{"gene":"THOC2","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2000,"finding":"THOC2 (Tho2) is a component of a nuclear oligomeric protein complex containing Hpr1, Mft1, and Thp2, physically associated via co-immunoprecipitation; this complex connects transcription elongation with mitotic recombination in yeast.","method":"Affinity purification (His6-HA-tagged Tho2), reciprocal co-immunoprecipitation with anti-Mft1 antibodies, genetic analysis of deletion mutants","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal methods (affinity purification + immunoprecipitation + genetic phenotyping), replicated across subunits","pmids":["11060033"],"is_preprint":false},{"year":1998,"finding":"THO2 is required for RNA polymerase II-dependent transcription elongation; tho2Δ reduces transcriptional efficiency and abolishes transcription through the lacZ sequence, and causes hyper-recombination between direct repeats in a transcription-dependent manner.","method":"In vivo transcriptional analysis of tho2Δ cells, recombination frequency assays, transcription-dependent recombination genetic analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo assays (transcription and recombination) in the same study, replicated in subsequent work","pmids":["9707445"],"is_preprint":false},{"year":2000,"finding":"RLR1 (THO2) functions in transcription at a step subsequent to initiation; rlr1 mutants specifically fail to express lacZ fusions while expressing native chromosomal genes at near-normal levels; RLR1 was isolated as a suppressor of SIN4 (a Mediator subcomplex component), placing THO2 in a pathway downstream of transcription initiation.","method":"Genetic suppressor screen (rlr1-1 as suppressor of sin4 mutation), lacZ reporter assays, epistasis analysis","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis plus reporter assays, single lab","pmids":["10675628"],"is_preprint":false},{"year":2002,"finding":"The DEAD-box RNA helicase Sub2 is a dosage-dependent suppressor of RLR1 (THO2) and is required for lacZ expression in yeast, placing Sub2 in the same mRNA export pathway as THO2 and suggesting THO2 links transcription to Sub2-mediated mRNP assembly/export.","method":"Dosage-dependent suppressor screen of rlr1-1 cold-sensitive phenotype, lacZ reporter assays, genetic analysis of sub2 mutants","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic suppressor screen with functional validation, single lab","pmids":["12034490"],"is_preprint":false},{"year":2002,"finding":"Null mutations in THO2 (and HPR1) impair transcription-coupled nucleotide excision repair (TCR) and, to a lesser extent, global genome repair (GGR), establishing that the THO complex affects both transcription elongation and DNA repair.","method":"UV sensitivity assays of hpr1Δ and tho2Δ yeast cells lacking GGR, molecular analysis of DNA repair using T4 endo V on the RPB2 transcribed strand","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct DNA repair molecular assay (T4 endo V) plus UV survival, single lab","pmids":["12000839"],"is_preprint":false},{"year":2015,"finding":"Missense variants in human THOC2 (a subunit of the TREX mRNA-export complex) cause X-linked intellectual disability; two variants lead to decreased stability of THOC2 protein and its TREX complex partners in patient-derived cells; structural modeling locates affected residues in RNA-binding domains of THOC2.","method":"X chromosome exome sequencing, patient-derived cell stability assays (Western blot for THOC2 and TREX partners), protein structural modeling","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — patient cell functional studies (protein stability) combined with structural modeling and genetic evidence across multiple families","pmids":["26166480"],"is_preprint":false},{"year":2018,"finding":"Additional missense THOC2 variants reduce protein stability, and splice-site variants produce C-terminally truncated THOC2 proteins; reduced THOC2 stability causes downstream destabilization of other TREX complex subunits (THOC1, THOC5, THOC6, THOC7).","method":"Functional studies in patient-derived cell lines (Western blotting for THOC2 and TREX subunit stability), analysis of splice-site variants and truncation products","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 2 / Strong — replicated across multiple patient cell lines, multiple TREX subunits assessed, orthogonal to prior study","pmids":["29851191"],"is_preprint":false},{"year":2013,"finding":"THOC2 knockdown in primary rat hippocampal neurons increased neurite extension, and knockdown in neuronal stem cells (LC1) increased their in vitro growth rate without modifying apoptosis; knockout of the THOC2 ortholog in C. elegans produced functional defects in specific sensory neurons.","method":"Thoc2 knockdown (siRNA/shRNA) in primary neurons and neuronal stem cells, C. elegans ortholog knockout with sensory neuron functional assays","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined cellular phenotype in multiple model systems, single study","pmids":["23749989"],"is_preprint":false},{"year":2020,"finding":"Reduced stability of THOC2 variant proteins has a flow-on effect on the stability of other NDD-associated THOC subunits; splicing-defective and deletion variants result in loss of small regions of the C-terminal THOC2 RNA-binding domain (RBD), establishing