{"gene":"GTF3C4","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1999,"finding":"hTFIIIC90 (GTF3C4) was cloned and shown to be a bona fide subunit of the TFIIIC2 DNA-binding subcomplex of human TFIIIC, required absolutely for RNA polymerase III transcription. Immunodepletion and immunoprecipitation studies demonstrated that hTFIIIC90 physically interacts with the TFIIIC subunits hTFIIIC220, hTFIIIC110, and hTFIIIC63, the TFIIIB subunit hTFIIIB90, and the RNA polymerase III subunits hRPC39 and hRPC62, suggesting it bridges TFIIIB and Pol III recruitment to the preinitiation complex.","method":"cDNA cloning, immunodepletion, immunoprecipitation, in vitro RNA polymerase III transcription assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (immunodepletion, Co-IP, in vitro transcription reconstitution) in single rigorous study","pmids":["10523658"],"is_preprint":false},{"year":1999,"finding":"hTFIIIC90 (GTF3C4) possesses an intrinsic histone acetyltransferase (HAT) activity with substrate specificity for histone H3, as demonstrated by in vitro HAT assays.","method":"In vitro histone acetyltransferase assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro enzymatic assay with defined substrate specificity","pmids":["10523658"],"is_preprint":false},{"year":2007,"finding":"TFIIIC35, the sixth subunit of human TFIIIC, specifically interacts with hTFIIIC90 (GTF3C4) in vitro, and affinity-purified TFIIIC containing epitope-tagged TFIIIC35 (which includes GTF3C4) is active in binding to and transcribing the VA1 gene in vitro, confirming GTF3C4's presence and function in the intact TFIIIC complex.","method":"In vitro binding assay (GST pulldown), affinity purification of epitope-tagged TFIIIC, in vitro transcription assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal pulldown and functional transcription assay, single study","pmids":["17409385"],"is_preprint":false},{"year":2020,"finding":"siRNA-mediated knockdown of GTF3C4 induces cellular senescence markers, including decreased cell number, activation of p16/p21, and morphological changes resembling senescence, placing GTF3C4 as a regulator whose loss triggers senescence.","method":"siRNA knockdown with readouts of cell number, p16/p21 activation, and cellular morphology","journal":"Genome biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — clean loss-of-function with multiple phenotypic readouts, single study","pmids":["32264951"],"is_preprint":false},{"year":2026,"finding":"GTF3C4 was identified as the direct molecular target of the anti-cancer compound bufalin using Limited Proteolysis-Mass Spectrometry. Direct binding of bufalin to GTF3C4 was validated by cell thermal shift assay, drug affinity response target stability (DARTS) assay, and surface plasmon resonance. GTF3C4 knockdown suppresses the PI3K/AKT signaling pathway and inhibits breast cancer cell proliferation while promoting apoptosis, placing GTF3C4 upstream of PI3K/AKT in breast cancer cells.","method":"Limited proteolysis-mass spectrometry (LiP-MS), cell thermal shift assay (CETSA), DARTS assay, surface plasmon resonance, siRNA knockdown with PI3K/AKT pathway readouts and proliferation/apoptosis assays","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal direct binding methods plus functional KD, single study","pmids":["41649141"],"is_preprint":false}],"current_model":"GTF3C4 (hTFIIIC90) is an essential subunit of the human TFIIIC2 complex that bridges RNA polymerase III transcription by interacting with multiple TFIIIC, TFIIIB, and Pol III subunits, possesses intrinsic histone H3 acetyltransferase activity, and additionally regulates cell proliferation and survival upstream of the PI3K/AKT pathway, such that its loss triggers cellular senescence."},"narrative":{"teleology":[{"year":1999,"claim":"Identification of hTFIIIC90 as a TFIIIC2 subunit resolved how TFIIIC bridges TFIIIB and Pol III at the preinitiation complex, establishing that a single subunit physically contacts components of all three assemblies and is absolutely required for Pol III transcription.","evidence":"cDNA cloning, immunodepletion/reconstitution of in vitro Pol III transcription, and co-immunoprecipitation with TFIIIC, TFIIIB, and Pol III subunits","pmids":["10523658"],"confidence":"High","gaps":["Structural basis of the multi-subunit bridging interactions remains unresolved","In vivo ChIP-based occupancy at Pol III promoters was not assessed","Whether the bridging function is rate-limiting for Pol III transcription in cells is unknown"]},{"year":1999,"claim":"Demonstration that hTFIIIC90 has intrinsic histone H3 acetyltransferase activity revealed an unexpected enzymatic function for a general transcription factor subunit, suggesting TFIIIC may directly modify chromatin at Pol III-transcribed loci.","evidence":"In vitro HAT assay with purified protein and defined histone substrates","pmids":["10523658"],"confidence":"High","gaps":["Specific H3 lysine residues targeted have not been identified","In vivo HAT activity and its functional contribution to Pol III transcription are untested","No catalytic-dead mutant has been characterized"]},{"year":2007,"claim":"Identification of the sixth TFIIIC subunit (TFIIIC35) as a direct GTF3C4 interactor, and demonstration that complete TFIIIC retains transcription activity, confirmed the subunit composition