{"gene":"EXOSC6","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1995,"finding":"MTR3 (EXOSC6) encodes an essential 28-kDa nucleolar protein in S. cerevisiae; mtr3-1 temperature-sensitive mutants accumulate poly(A)+ RNA in the nucleolus, with concurrent disorganization of the nucleolus and inhibition of rRNA synthesis and processing, indicating Mtr3p is required for mRNA export and ribosomal subunit export.","method":"Temperature-sensitive mutant analysis, indirect immunofluorescence/localization of poly(A)+ RNA, nucleolar morphology analysis","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct loss-of-function with defined cellular phenotypes (poly(A)+ accumulation, rRNA processing defects) in yeast ortholog; single lab but multiple orthogonal readouts","pmids":["8534909"],"is_preprint":false},{"year":2005,"finding":"Mtr3p (EXOSC6 yeast ortholog) functions as a core exosome subunit in nuclear RNA surveillance; inactivation of Mtr3p leads to accumulation of deadenylated and 3'-truncated mRNAs, a distinct phenotype from loss of the nuclear-specific component Rrp6p, placing Mtr3p in the core exosome degradation pathway.","method":"Conditional inactivation of core exosome components (Rrp41p, Mtr3p), Northern blot analysis of mRNA species in pap1-5 mutant background","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined RNA phenotype in yeast ortholog; single lab, multiple mutant combinations tested","pmids":["16260613"],"is_preprint":false},{"year":2007,"finding":"Mtr3p (EXOSC6 yeast ortholog), as a core exosome subunit, participates in degradation of cryptic transcripts from telomeric regions, the rDNA intergenic spacer (IGS1-R), and centromere CEN3; degradation of IGS1-R transcript was reduced in mtr3 mutant strains, demonstrating Mtr3p's role in exosome-mediated degradation of ncRNAs from repressed chromatin regions.","method":"Northern blot analysis in mtr3 deletion/mutant yeast strains, comparison with TRAMP component and Rrp6 mutants","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct genetic loss-of-function with defined RNA substrate phenotype; single lab, corroborated by parallel results with other exosome components","pmids":["18007593"],"is_preprint":false},{"year":2011,"finding":"Mutations in the core exosome gene MTR3 (EXOSC6 yeast ortholog) elicit microtubule phenotypes in S. cerevisiae, including misoriented spindles and altered astral microtubule length/number, linking Mtr3p/exosome RNA processing activity to cell cycle progression and microtubule organization.","method":"Genetic analysis (mtr3 mutant), fluorescence microscopy of microtubule structures, RNA-seq of cell cycle and MT-related transcripts","journal":"Yeast (Chichester, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with direct cell biological readout (MT imaging) and transcriptomic support; single lab, multiple orthogonal methods","pmids":["21919057"],"is_preprint":false},{"year":2013,"finding":"Mtr3 (EXOSC6 yeast ortholog) and Rrp41, as core exosome ring subunits, show co-evolutionary divergence patterns during fungal evolution; experimental mutagenesis of exosome core subunits demonstrated that coordinated changes in Rrp41 and Mtr3 maintain complex activity, revealing functional co-evolution between these subunits and their RNA substrates.","method":"Systematic mutagenesis of Rrp41 and Mtr3 exosome subunits, activity assays of mutant exosome complexes, bioinformatics co-evolution analysis validated experimentally","journal":"Proteins","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, activity assays on mutant complexes but limited mechanistic detail in abstract; co-evolutionary inference experimentally supported but partially","pmids":["23852635"],"is_preprint":false},{"year":2023,"finding":"EXOSC6 (Mtr3) is a component of the lower PH-like ring of the 10-subunit RNA exosome complex (along with EXOSC4/7/8/9/5; yeast Rrp41/42/43/45/46/Mtr3); the EXOSC2 cap subunit mediates interaction with the essential RNA helicase MTR4, and disruption of this interface impairs RNA exosome function, as shown by accumulation of exosome target RNAs and genetic interactions with mtr4 mutants.","method":"Structural modeling of patient missense mutation, yeast genetic complementation (rrp4-M68T modeling of EXOSC2 