the C-terminal RBD as functionally important for complex integrity.","method":"Ex vivo missense variant testing, patient-derived cell line protein stability assays (Western blot for THOC2 and TREX subunits), intragenic deletion analysis","journal":"Frontiers in molecular neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — replicated across 14 variants in multiple patient cell lines, consistent with prior independent study","pmids":["32116545"],"is_preprint":false},{"year":2024,"finding":"Compromised THOC2/TREX function (via a hypomorphic Thoc2 exon 37-38 deletion) in mice causes R-loop accumulation, DNA damage, and consequent cell death in brain development, establishing that perturbed R-loop homeostasis is a molecular mechanism underlying THOC2 syndrome.","method":"Mouse model (Thoc2Δ/Y hypomorphic deletion), R-loop accumulation assays, DNA damage markers, behavioral phenotyping (spatial learning, working memory, sensorimotor function)","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo mouse model with multiple orthogonal molecular assays (R-loop, DNA damage) and behavioral readouts","pmids":["38331934"],"is_preprint":false},{"year":2021,"finding":"THOC2 promotes stem-like properties and radioresistance of triple-negative breast cancer cells in a THOC5-dependent manner by facilitating the nuclear export of SOX2 and NANOG transcripts; silencing THOC2 decreases SOX2 and NANOG protein expression and radiosensitizes cells.","method":"THOC2/THOC5 siRNA knockdown in TNBC cell lines, nuclear/cytoplasmic RNA fractionation, protein expression analysis (Western blot), xenograft tumor growth assays","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined molecular (RNA export) and cellular (stemness, radiosensitivity) readouts, in vitro and in vivo, single lab","pmids":["34708581"],"is_preprint":false},{"year":2023,"finding":"Upon perturbation of mRNP biogenesis, yeast Tho2 independently (outside the THO complex) recruits the RNA exosome subunit Rrp6 to chromatin via its carboxy-terminal domain; other THO subunits are not required for this function, establishing a THO complex-independent role for Tho2 in cotranscriptional mRNP quality control.","method":"Genome-wide ChIP-seq of THO subunits (Tho2, Thp2, Hpr1, Mft1) under mRNP biogenesis perturbation (bacterial Rho helicase expression), epistasis analysis of Tho2 C-terminal domain","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide ChIP-seq with multiple subunit comparisons and domain mapping, orthogonal genetic approach","pmids":["37914399"],"is_preprint":false},{"year":2024,"finding":"Yeast Tho2 escorts the transcriptional terminator Nrd1 on chromatin; Tho2 deletion causes aberrant/arbitrary Nrd1 chromatin binding and increased Nrd1 recruitment to translation-associated aging-related genes, linking Tho2 to lifespan regulation through transcriptional control of aging genes.","method":"Genome-wide ChIP-seq of Nrd1 in tho2Δ mutants, replicative lifespan assays, genetic epistasis (hpr1Δ, tho2Δ, rrp6Δ, NRD1 overexpression), interaction assays","journal":"Aging cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP-seq plus genetic epistasis, single lab","pmids":["38769776"],"is_preprint":false},{"year":2023,"finding":"THOC2 knockdown in GBM cells alters Bcl-x pre-mRNA splicing, increasing the pro-apoptotic Bcl-xS isoform, and reduces L1CAM expression, impairing cell adhesion and migration; these effects correlate with reduced 5-FU resistance.","method":"shRNA knockdown of THOC2 in GBM cell lines, RNA sequencing for alternative splicing variants, RT-qPCR, xenograft mouse model","journal":"American journal of cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with RNA-seq splicing analysis and in vivo xenograft, single lab","pmids":["37424800"],"is_preprint":false}],"current_model":"THOC2 is the largest subunit of the evolutionarily conserved THO/TREX complex, physically associating with THOC1 (Hpr1), THOC5, THOC6, THOC7, Mft1, and Thp2 in a nuclear complex that couples RNA polymerase II transcription elongation to co-transcriptional mRNP assembly, RNA splicing, and nuclear mRNA export; reduced THOC2 stability destabilizes the entire TREX complex, causes R-loop accumulation and DNA damage, and in certain contexts THOC2 acts independently of other THO subunits to recruit the RNA exosome (Rrp6) to chromatin for mRNP quality control, with loss-of-function variants in humans causing X-linked intellectual disability and broader neurodevelopmental disorders."},"narrative":{"mechanistic_narrative":"THOC2 is the largest subunit of the conserved nuclear THO/TREX complex that couples RNA polymerase II transcription elongation to co-transcriptional mRNP assembly and nuclear mRNA export; the yeast ortholog (Tho2/Rlr1) was first defined as a component of an oligomeric complex with Hpr1, Mft1, and Thp2 and shown to act at a step downstream of transcription initiation, where its loss reduces elongation efficiency and promotes transcription-dependent hyper-recombination [PMID:11060033, PMID:9707445, PMID:10675628]. THOC2 links transcription to mRNP biogenesis through the DEAD-box helicase Sub2/UAP56, which lies in the same export pathway [PMID:12034490], and its function further supports transcription-coupled nucleotide excision repair [PMID:12000839]. THOC2 stability is essential for the integrity of the entire TREX