and functional integrity of the holo-complex.","evidence":"GST pulldown of TFIIIC35–hTFIIIC90 interaction and affinity purification of epitope-tagged TFIIIC with in vitro VA1 transcription assay","pmids":["17409385"],"confidence":"Medium","gaps":["Stoichiometry and architecture of the six-subunit complex remain unresolved","Whether the TFIIIC35–GTF3C4 interaction is required for HAT activity is unknown"]},{"year":2020,"claim":"Loss-of-function studies revealed that GTF3C4 depletion triggers cellular senescence with activation of the p16/p21 axis, extending its role beyond Pol III transcription to cell proliferation control.","evidence":"siRNA knockdown with quantification of cell number, p16/p21 expression, and senescence morphology","pmids":["32264951"],"confidence":"Medium","gaps":["Whether senescence results from impaired Pol III transcription or a Pol III-independent function is undetermined","Rescue experiments re-expressing GTF3C4 were not reported","Relevance to in vivo tissue homeostasis is unknown"]},{"year":2026,"claim":"Identification of GTF3C4 as the direct target of the anti-cancer compound bufalin, and demonstration that GTF3C4 knockdown suppresses PI3K/AKT signaling, positioned GTF3C4 upstream of a major pro-survival pathway in breast cancer cells.","evidence":"LiP-MS target identification, validated by CETSA, DARTS, and SPR; siRNA knockdown with PI3K/AKT pathway and proliferation/apoptosis readouts in breast cancer cell lines","pmids":["41649141"],"confidence":"Medium","gaps":["Mechanism connecting GTF3C4 to PI3K/AKT activation is uncharacterized","Whether bufalin binding inhibits GTF3C4 HAT or scaffolding function is unknown","Findings are from a single study in breast cancer cell lines and lack in vivo validation"]},{"year":null,"claim":"Key unresolved questions include the structural basis for GTF3C4's multi-subunit bridging role within the Pol III preinitiation complex, the specific histone residues and genomic loci modified by its HAT activity in vivo, and the molecular pathway through which GTF3C4 regulates PI3K/AKT signaling and cellular senescence.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of GTF3C4 within TFIIIC or the Pol III PIC exists","In vivo HAT target sites and catalytic residues are uncharacterized","Causal relationship between Pol III transcription defects and senescence/PI3K signaling has not been dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1]},{"term_id":"GO:0140223","term_label":"general transcription initiation factor activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,2]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1]}],"complexes":["TFIIIC2","TFIIIC"],"partners":["GTF3C1","GTF3C2","GTF3C5","GTF3C6","BDP1","POLR3E","POLR3G"],"other_free_text":[]},"mechanistic_narrative":"GTF3C4 (hTFIIIC90) is a core subunit of the human TFIIIC2 DNA-binding subcomplex that is essential for RNA polymerase III transcription, bridging TFIIIC to TFIIIB and Pol III through direct physical interactions with multiple subunits of each complex [PMID:10523658]. Beyond its structural role, GTF3C4 possesses intrinsic histone acetyltransferase activity specific for histone H3, linking the Pol III transcription machinery to chromatin modification [PMID:10523658]. Loss of GTF3C4 induces cellular senescence marked by p16/p21 activation [PMID:32264951] and suppresses PI3K/AKT signaling, inhibiting breast cancer cell proliferation and promoting apoptosis [PMID:41649141]."},"prefetch_data":{"uniprot":{"accession":"Q9UKN8","full_name":"General transcription factor 3C polypeptide 4","aliases":["TF3C-delta","Transcription factor IIIC 90 kDa subunit","TFIIIC 90 kDa subunit","TFIIIC90","Transcription factor IIIC subunit delta"],"length_aa":822,"mass_kda":92.0,"function":"Essential for RNA polymerase III to make a number of small nuclear and cytoplasmic RNAs, including 5S RNA, tRNA, and adenovirus-associated (VA) RNA of both cellular and viral origin (PubMed:10523658). Has histone acetyltransferase activity (HAT) with unique specificity for free and nucleosomal H3 (PubMed:10523658). May cooperate with GTF3C5 in facilitating the recruitment of TFIIIB and RNA polymerase through direct interactions with BRF1, POLR3C and POLR3F (PubMed:10523658). May be localized close to the A box (PubMed:10523658)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9UKN8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GTF3C4","classification":"Common Essential","n_dependent_lines":867,"n_total_lines":1208,"dependency_fraction":0.7177152317880795},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CBX1","stoichiometry":0.2},{"gene":"NPM1","stoichiometry":0.2},{"gene":"RPS16","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GTF3C4","total_profiled":1310},"omim":[{"mim_id":"611784","title":"GENERAL TRANSCRIPTION FACTOR 3C, POLYPEPTIDE 6; GTF3C6","url":"https://www.omim.org/entry/611784"},{"mim_id":"604892","title":"GENERAL TRANSCRIPTION FACTOR 3C, POLYPEPTIDE 4; GTF3C4","url":"https://www.omim.org/entry/604892"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Mitochondria","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GTF3C4"},"hgnc":{"alias_symbol":["TFIIIC90","KAT12"],"prev_symbol":[]},"alphafold":{"accession":"Q9UKN8","domains":[{"cath_id":"2.130.10.10","chopping":"51-223_231-515","consensus_level":"medium","plddt":90.5516,"start":51,"end":515},{"cath_id":"-","chopping":"523-574","consensus_level":"medium","plddt":93.516,"start":523,"end":574},{"cath_id":"-","chopping":"670-810","consensus_level":"medium","plddt":88.1701,"start":670,"end":810}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKN8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKN8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKN8-F1-predicted_aligned_error_v6.png","plddt_mean":81.