p.Met40Thr), Co-IP/biochemical interaction assay (Rrp4 M68T vs Mtr4), RNA target accumulation assays","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal biochemical interaction assay plus genetic epistasis in yeast model; single lab but multiple orthogonal methods; EXOSC6 defined as lower ring component by structural assignment","pmids":["36861343"],"is_preprint":false}],"current_model":"EXOSC6 (Mtr3p) is a core structural subunit of the evolutionarily conserved RNA exosome complex, residing in the lower PH-like hexameric ring, where it contributes to 3'→5' RNA degradation and surveillance of coding and non-coding RNAs in the nucleus; loss of Mtr3p function causes accumulation of aberrant poly(A)+ RNA in the nucleolus, defective rRNA processing, accumulation of deadenylated/3'-truncated mRNAs, impaired degradation of ncRNAs from repressed chromatin loci, and microtubule/cell cycle defects, collectively placing EXOSC6 as an essential structural and functional component of the RNA exosome required for nuclear RNA quality control."},"narrative":{"mechanistic_narrative":"EXOSC6 (yeast Mtr3p) is an essential structural subunit of the conserved 3'→5' RNA exosome, an enzymatic ribonucleoprotein machine that performs nuclear RNA surveillance and turnover of coding and non-coding transcripts [PMID:8534909, PMID:36861343]. Within the ten-subunit exosome it occupies the lower PH-like ring together with EXOSC4/7/8/9/5, the catalytic core that, via the EXOSC2 cap subunit, docks the RNA helicase MTR4 to feed substrates into the complex [PMID:36861343]. Loss of Mtr3p function produces a coherent set of RNA-processing defects: nucleolar accumulation of poly(A)+ RNA with disorganized nucleolar morphology and blocked rRNA synthesis/processing [PMID:8534909], accumulation of deadenylated and 3'-truncated mRNAs distinct from the Rrp6p-dependent pathway [PMID:16260613], and impaired degradation of cryptic non-coding transcripts arising from telomeric, rDNA intergenic spacer, and centromeric repressed chromatin loci [PMID:18007593]. Beyond RNA metabolism, mtr3 mutants also display microtubule and spindle-orientation abnormalities, linking exosome RNA-processing activity to cell-cycle progression [PMID:21919057]. The available corpus characterizes EXOSC6 largely through its yeast ortholog; no human-specific biochemical or disease-causative finding is present in the timeline.","teleology":[{"year":1995,"claim":"Established Mtr3p as an essential nucleolar factor whose loss blocks nuclear RNA export and ribosome biogenesis, first placing the gene in nuclear RNA metabolism.","evidence":"Temperature-sensitive mtr3-1 mutant analysis with poly(A)+ RNA localization and nucleolar morphology readouts in S. cerevisiae","pmids":["8534909"],"confidence":"Medium","gaps":["Did not define Mtr3p as an exosome subunit","No biochemical demonstration of catalytic role","Phenotypes are pleiotropic, leaving direct substrates unidentified"]},{"year":2005,"claim":"Resolved whether Mtr3p acts in the core degradation pathway by showing its inactivation yields deadenylated/3'-truncated mRNAs distinct from the nuclear-specific Rrp6p, positioning it in core exosome turnover.","evidence":"Conditional inactivation of core exosome subunits and Northern analysis of mRNA species in a pap1-5 background","pmids":["16260613"],"confidence":"Medium","gaps":["Does not establish whether Mtr3p itself is catalytic or purely structural","Single-lab genetic epistasis without reconstituted enzymology"]},{"year":2007,"claim":"Extended Mtr3p substrate range to non-coding cryptic transcripts from repressed chromatin, showing the exosome degrades RNAs from telomeric, rDNA spacer, and centromeric loci.","evidence":"Northern blot analysis in mtr3 mutant strains compared with TRAMP and Rrp6 mutants","pmids":["18007593"],"confidence":"Medium","gaps":["Mechanism of ncRNA targeting to the exosome not defined","Relationship to chromatin silencing left correlative"]},{"year":2011,"claim":"Connected exosome RNA-processing activity to cytoskeletal/cell-cycle control by demonstrating microtubule and spindle defects in mtr3 mutants.","evidence":"Genetic analysis of mtr3 mutants with microtubule fluorescence imaging and RNA-seq of cell-cycle/MT transcripts","pmids":["21919057"],"confidence":"Medium","gaps":["Causal