{"gene":"GTF2B","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1991,"finding":"TFIIB (GTF2B) is a ~33 kDa polypeptide required for RNA polymerase II transcription initiation; its sequence contains a region with amino acid similarity to prokaryotic sigma factors, an imperfect direct repeat, and clusters of basic residues. It was purified to homogeneity and cloned, establishing it as an essential basal transcription factor.","method":"Protein purification, cDNA cloning, in vitro transcription assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — purification to homogeneity, functional cDNA cloning, in vitro transcription reconstitution; foundational study replicated broadly","pmids":["1946368"],"is_preprint":false},{"year":1991,"finding":"Recombinant TFIIB expressed in E. coli binds directly to the acidic activating region of VP16, demonstrating that an acidic transcriptional activator can directly contact TFIIB without additional adaptor proteins. TFIIB binding is a rate-limiting step during preinitiation complex assembly that is enhanced by an acidic activator.","method":"Affinity chromatography with recombinant proteins, in vitro transcription rate measurements","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct binding demonstrated with bacterially expressed recombinant protein, replicated by multiple labs","pmids":["1922364"],"is_preprint":false},{"year":1992,"finding":"The yeast SUA7 gene encodes a TFIIB homolog that is essential for normal transcription start site selection in vivo; sua7 mutations cause a downstream shift in initiation at cyc1 and ADH1 loci, establishing TFIIB as a determinant of start site selection.","method":"Genetic suppressor screen, molecular cloning, primer extension analysis, in vivo transcription start site mapping","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with defined molecular phenotype (start-site shift), replicated at multiple loci","pmids":["1547497"],"is_preprint":false},{"year":1992,"finding":"Members of the steroid hormone receptor superfamily (COUP-TF, estrogen receptor, progesterone receptor) directly interact with TFIIB (S300-II) via protein-protein interactions, identifying TFIIB as a direct target of steroid hormone receptor transactivators.","method":"Protein-protein interaction assay with recombinant proteins, affinity chromatography","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding assay with recombinants; replicated by several independent labs for different nuclear receptors","pmids":["1517211"],"is_preprint":false},{"year":1992,"finding":"The N-terminal zinc-binding domain of TFIIB is required for recruitment of RNA polymerase II–TFIIF into the initiation complex, while the C-terminal repeat domain is required for interaction with TBP; mutagenesis of cysteine residues in the zinc finger abolishes Pol II recruitment without disrupting TBP binding, separating two functional domains.","method":"Site-directed mutagenesis, in vitro transcription, TBP-binding assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — active-site mutagenesis with functional dissection, replicated and extended by subsequent structural studies","pmids":["8516312"],"is_preprint":false},{"year":1993,"finding":"The C-terminal domain of TFIIB (residues 106–316, TFIIBc) is sufficient for interaction with TBP on DNA but cannot recruit RNA polymerase II; the N-terminal domain is required for Pol II recruitment. TFIIBc arrests complex formation at the TBP-binding step and acts as a dominant negative.","method":"Limited proteolysis, gel mobility-shift assay, in vitro transcription","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — proteolytic domain dissection combined with functional transcription assay and gel shift; two orthogonal methods","pmids":["8516311"],"is_preprint":false},{"year":1993,"finding":"The C-terminal domain of TFIIB contains two functional regions: the direct-repeat domain sufficient for TBP-promoter complex interaction, and the N-terminal domain required for subsequent transcription initiation steps (Pol II recruitment). The C-terminal protease-resistant core also extends the TBP footprint on promoter DNA, suggesting a cryptic DNA-binding potential.","method":"Deletion mutagenesis, in vitro transcription, DNase I footprinting, protease sensitivity assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — deletion analysis with multiple orthogonal functional assays in a single study","pmids":["8413225"],"is_preprint":false},{"year":1993,"finding":"Human thyroid hormone receptor beta (hTRβ) directly interacts with TFIIB at two contact sites: one in the N-terminus and one in the ligand-binding domain (LBD); each receptor region contacts distinct sites on TFIIB. Thyroid hormone significantly decreases the interaction of the LBD with TFIIB, suggesting receptor-mediated silencing operates through TFIIB.","method":"GST pulldown, deletion analysis, co-transfection/reporter assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct protein-protein interaction mapped by deletion analysis; functional correlation established by cotransfection","pmids":["8415616"],"is_preprint":false},{"year":1993,"finding":"Drosophila TAFII40 (homolog of human hTAFII32) directly binds both the VP16 activation domain and basal factor TFIIB, suggesting a ternary activator–coactivator–basal factor interaction during activated transcription.","method":"In vitro protein-protein interaction assay, affinity chromatography","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding demonstrated with purified recombinant proteins; independently confirmed for human hTAFII32","pmids":["8221891"],"is_preprint":false},{"year":1993,"finding":"ICP4 of herpes simplex virus forms a tripartite complex with TFIIB and TBP (or TFIID) on promoter DNA through direct protein-protein interactions, increasing the DNA-binding affinity of both ICP4 and TBP; this complex formation correlates with ICP4's ability to regulate gene expression.","method":"Gel retardation assay, DNase I footprinting, mutant analysis","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gel retardation and footprinting with defined mutants; two orthogonal methods in one study","pmids":["8392607"],"is_preprint":false},{"year":1994,"finding":"YY1, TFIIB, and RNA polymerase II are sufficient to direct specific basal transcription on a supercoiled template in a TBP-independent manner, demonstrating that TFIIB can function in a minimal initiation complex where YY1 substitutes for TBP.","method":"Reconstituted in vitro transcription with purified components","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — minimal reconstitution with three purified factors; demonstrates sufficiency in vitro","pmids":["8137426"],"is_preprint":false},{"year":1994,"finding":"Mutations in the largest subunit of RNA polymerase II (sua8/RPB1) cause downstream shifts in transcription start site selection identical to sua7 (TFIIB) mutations, and sua7 sua8 double mutants show synthetic lethality and non-allelic non-complementation, establishing a functional interaction between TFIIB and Rpb1 in start site selection.","method":"Genetic suppressor screen, primer extension, synthetic lethality analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis by genetic suppressor screen plus start-site mapping; replicated phenotype at multiple loci","pmids":["8264591"],"is_preprint":false},{"year":1995,"finding":"Crystal structure of the TFIIB–TBP–TATA-element ternary complex at 2.7 Å reveals: TFIIB core resembles cyclin A; TFIIB recognizes the preformed TBP-DNA complex through protein-protein and protein-DNA contacts; the N-terminal domain of core TFIIB forms the downstream surface of the complex, potentially fixing the transcription start site.","method":"X-ray crystallography at 2.7 Å resolution","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure; foundational study independently validated by multiple structural and biochemical follow-ups","pmids":["7675079"],"is_preprint":false},{"year":1995,"finding":"Solution NMR structure of the human TFIIB core domain (TFIIBc) reveals two direct repeats forming a pseudo-twofold symmetric alpha-helical fold similar to cyclin A; an extensive central basic surface including an amphipathic helix is critical for bridging TBP-DNA complex and RNA polymerase II.","method":"Multidimensional heteronuclear NMR spectroscopy","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with identification of functional surface; consistent with crystal structure data","pmids":["7671313"],"is_preprint":false},{"year":1995,"finding":"TFIIB binds beneath the concave surface of TBP, contacting DNA both upstream and downstream of the TATA box, as determined by hydroxyl-radical footprinting and gel mobility-shift assays. TFIIB requires at least 7 bp of DNA on either side of the TATA box to form a stable complex.","method":"Hydroxyl-radical footprinting, gel mobility-shift assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — footprinting combined with crystal structure mapping; replicated in structural studies","pmids":["7637813"],"is_preprint":false},{"year":1995,"finding":"Vitamin D receptor (VDR) directly binds TFIIB; cotransfection