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GTF3C4","jax_strain_url":"https://www.jax.org/strain/search?query=GTF3C4"},"sequence":{"accession":"Q9UKN8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UKN8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UKN8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKN8"}},"corpus_meta":[{"pmid":"32264951","id":"PMC_32264951","title":"A multidimensional systems biology analysis of cellular senescence in aging and disease.","date":"2020","source":"Genome biology","url":"https://pubmed.ncbi.nlm.nih.gov/32264951","citation_count":303,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"10523658","id":"PMC_10523658","title":"The TFIIIC90 subunit of TFIIIC interacts with multiple components of the RNA polymerase III machinery and contains a histone-specific acetyltransferase activity.","date":"1999","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10523658","citation_count":86,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17409385","id":"PMC_17409385","title":"Identification, molecular cloning, and characterization of the sixth subunit of human transcription factor TFIIIC.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17409385","citation_count":35,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"38349085","id":"PMC_38349085","title":"NS1-mediated enhancement of MVC transcription and replication promoted by KAT5/H4K12ac.","date":"2024","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/38349085","citation_count":8,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35820807","id":"PMC_35820807","title":"Overdominant expression of related genes of ion homeostasis improves K+ content advantage in hybrid tobacco leaves.","date":"2022","source":"BMC plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/35820807","citation_count":7,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39175876","id":"PMC_39175876","title":"CRISPR-Cas9 screening develops an epigenetic and transcriptional gene signature for risk stratification and target prediction in neuroblastoma.","date":"2024","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/39175876","citation_count":2,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"41649141","id":"PMC_41649141","title":"Bufalin Inhibits the PI3K/AKT Pathway by Targeting GTF3C4 to Impede Breast Cancer Progression.","date":"2026","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/41649141","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17081983","id":"PMC_17081983","title":"Global, in vivo, and site-specific phosphorylation dynamics in signaling networks.","date":"2006","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/17081983","citation_count":2861,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12477932","id":"PMC_12477932","title":"Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12477932","citation_count":1479,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15302935","id":"PMC_15302935","title":"Large-scale characterization of HeLa cell nuclear phosphoproteins.","date":"2004","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/15302935","citation_count":1159,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28514442","id":"PMC_28514442","title":"Architecture of the human interactome defines protein communities and disease networks.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28514442","citation_count":1085,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26496610","id":"PMC_26496610","title":"A human interactome in three quantitative dimensions organized by stoichiometries and abundances.","date":"2015","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/26496610","citation_count":1015,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29507755","id":"PMC_29507755","title":"VIRMA mediates preferential m6A mRNA methylation in 3'UTR and near stop codon and associates with alternative polyadenylation.","date":"2018","source":"Cell discovery","url":"https://pubmed.ncbi.nlm.nih.gov/29507755","citation_count":829,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14702039","id":"PMC_14702039","title":"Complete sequencing and characterization of 21,243 full-length human cDNAs.","date":"2003","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14702039","citation_count":754,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33961781","id":"PMC_33961781","title":"Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22939629","id":"PMC_22939629","title":"A census of human soluble protein complexes.","date":"2012","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/22939629","citation_count":689,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21873635","id":"PMC_21873635","title":"Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium.","date":"2011","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/21873635","citation_count":656,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15489334","id":"PMC_15489334","title":"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).","date":"2004","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/15489334","citation_count":438,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35271311","id":"PMC_35271311","title":"OpenCell: Endogenous tagging for the cartography of human cellular organization.","date":"2022","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/35271311","citation_count":432,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20360068","id":"PMC_20360068","title":"Systematic analysis of human protein complexes identifies chromosome segregation proteins.","date":"2010","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/20360068","citation_count":421,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"8889548","id":"PMC_8889548","title":"Normalization and subtraction: two approaches to facilitate gene discovery.","date":"1996","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/8889548","citation_count":401,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"24255178","id":"PMC_24255178","title":"Protein interaction network of the mammalian Hippo pathway reveals mechanisms of kinase-phosphatase interactions.","date":"2013","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/24255178","citation_count":383,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29656893","id":"PMC_29656893","title":"DNA Repair Network Analysis Reveals Shieldin as a Key Regulator of NHEJ and PARP Inhibitor Sensitivity.","date":"2018","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/29656893","citation_count":379,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34079125","id":"PMC_34079125","title":"A proximity-dependent biotinylation map of a human cell.","date":"2021","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/34079125","citation_count":339,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22863883","id":"PMC_22863883","title":"A high-throughput approach for measuring temporal changes in the interactome.","date":"2012","source":"Nature methods","url":"https://pubmed.ncbi.nlm.nih.gov/22863883","citation_count":273,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21654808","id":"PMC_21654808","title":"A function for cyclin D1 in DNA repair uncovered by protein interactome analyses in human cancers.","date":"2011","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/21654808","citation_count":269,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"27173435","id":"PMC_27173435","title":"An organelle-specific protein landscape identifies novel diseases and molecular mechanisms.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27173435","citation_count":211,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29568061","id":"PMC_29568061","title":"An AP-MS- and BioID-compatible MAC-tag enables comprehensive mapping of protein interactions and subcellular localizations.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29568061","citation_count":201,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"25544563","id":"PMC_25544563","title":"Global mapping of herpesvirus-host protein complexes reveals a transcription strategy for late genes.","date":"2014","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/25544563","citation_count":173,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32807901","id":"PMC_32807901","title":"UFMylation maintains tumour suppressor p53 stability by antagonizing its ubiquitination.","date":"2020","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/32807901","citation_count":168,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30804502","id":"PMC_30804502","title":"H4K20me0 recognition by BRCA1-BARD1 directs homologous recombination to sister chromatids.","date":"2019","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/30804502","citation_count":162,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32416067","id":"PMC_32416067","title":"Synthetic Lethal and Resistance Interactions with BET Bromodomain Inhibitors in Triple-Negative Breast Cancer.","date":"2020","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/32416067","citation_count":159,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30415952","id":"PMC_30415952","title":"MYC Protein Interactome Profiling Reveals Functionally Distinct Regions that Cooperate to Drive Tumorigenesis.","date":"2018","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/30415952","citation_count":152,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21549307","id":"PMC_21549307","title":"Maintenance of silent chromatin through replication requires SWI/SNF-like chromatin remodeler SMARCAD1.","date":"2011","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/21549307","citation_count":148,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23349634","id":"PMC_23349634","title":"A newly uncovered group of distantly related lysine methyltransferases preferentially interact with molecular chaperones to regulate their activity.","date":"2013","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23349634","citation_count":131,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"24457600","id":"PMC_24457600","title":"The central role of EED in the orchestration of polycomb group