RNA target linking exosome loss to MT phenotype not identified","Direct versus indirect contribution unresolved"]},{"year":2013,"claim":"Probed how core ring subunits maintain complex integrity, showing coordinated co-evolution of Rrp41 and Mtr3 preserves exosome activity.","evidence":"Systematic mutagenesis and activity assays of mutant exosome complexes with experimentally validated co-evolution analysis","pmids":["23852635"],"confidence":"Low","gaps":["Limited mechanistic detail on which interfaces drive co-evolution","Not independently confirmed beyond single study"]},{"year":2023,"claim":"Placed EXOSC6 structurally in the lower PH-like ring and clarified that the EXOSC2 cap mediates MTR4 helicase recruitment required for substrate delivery.","evidence":"Structural modeling of a patient mutation, yeast complementation, Co-IP interaction assay, and RNA target accumulation assays","pmids":["36861343"],"confidence":"Medium","gaps":["MTR4 interaction characterized via EXOSC2, not EXOSC6 directly","No human EXOSC6 disease mutation or biochemical characterization provided"]},{"year":null,"claim":"Whether EXOSC6 contributes catalytically or solely structurally to RNA degradation, and its specific role in human cells and disease, remains unresolved in this corpus.","evidence":"No direct human EXOSC6 functional or disease-causative study present in the timeline","pmids":[],"confidence":"Low","gaps":["No human EXOSC6 loss-of-function phenotype","No reconstituted activity assay isolating EXOSC6 contribution","No EXOSC6-specific structural data beyond ring assignment"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[5]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[1,2]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[1,2]}],"complexes":["RNA exosome"],"partners":["EXOSC4","EXOSC7","EXOSC8","EXOSC9","EXOSC5","EXOSC2","MTR4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5RKV6","full_name":"Exosome complex component MTR3","aliases":["Exosome component 6","mRNA transport regulator 3 homolog","hMtr3","p11"],"length_aa":272,"mass_kda":28.2,"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","subcellular_location":"Cytoplasm; Nucleus, nucleolus; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q5RKV6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/EXOSC6","classification":"Common Essential","n_dependent_lines":1196,"n_total_lines":1208,"dependency_fraction":0.9900662251655629},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/EXOSC6","total_profiled":1310},"omim":[{"mim_id":"606490","title":"EXOSOME COMPONENT 6; EXOSC6","url":"https://www.omim.org/entry/606490"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EXOSC6"},"hgnc":{"alias_symbol":["MTR3","hMtr3p","Mtr3p","EAP4","p11"],"prev_symbol":[]},"alphafold":{"accession":"Q5RKV6","domains":[{"cath_id":"3.30.230.70","chopping":"36-71_93-271","consensus_level":"medium","plddt":88.2108,"start":36,"end":271}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5RKV6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5RKV6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5RKV6-F1-predicted_aligned_error_v6.png","plddt_mean":80.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EXOSC6","jax_strain_url":"https://www.jax.org/strain/search?query=EXOSC6"},"sequence":{"accession":"Q5RKV6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5RKV6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5RKV6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5RKV6"}},"corpus_meta":[{"pmid":"18007593","id":"PMC_18007593","title":"Trf4 targets ncRNAs from telomeric and rDNA spacer regions and functions in rDNA copy number control.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/18007593","citation_count":158,"is_preprint":false},{"pmid":"16260613","id":"PMC_16260613","title":"A nuclear surveillance pathway for mRNAs with defective polyadenylation.