of VDR and TFIIB cooperatively activates a vitamin D-responsive reporter in P19 cells in a 1,25(OH)2D3-dependent manner, demonstrating functional interaction between TFIIB and a nuclear hormone receptor in vivo.","method":"GST fusion protein-protein binding assay, cotransfection reporter assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding assay complemented by in vivo cotransfection; two orthogonal methods","pmids":["7878015"],"is_preprint":false},{"year":1995,"finding":"The proline-rich activation domain of CTF1 selectively interacts with TFIIB (but not TBP) and facilitates TFIIB recruitment into TBP-DNA complexes during preinitiation complex assembly in both human and yeast systems.","method":"In vitro protein-protein interaction assay, TFIIB recruitment assay on immobilized templates","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding plus functional recruitment assay; tested in two species","pmids":["8183887"],"is_preprint":false},{"year":1995,"finding":"The Krüppel zinc-finger protein directly interacts with TFIIB to activate transcription when acting as a monomer from a proximal site; Kr dimers interact with TFIIEβ to repress transcription, demonstrating that the same transcription factor can activate or repress by engaging different components of the basal machinery.","method":"In vitro protein-protein interaction assay, in vitro transcription with purified components","journal":"Nature","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction and functional transcription assay; two orthogonal methods in single study","pmids":["7753175"],"is_preprint":false},{"year":1995,"finding":"A 10-amino-acid cluster of basic residues in the N-terminal A/B domain of thyroid hormone receptor alpha (cT3Rα, amino acids 21–30) is essential for TFIIB interaction and T3-dependent transcriptional activation; the TFIIB region primarily involved maps to residues 178–201 (an amphipathic α-helix).","method":"Deletion and point mutagenesis, in vitro binding assay, reporter cotransfection","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — mutagenesis-mapped binding with functional correlate; multiple receptor and TFIIB deletion constructs tested","pmids":["7623841"],"is_preprint":false},{"year":1995,"finding":"C/EBPα transactivation elements I and II (TE-I and TE-II) cooperatively mediate in vitro binding of C/EBPα to both TBP and TFIIB; the same amino acid motifs conserved in activating C/EBP family members are required for transcription activation in yeast and mammalian cells.","method":"In vitro binding assay, mutagenesis, transfection reporter assay in yeast and mammalian cells","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical binding + mutagenesis + functional assay across two systems","pmids":["7556073"],"is_preprint":false},{"year":1995,"finding":"TFIIB NMR structure shows conformational variability of the free core domain compared to the TBP-DNA-bound crystal structure; interaction with VP16 activation domain or with the N-terminal zinc ribbon domain of TFIIB induces chemical shift changes concentrated in the first repeat and interrepeat linker, suggesting TFIIB is conformationally pliable and that VP16 promotes a conformation primed for TBP-DNA binding.","method":"NMR spectroscopy, 15N relaxation analysis, chemical shift perturbation mapping","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR structural analysis; single lab, single method type","pmids":["9609687"],"is_preprint":false},{"year":1996,"finding":"High-resolution site-specific protein-DNA photocrosslinking of the human TBP–TFIIA–TFIIB–DNA quaternary complex reveals that TFIIA and TFIIB make more extensive interactions with promoter DNA than previously recognized; TBP, TFIIA, and TFIIB together surround two turns of promoter DNA, potentially forming a 'cylindrical clamp'.","method":"Site-specific protein-DNA photocrosslinking, UV crosslinking mapping","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — novel photocrosslinking method with systematic mapping across multiple DNA positions; single lab with thorough coverage","pmids":["8855228"],"is_preprint":false},{"year":1996,"finding":"Yeast SSU71/TFG1 (the largest subunit of TFIIF) genetically interacts with TFIIB: ssu71-1 suppresses both the cold-sensitive phenotype and downstream start-site shift of sua7 (TFIIB) mutants, establishing a functional interaction between TFIIB and TFIIF large subunit in transcription start site selection.","method":"Genetic suppressor screen, molecular cloning, primer extension, sequence analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with mechanistic phenotype; SSU71 identified independently as yeast TFIIF large subunit","pmids":["7724527"],"is_preprint":false},{"year":1996,"finding":"The Rpb9 (Ssu73) subunit of RNA polymerase II genetically interacts with TFIIB (sua7-1): rpb9/ssu73-1 suppresses the cold-sensitive growth phenotype and downstream start-site shift of sua7-1, identifying the C-terminus of Rpb9 as a functional partner of TFIIB in start site selection.","method":"Genetic suppressor analysis, allele sequencing, primer extension","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined molecular phenotype; single lab","pmids":["8692696"],"is_preprint":false},{"year":1997,"finding":"TBP residue Leu-189 (in the second stirrup-like loop) is specifically required for TFIIB interaction, distinct from residues (Lys-133, Lys-145, Lys-151) required for TFIIA and NC2 (Dr1) interactions, defining a specific TFIIB-binding surface on TBP. NC2 is shown to be identical to the negative cofactor Dr1.","method":"TBP mutant analysis, in vitro transcription, protein-protein interaction assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis mapped interaction interface; confirmed by functional assay","pmids":["7738039"],"is_preprint":false},{"year":1997,"finding":"Altered-specificity TBP–TFIIB interaction array demonstrates that many activators use the known TBP–TFIIB interaction to stimulate transcription in human cells, while the glutamine-rich activation domain of Sp1 activates transcription independently of this interaction.","method":"Engineered altered-specificity TATA-TBP-TFIIB array, transfection reporter assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — rational design of orthogonal interaction pair with in vivo functional validation; single lab but elegant experimental design","pmids":["9012349"],"is_preprint":false},{"year":1998,"finding":"Hepatitis B virus pX protein co-immunoprecipitates with TFIIB from nuclear extracts and interacts with TFIIB in vivo. TFIIB mutants unable to bind TBP block pX activity, while TFIIB mutants unable to bind Pol II retain activity that is restored by pX, indicating pX acts as a molecular bridge between TFIIB and Pol II to coactivate transcription.","method":"Co-immunoprecipitation, TFIIB mutant analysis, in vivo and in vitro transcription assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP combined with TFIIB mutant rescue in vivo and in vitro; two orthogonal methods","pmids":["9488473"],"is_preprint":false},{"year":1998,"finding":"Two portions of the Fcp1p CTD phosphatase C-terminal region directly bind the first cyclin-like repeat in the core domain of TFIIB; the closely related KEFGK motif in RAP74 (TFIIF large subunit) also mediates Fcp1p interaction; mutation of this RAP74 motif causes synthetic phenotypes with fcp1 mutants.","method":"Deletion and point mutagenesis, direct binding assay, genetic synthetic lethality","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding mapping + genetic epistasis; single lab, two orthogonal methods","pmids":["11003641"],"is_preprint":false},{"year":1998,"finding":"The N-terminal region of yeast TFIIB contains two adjacent functional domains: a zinc ribbon fold required for stable RNAP II binding, and a highly conserved adjacent homology block required for transcription start site selection, demonstrating these are separable functions.","method":"Site-directed mutagenesis, in vitro transcription, start site selection assay, TFIIB-Pol II complex formation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with functional dissection by multiple assays; separates two domains definitively","pmids":["9651390"],"is_preprint":false},{"year":1998,"finding":"The archaeal TFIIB homolog TFB (from Sulfolobus shibatae) mediates sequence-specific DNA interactions with the region flanking the A-box (TATA-like element) upstream of the promoter, contributing to promoter strength independently of TBP.","method":"Gel mobility shift, footprinting, in vitro transcription with promoter mutants","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple binding assays with promoter mutants; archaeal ortholog study","pmids":["9660923"],"is_preprint":false},{"year":1999,"finding":"Yeast SUB1 was identified as a suppressor of TFIIB mutations (E62G, R78H); SUB1 directly binds TFIIB in vitro and inhibits formation of TBP-TFIIB-promoter complexes; allele-specific interactions with ssu72 and sub1 establish functional relationships among TFIIB, Ssu72, and Sub1 in start site selection.","method":"Genetic suppressor screen, in vitro protein binding, TBP-TFIIB-DNA complex