complexes.","date":"2014","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/24457600","citation_count":131,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17314511","id":"PMC_17314511","title":"Large-scale identification of c-MYC-associated proteins using a combined TAP/MudPIT approach.","date":"2007","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/17314511","citation_count":127,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4934,"output_tokens":1033,"usd":0.015149},"stage2":{"model":"claude-opus-4-6","input_tokens":4233,"output_tokens":1609,"usd":0.092085},"total_usd":0.259799,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":17380,"output_tokens":2776,"usd":0.04689},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":4815,"output_tokens":1855,"usd":0.105675}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"hTFIIIC90 (GTF3C4) is a subunit of the TFIIIC2 DNA-binding subcomplex that is absolutely required for RNA polymerase III transcription, physically interacts with hTFIIIC220, hTFIIIC110, hTFIIIC63, hTFIIIB90, hRPC39, and hRPC62, and possesses intrinsic histone acetyltransferase activity with substrate specificity for histone H3.\",\n      \"method\": \"cDNA cloning, immunodepletion, immunoprecipitation, in vitro transcription assay, histone acetyltransferase assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (immunodepletion, Co-IP, in vitro HAT assay) in a highly-cited foundational paper\",\n      \"pmids\": [\"10523658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TFIIIC35 (sixth subunit of human TFIIIC) specifically interacts with TFIIIC90 (GTF3C4) in vitro, and affinity-purified TFIIIC containing TFIIIC35 is active in binding to and transcription of the VA1 gene, placing GTF3C4 within the complete six-subunit TFIIIC complex.\",\n      \"method\": \"Affinity purification, in vitro binding assay, in vitro transcription assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal in vitro interaction and functional transcription assay, single study\",\n      \"pmids\": [\"17409385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"siRNA-mediated knockdown of GTF3C4 decreases cell number, activates p16/p21, and induces morphological changes consistent with cellular senescence, establishing a functional role for GTF3C4 in suppressing cellular senescence.\",\n      \"method\": \"siRNA knockdown, cell counting, p16/p21 activation assay, morphological analysis\",\n      \"journal\": \"Genome biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with multiple senescence markers, single study\",\n      \"pmids\": [\"32264951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GTF3C4 directly binds the anti-cancer compound bufalin (confirmed by cell thermal shift assay, DARTS, and surface plasmon resonance), and GTF3C4 knockdown suppresses the PI3K/AKT signaling pathway, inhibits breast cancer cell proliferation, and promotes apoptosis, placing GTF3C4 upstream of PI3K/AKT.\",\n      \"method\": \"Limited proteolysis-mass spectrometry target identification, cell thermal shift assay, DARTS, surface plasmon resonance, GTF3C4 knockdown, RNA sequencing, PI3K/AKT pathway analysis, in vivo mouse model\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal binding assays plus KD with defined pathway readout, single study\",\n      \"pmids\": [\"41649141\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GTF3C4 (hTFIIIC90) is a subunit of the human TFIIIC2 complex with intrinsic histone H3 acetyltransferase activity that is essential for RNA polymerase III transcription through interactions with multiple TFIIIC, TFIIIB, and Pol III subunits; it also suppresses cellular senescence and, in cancer cells, promotes proliferation via the PI3K/AKT signaling pathway.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries only from KEEP papers.\n\n**ROUND-2 GUARD CLASSIFICATION:**\n\n**Retrieved Papers (7):**\n1. PMID:32264951 — CellAge database; GTF3C4 identified via siRNA as inducing senescence markers. KEEP (direct experiment on GTF3C4)\n2. PMID:10523658 — hTFIIIC90 (GTF3C4) characterization: HAT activity, interactions with TFIIIC/TFIIIB/Pol III subunits. KEEP\n3. PMID:17409385 — TFIIIC35 (sixth subunit); mentions interaction with TFIIIC90 (GTF3C4). KEEP\n4. PMID:38349085 — GTF3C4 expression increased in MVC infection, but study is about KAT5; GTF3C4 mentioned only as co-upregulated, no direct mechanistic finding about GTF3C4. EXCLUDE (expression correlation only)\n5. PMID:35820807 — Tobacco hybrid K+ content; GTF3C4 not relevant (plant study, symbol collision). EXCLUDE\n6. PMID:39175876 — CRISPR screen for NB prognosis; GTF3C4 is one of 10 genes in a prognostic model — no direct mechanistic experiment on GTF3C4 protein. EXCLUDE (prognostic biomarker only)\n7. PMID:41649141 — Bufalin targets GTF3C4, PI3K/AKT pathway, direct binding assays. KEEP\n\n**Gene2pubmed papers (30):**\n- PMID:17081983 — Large-scale phosphoproteomics; GTF3C4 detected as phosphoprotein. No specific mechanistic finding about GTF3C4. EXCLUDE (phosphoproteomics screen)\n- PMID:12477932 — MGC cDNA sequencing. EXCLUDE\n- PMID:15302935 — Large-scale phosphoproteomics HeLa nuclei. EXCLUDE\n- PMID:28514442 — BioPlex 2.0 interactome; GTF3C4 appears as interaction partner. EXCLUDE (no specific mechanistic finding)\n- PMID:26496610 — HeLa interactome; GTF3C4 as interaction node. EXCLUDE\n- PMID:29507755 — m6A methyltransferase complex; no GTF3C4-specific finding. EXCLUDE\n- PMID:14702039 — FLJ cDNA sequencing. EXCLUDE\n- PMID:33961781 — BioPlex 3.0; interactome screen. EXCLUDE\n- PMID:22939629 — Census of protein complexes; GTF3C4 in complex. EXCLUDE\n- PMID:21873635 — GO phylogenetic propagation. EXCLUDE\n- PMID:15489334 — MGC project. EXCLUDE\n- PMID:35271311 — OpenCell localization; GTF3C4 localization data. KEEP (direct localization experiment)\n- PMID:20360068 — MitoCheck; chromosome segregation complexes. EXCLUDE (no specific GTF3C4 finding)\n- PMID:8889548 — cDNA library normalization. EXCLUDE\n- PMID:24255178 — Hippo pathway network; no GTF3C4-specific finding. EXCLUDE\n- PMID:29656893 — Shieldin/DNA repair; no GTF3C4-specific finding. EXCLUDE\n- PMID:34079125 — BioID map; GTF3C4 localization. KEEP (direct localization)\n- PMID:22863883 — SEC-MS interactome; GTF3C4 in complex. EXCLUDE (no specific finding)\n- PMID:21654808 — Cyclin D1 interactome; no GTF3C4-specific finding. EXCLUDE\n- PMID:27173435 — Ciliary proteome; no GTF3C4-specific finding. EXCLUDE\n- PMID:29568061 — MAC-tag AP-MS/BioID; no GTF3C4-specific finding. EXCLUDE\n- PMID:25544563 — KSHV host interactions; no GTF3C4-specific finding. EXCLUDE\n- PMID:32807901 — UFMylation/p53; no GTF3C4-specific finding. EXCLUDE\n- PMID:30804502 — BRCA1-BARD1/H4K20me0; no GTF3C4-specific finding. EXCLUDE\n- PMID:32416067 — BET inhibitors TNBC; no GTF3C4-specific finding. EXCLUDE\n- PMID:30415952 — MYC interactome; no GTF3C4-specific finding. EXCLUDE\n- PMID:21549307 — SMARCAD1/chromatin; no GTF3C4-specific finding. EXCLUDE\n- PMID:23349634 — Methyltransferases/chaperones; no GTF3C4-specific finding. EXCLUDE\n- PMID:24457600 — EED/PRC; no GTF3C4-specific finding. EXCLUDE\n- PMID:17314511 — c-MYC TAP/MudPIT; no GTF3C4-specific finding. EXCLUDE\n\n**OpenCell (PMID:35271311) and BioID (PMID:34079125):** These are proteome-scale localization studies. GTF3C4 would be assigned a subcellular localization, but the papers don't describe a specific mechanistic experiment on GTF3C4 with functional consequence — they are resource papers. EXCLUDE from discoveries (no functional consequence linked to localization for this specific protein).\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"hTFIIIC90 (GTF3C4) was cloned and shown to be a bona fide subunit of the TFIIIC2 DNA-binding subcomplex of human TFIIIC, required absolutely for RNA polymerase III transcription. Immunodepletion and immunoprecipitation studies demonstrated that hTFIIIC90 physically interacts with the TFIIIC subunits hTFIIIC220, hTFIIIC110, and hTFIIIC63, the TFIIIB subunit hTFIIIB90, and the RNA polymerase III subunits hRPC39 and hRPC62, suggesting it bridges TFIIIB and Pol III recruitment to the preinitiation complex.\",\n      \"method\": \"cDNA cloning, immunodepletion, immunoprecipitation, in vitro RNA polymerase III transcription assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (immunodepletion, Co-IP, in vitro transcription reconstitution) in single rigorous study\",\n      \"pmids\": [\"10523658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"hTFIIIC90 (GTF3C4) possesses an intrinsic histone acetyltransferase (HAT) activity with substrate specificity for histone H3, as demonstrated by in vitro HAT assays.\",\n      \"method\": \"In vitro histone acetyltransferase assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro enzymatic assay with defined substrate specificity\",\n      \"pmids\": [\"10523658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TFIIIC35, the sixth subunit of human TFIIIC, specifically interacts with hTFIIIC90 (GTF3C4) in vitro, and affinity-purified TFIIIC containing epitope-tagged TFIIIC35 (which includes GTF3C4) is active in binding to and transcribing the VA1 gene in vitro, confirming GTF3C4's presence and function in the intact TFIIIC complex.\",\n      \"method\": \"In vitro binding assay (GST pulldown), affinity purification of epitope-tagged TFIIIC, in vitro transcription assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal pulldown and functional transcription assay, single study\",\n      \"pmids\": [\"17409385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"siRNA-mediated knockdown of GTF3C4 induces cellular senescence markers, including decreased cell number, activation of p16/p21, and morphological changes resembling senescence, placing GTF3C4 as a regulator whose loss triggers senescence.\",\n      \"method\": \"siRNA knockdown with readouts of cell number, p16/p21 activation, and cellular morphology\",\n      \"journal\": \"Genome biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — clean loss-of-function with multiple phenotypic readouts, single study\",\n      \"pmids\": [\"32264951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GTF3C4 was identified as the direct molecular target of the anti-cancer compound bufalin using Limited Proteolysis-Mass Spectrometry. Direct binding of bufalin to GTF3C4 was validated by cell thermal shift assay, drug affinity response target stability (DARTS) assay, and surface plasmon resonance. GTF3C4 knockdown suppresses the PI3K/AKT signaling pathway and inhibits breast cancer cell proliferation while promoting apoptosis, placing GTF3C4 upstream of PI3K/AKT in breast cancer cells.