complex: destabilizing variants of THOC2 trigger downstream loss of partner subunits THOC1, THOC5, THOC6, and THOC7, with the C-terminal RNA-binding domain being critical for complex assembly [PMID:26166480, PMID:29851191, PMID:32116545]. Loss-of-function THOC2 variants cause X-linked intellectual disability and broader neurodevelopmental disorder, and a hypomorphic mouse model establishes that compromised THOC2/TREX function drives R-loop accumulation, DNA damage, and cell death during brain development as the molecular basis of THOC2 syndrome [PMID:26166480, PMID:38331934]. Beyond its core complex role, Tho2 can act independently of other THO subunits—recruiting the RNA exosome subunit Rrp6 to chromatin via its C-terminal domain for cotranscriptional mRNP quality control and escorting the terminator Nrd1 on chromatin [PMID:37914399, PMID:38769776]. In cancer contexts, THOC2 promotes nuclear export of SOX2 and NANOG transcripts to sustain stem-like properties and radioresistance, and influences Bcl-x alternative splicing and L1CAM expression [PMID:34708581, PMID:37424800].","teleology":[{"year":1998,"claim":"Established that THO2 acts within transcription itself rather than only downstream, answering whether the gene affects mRNA production at the elongation step and linking elongation defects to genome instability.","evidence":"In vivo transcription and recombination assays in tho2Δ yeast","pmids":["9707445"],"confidence":"High","gaps":["Did not define the physical complex mediating the effect","Mechanism connecting elongation to recombination not resolved"]},{"year":2000,"claim":"Defined the physical THO complex and placed THO2 at a step subsequent to initiation, establishing the molecular assembly through which it couples transcription to recombination.","evidence":"Affinity purification and reciprocal Co-IP of Tho2 with Hpr1/Mft1/Thp2; genetic suppressor screen against sin4","pmids":["11060033","10675628"],"confidence":"High","gaps":["Stoichiometry and architecture of the complex not determined","Direct RNA-binding role of Tho2 not shown"]},{"year":2002,"claim":"Connected the THO complex to mRNA export and DNA repair, showing THO2 links transcription to Sub2-mediated mRNP assembly and supports transcription-coupled repair.","evidence":"Dosage suppressor screen with sub2; UV survival and T4 endo V repair assays in tho2Δ/hpr1Δ yeast","pmids":["12034490","12000839"],"confidence":"Medium","gaps":["Direct physical interaction between Tho2 and Sub2 not demonstrated","Whether repair defect is secondary to elongation/export defect unresolved"]},{"year":2013,"claim":"Extended THOC2 function to metazoan neuronal biology, showing loss-of-function alters neurite extension, stem cell growth, and sensory neuron function across model systems.","evidence":"Thoc2 knockdown in rat neurons and neuronal stem cells; C. elegans ortholog knockout","pmids":["23749989"],"confidence":"Medium","gaps":["Molecular link between RNA export and neuronal phenotype not defined","No human disease connection established here"]},{"year":2015,"claim":"Identified THOC2 as a human X-linked intellectual disability gene and showed the disease mechanism is destabilization of THOC2 and its TREX partners, mapping affected residues to RNA-binding domains.","evidence":"X-exome sequencing, patient-cell protein stability assays, structural modeling","pmids":["26166480"],"confidence":"High","gaps":["Downstream transcriptomic consequences in patient neurons not characterized","Genotype-phenotype relationship across variants incomplete"]},{"year":2018,"claim":"Broadened the variant spectrum and confirmed that reduced THOC2 stability propagates to destabilize the wider TREX complex (THOC1/5/6/7), reinforcing the stability-based disease mechanism.","evidence":"Patient-derived cell stability assays for THOC2 and multiple TREX subunits; splice/truncation variant analysis","pmids":["29851191"],"confidence":"High","gaps":["Functional RNA-export defect not directly quantified","How partial complex destabilization maps to phenotype severity unknown"]},{"year":2020,"claim":"Pinpointed the C-terminal RNA-binding domain as functionally critical for complex integrity, refining which structural region underlies pathogenic destabilization.","evidence":"Ex vivo testing of 14 variants and intragenic deletions in patient cells with TREX subunit stability readouts","pmids":["32116545"],"confidence":"High","gaps":["Atomic structure of the C-terminal RBD not resolved","RNA targets bound by this domain not identified"]},{"year":2021,"claim":"Revealed a cancer-relevant export function, showing THOC2 drives nuclear export of stemness transcripts SOX2 and NANOG to confer stem-like properties and radioresistance.","evidence":"THOC2/THOC5 knockdown with RNA fractionation, protein analysis, and xenografts in TNBC","pmids":["34708581"],"confidence":"Medium","gaps":["Selectivity for specific transcripts mechanistically unexplained","Single-lab finding without independent replication"]},{"year":2023,"claim":"Uncovered a THO-complex-independent role for Tho2 in mRNP quality control and demonstrated splicing/adhesion consequences of THOC2 loss in cancer cells.","evidence":"Genome-wide ChIP-seq of THO subunits under mRNP perturbation with C-terminal domain mapping (yeast); shRNA knockdown with RNA-seq splicing analysis (GBM)","pmids":["37914399","37424800"],"confidence":"Medium","gaps":["Whether the exosome-recruiting role is conserved in human THOC2 untested","Direct binding of Tho2 C-terminus to Rrp6 not biochemically reconstituted"]},{"year":2024,"claim":"Established R-loop dysregulation as the in vivo molecular mechanism of THOC2 syndrome and linked Tho2 to terminator escort and lifespan control.","evidence":"Hypomorphic Thoc2 mouse with R-loop/DNA-damage and behavioral assays; Nrd1 ChIP-seq and lifespan assays in yeast","pmids":["38331934","38769776"],"confidence":"Medium","gaps":["Causal chain from R-loops to specific neuronal cell death not fully resolved","Whether Nrd1-escort function is conserved beyond yeast unknown"]},{"year":null,"claim":"How THOC2 selects specific transcripts for export and quality control, and how this transcript selectivity translates into tissue-specific neurodevelopmental and oncogenic outcomes, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of human THOC2 within assembled TREX","RNA-binding specificity of THOC2 not mapped","Mechanism of THO-independent functions in human cells uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[5,8]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[11,12]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[3,10,11]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[4,9]}],"complexes":["THO/TREX complex"],"partners":["THOC1","THOC5","THOC6","THOC7","MFT1","THP2","SUB2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NI27","full_name":"THO complex subunit 2","aliases":["hTREX120"],"length_aa":1593,"mass_kda":182.8,"function":"Component of the THO subcomplex of the TREX complex which is thought to couple mRNA transcription, processing and nuclear export, and which specifically associates with spliced mRNA and not with unspliced pre-mRNA (PubMed:15833825, PubMed:15998806, PubMed:17190602). Required for efficient export of polyadenylated RNA and spliced mRNA (PubMed:23222130). The THOC1-THOC2-THOC3 core complex alone is sufficient to bind export factor NXF1-NXT1 and promote ATPase activity of DDX39B; in the complex THOC2 is the only component that directly interacts with DDX39B (PubMed:33191911). TREX is recruited to spliced mRNAs by a transcription-independent mechanism, binds to mRNA upstream of the exon-junction complex (EJC) and is recruited in a splicing- and cap-dependent manner to a region near the 5' end of the mRNA where it functions in mRNA export to the cytoplasm via the TAP/NXF1 pathway (PubMed:15833825, PubMed:15998806, PubMed:17190602). Required for NXF1 localization to the nuclear rim (PubMed:22893130). THOC2 (and probably the THO complex) is involved in releasing mRNA from nuclear speckle domains (Microbial infection) The TREX complex is essential for the export of Kaposi's sarcoma-associated herpesvirus (KSHV) intronless mRNAs and infectious virus production","subcellular_location":"Nucleus; Nucleus speckle; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q8NI27/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/THOC2","classification":"Common Essential","n_dependent_lines":1199,"n_total_lines":1208,"dependency_fraction":0.9925496688741722},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"DDX39B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/THOC2","total_profiled":1310},"omim":[{"mim_id":"617468","title":"ARTHROGRYPOSIS MULTIPLEX CONGENITA 1, NEUROGENIC, WITH MYELIN DEFECT; AMC1","url":"https://www.omim.org/entry/617468"},{"mim_id":"615403","title":"THO COMPLEX, SUBUNIT 6; THOC6","url":"https://www.omim.org/entry/615403"},{"mim_id":"612733","title":"THO COMPLEX, SUBUNIT 5; THOC5","url":"https://www.omim.org/entry/612733"},{"mim_id":"611965","title":"THO COMPLEX, SUBUNIT 7; THOC7","url":"https://www.omim.org/entry/611965"},{"mim_id":"606929","title":"THO COMPLEX, SUBUNIT 3; THOC3","url":"https://www.omim.org/entry/606929"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/THOC2"},"hgnc":{"alias_symbol":["THO2","dJ506G2.1"],"prev_symbol":["CXorf3","MRX12","MRX35"]},"alphafold":{"accession":"Q8NI27","domains":[{"cath_id":"-","chopping":"11-127","consensus_level":"high","plddt":80.6777,"start":11,"end":127},{"cath_id":"-","chopping":"371-499","consensus_level":"medium","plddt":84.3519,"start":371,"end":499},{"cath_id":"-","chopping":"532-625","consensus_level":"medium","plddt":90.6913,"start":532,"end":625},{"cath_id":"-","chopping":"631-797","consensus_level":"medium","plddt":85.6965,"start":631,"end":797}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NI27","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NI27-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NI27-F1-predicted_aligned_error_v6.png","plddt_mean":72.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=THOC2","jax_strain_url":"https://www.jax.org/strain/search?query=THOC2"},"sequence":{"accession":"Q8NI27","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NI27.