formation assay, allele specificity analysis","journal":"The EMBO journal / Genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetics plus direct binding plus complex-assembly assay; allele-specificity establishes specific functional interaction","pmids":["8617240","10511545"],"is_preprint":false},{"year":1999,"finding":"A yeast TFIIB S53P substitution specifically impairs activator-dependent (Pho4- and Adr1-mediated) transcription without affecting basal transcription. Pho4 directly interacts with TFIIB in vitro, and this interaction is reduced by S53P. Pho4 binding induces a conformational change in TFIIB detectable by enhanced V8 protease sensitivity.","method":"Genetic screen, in vitro protein-protein interaction assay, protease sensitivity assay, reporter transcription assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis + direct binding + conformational assay; multiple orthogonal methods in single study","pmids":["10077585"],"is_preprint":false},{"year":1999,"finding":"TFIIB mutations E62G and TATA box mutations severely impair transcription without large defects in preinitiation complex formation, demonstrating post-recruitment roles for TFIIB and the TATA box after factor recruitment to the promoter.","method":"Immobilized promoter assay, conditional mutant cell extracts, PIC assembly and activity measurement","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional dissection with separation of recruitment and post-recruitment roles; single lab with multiple orthogonal assays","pmids":["9887099"],"is_preprint":false},{"year":2001,"finding":"The TFIIB recognition element (BRE) upstream of the TATA box suppresses basal transcription; an activator can disrupt the TFIIB-BRE interaction within a promoter-bound complex, revealing a novel activator function in modulating core promoter recognition by TFIIB.","method":"Transcription assay with BRE-mutant promoters, protein-DNA footprinting, functional analyses","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional transcription assay combined with footprinting; two orthogonal methods demonstrating activator-mediated disruption","pmids":["11711430"],"is_preprint":false},{"year":2003,"finding":"Site-specific photocrosslinking and hydroxyl radical probing in the preinitiation complex reveal that the TFIIB zinc ribbon domain interacts with the Pol II Dock domain, overlapping the RNA exit point. In the full PIC (but not the smaller Pol II-TFIIB complex), the TFIIB linker and core domains are positioned over the central cleft and wall of Pol II.","method":"Site-specific photocrosslinking, directed hydroxyl radical probing, mutational analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — novel crosslinking technology with mutational validation; consistent with subsequent crystal structures","pmids":["14536083"],"is_preprint":false},{"year":2004,"finding":"Crystal structure of the Pol II–TFIIB complex at 4.5 Å reveals three key features: (1) the N-terminal zinc ribbon of TFIIB contacts the Pol II Dock domain near the RNA exit path; (2) the B-finger domain inserts into the Pol II active center; (3) the C-terminal domain interacts with both Pol II and TBP-promoter DNA to orient DNA for unwinding and transcription start.","method":"X-ray crystallography at 4.5 Å resolution","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure replicated in two independent studies at similar resolution","pmids":["14963322"],"is_preprint":false},{"year":2004,"finding":"A core promoter element downstream of the TATA box (downstream BRE) is recognized by TFIIB through a DNA-binding domain distinct from the helix-turn-helix motif used for the upstream BRE; the two TFIIB-recognition elements cooperate in a promoter context-dependent manner.","method":"Promoter element mutagenesis, in vitro transcription, TFIIB DNA-binding assay","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional transcription assay plus direct DNA-binding analysis; defined two independent TFIIB DNA-recognition modules","pmids":["16230532"],"is_preprint":false},{"year":2004,"finding":"Functional interaction between the TFIIB B-finger domain (R78C mutation) and the lobe domain of the Rpb2 subunit of RNA polymerase II is required for accurate transcription start site selection; the TFIIB R78C mutant supports initiation but yields altered abortive initiation products, and lobe/jaw mutations in Rpb2 suppress the TFIIB defect.","method":"Genetic suppressor analysis, in vitro transcription, run-on transcription, abortive initiation assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis between TFIIB B-finger and Rpb2 lobe domain with biochemical validation; multiple assays","pmids":["15082791"],"is_preprint":false},{"year":2005,"finding":"Regardless of TATA box–start site spacing, the upstream transcription bubble edge forms 20 bp from the TATA box, expanding to 18 unwound bases before abrupt collapse (re-annealing) when RNA is ≥7 nt. Bubble collapse coincides with loss of TFIIH helicase requirement and suppresses pausing caused by the TFIIB B-finger within the complex, linking TFIIB B-finger displacement to promoter clearance.","method":"Promoter spacing mutagenesis, permanganate footprinting of transcription bubbles, quantitative elongation assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mechanistic dissection by footprinting and functional assay; defines TFIIB B-finger role in promoter clearance","pmids":["15989968"],"is_preprint":false},{"year":2007,"finding":"TFIIB plays a transcription-independent role in gene looping: TFIIB crosslinks to both the promoter and the terminator of genes, and the TFIIB E62K mutation adversely affects looping at all genes tested. TFIIB association with the terminator depends on Ssu72 and is independent of TBP, while promoter association is unaffected.","method":"Chromatin immunoprecipitation (ChIP), chromosome conformation capture (3C), gene looping analysis with TFIIB mutants","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP and 3C on multiple loci with defined TFIIB mutant; two orthogonal methods establish terminator localization and looping function","pmids":["17803944"],"is_preprint":false},{"year":2007,"finding":"Expansion of the TBP polyglutamine (polyQ) tract enhances the TBP–TFIIB interaction while reducing TBP dimerization; in SCA17 transgenic mice, increased TFIIB occupancy of the Hspb1 promoter is decreased, and overexpression of TFIIB alleviates mutant TBP-induced neuritic defects.","method":"Co-immunoprecipitation, ChIP, transgenic mouse model, lentiviral TFIIB overexpression","journal":"Nature neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ChIP plus in vivo rescue; single lab, multiple methods","pmids":["17994014"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of the complete Pol II–TFIIB complex at 4.3 Å reveals the mechanism of transcription initiation: B-core domain binds the Pol II wall to position promoter DNA; B-linker binds the Pol II rudder/clamp to assist DNA opening; B-reader approaches the active site to scan for the start site; RNA synthesis and upstream DNA rewinding displace B-reader and B-linker respectively, triggering TFIIB release and elongation complex formation.","method":"X-ray crystallography at 4.3 Å, complementary functional analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with functional validation; consistent with independent Kornberg lab structure","pmids":["19820686"],"is_preprint":false},{"year":2009,"finding":"A new Pol II–TFIIB crystal structure at 3.8 Å reveals the C-terminal domain of TFIIB located above the active center cleft and the linker snaking toward the active center; this structure is complementary to the prior 4.5 Å structure, together revealing how TFIIB positions promoter DNA over the Pol II cleft.","method":"X-ray crystallography at 3.8 Å under different solution conditions","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure complementary to prior structural work; two independent labs solved related structures","pmids":["19965383"],"is_preprint":false},{"year":2010,"finding":"TFIIB is phosphorylated at serine 65 in vivo, and this modification is present in PICs. Serine 65 phosphorylation is required after RNA pol II CTD serine 5 phosphorylation but before productive initiation; it regulates TFIIB's interaction with the CstF-64 component of the 3′ cleavage/polyadenylation complex, directing CstF recruitment to terminators and CPSF/CstF recruitment to promoters.","method":"Phosphorylation site identification, phospho-specific antibody, co-immunoprecipitation, ChIP, functional transcription assay with phospho-mutants","journal":"Current biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — phosphorylation identified in vivo, mapped to specific residue, with functional interaction analysis; multiple orthogonal methods","pmids":["20226668"],"is_preprint":false},{"year":2011,"finding":"TFIIF is not required for initiation or promoter clearance by RNA pol II. However, TFIIF stabilizes TFIIB within early elongation complexes; in the absence of TFIIF, TFIIB is lost immediately after initiation rather than at the normal +12–13 position.","method":"TFIIF depletion/phosphorylation (casein kinase 2), PIC assembly assay, TFIIB retention analysis in elongation complexes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional dissection with biochemical reconstitution; separates initiation from TFIIB stabilization function of TFIIF","pmids":["21896726"],"is_preprint":false},{"year":2011,"finding":"RAP74 (large subunit of TFIIF) directly and independently binds TFIIB via its C-terminal region; RAP74 blocks TFIIB-RAP30 binding both by binding TFIIB and by binding RAP30, indicating that in the intact TFIIF complex, TFIIB-TFIIF contact is maintained exclusively through RAP74.","method":"Deletion mutagenesis, direct binding assay, in vitro transcription","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding mapping with deletion mutants; functional transcription correlation","pmids":["8662660"],"is_preprint":false},{"year":2012,"finding":"Crystal structures of the Pol II–TFIIB complex at 3.4 Å and of an initially transcribing complex with DNA template and 6-nt RNA reveal: (1) TFIIB partially closes the Pol II cleft to position DNA; (2) B-reader binds the DNA template strand upstream of the active site to assist start site selection; (3) TFIIB rearranges active-site residues and induces metal B binding; (4) TFIIB prevents DNA-RNA hybrid tilting during short RNA synthesis; (5) RNA beyond 12–13 nt clashes with TFIIB, triggering TFIIB displacement and elongation complex formation.","method":"X-ray crystallography at 3.4 Å (apo complex) and initially transcribing complex; functional mutational analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution structures of multiple states with functional validation; provides complete mechanistic model for TFIIB function in initiation through elongation transition","pmids":["23151482"],"is_preprint":false},{"year":2016,"finding":"Single-molecule imaging reveals that TFIIB binding to the promoter is highly transient (average residence time ~1.5 sec), whereas TFIID and TFIIA bind stably. Stable TFIIB association and PIC progression occur only in the presence of Pol II–TFIIF, defining a checkpoint where transient-to-stable TFIIB binding requires downstream factor recruitment.","method":"Single-molecule fluorescence imaging, live-cell imaging, reconstituted in vitro single-molecule transcription platform","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule reconstitution with purified factors complemented by live-cell imaging; novel mechanistic insight on PIC dynamics","pmids":["27798851"],"is_preprint":false},{"year":2022,"finding":"Rapid acute depletion of TFIIB in human cells (PRO-Seq) shows that TFIIB depletion has the largest general effect on Pol II promoter activity compared to TBP, TAF1, and XPB depletions; TFIIB depletion also correlates with apparent transcription termination defects downstream of genes, consistent with TFIIB's role in linking initiation and termination.","method":"Rapid acute protein depletion (auxin-inducible degron), precision nuclear run-on sequencing (PRO-Seq) at >70,000 promoters","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide quantitative measurement after acute depletion; large-scale dataset with specific TFIIB-dependent termination phenotype","pmids":["35947745"],"is_preprint":false}],"current_model":"TFIIB (GTF2B) is an essential RNA polymerase II general transcription factor that bridges promoter-bound TBP (via its C-terminal cyclin-like core domain) and Pol II (via its N-terminal zinc ribbon binding the Pol II Dock domain); its B-linker assists DNA opening, its B-reader positions the template strand to scan for the transcription start site and allosterically stimulates initial RNA synthesis, and the growing RNA chain (beyond ~12–13 nt) sterically displaces TFIIB to trigger promoter clearance; TFIIB also recognizes two flanking core promoter elements (upstream and downstream BREs) through independent DNA-binding motifs, undergoes serine 65 phosphorylation that links the promoter to 3′ cleavage/polyadenylation machinery, and participates in gene looping by associating with both promoter and terminator regions in an Ssu72-dependent manner; in addition, TFIIB is a direct target of numerous transcriptional activators (VP16, nuclear hormone receptors, and others) that stimulate preinitiation complex assembly by enhancing TFIIB recruitment or inducing productive conformational changes."},"narrative":{"mechanistic_narrative":"GTF2B encodes TFIIB, an essential general transcription factor for RNA polymerase II that nucleates preinitiation complex assembly and governs the transition from promoter recognition to productive initiation [PMID:1946368, PMID:35947745]. TFIIB is organized into two functionally separable modules: a C-terminal core of two cyclin A–like direct repeats that recognizes the preformed TBP–TATA complex and extends contacts to promoter DNA, and an N-terminal zinc-ribbon region that recruits RNA polymerase II–TFIIF; mutation of the core abolishes Pol II recruitment without disrupting TBP binding, while the zinc ribbon is dispensable for TBP contact [PMID:8516312, PMID:8516311, PMID:8413225, PMID:7675079, PMID:7671313]. Within the assembled complex, TFIIB sits beneath the concave face of TBP and surrounds promoter DNA, and its zinc ribbon contacts the Pol II Dock domain near the RNA exit path while its linker, reader, and core elements reach over the active-center cleft to position template DNA, assist DNA opening, and scan for the transcription start site [PMID:7637813, PMID:8855228, PMID:14536083, PMID:14963322, PMID:19820686, PMID:23151482]. Accordingly, TFIIB and TATA-box mutations impair transcription after recruitment, and TFIIB determines start-site selection through genetic and functional interactions with the Pol II Rpb1, Rpb2, and Rpb9 subunits and with TFIIF [PMID:1547497, PMID:8264591, PMID:7724527, PMID:8692696, PMID:9651390, PMID:9887099, PMID:15082791]. As RNA synthesis proceeds beyond ~12–13 nt the growing transcript and upstream DNA rewinding sterically displace the B-reader and B-linker, triggering TFIIB release and promoter clearance, with TFIIF stabilizing TFIIB in early elongation until that point [PMID:15989968, PMID:19820686, PMID:21896726, PMID:23151482]. TFIIB additionally recognizes flanking core-promoter BRE elements through distinct DNA-binding modules, links initiation to 3′ processing via serine-65 phosphorylation that controls CstF/CPSF recruitment, and participates in Ssu72-dependent gene looping by associating with both promoters and terminators [PMID:11711430, PMID:16230532, PMID:17803944, PMID:20226668, PMID:35947745]. TFIIB is also a direct convergence point for transcriptional regulators, contacting the acidic activator VP16 and nuclear hormone receptors among others to enhance its recruitment or induce productive conformational changes [PMID:1922364, PMID:1517211, PMID:8415616, PMID:7878015, PMID:9609687, PMID:10077585]. Single-molecule imaging shows TFIIB promoter binding is highly transient and is stabilized only upon Pol II–TFIIF recruitment, defining a kinetic checkpoint in PIC progression [PMID:27798851].","teleology":[{"year":1991,"claim":"Established TFIIB as a discrete, essential basal factor required for Pol II transcription initiation, defining the molecular entity itself.","evidence":"protein purification to homogeneity, cDNA cloning, and in vitro transcription reconstitution","pmids":["1946368"],"confidence":"High","gaps":["No structural model of how TFIIB engages the initiation machinery","Molecular basis of essentiality not defined"]},{"year":1991,"claim":"Showed that an acidic activator directly contacts TFIIB to accelerate a rate-limiting recruitment step, establishing TFIIB as a target of transcriptional activation.","evidence":"affinity chromatography with recombinant VP16 and TFIIB plus in vitro transcription rate measurement","pmids":["1922364"],"confidence":"High","gaps":["Surface on TFIIB contacted by VP16 not mapped","Whether all activators use this route unknown"]},{"year":1992,"claim":"Demonstrated in vivo that TFIIB is a determinant of transcription start-site selection, extending its role beyond simple assembly.","evidence":"yeast SUA7 suppressor genetics and primer-extension start-site mapping at cyc1 and ADH1","pmids":["1547497"],"confidence":"High","gaps":["Mechanism by which TFIIB sets the start site not resolved","Pol II partners in selection not yet identified"]},{"year":1993,"claim":"Resolved TFIIB into separable N-terminal (Pol II recruitment) and C-terminal (TBP binding) functional domains, defining its bridging architecture.","evidence":"site-directed and deletion mutagenesis, limited proteolysis, footprinting, and in vitro transcription/TBP-binding assays","pmids":["8516312","8516311","8413225"],"confidence":"High","gaps":["Atomic structure of the domains not yet known","How the two domains coordinate during assembly unclear"]},{"year":1992,"claim":"Identified nuclear hormone receptors as direct TFIIB-binding regulators, showing receptor transactivation and hormone-modulated silencing operate through TFIIB.","evidence":"recombinant binding/GST pulldown and reporter cotransfection for COUP-TF, ER, PR, thyroid and vitamin D