{"gene":"TAF3","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2001,"finding":"TAF3 (TAF(II)140) contains a histone fold domain (HFD) and a PHD finger, is a component of the TFIID complex (demonstrated by immunoprecipitation), and its HFD selectively heterodimerizes with TAF(II)30 (human homologue of yTAF(II)25), establishing it as a metazoan homologue of yeast TAF(II)47.","method":"Immunoprecipitation, sequence analysis, HFD heterodimerization assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal immunoprecipitation and domain heterodimerization assay, single lab, two orthogonal methods","pmids":["11438666"],"is_preprint":false},{"year":2008,"finding":"The PHD finger of TAF3 specifically binds the H3K4me3 histone mark. NMR solution structure of the TAF3-PHD finger and its complex with H3K4me3 peptide reveals that cation-pi interactions via two aromatic residues in a unique K4me3-binding pocket mediate binding, and asymmetric dimethylation of H3R2 interferes with this interaction, suggesting a H3R2/K4 methyl-methyl switch regulating TFIID-promoter association.","method":"NMR structure determination, mutagenesis, affinity measurements","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure plus mutagenesis plus affinity measurements in one rigorous study, multiple orthogonal methods","pmids":["18682226"],"is_preprint":false},{"year":2008,"finding":"TAF3 forms a complex with TRF3 (TAF3/TRF3 complex) that replaces canonical TFIID at the Myogenin promoter during myogenesis; a specific domain of TAF3 mediates coactivator functions targeted by MyoD, and this complex is required for MyoD-dependent activation of myogenin transcription in vitro and in cell-based assays.","method":"Purified reconstituted in vitro transcription system, in vitro and cell-based assays, domain mapping","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro transcription system with purified components plus cell-based assays, multiple orthogonal methods","pmids":["18851836"],"is_preprint":false},{"year":2008,"finding":"TAF3 (and its Drosophila homologue BIP2) physically interacts with p53 (human and Drosophila); the interaction involves the C-terminus of p53 and the central region of TAF3, and elevated TAF3 expression inhibits p53-dependent transcription activation and decreases p53 protein levels in human cell lines.","method":"Yeast two-hybrid, in vitro binding assay, cell-based transcription assay, overexpression","journal":"BMC molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding plus functional cell assay, single lab, multiple methods","pmids":["18549481"],"is_preprint":false},{"year":2009,"finding":"In zebrafish, Taf3 selectively interacts with Trf3 but not Tbp; both are bound to the mespa promoter and required for mespa expression; a Trf3 mutant disrupting the Taf3–Trf3 interaction abolishes mespa transcription, early development, and hematopoiesis, establishing that a selective Trf3–Taf3 interaction is required for initiation of hematopoiesis.","method":"Morpholino knockdown in zebrafish, ChIP, protein interaction assay, mutant rescue","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined phenotype, ChIP, and interaction mutant, single lab, multiple orthogonal approaches","pmids":["19777587"],"is_preprint":false},{"year":2011,"finding":"In embryonic stem cells, TAF3 localizes to a subset of chromosomal regions co-bound by CTCF/cohesin; CTCF directly recruits TAF3 to promoter-distal sites; TAF3-dependent DNA looping occurs between these distal sites and core promoters occupied by TAF3/CTCF/cohesin, implicating TAF3 in long-range chromatin regulatory interactions that maintain ES cell lineage balance.","method":"Genome-wide ChIP-seq, chromosome conformation capture (DNA looping assay), co-IP (CTCF-TAF3 interaction), TAF3 knockdown with lineage differentiation readout","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide ChIP-seq, DNA looping, direct protein interaction, and KD phenotype, multiple orthogonal methods in one study","pmids":["21884934"],"is_preprint":false},{"year":2013,"finding":"H3K4me3 interactions with the PHD finger of TAF3 direct global TFIID recruitment to active genes; H3K4me3 enhances p53-dependent transcription by stimulating preinitiation complex (PIC) formation; H3K4me3-TAF3/TFIID interactions can act independently or cooperatively with the TATA box to direct PIC assembly, regulating gene-selective p53 functions in response to genotoxic stress.","method":"ChIP-seq, in vitro transcription/PIC assembly assay, TAF3 PHD mutants, p53 target gene analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro PIC assembly assay with mutants plus genome-wide ChIP-seq plus cell-based stress response, multiple orthogonal methods","pmids":["23452851"],"is_preprint":false},{"year":2015,"finding":"The