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16260613","citation_count":85,"is_preprint":false},{"pmid":"23865454","id":"PMC_23865454","title":"Selenocysteine confers resistance to inactivation by oxidation in thioredoxin reductase: comparison of selenium and sulfur enzymes.","date":"2013","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23865454","citation_count":77,"is_preprint":false},{"pmid":"17203189","id":"PMC_17203189","title":"Synergistic inhibition of breast cancer cell lines with a dual inhibitor of EGFR-HER-2/neu and a Bcl-2 inhibitor.","date":"2007","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/17203189","citation_count":49,"is_preprint":false},{"pmid":"8534909","id":"PMC_8534909","title":"Mutations in nucleolar proteins lead to nucleolar accumulation of polyA+ RNA in Saccharomyces cerevisiae.","date":"1995","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/8534909","citation_count":47,"is_preprint":false},{"pmid":"18345606","id":"PMC_18345606","title":"Identification of breast cancer peptide epitopes presented by HLA-A*0201.","date":"2008","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/18345606","citation_count":46,"is_preprint":false},{"pmid":"17385893","id":"PMC_17385893","title":"Structural and biochemical studies reveal differences in the catalytic mechanisms of mammalian and Drosophila melanogaster thioredoxin reductases.","date":"2007","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17385893","citation_count":33,"is_preprint":false},{"pmid":"14606518","id":"PMC_14606518","title":"Insulin-like growth factor-1 rescues the mutated FGF receptor 3 (G380R) expressing ATDC5 cells from apoptosis through phosphatidylinositol 3-kinase and MAPK.","date":"2003","source":"Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research","url":"https://pubmed.ncbi.nlm.nih.gov/14606518","citation_count":31,"is_preprint":false},{"pmid":"23856293","id":"PMC_23856293","title":"Identification of Sirtuin 3, a mitochondrial protein deacetylase, as a new contributor to tamoxifen resistance in breast cancer cells.","date":"2013","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/23856293","citation_count":31,"is_preprint":false},{"pmid":"17661444","id":"PMC_17661444","title":"Investigation of the C-terminal redox center of high-Mr thioredoxin reductase by protein engineering and semisynthesis.","date":"2007","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17661444","citation_count":29,"is_preprint":false},{"pmid":"21182838","id":"PMC_21182838","title":"Matrin 3 as a key regulator of endothelial cell survival.","date":"2010","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/21182838","citation_count":24,"is_preprint":false},{"pmid":"21919057","id":"PMC_21919057","title":"Pronounced and extensive microtubule defects in a Saccharomyces cerevisiae DIS3 mutant.","date":"2011","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/21919057","citation_count":18,"is_preprint":false},{"pmid":"19026486","id":"PMC_19026486","title":"Mislocalization of cell-cell adhesion complexes in tamoxifen-resistant breast cancer cells with elevated c-Src tyrosine kinase activity.","date":"2008","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/19026486","citation_count":18,"is_preprint":false},{"pmid":"30760080","id":"PMC_30760080","title":"The anti-cancer drug 5-fluorouracil affects cell cycle regulators and potential regulatory long non-coding RNAs in yeast.","date":"2019","source":"RNA biology","url":"https://pubmed.ncbi.nlm.nih.gov/30760080","citation_count":14,"is_preprint":false},{"pmid":"23852635","id":"PMC_23852635","title":"Experimental analysis of co-evolution within protein complexes: the yeast exosome as a model.","date":"2013","source":"Proteins","url":"https://pubmed.ncbi.nlm.nih.gov/23852635","citation_count":6,"is_preprint":false},{"pmid":"39759149","id":"PMC_39759149","title":"Multipool-CEST and CEST-based pH assessment as predictive tools for glioma grading, IDH mutation, 1p/19q codeletion, and MGMT promoter methylation in gliomas.","date":"2024","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/39759149","citation_count":5,"is_preprint":false},{"pmid":"39098536","id":"PMC_39098536","title":"S. aureus Eap is a polyvalent inhibitor of neutrophil serine proteases.","date":"2024","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39098536","citation_count":4,"is_preprint":false},{"pmid":"36861343","id":"PMC_36861343","title":"In vivo characterization of the critical interaction between the RNA exosome and the essential RNA helicase Mtr4 in Saccharomyces cerevisiae.","date":"2023","source":"G3 (Bethesda, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/36861343","citation_count":4,"is_preprint":false},{"pmid":"35842572","id":"PMC_35842572","title":"Proteomic analysis of low- and high-grade human colon adenocarcinoma tissues and tissue-derived primary cell lines reveals unique biological functions of tumours and new protein biomarker candidates.","date":"2022","source":"Clinical proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/35842572","citation_count":2,"is_preprint":false},{"pmid":"33423171","id":"PMC_33423171","title":"1H, 15N, and 13C backbone resonance assignments of the C4b-binding region from the S. aureus extracellular adherence protein.","date":"2021","source":"Biomolecular NMR assignments","url":"https://pubmed.ncbi.nlm.nih.gov/33423171","citation_count":1,"is_preprint":false},{"pmid":"37315317","id":"PMC_37315317","title":"Alterations in the expression pattern of RBC membrane associated proteins (RMAPs) in whole body γ-irradiated Sprague Dawley rats.","date":"2023","source":"International journal of radiation biology","url":"https://pubmed.ncbi.nlm.nih.gov/37315317","citation_count":0,"is_preprint":false},{"pmid":"40588408","id":"PMC_40588408","title":"[Multi-omics Mendelian randomization study on the causality between non-ionizing radiation and facial aging].","date":"2025","source":"Zhonghua shao shang yu chuang mian xiu fu za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/40588408","citation_count":0,"is_preprint":false},{"pmid":"42069025","id":"PMC_42069025","title":"Deep-learning saturation transfer magnetic resonance fingerprinting (ST-MRF) in patients with Parkinson's disease.","date":"2026","source":"NeuroImage","url":"https://pubmed.ncbi.nlm.nih.gov/42069025","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15989,"output_tokens":1811,"usd":0.037566,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8666,"output_tokens":2405,"usd":0.051728,"stage2_stop_reason":"end_turn"},"total_usd":0.089294,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"MTR3 (EXOSC6) encodes an essential 28-kDa nucleolar protein in S. cerevisiae; mtr3-1 temperature-sensitive mutants accumulate poly(A)+ RNA in the nucleolus, with concurrent disorganization of the nucleolus and inhibition of rRNA synthesis and processing, indicating Mtr3p is required for mRNA export and ribosomal subunit export.\",\n      \"method\": \"Temperature-sensitive mutant analysis, indirect immunofluorescence/localization of poly(A)+ RNA, nucleolar morphology analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct loss-of-function with defined cellular phenotypes (poly(A)+ accumulation, rRNA processing defects) in yeast ortholog; single lab but multiple orthogonal readouts\",\n      \"pmids\": [\"8534909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Mtr3p (EXOSC6 yeast ortholog) functions as a core exosome subunit in nuclear RNA surveillance; inactivation of Mtr3p leads to accumulation of deadenylated and 3'-truncated mRNAs, a distinct phenotype from loss of the nuclear-specific component Rrp6p, placing Mtr3p in the core exosome degradation pathway.\",\n      \"method\": \"Conditional inactivation of core exosome components (Rrp41p, Mtr3p), Northern blot analysis of mRNA species in pap1-5 mutant background\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined RNA phenotype in yeast ortholog; single lab, multiple mutant combinations tested\",\n      \"pmids\": [\"16260613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Mtr3p (EXOSC6 yeast ortholog), as a core exosome subunit, participates in degradation of cryptic transcripts from telomeric regions, the rDNA intergenic spacer (IGS1-R), and centromere CEN3; degradation of IGS1-R transcript was reduced in mtr3 mutant strains, demonstrating Mtr3p's role in exosome-mediated degradation of ncRNAs from repressed chromatin regions.\",\n      \"method\": \"Northern blot analysis in mtr3 deletion/mutant yeast strains, comparison with TRAMP component and Rrp6 mutants\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct genetic loss-of-function with defined RNA substrate phenotype; single lab, corroborated by parallel results with other exosome components\",\n      \"pmids\": [\"18007593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Mutations in the core exosome gene MTR3 (EXOSC6 yeast ortholog) elicit microtubule phenotypes in S. cerevisiae, including misoriented spindles and altered astral microtubule length/number, linking Mtr3p/exosome RNA processing activity to cell cycle progression and microtubule organization.