\",\n      \"method\": \"Limited proteolysis-mass spectrometry (LiP-MS), cell thermal shift assay (CETSA), DARTS assay, surface plasmon resonance, siRNA knockdown with PI3K/AKT pathway readouts and proliferation/apoptosis assays\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal direct binding methods plus functional KD, single study\",\n      \"pmids\": [\"41649141\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GTF3C4 (hTFIIIC90) is an essential subunit of the human TFIIIC2 complex that bridges RNA polymerase III transcription by interacting with multiple TFIIIC, TFIIIB, and Pol III subunits, possesses intrinsic histone H3 acetyltransferase activity, and additionally regulates cell proliferation and survival upstream of the PI3K/AKT pathway, such that its loss triggers cellular senescence.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GTF3C4 (hTFIIIC90) is a subunit of the six-subunit human TFIIIC2 complex that is essential for RNA polymerase III transcription and possesses intrinsic histone acetyltransferase (HAT) activity with specificity for histone H3 [PMID:10523658]. Within TFIIIC, it directly interacts with subunits hTFIIIC220, hTFIIIC110, hTFIIIC63, and TFIIIC35, and bridges to the Pol III machinery through contacts with hTFIIIB90, hRPC39, and hRPC62 [PMID:10523658, PMID:17409385]. Loss of GTF3C4 activates p16/p21 and induces cellular senescence [PMID:32264951], and in breast cancer cells its knockdown suppresses the PI3K/AKT signaling pathway, inhibiting proliferation and promoting apoptosis [PMID:41649141].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of hTFIIIC90 as an essential TFIIIC2 subunit with histone H3 acetyltransferase activity resolved how TFIIIC couples promoter recognition to chromatin modification during Pol III transcription.\",\n      \"evidence\": \"cDNA cloning, immunodepletion/reconstitution of in vitro Pol III transcription, co-immunoprecipitation with multiple TFIIIC/TFIIIB/Pol III subunits, and in vitro HAT assay\",\n      \"pmids\": [\"10523658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"HAT activity has not been shown to be required for transcriptional function in vivo\",\n        \"Structural basis of GTF3C4 interactions with TFIIIB and Pol III subunits is unknown\",\n        \"Whether the HAT activity targets non-histone substrates has not been tested\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrating that the sixth TFIIIC subunit (TFIIIC35) binds specifically to GTF3C4 completed the subunit architecture of human TFIIIC and confirmed GTF3C4 as a central interaction hub within the complex.\",\n      \"evidence\": \"In vitro binding assay between recombinant TFIIIC35 and TFIIIC90, affinity-purified six-subunit TFIIIC tested in VA1 transcription\",\n      \"pmids\": [\"17409385\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The stoichiometry and structural arrangement of the six-subunit complex remain unresolved\",\n        \"Whether TFIIIC35–GTF3C4 interaction is required for all Pol III gene classes is untested\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Knockdown of GTF3C4 inducing cellular senescence via p16/p21 activation established a role beyond basal transcription, linking Pol III machinery to cell proliferation control.\",\n      \"evidence\": \"siRNA knockdown in human cells with senescence marker quantification and morphological analysis\",\n      \"pmids\": [\"32264951\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the senescence phenotype is mediated through reduced Pol III transcription or an independent GTF3C4 function is unclear\",\n        \"Rescue experiments with catalytic-dead or interaction-deficient mutants have not been performed\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identifying GTF3C4 as a direct target of bufalin and showing that its depletion suppresses PI3K/AKT signaling positioned GTF3C4 as a regulatory node connecting Pol III transcription to growth-factor signaling in cancer cells.\",\n      \"evidence\": \"CETSA, DARTS, SPR for direct binding; GTF3C4 knockdown with RNA-seq and PI3K/AKT pathway analysis in breast cancer cells and in vivo xenograft models\",\n      \"pmids\": [\"41649141\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The molecular mechanism by which GTF3C4 activates PI3K/AKT is unknown\",\n        \"Whether bufalin binding inhibits GTF3C4 HAT activity or complex assembly has not been determined\",\n        \"Generalizability beyond breast cancer cell lines has not been tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GTF3C4's HAT activity, TFIIIC complex membership, and PI3K/AKT regulation are mechanistically integrated remains an open question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure of GTF3C4 alone or within the human TFIIIC complex is available\",\n        \"Whether HAT activity is catalytically required for the senescence-suppressive or PI3K/AKT-activating functions is untested\",\n        \"In vivo ChIP or genomic occupancy data linking GTF3C4-dependent chromatin modification to specific target loci are lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\"TFIIIC2\"],\n    \"partners\": [\"GTF3C1\", \"GTF3C2\", \"GTF3C3\", \"GTF3C6\", \"BDP1\", \"POLR3E\", \"POLR3F\"],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"GTF3C4 (hTFIIIC90) is a core subunit of the human TFIIIC2 DNA-binding subcomplex that is essential for RNA polymerase III transcription, bridging TFIIIC to TFIIIB and Pol III through direct physical interactions with multiple subunits of each complex [PMID:10523658]. Beyond its structural role, GTF3C4 possesses intrinsic histone acetyltransferase activity specific for histone H3, linking the Pol III transcription machinery to chromatin modification [PMID:10523658]. Loss of GTF3C4 induces cellular senescence marked by p16/p21 activation [PMID:32264951] and suppresses PI3K/AKT signaling, inhibiting breast cancer cell proliferation and promoting apoptosis [PMID:41649141].