PHD finger of TAF3 directly binds nuclear phosphoinositides (PI) at a site distinct from the H3K4me3-binding region; PI binding modulates TAF3 association with H3K4me3 in vitro and with chromatin in vivo; PIP4K2B regulates nuclear PI5P levels and, through TAF3, controls myogenic gene expression during myoblast differentiation.","method":"Targeted PI-binding screen, in vitro lipid-binding assay, TAF3 PHD mutant analysis, ChIP, myoblast differentiation assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro binding assay with separation-of-function mutants, chromatin association in vivo, and functional gene expression readout, multiple orthogonal methods","pmids":["25866244"],"is_preprint":false}],"current_model":"TAF3 is a TFIID subunit whose PHD finger directly reads the H3K4me3 histone mark (structural basis defined by NMR) to direct TFIID recruitment and preinitiation complex assembly at active genes; its PHD finger also binds nuclear phosphoinositides at a distinct site, allowing signal-dependent modulation of chromatin association; TAF3 can form an alternative TRF3/TAF3 complex that replaces canonical TFIID at muscle-specific promoters to support MyoD-dependent myogenin transcription; in ES cells TAF3 is recruited by CTCF to promoter-distal sites and mediates long-range DNA looping to core promoters, safeguarding lineage-balanced transcription; and TAF3 physically interacts with p53 to negatively modulate its transcriptional activity."},"narrative":{"mechanistic_narrative":"TAF3 is a TFIID subunit that couples core promoter recognition to the chromatin and signaling state of active genes, functioning as a histone-mark reader and an adaptor for alternative transcription complexes [PMID:11438666, PMID:18682226, PMID:23452851]. Originally identified as a histone-fold-containing TFIID component that heterodimerizes with TAF10 via its HFD [PMID:11438666], TAF3 uses its PHD finger to selectively read the H3K4me3 mark through cation-pi interactions in a dedicated binding pocket, a recognition event blocked by asymmetric dimethylation of H3R2, establishing an H3R2/K4 methyl-methyl switch [PMID:18682226]. This H3K4me3-PHD interaction directs global TFIID recruitment to active genes and stimulates preinitiation complex assembly, including cooperative regulation of gene-selective p53 target genes under genotoxic stress [PMID:23452851]. The same PHD finger binds nuclear phosphoinositides at a site distinct from the H3K4me3 pocket, and this lipid binding modulates chromatin association, linking PIP4K2B-controlled nuclear PI5P levels to TAF3-dependent myogenic gene expression [PMID:25866244]. Beyond canonical TFIID, TAF3 forms an alternative TRF3/TAF3 complex that replaces TFIID at the myogenin promoter to support MyoD-dependent myogenesis [PMID:18851836] and, in zebrafish, the selective Trf3-Taf3 interaction at the mespa promoter is required for early development and hematopoiesis [PMID:19777587]. In embryonic stem cells, TAF3 is recruited by CTCF to promoter-distal sites and mediates long-range DNA looping to core promoters to safeguard lineage-balanced transcription [PMID:21884934]. TAF3 also physically interacts with p53 and, when overexpressed, inhibits p53-dependent transcription [PMID:18549481].","teleology":[{"year":2001,"claim":"Establishing TAF3 as a bona fide TFIID subunit and defining its domain architecture was needed to place it in the general transcription machinery.","evidence":"Immunoprecipitation, sequence analysis, and HFD heterodimerization assay identifying the histone fold and PHD finger and TAF10 partnership","pmids":["11438666"],"confidence":"Medium","gaps":["Did not assign a function to the PHD finger","Did not address whether TAF3 acts outside canonical TFIID"]},{"year":2008,"claim":"Defining the PHD finger as an H3K4me3 reader explained how TFIID could be targeted to active chromatin via a histone mark.","evidence":"NMR structure of the TAF3-PHD finger in complex with H3K4me3 peptide plus mutagenesis and affinity measurements","pmids":["18682226"],"confidence":"High","gaps":["Structural study alone did not establish genome-wide consequences of the interaction","The H3R2/K4 methyl switch was inferred biochemically without in vivo demonstration"]},{"year":2008,"claim":"Discovery of the TRF3/TAF3 complex showed TAF3 can substitute for canonical TFIID at a tissue-specific promoter, revealing a promoter-selective transcription mechanism in myogenesis.","evidence":"Purified reconstituted in vitro transcription system, cell-based assays, and domain mapping at the myogenin promoter","pmids":["18851836"],"confidence":"High","gaps":["Scope of TRF3/TAF3 target promoters beyond myogenin not defined","Mechanism of TFIID-to-TRF3/TAF3 switching not resolved"]},{"year":2008,"claim":"The TAF3-p53 interaction