\",\n      \"method\": \"Genetic analysis (mtr3 mutant), fluorescence microscopy of microtubule structures, RNA-seq of cell cycle and MT-related transcripts\",\n      \"journal\": \"Yeast (Chichester, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with direct cell biological readout (MT imaging) and transcriptomic support; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"21919057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mtr3 (EXOSC6 yeast ortholog) and Rrp41, as core exosome ring subunits, show co-evolutionary divergence patterns during fungal evolution; experimental mutagenesis of exosome core subunits demonstrated that coordinated changes in Rrp41 and Mtr3 maintain complex activity, revealing functional co-evolution between these subunits and their RNA substrates.\",\n      \"method\": \"Systematic mutagenesis of Rrp41 and Mtr3 exosome subunits, activity assays of mutant exosome complexes, bioinformatics co-evolution analysis validated experimentally\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, activity assays on mutant complexes but limited mechanistic detail in abstract; co-evolutionary inference experimentally supported but partially\",\n      \"pmids\": [\"23852635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"EXOSC6 (Mtr3) is a component of the lower PH-like ring of the 10-subunit RNA exosome complex (along with EXOSC4/7/8/9/5; yeast Rrp41/42/43/45/46/Mtr3); the EXOSC2 cap subunit mediates interaction with the essential RNA helicase MTR4, and disruption of this interface impairs RNA exosome function, as shown by accumulation of exosome target RNAs and genetic interactions with mtr4 mutants.\",\n      \"method\": \"Structural modeling of patient missense mutation, yeast genetic complementation (rrp4-M68T modeling of EXOSC2 p.Met40Thr), Co-IP/biochemical interaction assay (Rrp4 M68T vs Mtr4), RNA target accumulation assays\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal biochemical interaction assay plus genetic epistasis in yeast model; single lab but multiple orthogonal methods; EXOSC6 defined as lower ring component by structural assignment\",\n      \"pmids\": [\"36861343\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"EXOSC6 (Mtr3p) is a core structural subunit of the evolutionarily conserved RNA exosome complex, residing in the lower PH-like hexameric ring, where it contributes to 3'→5' RNA degradation and surveillance of coding and non-coding RNAs in the nucleus; loss of Mtr3p function causes accumulation of aberrant poly(A)+ RNA in the nucleolus, defective rRNA processing, accumulation of deadenylated/3'-truncated mRNAs, impaired degradation of ncRNAs from repressed chromatin loci, and microtubule/cell cycle defects, collectively placing EXOSC6 as an essential structural and functional component of the RNA exosome required for nuclear RNA quality control.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EXOSC6 (yeast Mtr3p) is an essential structural subunit of the conserved 3'→5' RNA exosome, an enzymatic ribonucleoprotein machine that performs nuclear RNA surveillance and turnover of coding and non-coding transcripts [#0, #5]. Within the ten-subunit exosome it occupies the lower PH-like ring together with EXOSC4/7/8/9/5, the catalytic core that, via the EXOSC2 cap subunit, docks the RNA helicase MTR4 to feed substrates into the complex [#5]. Loss of Mtr3p function produces a coherent set of RNA-processing defects: nucleolar accumulation of poly(A)+ RNA with disorganized nucleolar morphology and blocked rRNA synthesis/processing [#0], accumulation of deadenylated and 3'-truncated mRNAs distinct from the Rrp6p-dependent pathway [#1], and impaired degradation of cryptic non-coding transcripts arising from telomeric, rDNA intergenic spacer, and centromeric repressed chromatin loci [#2]. Beyond RNA metabolism, mtr3 mutants also display microtubule and spindle-orientation abnormalities, linking exosome RNA-processing activity to cell-cycle progression [#3]. The available corpus characterizes EXOSC6 largely through its yeast ortholog; no human-specific biochemical or disease-causative finding is present in the timeline.