receptors","pmids":["1517211","8415616","7878015","7623841"],"confidence":"Medium","gaps":["Binding surfaces partially mapped","Functional consequence for PIC kinetics not quantified in all cases"]},{"year":1994,"claim":"Showed TFIIB can support minimal initiation and that its start-site function is tied to specific Pol II subunits, placing it in a defined functional network with the polymerase.","evidence":"reconstituted YY1/TFIIB/Pol II transcription and sua7–sua8(RPB1) synthetic lethality with start-site mapping","pmids":["8137426","8264591"],"confidence":"High","gaps":["Physical basis of the TFIIB–Rpb1 interaction not defined","TBP-independent route physiological relevance unclear"]},{"year":1995,"claim":"Provided the structural basis for TFIIB recognition of the TBP–TATA complex, revealing a cyclin A–like fold and DNA contacts flanking the TATA box.","evidence":"2.7 Å crystal structure of TFIIB–TBP–TATA, solution NMR of the core domain, and hydroxyl-radical footprinting","pmids":["7675079","7671313","7637813"],"confidence":"High","gaps":["Pol II-bound conformation not captured","Position of the N-terminal zinc ribbon relative to Pol II unresolved"]},{"year":1996,"claim":"Mapped TFIIB as part of a DNA-encircling clamp and defined its genetic partners in TFIIF, refining the geometry and network of the early complex.","evidence":"site-specific protein–DNA photocrosslinking of the TBP–TFIIA–TFIIB–DNA complex and SSU71/TFG1 suppressor genetics","pmids":["8855228","7724527"],"confidence":"High","gaps":["Direct TFIIB–TFIIF contact surface not yet defined","Order of clamp assembly steps unclear"]},{"year":1998,"claim":"Distinguished post-recruitment functions of TFIIB and separated its zinc-ribbon (Pol II binding) from an adjacent start-site-selection homology block.","evidence":"immobilized-template PIC assays with E62G mutant and mutagenesis dissecting yeast TFIIB N-terminal domains","pmids":["9887099","9651390"],"confidence":"High","gaps":["Structural correlate of the start-site homology block lacking","Catalytic contribution to initiation not yet visualized"]},{"year":2001,"claim":"Defined TFIIB recognition of core-promoter BRE elements and showed activators can modulate this DNA recognition, linking TFIIB to promoter-strength control.","evidence":"transcription assays with BRE-mutant promoters and protein–DNA footprinting","pmids":["11711430"],"confidence":"High","gaps":["Downstream BRE recognition module not yet identified","Generality across promoter classes untested"]},{"year":2004,"claim":"Delivered the Pol II–TFIIB structure showing the zinc ribbon at the Dock domain and the B-finger reaching into the active center, plus a second BRE-binding module, unifying the assembly and initiation roles.","evidence":"X-ray crystallography of Pol II–TFIIB, crosslinking/hydroxyl-radical probing, B-finger/Rpb2 genetics, and downstream-BRE DNA-binding assays","pmids":["14963322","14536083","15082791","16230532"],"confidence":"High","gaps":["Resolution insufficient to model template-strand path fully","How the B-finger times initiation not resolved"]},{"year":2005,"claim":"Linked B-finger displacement to transcription-bubble collapse and promoter clearance, establishing TFIIB's role in the initiation-to-elongation transition.","evidence":"permanganate footprinting of bubbles across promoter-spacing mutants with quantitative elongation assays","pmids":["15989968"],"confidence":"High","gaps":["Exact RNA length triggering displacement defined only functionally here","Coupling to TFIIH release mechanistically incomplete"]},{"year":2007,"claim":"Revealed a transcription-architectural role for TFIIB in Ssu72-dependent gene looping by bridging promoters and terminators.","evidence":"ChIP and 3C across multiple loci with the looping-defective E62K mutant","pmids":["17803944"],"confidence":"High","gaps":["Direct TFIIB–terminator contacts not biochemically reconstituted","Functional output of looping for re-initiation not quantified"]},{"year":2009,"claim":"Completed the structural mechanism of initiation, defining B-linker (DNA opening), B-reader (start-site scanning), and the displacement logic that triggers TFIIB release.","evidence":"Pol II–TFIIB crystal structures at 4.3 and 3.8 Å with functional analysis","pmids":["19820686","19965383"],"confidence":"High","gaps":["State with nascent RNA not yet captured","Allosteric activation of synthesis only inferred"]},{"year":2010,"claim":"Connected TFIIB to 3′-end processing through serine-65 phosphorylation that controls CstF/CPSF recruitment, mechanistically coupling initiation and termination.","evidence":"phospho-site mapping, phospho-specific antibody, Co-IP, ChIP, and phospho-mutant transcription assays","pmids":["20226668"],"confidence":"High","gaps":["Kinase responsible for S65 phosphorylation not identified","Stoichiometry across the transcription cycle unknown"]},{"year":2012,"claim":"Provided the definitive multi-state structural model of TFIIB action from cleft closure and start-site scanning through RNA-driven displacement at ~12–13 nt.","evidence":"crystal structures of apo Pol II–TFIIB at 3.4 Å and an initially transcribing complex with 6-nt RNA, plus functional mutagenesis","pmids":["23151482"],"confidence":"High","gaps":["Activator-induced conformational states not captured in this framework","Human-specific differences from yeast model not addressed"]},{"year":2016,"claim":"Showed TFIIB promoter binding is highly transient and stabilized only by Pol II–TFIIF, defining a kinetic checkpoint in PIC formation.","evidence":"single-molecule fluorescence imaging in reconstituted and live-cell systems","pmids":["27798851"],"confidence":"High","gaps":["In vivo determinants of residence time not fully defined","Relationship of transient binding to bursting unclear"]},{"year":2022,"claim":"Quantified the genome-wide requirement for TFIIB in human cells, confirming it is the dominant determinant of Pol II promoter activity and revealing termination defects upon depletion.","evidence":"auxin-inducible acute depletion with PRO-Seq across >70,000 promoters","pmids":["35947745"],"confidence":"High","gaps":["Direct vs indirect termination effects not separated","Promoter features dictating differential sensitivity not defined"]},{"year":null,"claim":"How activator-induced conformational changes in TFIIB are coupled to the kinetic stabilization checkpoint and to TFIIB's roles in looping and 3′ processing remains unresolved.","evidence":"no single study in the corpus integrates activator-driven TFIIB conformational change with single-molecule PIC dynamics and the initiation–termination coupling","pmids":[],"confidence":"Medium","gaps":["Structural basis of the activator-primed TFIIB state lacking","Mechanistic link between S65 phosphorylation, looping, and termination not unified","Kinase and regulatory inputs to TFIIB in human cells uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,25,33]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[14,33,36,21]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,5,35,41]},{"term_id":"GO:0140223","term_label":"general transcription initiation factor activity","supporting_discovery_ids":[0,32,48]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[26,39,40]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,41,46,48]}],"complexes":["RNA polymerase II preinitiation complex"],"partners":["TBP","POLR2A","GTF2F1","GTF2A1","SSU72","SUB1","FCP1","VP16"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q00403","full_name":"Transcription initiation factor IIB","aliases":["General transcription factor TFIIB","S300-II"],"length_aa":316,"mass_kda":34.8,"function":"General transcription factor that plays a role in transcription initiation by RNA polymerase II (Pol II). Involved in the pre-initiation complex (PIC) formation and Pol II recruitment at promoter DNA (PubMed:12931194, PubMed:1517211, PubMed:1876184, PubMed:1946368, PubMed:27193682, PubMed:3029109, PubMed:3818643, PubMed:7601352, PubMed:8413225, PubMed:8515820, PubMed:8516311, PubMed:8516312, PubMed:9420329). Together with the TATA box-bound TBP forms the core initiation complex and provides a bridge between TBP and the Pol II-TFIIF complex (PubMed:8413225, PubMed:8504927, PubMed:8515820, PubMed:8516311, PubMed:8516312). Released from the PIC early following the onset of transcription during the initiation and elongation transition and reassociates with TBP during the next transcription cycle (PubMed:7601352). Associates with chromatin to core promoter-specific regions (PubMed:12931194, PubMed:24441171). Binds to two distinct DNA core promoter consensus sequence elements in a TBP-independent manner; these IIB-recognition elements (BREs) are localized immediately upstream (BREu), 5'-[GC][GC][GA]CGCC-3', and downstream (BREd), 5'-[GA]T[TGA][TG][GT][TG][TG]-3', of the TATA box element (PubMed:10619841, PubMed:16230532, PubMed:7675079, PubMed:9420329). Modulates transcription start site selection (PubMed:10318856). Also exhibits autoacetyltransferase activity that contributes to the activated transcription (PubMed:12931194)","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q00403/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GTF2B","classification":"Common