indicated TAF3 can negatively modulate a sequence-specific activator, beyond its general TFIID role.","evidence":"Yeast two-hybrid, in vitro binding, and cell-based transcription assays with TAF3 overexpression in human and Drosophila","pmids":["18549481"],"confidence":"Medium","gaps":["Effect shown by overexpression rather than endogenous loss-of-function","Mechanism reconciling repression here with later H3K4me3-enhanced p53 transcription unclear"]},{"year":2009,"claim":"Demonstrating that a selective Trf3-Taf3 interaction is required in vivo extended the alternative-complex model to whole-organism developmental processes.","evidence":"Morpholino knockdown, ChIP, interaction assay, and mutant rescue at the mespa promoter in zebrafish","pmids":["19777587"],"confidence":"Medium","gaps":["Direct biochemical reconstitution of the zebrafish complex not performed","Whether mammalian hematopoiesis uses the same mechanism not addressed"]},{"year":2011,"claim":"Identifying CTCF-dependent recruitment of TAF3 to distal sites and TAF3-mediated DNA looping revealed a role in long-range chromatin architecture rather than only proximal PIC assembly.","evidence":"Genome-wide ChIP-seq, chromosome conformation capture, co-IP, and TAF3 knockdown with lineage differentiation readout in ES cells","pmids":["21884934"],"confidence":"High","gaps":["Whether looping requires the PHD/H3K4me3 reading function not separated","Direct interface mediating the CTCF-TAF3 interaction not mapped"]},{"year":2013,"claim":"Connecting the PHD-H3K4me3 interaction to genome-wide TFIID recruitment and stress-induced p53 target selection demonstrated the functional output of histone-mark reading.","evidence":"ChIP-seq, in vitro PIC assembly assays with TAF3 PHD mutants, and p53 target gene analysis under genotoxic stress","pmids":["23452851"],"confidence":"High","gaps":["Interplay between H3K4me3-enhanced p53 transcription and earlier reported TAF3-mediated p53 repression unresolved","Relative contribution of TATA box versus H3K4me3 across the genome not quantified"]},{"year":2015,"claim":"Showing that the PHD finger also binds nuclear phosphoinositides at a distinct site established a signal-dependent layer of control over TAF3 chromatin association.","evidence":"Targeted PI-binding screen, in vitro lipid-binding with separation-of-function PHD mutants, ChIP, and myoblast differentiation assay linking PIP4K2B/PI5P to TAF3","pmids":["25866244"],"confidence":"High","gaps":["How PI binding is dynamically regulated at specific loci in vivo not resolved","Whether PI binding affects the CTCF-looping or p53 functions not tested"]},{"year":null,"claim":"How TAF3's distinct activities — canonical TFIID H3K4me3 reading, alternative TRF3/TAF3 complex formation, CTCF-mediated looping, phosphoinositide sensing, and p53 modulation — are coordinated within a cell remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model integrating PHD-mediated histone, lipid, and protein interactions","Switching logic between canonical TFIID and TRF3/TAF3 complexes uncharacterized","Endogenous regulation of TAF3 partner choice not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[1,6]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[2,6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[7]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,5,7]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[1,5,6]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1,6]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1,5]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,4,5]}],"complexes":["TFIID","TRF3/TAF3 complex"],"partners":["TAF10","TRF3","MYOD","P53","CTCF"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5VWG9","full_name":"Transcription initiation factor TFIID subunit 3","aliases":["140 kDa TATA box-binding protein-associated factor","TBP-associated factor 3","Transcription initiation factor TFIID 140 kDa subunit","TAF(II)140","TAF140","TAFII-140","TAFII140"],"length_aa":929,"mass_kda":103.6,"function":"The TFIID basal transcription factor complex plays a major role in the initiation of RNA polymerase II (Pol II)-dependent transcription (PubMed:33795473). TFIID recognizes and binds promoters with or without a TATA box via its subunit TBP, a TATA-box-binding protein, and promotes assembly of the pre-initiation complex (PIC) (PubMed:33795473). The TFIID complex consists of TBP and TBP-associated factors (TAFs), including TAF1, TAF2, TAF3, TAF4, TAF5, TAF6, TAF7, TAF8, TAF9, TAF10, TAF11, TAF12 and TAF13 (PubMed:33795473). The TFIID complex structure can be divided into 3 modules TFIID-A, TFIID-B, and TFIID-C (PubMed:33795473). TAF3 forms the TFIID-A module together with TAF5 and TBP (PubMed:33795473). Required in complex with TBPL2 for the differentiation of myoblasts into