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NI27/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NI27"}},"corpus_meta":[{"pmid":"11060033","id":"PMC_11060033","title":"A protein complex containing Tho2, Hpr1, Mft1 and a novel protein, Thp2, connects transcription elongation with mitotic recombination in Saccharomyces cerevisiae.","date":"2000","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/11060033","citation_count":257,"is_preprint":false},{"pmid":"9707445","id":"PMC_9707445","title":"A novel yeast gene, THO2, is involved in RNA pol II transcription and provides new evidence for transcriptional elongation-associated recombination.","date":"1998","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/9707445","citation_count":131,"is_preprint":false},{"pmid":"26166480","id":"PMC_26166480","title":"THOC2 Mutations Implicate mRNA-Export Pathway in X-Linked Intellectual Disability.","date":"2015","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26166480","citation_count":61,"is_preprint":false},{"pmid":"34708581","id":"PMC_34708581","title":"THOC2 and THOC5 Regulate Stemness and Radioresistance in Triple-Negative Breast Cancer.","date":"2021","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/34708581","citation_count":48,"is_preprint":false},{"pmid":"23749989","id":"PMC_23749989","title":"A de novo X;8 translocation creates a PTK2-THOC2 gene fusion with THOC2 expression knockdown in a patient with psychomotor retardation and congenital cerebellar hypoplasia.","date":"2013","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23749989","citation_count":32,"is_preprint":false},{"pmid":"8825049","id":"PMC_8825049","title":"Localisation of a new gene for non-specific mental retardation to Xq22-q26 (MRX35).","date":"1996","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8825049","citation_count":30,"is_preprint":false},{"pmid":"31680623","id":"PMC_31680623","title":"Knockdown THOC2 suppresses the proliferation and invasion of 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N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/37914399","citation_count":2,"is_preprint":false},{"pmid":"40107550","id":"PMC_40107550","title":"Targeting mRNA export complex macromolecules THO subunits (Thoc2 and Thoc5) for somatic cell reprograming.","date":"2025","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/40107550","citation_count":0,"is_preprint":false},{"pmid":"41604663","id":"PMC_41604663","title":"Mutation in THO2, a component of THO/TREX complex, causes transcriptional gene silencing and genome-wide DNA methylation changes.","date":"2026","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/41604663","citation_count":0,"is_preprint":false},{"pmid":"38436395","id":"PMC_38436395","title":"Color tunable luminescence in ThO2:Er3+,Yb3+ nanocrystals: a promising new platform for upconversion.","date":"2024","source":"Physical chemistry chemical physics : PCCP","url":"https://pubmed.ncbi.nlm.nih.gov/38436395","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.05.680468","title":"XIST Self-regulates its Association with THOC2 and the Nuclear Epigenetic Machinery via miR-186 in Alzheimer’s disease","date":"2025-10-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.05.680468","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12717,"output_tokens":3406,"usd":0.044621,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10970,"output_tokens":3419,"usd":0.070163,"stage2_stop_reason":"end_turn"},"total_usd":0.114784,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"THOC2 (Tho2) is a component of a nuclear oligomeric protein complex containing Hpr1, Mft1, and Thp2, physically associated via co-immunoprecipitation; this complex connects transcription elongation with mitotic recombination in yeast.\",\n      \"method\": \"Affinity purification (His6-HA-tagged Tho2), reciprocal co-immunoprecipitation with anti-Mft1 antibodies, genetic analysis of deletion mutants\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal methods (affinity purification + immunoprecipitation + genetic phenotyping), replicated across subunits\",\n      \"pmids\": [\"11060033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"THO2 is required for RNA polymerase II-dependent transcription elongation; tho2Δ reduces transcriptional efficiency and abolishes transcription through the lacZ sequence, and causes hyper-recombination between direct repeats in a transcription-dependent manner.\",\n      \"method\": \"In vivo transcriptional analysis of tho2Δ cells, recombination frequency assays, transcription-dependent recombination genetic analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo assays (transcription and recombination) in the same study, replicated in subsequent work\",\n      \"pmids\": [\"9707445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"RLR1 (THO2) functions in transcription at a step subsequent to initiation; rlr1 mutants specifically fail to express lacZ fusions while expressing native chromosomal genes at near-normal levels; RLR1 was isolated as a suppressor of SIN4 (a Mediator subcomplex component), placing THO2 in a pathway downstream of transcription initiation.\",\n      \"method\": \"Genetic suppressor screen (rlr1-1 as suppressor of sin4 mutation), lacZ reporter assays, epistasis analysis\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis plus reporter assays, single lab\",\n      \"pmids\": [\"10675628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The DEAD-box RNA helicase Sub2 is a dosage-dependent suppressor of RLR1 (THO2) and is required for lacZ expression in yeast, placing Sub2 in the same mRNA export pathway as THO2 and suggesting THO2 links transcription to Sub2-mediated mRNP assembly/export.