Essential","n_dependent_lines":1207,"n_total_lines":1208,"dependency_fraction":0.9991721854304636},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"POLR2A","stoichiometry":10.0},{"gene":"POLR2B","stoichiometry":10.0},{"gene":"POLR2C","stoichiometry":10.0},{"gene":"POLR2F","stoichiometry":10.0},{"gene":"POLR2G","stoichiometry":10.0},{"gene":"POLR2E","stoichiometry":4.0},{"gene":"POLR2H","stoichiometry":4.0},{"gene":"POLR2I","stoichiometry":4.0},{"gene":"POLR2K","stoichiometry":4.0},{"gene":"MED11","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GTF2B","total_profiled":1310},"omim":[{"mim_id":"617680","title":"SSU72 HOMOLOG, RNA POLYMERASE II CTD PHOSPHATASE; SSU72","url":"https://www.omim.org/entry/617680"},{"mim_id":"610252","title":"MICRO RNA 1-2; MIR1-2","url":"https://www.omim.org/entry/610252"},{"mim_id":"609326","title":"MICRO RNA 1-1; MIR1-1","url":"https://www.omim.org/entry/609326"},{"mim_id":"608899","title":"GTF2I REPEAT DOMAIN-CONTAINING PROTEIN 2, ALPHA","url":"https://www.omim.org/entry/608899"},{"mim_id":"608431","title":"G3BP STRESS GRANULE ASSEMBLY FACTOR 1; G3BP1","url":"https://www.omim.org/entry/608431"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GTF2B"},"hgnc":{"alias_symbol":["TFIIB"],"prev_symbol":[]},"alphafold":{"accession":"Q00403","domains":[{"cath_id":"1.10.472.10","chopping":"109-201","consensus_level":"high","plddt":93.8103,"start":109,"end":201},{"cath_id":"1.10.472.10","chopping":"210-311","consensus_level":"high","plddt":94.3433,"start":210,"end":311}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q00403","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q00403-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q00403-F1-predicted_aligned_error_v6.png","plddt_mean":87.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GTF2B","jax_strain_url":"https://www.jax.org/strain/search?query=GTF2B"},"sequence":{"accession":"Q00403","fasta_url":"https://rest.uniprot.org/uniprotkb/Q00403.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q00403/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q00403"}},"corpus_meta":[{"pmid":"7675079","id":"PMC_7675079","title":"Crystal structure of a TFIIB-TBP-TATA-element ternary complex.","date":"1995","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/7675079","citation_count":483,"is_preprint":false},{"pmid":"8221891","id":"PMC_8221891","title":"Drosophila TAFII40 interacts with both a VP16 activation domain and the basal transcription factor TFIIB.","date":"1993","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/8221891","citation_count":390,"is_preprint":false},{"pmid":"1922364","id":"PMC_1922364","title":"Binding of general transcription factor TFIIB to an acidic activating region.","date":"1991","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/1922364","citation_count":351,"is_preprint":false},{"pmid":"8415616","id":"PMC_8415616","title":"Interaction of human thyroid hormone receptor beta with transcription factor TFIIB may mediate target gene derepression and activation by thyroid hormone.","date":"1993","source":"Proceedings of the National Academy of Sciences of the United States of 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It was purified to homogeneity and cloned, establishing it as an essential basal transcription factor.\",\n      \"method\": \"Protein purification, cDNA cloning, in vitro transcription assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purification to homogeneity, functional cDNA cloning, in vitro transcription reconstitution; foundational study replicated broadly\",\n      \"pmids\": [\"1946368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Recombinant TFIIB expressed in E. coli binds directly to the acidic activating region of VP16, demonstrating that an acidic transcriptional activator can directly contact TFIIB without additional adaptor proteins. TFIIB binding is a rate-limiting step during preinitiation complex assembly that is enhanced by an acidic activator.\",\n      \"method\": \"Affinity chromatography with recombinant proteins, in vitro transcription rate measurements\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct binding demonstrated with bacterially expressed recombinant protein, replicated by multiple labs\",\n      \"pmids\": [\"1922364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"The yeast SUA7 gene encodes a TFIIB homolog that is essential for normal transcription start site selection in vivo; sua7 mutations cause a downstream shift in initiation at cyc1 and ADH1 loci, establishing TFIIB as a determinant of start site selection.\",\n      \"method\": \"Genetic suppressor screen, molecular cloning, primer extension analysis, in vivo transcription start site mapping\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with defined molecular phenotype (start-site shift), replicated at multiple loci\",\n      \"pmids\": [\"1547497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Members of the steroid hormone receptor superfamily (COUP-TF, estrogen receptor, progesterone receptor) directly interact with TFIIB (S300-II) via protein-protein interactions, identifying TFIIB as a direct target of steroid hormone receptor transactivators.\",\n      \"method\": \"Protein-protein interaction assay with recombinant proteins, affinity chromatography\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding assay with recombinants; replicated by several independent labs for different nuclear receptors\",\n      \"pmids\": [\"1517211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"The N-terminal zinc-binding domain of TFIIB is required for recruitment of RNA polymerase II–TFIIF into the initiation complex, while the C-terminal repeat domain is required for interaction with TBP; mutagenesis of cysteine residues in the zinc finger abolishes Pol II recruitment without disrupting TBP binding, separating two functional domains.\",\n      \"method\": \"Site-directed mutagenesis, in vitro transcription, TBP-binding assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — active-site mutagenesis with functional dissection, replicated and extended by subsequent structural studies\",\n      \"pmids\": [\"8516312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The C-terminal domain of TFIIB (residues 106–316, TFIIBc) is sufficient for interaction with TBP on DNA but cannot recruit RNA polymerase II; the N-terminal domain is required for Pol II recruitment. TFIIBc arrests complex formation at the TBP-binding step and acts as a dominant negative.\",\n      \"method\": \"Limited proteolysis, gel mobility-shift assay, in vitro transcription\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — proteolytic domain dissection combined with functional transcription assay and gel shift; two orthogonal methods\",\n      \"pmids\": [\"8516311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The C-terminal domain of TFIIB contains two functional regions: the direct-repeat domain sufficient for TBP-promoter complex interaction, and the N-terminal domain required for subsequent transcription initiation steps (Pol II recruitment). The C-terminal protease-resistant core also extends the TBP footprint on promoter DNA, suggesting a cryptic DNA-binding potential.\",\n      \"method\": \"Deletion mutagenesis, in vitro transcription, DNase I footprinting, protease sensitivity assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — deletion analysis with multiple orthogonal functional assays in a single study\",\n      \"pmids\": [\"8413225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human thyroid hormone receptor beta (hTRβ) directly interacts with TFIIB at two contact sites: one in the N-terminus and one in the ligand-binding domain (LBD); each receptor region contacts distinct sites on TFIIB. Thyroid hormone significantly decreases the interaction of the LBD with TFIIB, suggesting receptor-mediated silencing operates through TFIIB.\",\n      \"method\": \"GST pulldown, deletion analysis, co-transfection/reporter assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct protein-protein interaction mapped by deletion analysis; functional correlation established by cotransfection\",\n      \"pmids\": [\"8415616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Drosophila TAFII40 (homolog of human hTAFII32) directly binds both the VP16 activation domain and basal factor TFIIB, suggesting a ternary activator–coactivator–basal factor interaction during activated transcription.\",\n      \"method\": \"In vitro protein-protein interaction assay, affinity chromatography\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding demonstrated with purified recombinant proteins; independently confirmed for human hTAFII32\",\n      \"pmids\": [\"8221891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"ICP4 of herpes simplex virus forms a tripartite complex with TFIIB and TBP (or TFIID) on promoter DNA through direct protein-protein interactions, increasing the DNA-binding affinity of both ICP4 and TBP; this complex formation correlates with ICP4's ability to regulate gene expression.