myocytes (PubMed:11438666). The TAF3-TBPL2 complex replaces TFIID at specific promoters at an early stage in the differentiation process (PubMed:11438666)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q5VWG9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TAF3","classification":"Not Classified","n_dependent_lines":177,"n_total_lines":1208,"dependency_fraction":0.14652317880794702},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"TBP","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/TAF3","total_profiled":1310},"omim":[{"mim_id":"606576","title":"TAF3 RNA POLYMERASE II, TATA BOX-BINDING PROTEIN-ASSOCIATED FACTOR, 140-KD; TAF3","url":"https://www.omim.org/entry/606576"},{"mim_id":"313650","title":"TAF1 RNA POLYMERASE II, TATA BOX-BINDING PROTEIN-ASSOCIATED FACTOR, 250-KD; TAF1","url":"https://www.omim.org/entry/313650"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear membrane","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TAF3"},"hgnc":{"alias_symbol":["TAF140","TAFII140"],"prev_symbol":[]},"alphafold":{"accession":"Q5VWG9","domains":[{"cath_id":"1.10.20.10","chopping":"2-94","consensus_level":"high","plddt":92.3972,"start":2,"end":94},{"cath_id":"3.30.40.10","chopping":"857-926","consensus_level":"high","plddt":78.1196,"start":857,"end":926}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VWG9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VWG9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VWG9-F1-predicted_aligned_error_v6.png","plddt_mean":55.03},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TAF3","jax_strain_url":"https://www.jax.org/strain/search?query=TAF3"},"sequence":{"accession":"Q5VWG9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5VWG9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5VWG9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VWG9"}},"corpus_meta":[{"pmid":"23452851","id":"PMC_23452851","title":"H3K4me3 interactions with TAF3 regulate preinitiation complex assembly and selective gene activation.","date":"2013","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/23452851","citation_count":360,"is_preprint":false},{"pmid":"21884934","id":"PMC_21884934","title":"Control of embryonic stem cell lineage commitment by core promoter factor, TAF3.","date":"2011","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21884934","citation_count":144,"is_preprint":false},{"pmid":"18851836","id":"PMC_18851836","title":"MyoD targets TAF3/TRF3 to activate myogenin transcription.","date":"2008","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/18851836","citation_count":127,"is_preprint":false},{"pmid":"18682226","id":"PMC_18682226","title":"Structural insight into the recognition of the H3K4me3 mark by the TFIID subunit TAF3.","date":"2008","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/18682226","citation_count":106,"is_preprint":false},{"pmid":"11438666","id":"PMC_11438666","title":"The TFIID components human TAF(II)140 and Drosophila BIP2 (TAF(II)155) are novel metazoan homologues of yeast TAF(II)47 containing a histone fold and a PHD finger.","date":"2001","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11438666","citation_count":62,"is_preprint":false},{"pmid":"25866244","id":"PMC_25866244","title":"The basal transcription complex component TAF3 transduces changes in nuclear phosphoinositides into transcriptional output.","date":"2015","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/25866244","citation_count":59,"is_preprint":false},{"pmid":"19777587","id":"PMC_19777587","title":"Selective interaction between Trf3 and Taf3 required for early development and hematopoiesis.","date":"2009","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/19777587","citation_count":27,"is_preprint":false},{"pmid":"18549481","id":"PMC_18549481","title":"TATA binding protein associated factor 3 (TAF3) interacts with p53 and inhibits its function.","date":"2008","source":"BMC molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18549481","citation_count":18,"is_preprint":false},{"pmid":"23935956","id":"PMC_23935956","title":"Genome wide association analysis of a founder population identified TAF3 as a gene for MCHC in humans.