\",\n      \"method\": \"Dosage-dependent suppressor screen of rlr1-1 cold-sensitive phenotype, lacZ reporter assays, genetic analysis of sub2 mutants\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic suppressor screen with functional validation, single lab\",\n      \"pmids\": [\"12034490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Null mutations in THO2 (and HPR1) impair transcription-coupled nucleotide excision repair (TCR) and, to a lesser extent, global genome repair (GGR), establishing that the THO complex affects both transcription elongation and DNA repair.\",\n      \"method\": \"UV sensitivity assays of hpr1Δ and tho2Δ yeast cells lacking GGR, molecular analysis of DNA repair using T4 endo V on the RPB2 transcribed strand\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct DNA repair molecular assay (T4 endo V) plus UV survival, single lab\",\n      \"pmids\": [\"12000839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Missense variants in human THOC2 (a subunit of the TREX mRNA-export complex) cause X-linked intellectual disability; two variants lead to decreased stability of THOC2 protein and its TREX complex partners in patient-derived cells; structural modeling locates affected residues in RNA-binding domains of THOC2.\",\n      \"method\": \"X chromosome exome sequencing, patient-derived cell stability assays (Western blot for THOC2 and TREX partners), protein structural modeling\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — patient cell functional studies (protein stability) combined with structural modeling and genetic evidence across multiple families\",\n      \"pmids\": [\"26166480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Additional missense THOC2 variants reduce protein stability, and splice-site variants produce C-terminally truncated THOC2 proteins; reduced THOC2 stability causes downstream destabilization of other TREX complex subunits (THOC1, THOC5, THOC6, THOC7).\",\n      \"method\": \"Functional studies in patient-derived cell lines (Western blotting for THOC2 and TREX subunit stability), analysis of splice-site variants and truncation products\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — replicated across multiple patient cell lines, multiple TREX subunits assessed, orthogonal to prior study\",\n      \"pmids\": [\"29851191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"THOC2 knockdown in primary rat hippocampal neurons increased neurite extension, and knockdown in neuronal stem cells (LC1) increased their in vitro growth rate without modifying apoptosis; knockout of the THOC2 ortholog in C. elegans produced functional defects in specific sensory neurons.\",\n      \"method\": \"Thoc2 knockdown (siRNA/shRNA) in primary neurons and neuronal stem cells, C. elegans ortholog knockout with sensory neuron functional assays\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined cellular phenotype in multiple model systems, single study\",\n      \"pmids\": [\"23749989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Reduced stability of THOC2 variant proteins has a flow-on effect on the stability of other NDD-associated THOC subunits; splicing-defective and deletion variants result in loss of small regions of the C-terminal THOC2 RNA-binding domain (RBD), establishing the C-terminal RBD as functionally important for complex integrity.\",\n      \"method\": \"Ex vivo missense variant testing, patient-derived cell line protein stability assays (Western blot for THOC2 and TREX subunits), intragenic deletion analysis\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — replicated across 14 variants in multiple patient cell lines, consistent with prior independent study\",\n      \"pmids\": [\"32116545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Compromised THOC2/TREX function (via a hypomorphic Thoc2 exon 37-38 deletion) in mice causes R-loop accumulation, DNA damage, and consequent cell death in brain development, establishing that perturbed R-loop homeostasis is a molecular mechanism underlying THOC2 syndrome.\",\n      \"method\": \"Mouse model (Thoc2Δ/Y hypomorphic deletion), R-loop accumulation assays, DNA damage markers, behavioral phenotyping (spatial learning, working memory, sensorimotor function)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo mouse model with multiple orthogonal molecular assays (R-loop, DNA damage) and behavioral readouts\",\n      \"pmids\": [\"38331934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"THOC2 promotes stem-like properties and radioresistance of triple-negative breast cancer cells in a THOC5-dependent manner by facilitating the nuclear export of SOX2 and NANOG transcripts; silencing THOC2 decreases SOX2 and NANOG protein expression and radiosensitizes cells.\",\n      \"method\": \"THOC2/THOC5 siRNA knockdown in TNBC cell lines, nuclear/cytoplasmic RNA fractionation, protein expression analysis (Western blot), xenograft tumor growth assays\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined molecular (RNA export) and cellular (stemness, radiosensitivity) readouts, in vitro and in vivo, single lab\",\n      \"pmids\": [\"34708581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Upon perturbation of mRNP biogenesis, yeast Tho2 independently (outside the THO complex) recruits the RNA exosome subunit Rrp6 to chromatin via its carboxy-terminal domain; other THO subunits are not required for this function, establishing a THO complex-independent role for Tho2 in cotranscriptional mRNP quality control.