\",\n      \"method\": \"Gel retardation assay, DNase I footprinting, mutant analysis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gel retardation and footprinting with defined mutants; two orthogonal methods in one study\",\n      \"pmids\": [\"8392607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"YY1, TFIIB, and RNA polymerase II are sufficient to direct specific basal transcription on a supercoiled template in a TBP-independent manner, demonstrating that TFIIB can function in a minimal initiation complex where YY1 substitutes for TBP.\",\n      \"method\": \"Reconstituted in vitro transcription with purified components\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — minimal reconstitution with three purified factors; demonstrates sufficiency in vitro\",\n      \"pmids\": [\"8137426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Mutations in the largest subunit of RNA polymerase II (sua8/RPB1) cause downstream shifts in transcription start site selection identical to sua7 (TFIIB) mutations, and sua7 sua8 double mutants show synthetic lethality and non-allelic non-complementation, establishing a functional interaction between TFIIB and Rpb1 in start site selection.\",\n      \"method\": \"Genetic suppressor screen, primer extension, synthetic lethality analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis by genetic suppressor screen plus start-site mapping; replicated phenotype at multiple loci\",\n      \"pmids\": [\"8264591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Crystal structure of the TFIIB–TBP–TATA-element ternary complex at 2.7 Å reveals: TFIIB core resembles cyclin A; TFIIB recognizes the preformed TBP-DNA complex through protein-protein and protein-DNA contacts; the N-terminal domain of core TFIIB forms the downstream surface of the complex, potentially fixing the transcription start site.\",\n      \"method\": \"X-ray crystallography at 2.7 Å resolution\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure; foundational study independently validated by multiple structural and biochemical follow-ups\",\n      \"pmids\": [\"7675079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Solution NMR structure of the human TFIIB core domain (TFIIBc) reveals two direct repeats forming a pseudo-twofold symmetric alpha-helical fold similar to cyclin A; an extensive central basic surface including an amphipathic helix is critical for bridging TBP-DNA complex and RNA polymerase II.\",\n      \"method\": \"Multidimensional heteronuclear NMR spectroscopy\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with identification of functional surface; consistent with crystal structure data\",\n      \"pmids\": [\"7671313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"TFIIB binds beneath the concave surface of TBP, contacting DNA both upstream and downstream of the TATA box, as determined by hydroxyl-radical footprinting and gel mobility-shift assays. TFIIB requires at least 7 bp of DNA on either side of the TATA box to form a stable complex.\",\n      \"method\": \"Hydroxyl-radical footprinting, gel mobility-shift assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — footprinting combined with crystal structure mapping; replicated in structural studies\",\n      \"pmids\": [\"7637813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Vitamin D receptor (VDR) directly binds TFIIB; cotransfection of VDR and TFIIB cooperatively activates a vitamin D-responsive reporter in P19 cells in a 1,25(OH)2D3-dependent manner, demonstrating functional interaction between TFIIB and a nuclear hormone receptor in vivo.\",\n      \"method\": \"GST fusion protein-protein binding assay, cotransfection reporter assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding assay complemented by in vivo cotransfection; two orthogonal methods\",\n      \"pmids\": [\"7878015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The proline-rich activation domain of CTF1 selectively interacts with TFIIB (but not TBP) and facilitates TFIIB recruitment into TBP-DNA complexes during preinitiation complex assembly in both human and yeast systems.\",\n      \"method\": \"In vitro protein-protein interaction assay, TFIIB recruitment assay on immobilized templates\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding plus functional recruitment assay; tested in two species\",\n      \"pmids\": [\"8183887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The Krüppel zinc-finger protein directly interacts with TFIIB to activate transcription when acting as a monomer from a proximal site; Kr dimers interact with TFIIEβ to repress transcription, demonstrating that the same transcription factor can activate or repress by engaging different components of the basal machinery.\",\n      \"method\": \"In vitro protein-protein interaction assay, in vitro transcription with purified components\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction and functional transcription assay; two orthogonal methods in single study\",\n      \"pmids\": [\"7753175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"A 10-amino-acid cluster of basic residues in the N-terminal A/B domain of thyroid hormone receptor alpha (cT3Rα, amino acids 21–30) is essential for TFIIB interaction and T3-dependent transcriptional activation; the TFIIB region primarily involved maps to residues 178–201 (an amphipathic α-helix).\",\n      \"method\": \"Deletion and point mutagenesis, in vitro binding assay, reporter cotransfection\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — mutagenesis-mapped binding with functional correlate; multiple receptor and TFIIB deletion constructs tested\",\n      \"pmids\": [\"7623841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"C/EBPα transactivation elements I and II (TE-I and TE-II) cooperatively mediate in vitro binding of C/EBPα to both TBP and TFIIB; the same amino acid motifs conserved in activating C/EBP family members are required for transcription activation in yeast and mammalian cells.\",\n      \"method\": \"In vitro binding assay, mutagenesis, transfection reporter assay in yeast and mammalian cells\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical binding + mutagenesis + functional assay across two systems\",\n      \"pmids\": [\"7556073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"TFIIB NMR structure shows conformational variability of the free core domain compared to the TBP-DNA-bound crystal structure; interaction with VP16 activation domain or with the N-terminal zinc ribbon domain of TFIIB induces chemical shift changes concentrated in the first repeat and interrepeat linker, suggesting TFIIB is conformationally pliable and that VP16 promotes a conformation primed for TBP-DNA binding.\",\n      \"method\": \"NMR spectroscopy, 15N relaxation analysis, chemical shift perturbation mapping\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural analysis; single lab, single method type\",\n      \"pmids\": [\"9609687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"High-resolution site-specific protein-DNA photocrosslinking of the human TBP–TFIIA–TFIIB–DNA quaternary complex reveals that TFIIA and TFIIB make more extensive interactions with promoter DNA than previously recognized; TBP, TFIIA, and TFIIB together surround two turns of promoter DNA, potentially forming a 'cylindrical clamp'.\",\n      \"method\": \"Site-specific protein-DNA photocrosslinking, UV crosslinking mapping\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel photocrosslinking method with systematic mapping across multiple DNA positions; single lab with thorough coverage\",\n      \"pmids\": [\"8855228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Yeast SSU71/TFG1 (the largest subunit of TFIIF) genetically interacts with TFIIB: ssu71-1 suppresses both the cold-sensitive phenotype and downstream start-site shift of sua7 (TFIIB) mutants, establishing a functional interaction between TFIIB and TFIIF large subunit in transcription start site selection.\",\n      \"method\": \"Genetic suppressor screen, molecular cloning, primer extension, sequence analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with mechanistic phenotype; SSU71 identified independently as yeast TFIIF large subunit\",\n      \"pmids\": [\"7724527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The Rpb9 (Ssu73) subunit of RNA polymerase II genetically interacts with TFIIB (sua7-1): rpb9/ssu73-1 suppresses the cold-sensitive growth phenotype and downstream start-site shift of sua7-1, identifying the C-terminus of Rpb9 as a functional partner of TFIIB in start site selection.\",\n      \"method\": \"Genetic suppressor analysis, allele sequencing, primer extension\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined molecular phenotype; single lab\",\n      \"pmids\": [\"8692696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"TBP residue Leu-189 (in the second stirrup-like loop) is specifically required for TFIIB interaction, distinct from residues (Lys-133, Lys-145, Lys-151) required for TFIIA and NC2 (Dr1) interactions, defining a specific TFIIB-binding surface on TBP. NC2 is shown to be identical to the negative cofactor Dr1.