\"\n,\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established Mtr3p as an essential nucleolar factor whose loss blocks nuclear RNA export and ribosome biogenesis, first placing the gene in nuclear RNA metabolism.\",\n      \"evidence\": \"Temperature-sensitive mtr3-1 mutant analysis with poly(A)+ RNA localization and nucleolar morphology readouts in S. cerevisiae\",\n      \"pmids\": [\"8534909\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define Mtr3p as an exosome subunit\", \"No biochemical demonstration of catalytic role\", \"Phenotypes are pleiotropic, leaving direct substrates unidentified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved whether Mtr3p acts in the core degradation pathway by showing its inactivation yields deadenylated/3'-truncated mRNAs distinct from the nuclear-specific Rrp6p, positioning it in core exosome turnover.\",\n      \"evidence\": \"Conditional inactivation of core exosome subunits and Northern analysis of mRNA species in a pap1-5 background\",\n      \"pmids\": [\"16260613\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not establish whether Mtr3p itself is catalytic or purely structural\", \"Single-lab genetic epistasis without reconstituted enzymology\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended Mtr3p substrate range to non-coding cryptic transcripts from repressed chromatin, showing the exosome degrades RNAs from telomeric, rDNA spacer, and centromeric loci.\",\n      \"evidence\": \"Northern blot analysis in mtr3 mutant strains compared with TRAMP and Rrp6 mutants\",\n      \"pmids\": [\"18007593\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of ncRNA targeting to the exosome not defined\", \"Relationship to chromatin silencing left correlative\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected exosome RNA-processing activity to cytoskeletal/cell-cycle control by demonstrating microtubule and spindle defects in mtr3 mutants.\",\n      \"evidence\": \"Genetic analysis of mtr3 mutants with microtubule fluorescence imaging and RNA-seq of cell-cycle/MT transcripts\",\n      \"pmids\": [\"21919057\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal RNA target linking exosome loss to MT phenotype not identified\", \"Direct versus indirect contribution unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Probed how core ring subunits maintain complex integrity, showing coordinated co-evolution of Rrp41 and Mtr3 preserves exosome activity.\",\n      \"evidence\": \"Systematic mutagenesis and activity assays of mutant exosome complexes with experimentally validated co-evolution analysis\",\n      \"pmids\": [\"23852635\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Limited mechanistic detail on which interfaces drive co-evolution\", \"Not independently confirmed beyond single study\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed EXOSC6 structurally in the lower PH-like ring and clarified that the EXOSC2 cap mediates MTR4 helicase recruitment required for substrate delivery.\",\n      \"evidence\": \"Structural modeling of a patient mutation, yeast complementation, Co-IP interaction assay, and RNA target accumulation assays\",\n      \"pmids\": [\"36861343\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MTR4 interaction characterized via EXOSC2, not EXOSC6 directly\", \"No human EXOSC6 disease mutation or biochemical characterization provided\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether EXOSC6 contributes catalytically or solely structurally to RNA degradation, and its specific role in human cells and disease, remains unresolved in this corpus.\",\n      \"evidence\": \"No direct human EXOSC6 functional or disease-causative study present in the timeline\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No human EXOSC6 loss-of-function phenotype\", \"No reconstituted activity assay isolating EXOSC6 contribution\", \"No EXOSC6-specific structural data beyond ring assignment\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\"RNA exosome\"],\n    \"partners\": [\"EXOSC4\", \"EXOSC7\", \"EXOSC8\", \"EXOSC9\", \"EXOSC5\", \"EXOSC2\", \"MTR4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}