\",\n      \"method\": \"Genome-wide ChIP-seq of THO subunits (Tho2, Thp2, Hpr1, Mft1) under mRNP biogenesis perturbation (bacterial Rho helicase expression), epistasis analysis of Tho2 C-terminal domain\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide ChIP-seq with multiple subunit comparisons and domain mapping, orthogonal genetic approach\",\n      \"pmids\": [\"37914399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Yeast Tho2 escorts the transcriptional terminator Nrd1 on chromatin; Tho2 deletion causes aberrant/arbitrary Nrd1 chromatin binding and increased Nrd1 recruitment to translation-associated aging-related genes, linking Tho2 to lifespan regulation through transcriptional control of aging genes.\",\n      \"method\": \"Genome-wide ChIP-seq of Nrd1 in tho2Δ mutants, replicative lifespan assays, genetic epistasis (hpr1Δ, tho2Δ, rrp6Δ, NRD1 overexpression), interaction assays\",\n      \"journal\": \"Aging cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP-seq plus genetic epistasis, single lab\",\n      \"pmids\": [\"38769776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"THOC2 knockdown in GBM cells alters Bcl-x pre-mRNA splicing, increasing the pro-apoptotic Bcl-xS isoform, and reduces L1CAM expression, impairing cell adhesion and migration; these effects correlate with reduced 5-FU resistance.\",\n      \"method\": \"shRNA knockdown of THOC2 in GBM cell lines, RNA sequencing for alternative splicing variants, RT-qPCR, xenograft mouse model\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with RNA-seq splicing analysis and in vivo xenograft, single lab\",\n      \"pmids\": [\"37424800\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"THOC2 is the largest subunit of the evolutionarily conserved THO/TREX complex, physically associating with THOC1 (Hpr1), THOC5, THOC6, THOC7, Mft1, and Thp2 in a nuclear complex that couples RNA polymerase II transcription elongation to co-transcriptional mRNP assembly, RNA splicing, and nuclear mRNA export; reduced THOC2 stability destabilizes the entire TREX complex, causes R-loop accumulation and DNA damage, and in certain contexts THOC2 acts independently of other THO subunits to recruit the RNA exosome (Rrp6) to chromatin for mRNP quality control, with loss-of-function variants in humans causing X-linked intellectual disability and broader neurodevelopmental disorders.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"THOC2 is the largest subunit of the conserved nuclear THO/TREX complex that couples RNA polymerase II transcription elongation to co-transcriptional mRNP assembly and nuclear mRNA export; the yeast ortholog (Tho2/Rlr1) was first defined as a component of an oligomeric complex with Hpr1, Mft1, and Thp2 and shown to act at a step downstream of transcription initiation, where its loss reduces elongation efficiency and promotes transcription-dependent hyper-recombination [#0, #1, #2]. THOC2 links transcription to mRNP biogenesis through the DEAD-box helicase Sub2/UAP56, which lies in the same export pathway [#3], and its function further supports transcription-coupled nucleotide excision repair [#4]. THOC2 stability is essential for the integrity of the entire TREX complex: destabilizing variants of THOC2 trigger downstream loss of partner subunits THOC1, THOC5, THOC6, and THOC7, with the C-terminal RNA-binding domain being critical for complex assembly [#5, #6, #8]. Loss-of-function THOC2 variants cause X-linked intellectual disability and broader neurodevelopmental disorder, and a hypomorphic mouse model establishes that compromised THOC2/TREX function drives R-loop accumulation, DNA damage, and cell death during brain development as the molecular basis of THOC2 syndrome [#5, #9]. Beyond its core complex role, Tho2 can act independently of other THO subunits—recruiting the RNA exosome subunit Rrp6 to chromatin via its C-terminal domain for cotranscriptional mRNP quality control and escorting the terminator Nrd1 on chromatin [#11, #12]. In cancer contexts, THOC2 promotes nuclear export of SOX2 and NANOG transcripts to sustain stem-like properties and radioresistance, and influences Bcl-x alternative splicing and L1CAM expression [#10, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that THO2 acts within transcription itself rather than only downstream, answering whether the gene affects mRNA production at the elongation step and linking elongation defects to genome instability.\",\n      \"evidence\": \"In vivo transcription and recombination assays in tho2\\u0394 yeast\",\n      \"pmids\": [\"9707445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the physical complex mediating the effect\", \"Mechanism connecting elongation to recombination not resolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the physical THO complex and placed THO2 at a step subsequent to initiation, establishing the molecular assembly through which it couples transcription to recombination.\",\n      \"evidence\": \"Affinity purification and reciprocal Co-IP of Tho2 with Hpr1/Mft1/Thp2; genetic suppressor screen against sin4\",\n      \"pmids\": [\"11060033\", \"10675628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and architecture of the complex not determined\", \"Direct RNA-binding role of Tho2 not shown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected the THO complex to mRNA export and DNA repair, showing THO2 links transcription to Sub2-mediated mRNP assembly and supports transcription-coupled repair.