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23935956","citation_count":10,"is_preprint":false},{"pmid":"39545712","id":"PMC_39545712","title":"Pediatric Mesenchymal Tumor With MN1::TAF3 Fusion.","date":"2024","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/39545712","citation_count":2,"is_preprint":false},{"pmid":"39378380","id":"PMC_39378380","title":"Spindle Cell Neoplasm With a Novel MN1::TAF3 Fusion: A Rare Case in a Toddler.","date":"2024","source":"Journal of pediatric hematology/oncology","url":"https://pubmed.ncbi.nlm.nih.gov/39378380","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.12.603224","title":"NanoTag - an IgG-free method for mapping DNA-protein interactions","date":"2024-07-12","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.12.603224","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6979,"output_tokens":2180,"usd":0.026818,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9142,"output_tokens":3288,"usd":0.063955,"stage2_stop_reason":"end_turn"},"total_usd":0.090773,"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\": 2001,\n      \"finding\": \"TAF3 (TAF(II)140) contains a histone fold domain (HFD) and a PHD finger, is a component of the TFIID complex (demonstrated by immunoprecipitation), and its HFD selectively heterodimerizes with TAF(II)30 (human homologue of yTAF(II)25), establishing it as a metazoan homologue of yeast TAF(II)47.\",\n      \"method\": \"Immunoprecipitation, sequence analysis, HFD heterodimerization assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal immunoprecipitation and domain heterodimerization assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"11438666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The PHD finger of TAF3 specifically binds the H3K4me3 histone mark. NMR solution structure of the TAF3-PHD finger and its complex with H3K4me3 peptide reveals that cation-pi interactions via two aromatic residues in a unique K4me3-binding pocket mediate binding, and asymmetric dimethylation of H3R2 interferes with this interaction, suggesting a H3R2/K4 methyl-methyl switch regulating TFIID-promoter association.\",\n      \"method\": \"NMR structure determination, mutagenesis, affinity measurements\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure plus mutagenesis plus affinity measurements in one rigorous study, multiple orthogonal methods\",\n      \"pmids\": [\"18682226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TAF3 forms a complex with TRF3 (TAF3/TRF3 complex) that replaces canonical TFIID at the Myogenin promoter during myogenesis; a specific domain of TAF3 mediates coactivator functions targeted by MyoD, and this complex is required for MyoD-dependent activation of myogenin transcription in vitro and in cell-based assays.\",\n      \"method\": \"Purified reconstituted in vitro transcription system, in vitro and cell-based assays, domain mapping\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro transcription system with purified components plus cell-based assays, multiple orthogonal methods\",\n      \"pmids\": [\"18851836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TAF3 (and its Drosophila homologue BIP2) physically interacts with p53 (human and Drosophila); the interaction involves the C-terminus of p53 and the central region of TAF3, and elevated TAF3 expression inhibits p53-dependent transcription activation and decreases p53 protein levels in human cell lines.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, cell-based transcription assay, overexpression\",\n      \"journal\": \"BMC molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding plus functional cell assay, single lab, multiple methods\",\n      \"pmids\": [\"18549481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In zebrafish, Taf3 selectively interacts with Trf3 but not Tbp; both are bound to the mespa promoter and required for mespa expression; a Trf3 mutant disrupting the Taf3–Trf3 interaction abolishes mespa transcription, early development, and hematopoiesis, establishing that a selective Trf3–Taf3 interaction is required for initiation of hematopoiesis.\",\n      \"method\": \"Morpholino knockdown in zebrafish, ChIP, protein interaction assay, mutant rescue\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined phenotype, ChIP, and interaction mutant, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"19777587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In embryonic stem cells, TAF3 localizes to a subset of chromosomal regions co-bound by CTCF/cohesin; CTCF directly recruits TAF3 to promoter-distal sites; TAF3-dependent DNA looping occurs between these distal sites and core promoters occupied by TAF3/CTCF/cohesin, implicating TAF3 in long-range chromatin regulatory interactions that maintain ES cell lineage balance.\",\n      \"method\": \"Genome-wide ChIP-seq, chromosome conformation capture (DNA looping assay), co-IP (CTCF-TAF3 interaction), TAF3 knockdown with lineage differentiation readout\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide ChIP-seq, DNA looping, direct protein interaction, and KD phenotype, multiple orthogonal methods in one study\",\n      \"pmids\": [\"21884934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"H3K4me3 interactions with the PHD finger of TAF3 direct global TFIID recruitment to active genes; H3K4me3 enhances p53-dependent transcription by stimulating preinitiation complex (PIC) formation; H3K4me3-TAF3/TFIID interactions can act independently or cooperatively with the TATA box to direct PIC assembly, regulating gene-selective p53 functions in response to genotoxic stress.