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of hTFIIIC90 as a TFIIIC2 subunit resolved how TFIIIC bridges TFIIIB and Pol III at the preinitiation complex, establishing that a single subunit physically contacts components of all three assemblies and is absolutely required for Pol III transcription.\",\n      \"evidence\": \"cDNA cloning, immunodepletion/reconstitution of in vitro Pol III transcription, and co-immunoprecipitation with TFIIIC, TFIIIB, and Pol III subunits\",\n      \"pmids\": [\"10523658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the multi-subunit bridging interactions remains unresolved\",\n        \"In vivo ChIP-based occupancy at Pol III promoters was not assessed\",\n        \"Whether the bridging function is rate-limiting for Pol III transcription in cells is unknown\"\n      ]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstration that hTFIIIC90 has intrinsic histone H3 acetyltransferase activity revealed an unexpected enzymatic function for a general transcription factor subunit, suggesting TFIIIC may directly modify chromatin at Pol III-transcribed loci.\",\n      \"evidence\": \"In vitro HAT assay with purified protein and defined histone substrates\",\n      \"pmids\": [\"10523658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific H3 lysine residues targeted have not been identified\",\n        \"In vivo HAT activity and its functional contribution to Pol III transcription are untested\",\n        \"No catalytic-dead mutant has been characterized\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identification of the sixth TFIIIC subunit (TFIIIC35) as a direct GTF3C4 interactor, and demonstration that complete TFIIIC retains transcription activity, confirmed the subunit composition and functional integrity of the holo-complex.\",\n      \"evidence\": \"GST pulldown of TFIIIC35–hTFIIIC90 interaction and affinity purification of epitope-tagged TFIIIC with in vitro VA1 transcription assay\",\n      \"pmids\": [\"17409385\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Stoichiometry and architecture of the six-subunit complex remain unresolved\",\n        \"Whether the TFIIIC35–GTF3C4 interaction is required for HAT activity is unknown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Loss-of-function studies revealed that GTF3C4 depletion triggers cellular senescence with activation of the p16/p21 axis, extending its role beyond Pol III transcription to cell proliferation control.\",\n      \"evidence\": \"siRNA knockdown with quantification of cell number, p16/p21 expression, and senescence morphology\",\n      \"pmids\": [\"32264951\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether senescence results from impaired Pol III transcription or a Pol III-independent function is undetermined\",\n        \"Rescue experiments re-expressing GTF3C4 were not reported\",\n        \"Relevance to in vivo tissue homeostasis is unknown\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identification of GTF3C4 as the direct target of the anti-cancer compound bufalin, and demonstration that GTF3C4 knockdown suppresses PI3K/AKT signaling, positioned GTF3C4 upstream of a major pro-survival pathway in breast cancer cells.\",\n      \"evidence\": \"LiP-MS target identification, validated by CETSA, DARTS, and SPR; siRNA knockdown with PI3K/AKT pathway and proliferation/apoptosis readouts in breast cancer cell lines\",\n      \"pmids\": [\"41649141\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism connecting GTF3C4 to PI3K/AKT activation is uncharacterized\",\n        \"Whether bufalin binding inhibits GTF3C4 HAT or scaffolding function is unknown\",\n        \"Findings are from a single study in breast cancer cell lines and lack in vivo validation\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for GTF3C4's multi-subunit bridging role within the Pol III preinitiation complex, the specific histone residues and genomic loci modified by its HAT activity in vivo, and the molecular pathway through which GTF3C4 regulates PI3K/AKT signaling and cellular senescence.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of GTF3C4 within TFIIIC or the Pol III PIC exists\",\n        \"In vivo HAT target sites and catalytic residues are uncharacterized\",\n        \"Causal relationship between Pol III transcription defects and senescence/PI3K signaling has not been dissected\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0140223\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [\n      \"TFIIIC2\",\n      \"TFIIIC\"\n    ],\n    \"partners\": [\n      \"GTF3C1\",\n      \"GTF3C2\",\n      \"GTF3C5\",\n      \"GTF3C6\",\n      \"BDP1\",\n      \"POLR3E\",\n      \"POLR3G\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}