA preferentially at C sites in vitro, acts as an endogenous source of mutations via C>A transversions in human kidney renal clear cell carcinoma cells, and sensitizes these cells to PARP inhibitors.\",\n      \"method\": \"In vitro ssDNA cleavage assays, statistical correlation of EXOSC1 expression with mutation spectra in KIRC, cell sensitivity assays with PARP inhibitors\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — in vitro enzymatic activity on ssDNA combined with cellular mutation pattern analysis; novel claimed activity (ssDNA cleavage) not independently replicated\",\n      \"pmids\": [\"34159897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The EXOSC1 variant p.Arg183Trp causes a slow-growth phenotype in yeast when expressed as the human variant, while EXOSC1-Ser35Leu is lethal in the same model, demonstrating impaired exosome function. Protein levels of both EXOSC1 variants are reduced compared with wild-type when expressed in budding yeast, confirming pathogenicity through reduced protein stability.\",\n      \"method\": \"Yeast complementation and growth assays, Western blotting for protein levels in yeast\",\n      \"journal\": \"American journal of medical genetics. Part A\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional growth assay and protein quantification, two independent EXOSC1 variants tested, yeast model system\",\n      \"pmids\": [\"37024942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Exosc1 null mouse embryos implant and form an egg cylinder but are developmentally delayed and fail to initiate gastrulation by embryonic day 7.5, demonstrating that EXOSC1 is essential for early mammalian development at the gastrulation stage.\",\n      \"method\": \"Homozygous knockout mouse embryo analysis, embryo recovery at defined developmental stages, morphological and lineage-specification analysis\",\n      \"journal\": \"Gene expression patterns\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean knockout with defined developmental phenotype, single study, no molecular rescue performed\",\n      \"pmids\": [\"37940010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CARM1 methylates arginine 6 of EXOSC1, protecting it from proteasome-mediated degradation. This post-translational methylation event enhances RNA exosome activity, attenuates nuclear export of retroelement transcripts by the mRNA export pathway, and thereby suppresses the viral mimicry response and antitumor immunity.\",\n      \"method\": \"Mass spectrometry identification of methylation site, proteasome inhibitor assays, RNAseq, functional pathway analysis in tumor cell lines\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry identification of specific PTM site combined with functional consequences, single lab, novel finding\",\n      \"pmids\": [\"40203080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Using inducible CRISPR/Cas9 knockouts in mouse embryonic stem cells, Exosc1 is identified as the terminally incorporated cap subunit in a sequential RNA exosome assembly pathway (initiated by Exosc2, Exosc4, and Exosc7). Unlike other structural subunits, Exosc1 is dispensable for cell viability, revealing that the RNA exosome has a modular, functionally resilient architecture. Orphan exosome subunits are degraded by the ubiquitin-proteasome system.\",\n      \"method\": \"Inducible dual-guide CRISPR/Cas9 knockout system in mESCs, proteomics, assembly hierarchy analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic genetic perturbation with proteomics readout, multiple subunits tested, preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.03.14.643291\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"EXOSC1 (hCsl4p/Csl4p) is a structural cap subunit of the RNA exosome that is terminally incorporated into the complex during a sequential assembly process, where it directly interacts with exosome subunits EXOSC6 (hRrp46p) and EXOSC7 (hRrp42p) to anchor into the nine-subunit ring; its zinc-ribbon and S1 RNA-binding domains contribute to substrate-specific mRNA degradation (but not to rRNA/snRNA processing or viability), it channels structured RNA substrates to the catalytic core, it is stabilized by CARM1-mediated arginine-6 methylation that prevents proteasomal degradation, and loss of EXOSC1 disrupts EXO9 complex integrity and causes pontocerebellar hypoplasia in humans and failure of gastrulation in mice.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EXOSC1 (hCsl4p/Csl4p) is a structural cap subunit of the RNA exosome, the conserved 3'-to-5' RNA-degradation machine, where it sits atop the hexameric RNase-PH ring and helps form the RNA-binding cap that channels substrate through the central pore for processive degradation [#3, #4]. In human cells it incorporates into the exosome through direct protein-protein interactions with the EXOSC6 (hRrp42p) and EXOSC7 (hRrp46p) subunits, and mutants unable to bind these partners fail to associate with the complex [#2]; EXOSC1 is required for stable assembly of the nine-subunit EXO9 complex [#12]. EXOSC1 is itself catalytically inert but contributes substrate specificity and binding: its zinc-ribbon and S1 RNA-binding domains are required for exosome-mediated mRNA decay yet are dispensable for rRNA/snRNA processing and viability, genetically separating distinct exosome functions, and cap-conferred substrate binding promotes degradation of structured RNAs and transcripts with particular 3'-end composition [#0, #5, #6, #7]. Human EXOSC1 functionally substitutes for yeast Csl4p and physically interacts with the catalytic Dis3p exonuclease [#9]. CARM1-mediated methylation of arginine 6 protects EXOSC1 from proteasomal degradation, thereby enhancing exosome activity and suppressing the viral-mimicry response by limiting nuclear export of retroelement transcripts [#16]. Loss-of-function variants cause pontocerebellar hypoplasia type 1 by reducing EXOSC1 protein and EXO9 complex abundance [#12, #14], and Exosc1-null mouse embryos fail to initiate gastrulation, establishing an essential developmental role [#15]. A reported in vitro single-stranded DNA cleavage activity links EXOSC1 to C>A mutational signatures in renal carcinoma cells [#13].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that the exosome cap subunit Csl4p carries a function-specific RNA-binding domain, separating mRNA degradation from rRNA/snRNA processing.