\",\n      \"method\": \"ChIP-seq, in vitro transcription/PIC assembly assay, TAF3 PHD mutants, p53 target gene analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro PIC assembly assay with mutants plus genome-wide ChIP-seq plus cell-based stress response, multiple orthogonal methods\",\n      \"pmids\": [\"23452851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The PHD finger of TAF3 directly binds nuclear phosphoinositides (PI) at a site distinct from the H3K4me3-binding region; PI binding modulates TAF3 association with H3K4me3 in vitro and with chromatin in vivo; PIP4K2B regulates nuclear PI5P levels and, through TAF3, controls myogenic gene expression during myoblast differentiation.\",\n      \"method\": \"Targeted PI-binding screen, in vitro lipid-binding assay, TAF3 PHD mutant analysis, ChIP, myoblast differentiation assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro binding assay with separation-of-function mutants, chromatin association in vivo, and functional gene expression readout, multiple orthogonal methods\",\n      \"pmids\": [\"25866244\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TAF3 is a TFIID subunit whose PHD finger directly reads the H3K4me3 histone mark (structural basis defined by NMR) to direct TFIID recruitment and preinitiation complex assembly at active genes; its PHD finger also binds nuclear phosphoinositides at a distinct site, allowing signal-dependent modulation of chromatin association; TAF3 can form an alternative TRF3/TAF3 complex that replaces canonical TFIID at muscle-specific promoters to support MyoD-dependent myogenin transcription; in ES cells TAF3 is recruited by CTCF to promoter-distal sites and mediates long-range DNA looping to core promoters, safeguarding lineage-balanced transcription; and TAF3 physically interacts with p53 to negatively modulate its transcriptional activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TAF3 is a TFIID subunit that couples core promoter recognition to the chromatin and signaling state of active genes, functioning as a histone-mark reader and an adaptor for alternative transcription complexes [#0, #1, #6]. Originally identified as a histone-fold-containing TFIID component that heterodimerizes with TAF10 via its HFD [#0], TAF3 uses its PHD finger to selectively read the H3K4me3 mark through cation-pi interactions in a dedicated binding pocket, a recognition event blocked by asymmetric dimethylation of H3R2, establishing an H3R2/K4 methyl-methyl switch [#1]. This H3K4me3-PHD interaction directs global TFIID recruitment to active genes and stimulates preinitiation complex assembly, including cooperative regulation of gene-selective p53 target genes under genotoxic stress [#6]. The same PHD finger binds nuclear phosphoinositides at a site distinct from the H3K4me3 pocket, and this lipid binding modulates chromatin association, linking PIP4K2B-controlled nuclear PI5P levels to TAF3-dependent myogenic gene expression [#7]. Beyond canonical TFIID, TAF3 forms an alternative TRF3/TAF3 complex that replaces TFIID at the myogenin promoter to support MyoD-dependent myogenesis [#2] and, in zebrafish, the selective Trf3-Taf3 interaction at the mespa promoter is required for early development and hematopoiesis [#4]. In embryonic stem cells, TAF3 is recruited by CTCF to promoter-distal sites and mediates long-range DNA looping to core promoters to safeguard lineage-balanced transcription [#5]. TAF3 also physically interacts with p53 and, when overexpressed, inhibits p53-dependent transcription [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing TAF3 as a bona fide TFIID subunit and defining its domain architecture was needed to place it in the general transcription machinery.\",\n      \"evidence\": \"Immunoprecipitation, sequence analysis, and HFD heterodimerization assay identifying the histone fold and PHD finger and TAF10 partnership\",\n      \"pmids\": [\"11438666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Did not assign a function to the PHD finger\",\n        \"Did not address whether TAF3 acts outside canonical TFIID\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defining the PHD finger as an H3K4me3 reader explained how TFIID could be targeted to active chromatin via a histone mark.