\",\n      \"evidence\": \"Dosage suppressor screen with sub2; UV survival and T4 endo V repair assays in tho2\\u0394/hpr1\\u0394 yeast\",\n      \"pmids\": [\"12034490\", \"12000839\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction between Tho2 and Sub2 not demonstrated\", \"Whether repair defect is secondary to elongation/export defect unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended THOC2 function to metazoan neuronal biology, showing loss-of-function alters neurite extension, stem cell growth, and sensory neuron function across model systems.\",\n      \"evidence\": \"Thoc2 knockdown in rat neurons and neuronal stem cells; C. elegans ortholog knockout\",\n      \"pmids\": [\"23749989\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between RNA export and neuronal phenotype not defined\", \"No human disease connection established here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified THOC2 as a human X-linked intellectual disability gene and showed the disease mechanism is destabilization of THOC2 and its TREX partners, mapping affected residues to RNA-binding domains.\",\n      \"evidence\": \"X-exome sequencing, patient-cell protein stability assays, structural modeling\",\n      \"pmids\": [\"26166480\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream transcriptomic consequences in patient neurons not characterized\", \"Genotype-phenotype relationship across variants incomplete\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Broadened the variant spectrum and confirmed that reduced THOC2 stability propagates to destabilize the wider TREX complex (THOC1/5/6/7), reinforcing the stability-based disease mechanism.\",\n      \"evidence\": \"Patient-derived cell stability assays for THOC2 and multiple TREX subunits; splice/truncation variant analysis\",\n      \"pmids\": [\"29851191\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional RNA-export defect not directly quantified\", \"How partial complex destabilization maps to phenotype severity unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Pinpointed the C-terminal RNA-binding domain as functionally critical for complex integrity, refining which structural region underlies pathogenic destabilization.\",\n      \"evidence\": \"Ex vivo testing of 14 variants and intragenic deletions in patient cells with TREX subunit stability readouts\",\n      \"pmids\": [\"32116545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the C-terminal RBD not resolved\", \"RNA targets bound by this domain not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a cancer-relevant export function, showing THOC2 drives nuclear export of stemness transcripts SOX2 and NANOG to confer stem-like properties and radioresistance.\",\n      \"evidence\": \"THOC2/THOC5 knockdown with RNA fractionation, protein analysis, and xenografts in TNBC\",\n      \"pmids\": [\"34708581\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Selectivity for specific transcripts mechanistically unexplained\", \"Single-lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Uncovered a THO-complex-independent role for Tho2 in mRNP quality control and demonstrated splicing/adhesion consequences of THOC2 loss in cancer cells.\",\n      \"evidence\": \"Genome-wide ChIP-seq of THO subunits under mRNP perturbation with C-terminal domain mapping (yeast); shRNA knockdown with RNA-seq splicing analysis (GBM)\",\n      \"pmids\": [\"37914399\", \"37424800\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the exosome-recruiting role is conserved in human THOC2 untested\", \"Direct binding of Tho2 C-terminus to Rrp6 not biochemically reconstituted\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established R-loop dysregulation as the in vivo molecular mechanism of THOC2 syndrome and linked Tho2 to terminator escort and lifespan control.\",\n      \"evidence\": \"Hypomorphic Thoc2 mouse with R-loop/DNA-damage and behavioral assays; Nrd1 ChIP-seq and lifespan assays in yeast\",\n      \"pmids\": [\"38331934\", \"38769776\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal chain from R-loops to specific neuronal cell death not fully resolved\", \"Whether Nrd1-escort function is conserved beyond yeast unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How THOC2 selects specific transcripts for export and quality control, and how this transcript selectivity translates into tissue-specific neurodevelopmental and oncogenic outcomes, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of human THOC2 within assembled TREX\", \"RNA-binding specificity of THOC2 not mapped\", \"Mechanism of THO-independent functions in human cells uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [5, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [11, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [3, 10, 11]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [4, 9]}\n    ],\n    \"complexes\": [\"THO/TREX complex\"],\n    \"partners\": [\"THOC1\", \"THOC5\", \"THOC6\", \"THOC7\", \"MFT1\", \"THP2\", \"SUB2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}