\",\n      \"evidence\": \"Genetic epistasis and a point mutation (ski4-1, G253E) with mRNA half-life and RNA processing assays in S. cerevisiae\",\n      \"pmids\": [\"11027292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the structural basis of the RNA-binding domain\", \"Human ortholog not yet characterized\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified the human ortholog hCsl4p as a bona fide component of the human exosome (PM/Scl complex).\",\n      \"evidence\": \"ELISA and Western blotting of recombinant hCsl4p with patient autoimmune sera\",\n      \"pmids\": [\"11879549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Autoantibody recognition does not define molecular function\", \"No interaction map within the complex\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined how EXOSC1 anchors into the exosome, showing direct interactions with EXOSC6 (hRrp42p) and EXOSC7 (hRrp46p) are required for incorporation.\",\n      \"evidence\": \"Mammalian two-hybrid, GST pull-down, and co-IP with loss-of-function mutants\",\n      \"pmids\": [\"11812149\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve assembly order relative to other subunits\", \"No structural model of the human interface\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved the structural role of Csl4 as part of a trimeric cap forming an RNA entry pore that channels substrate to the catalytic core for processive degradation.\",\n      \"evidence\": \"X-ray crystallography of archaeal exosome with and without bound RNA\",\n      \"pmids\": [\"16285927\", \"17380186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Archaeal system; human-specific contacts not directly resolved\", \"Does not address cofactor-dependent structured-RNA handling in vivo\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated that Csl4 confers distinct substrate selectivity and recruits the archaea-specific DnaG, showing the cap is a modular determinant of specificity rather than a passive scaffold.\",\n      \"evidence\": \"In vitro reconstitution of archaeal exosomes with defined caps, comparative RNA degradation and binding assays\",\n      \"pmids\": [\"19053279\", \"20488184\", \"23324612\", \"24789718\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DnaG is archaea-specific; no human cap-specific cofactor identified\", \"Csl4 itself has no catalytic activity\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Confirmed functional conservation by showing human hCsl4p rescues yeast ski4 loss and interacts with the Dis3p catalytic exonuclease.\",\n      \"evidence\": \"Yeast complementation, superkiller phenotype analysis, co-IP with Dis3p, site-directed mutagenesis\",\n      \"pmids\": [\"22068837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"N-terminal third dispensable but its native role unclear\", \"Human in-cell substrate specificity not mapped\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked EXOSC1 to human disease by showing a missense variant reduces EXOSC1 and EXO9 complex abundance and causes pontocerebellar hypoplasia type 1.\",\n      \"evidence\": \"Exome sequencing, immunoblotting, blue native PAGE on patient cells\",\n      \"pmids\": [\"33463720\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tissue-specific basis of neurodegeneration not explained\", \"No rescue experiment in patient cells\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Reported a non-canonical activity, proposing EXOSC1 cleaves ssDNA at C sites and contributes to C>A mutagenesis and PARP-inhibitor sensitivity in renal carcinoma.\",\n      \"evidence\": \"In vitro ssDNA cleavage assays plus mutation-spectrum correlation and cell sensitivity assays in KIRC\",\n      \"pmids\": [\"34159897\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Novel ssDNA-cleavage activity not independently replicated\", \"Mechanistic link between exosome role and DNA cleavage unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Validated pathogenicity of EXOSC1 variants and tied disease to reduced protein stability and impaired exosome function.\",\n      \"evidence\": \"Yeast complementation/growth assays and Western blotting of human variants in budding yeast; knockout mouse embryo phenotyping\",\n      \"pmids\": [\"37024942\", \"37940010\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cross-species variant modeling may not capture human-specific effects\", \"Molecular cause of gastrulation failure not defined; no rescue performed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified CARM1-mediated arginine-6 methylation as a stabilizing post-translational switch controlling EXOSC1 abundance, exosome activity, and the viral-mimicry/antitumor immune response.\",\n      \"evidence\": \"Mass spectrometry, proteasome inhibitor assays, RNAseq and pathway analysis in tumor cell lines\",\n      \"pmids\": [\"40203080\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; physiological generality beyond tumor cells unclear\", \"How methylation alters complex stability mechanistically not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed EXOSC1 as the terminally incorporated cap subunit in a sequential exosome assembly hierarchy and showed it is dispensable for viability, revealing modular, resilient architecture.\",\n      \"evidence\": \"Inducible dual-guide CRISPR/Cas9 knockouts and proteomics in mouse embryonic stem cells (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.14.643291\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Dispensability for viability contrasts with embryonic lethality in vivo; reconciliation needed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How EXOSC1's cap-mediated substrate selectivity and its proposed ssDNA-cleavage activity are integrated, regulated, and deployed across tissues to produce the human disease and developmental phenotypes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human-cell structural model of the assembled cap with EXOSC1\", \"Substrate repertoire degraded via EXOSC1 in human cells undefined\", \"Reconciliation of in vitro dispensability with embryonic essentiality\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 3, 4, 6, 7]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 3, 12, 17]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [6, 7]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 3, 4, 6]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [\"RNA exosome (EXO9 / PM-Scl complex)\"],\n    \"partners\": [\"EXOSC6\", \"EXOSC7\", \"DIS3\", \"CARM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}