\",\n      \"evidence\": \"NMR structure of the TAF3-PHD finger in complex with H3K4me3 peptide plus mutagenesis and affinity measurements\",\n      \"pmids\": [\"18682226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural study alone did not establish genome-wide consequences of the interaction\",\n        \"The H3R2/K4 methyl switch was inferred biochemically without in vivo demonstration\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery of the TRF3/TAF3 complex showed TAF3 can substitute for canonical TFIID at a tissue-specific promoter, revealing a promoter-selective transcription mechanism in myogenesis.\",\n      \"evidence\": \"Purified reconstituted in vitro transcription system, cell-based assays, and domain mapping at the myogenin promoter\",\n      \"pmids\": [\"18851836\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Scope of TRF3/TAF3 target promoters beyond myogenin not defined\",\n        \"Mechanism of TFIID-to-TRF3/TAF3 switching not resolved\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The TAF3-p53 interaction indicated TAF3 can negatively modulate a sequence-specific activator, beyond its general TFIID role.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, and cell-based transcription assays with TAF3 overexpression in human and Drosophila\",\n      \"pmids\": [\"18549481\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Effect shown by overexpression rather than endogenous loss-of-function\",\n        \"Mechanism reconciling repression here with later H3K4me3-enhanced p53 transcription unclear\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that a selective Trf3-Taf3 interaction is required in vivo extended the alternative-complex model to whole-organism developmental processes.\",\n      \"evidence\": \"Morpholino knockdown, ChIP, interaction assay, and mutant rescue at the mespa promoter in zebrafish\",\n      \"pmids\": [\"19777587\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical reconstitution of the zebrafish complex not performed\",\n        \"Whether mammalian hematopoiesis uses the same mechanism not addressed\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identifying CTCF-dependent recruitment of TAF3 to distal sites and TAF3-mediated DNA looping revealed a role in long-range chromatin architecture rather than only proximal PIC assembly.\",\n      \"evidence\": \"Genome-wide ChIP-seq, chromosome conformation capture, co-IP, and TAF3 knockdown with lineage differentiation readout in ES cells\",\n      \"pmids\": [\"21884934\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether looping requires the PHD/H3K4me3 reading function not separated\",\n        \"Direct interface mediating the CTCF-TAF3 interaction not mapped\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connecting the PHD-H3K4me3 interaction to genome-wide TFIID recruitment and stress-induced p53 target selection demonstrated the functional output of histone-mark reading.\",\n      \"evidence\": \"ChIP-seq, in vitro PIC assembly assays with TAF3 PHD mutants, and p53 target gene analysis under genotoxic stress\",\n      \"pmids\": [\"23452851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Interplay between H3K4me3-enhanced p53 transcription and earlier reported TAF3-mediated p53 repression unresolved\",\n        \"Relative contribution of TATA box versus H3K4me3 across the genome not quantified\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showing that the PHD finger also binds nuclear phosphoinositides at a distinct site established a signal-dependent layer of control over TAF3 chromatin association.\",\n      \"evidence\": \"Targeted PI-binding screen, in vitro lipid-binding with separation-of-function PHD mutants, ChIP, and myoblast differentiation assay linking PIP4K2B/PI5P to TAF3\",\n      \"pmids\": [\"25866244\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How PI binding is dynamically regulated at specific loci in vivo not resolved\",\n        \"Whether PI binding affects the CTCF-looping or p53 functions not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TAF3's distinct activities — canonical TFIID H3K4me3 reading, alternative TRF3/TAF3 complex formation, CTCF-mediated looping, phosphoinositide sensing, and p53 modulation — are coordinated within a cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No unified model integrating PHD-mediated histone, lipid, and protein interactions\",\n        \"Switching logic between canonical TFIID and TRF3/TAF3 complexes uncharacterized\",\n        \"Endogenous regulation of TAF3 partner choice not defined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 5, 7]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [1, 5, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1, 6]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 4, 5]}\n    ],\n    \"complexes\": [\n      \"TFIID\",\n      \"TRF3/TAF3 complex\"\n    ],\n    \"partners\": [\n      \"TAF10\",\n      \"TRF3\",\n      \"MyoD\",\n      \"p53\",\n      \"CTCF\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}