\",\n      \"method\": \"TBP mutant analysis, in vitro transcription, protein-protein interaction assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis mapped interaction interface; confirmed by functional assay\",\n      \"pmids\": [\"7738039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Altered-specificity TBP–TFIIB interaction array demonstrates that many activators use the known TBP–TFIIB interaction to stimulate transcription in human cells, while the glutamine-rich activation domain of Sp1 activates transcription independently of this interaction.\",\n      \"method\": \"Engineered altered-specificity TATA-TBP-TFIIB array, transfection reporter assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — rational design of orthogonal interaction pair with in vivo functional validation; single lab but elegant experimental design\",\n      \"pmids\": [\"9012349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Hepatitis B virus pX protein co-immunoprecipitates with TFIIB from nuclear extracts and interacts with TFIIB in vivo. TFIIB mutants unable to bind TBP block pX activity, while TFIIB mutants unable to bind Pol II retain activity that is restored by pX, indicating pX acts as a molecular bridge between TFIIB and Pol II to coactivate transcription.\",\n      \"method\": \"Co-immunoprecipitation, TFIIB mutant analysis, in vivo and in vitro transcription assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP combined with TFIIB mutant rescue in vivo and in vitro; two orthogonal methods\",\n      \"pmids\": [\"9488473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Two portions of the Fcp1p CTD phosphatase C-terminal region directly bind the first cyclin-like repeat in the core domain of TFIIB; the closely related KEFGK motif in RAP74 (TFIIF large subunit) also mediates Fcp1p interaction; mutation of this RAP74 motif causes synthetic phenotypes with fcp1 mutants.\",\n      \"method\": \"Deletion and point mutagenesis, direct binding assay, genetic synthetic lethality\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding mapping + genetic epistasis; single lab, two orthogonal methods\",\n      \"pmids\": [\"11003641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The N-terminal region of yeast TFIIB contains two adjacent functional domains: a zinc ribbon fold required for stable RNAP II binding, and a highly conserved adjacent homology block required for transcription start site selection, demonstrating these are separable functions.\",\n      \"method\": \"Site-directed mutagenesis, in vitro transcription, start site selection assay, TFIIB-Pol II complex formation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with functional dissection by multiple assays; separates two domains definitively\",\n      \"pmids\": [\"9651390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The archaeal TFIIB homolog TFB (from Sulfolobus shibatae) mediates sequence-specific DNA interactions with the region flanking the A-box (TATA-like element) upstream of the promoter, contributing to promoter strength independently of TBP.\",\n      \"method\": \"Gel mobility shift, footprinting, in vitro transcription with promoter mutants\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple binding assays with promoter mutants; archaeal ortholog study\",\n      \"pmids\": [\"9660923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Yeast SUB1 was identified as a suppressor of TFIIB mutations (E62G, R78H); SUB1 directly binds TFIIB in vitro and inhibits formation of TBP-TFIIB-promoter complexes; allele-specific interactions with ssu72 and sub1 establish functional relationships among TFIIB, Ssu72, and Sub1 in start site selection.\",\n      \"method\": \"Genetic suppressor screen, in vitro protein binding, TBP-TFIIB-DNA complex formation assay, allele specificity analysis\",\n      \"journal\": \"The EMBO journal / Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetics plus direct binding plus complex-assembly assay; allele-specificity establishes specific functional interaction\",\n      \"pmids\": [\"8617240\", \"10511545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A yeast TFIIB S53P substitution specifically impairs activator-dependent (Pho4- and Adr1-mediated) transcription without affecting basal transcription. Pho4 directly interacts with TFIIB in vitro, and this interaction is reduced by S53P. Pho4 binding induces a conformational change in TFIIB detectable by enhanced V8 protease sensitivity.\",\n      \"method\": \"Genetic screen, in vitro protein-protein interaction assay, protease sensitivity assay, reporter transcription assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis + direct binding + conformational assay; multiple orthogonal methods in single study\",\n      \"pmids\": [\"10077585\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"TFIIB mutations E62G and TATA box mutations severely impair transcription without large defects in preinitiation complex formation, demonstrating post-recruitment roles for TFIIB and the TATA box after factor recruitment to the promoter.\",\n      \"method\": \"Immobilized promoter assay, conditional mutant cell extracts, PIC assembly and activity measurement\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional dissection with separation of recruitment and post-recruitment roles; single lab with multiple orthogonal assays\",\n      \"pmids\": [\"9887099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The TFIIB recognition element (BRE) upstream of the TATA box suppresses basal transcription; an activator can disrupt the TFIIB-BRE interaction within a promoter-bound complex, revealing a novel activator function in modulating core promoter recognition by TFIIB.\",\n      \"method\": \"Transcription assay with BRE-mutant promoters, protein-DNA footprinting, functional analyses\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional transcription assay combined with footprinting; two orthogonal methods demonstrating activator-mediated disruption\",\n      \"pmids\": [\"11711430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Site-specific photocrosslinking and hydroxyl radical probing in the preinitiation complex reveal that the TFIIB zinc ribbon domain interacts with the Pol II Dock domain, overlapping the RNA exit point. In the full PIC (but not the smaller Pol II-TFIIB complex), the TFIIB linker and core domains are positioned over the central cleft and wall of Pol II.\",\n      \"method\": \"Site-specific photocrosslinking, directed hydroxyl radical probing, mutational analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — novel crosslinking technology with mutational validation; consistent with subsequent crystal structures\",\n      \"pmids\": [\"14536083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Crystal structure of the Pol II–TFIIB complex at 4.5 Å reveals three key features: (1) the N-terminal zinc ribbon of TFIIB contacts the Pol II Dock domain near the RNA exit path; (2) the B-finger domain inserts into the Pol II active center; (3) the C-terminal domain interacts with both Pol II and TBP-promoter DNA to orient DNA for unwinding and transcription start.\",\n      \"method\": \"X-ray crystallography at 4.5 Å resolution\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure replicated in two independent studies at similar resolution\",\n      \"pmids\": [\"14963322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A core promoter element downstream of the TATA box (downstream BRE) is recognized by TFIIB through a DNA-binding domain distinct from the helix-turn-helix motif used for the upstream BRE; the two TFIIB-recognition elements cooperate in a promoter context-dependent manner.\",\n      \"method\": \"Promoter element mutagenesis, in vitro transcription, TFIIB DNA-binding assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional transcription assay plus direct DNA-binding analysis; defined two independent TFIIB DNA-recognition modules\",\n      \"pmids\": [\"16230532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Functional interaction between the TFIIB B-finger domain (R78C mutation) and the lobe domain of the Rpb2 subunit of RNA polymerase II is required for accurate transcription start site selection; the TFIIB R78C mutant supports initiation but yields altered abortive initiation products, and lobe/jaw mutations in Rpb2 suppress the TFIIB defect.\",\n      \"method\": \"Genetic suppressor analysis, in vitro transcription, run-on transcription, abortive initiation assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis between TFIIB B-finger and Rpb2 lobe domain with biochemical validation; multiple assays\",\n      \"pmids\": [\"15082791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Regardless of TATA box–start site spacing, the upstream transcription bubble edge forms 20 bp from the TATA box, expanding to 18 unwound bases before abrupt collapse (re-annealing) when RNA is ≥7 nt. Bubble collapse coincides with loss of TFIIH helicase requirement and suppresses pausing caused by the TFIIB B-finger within the complex, linking TFIIB B-finger displacement to promoter clearance.\",\n      \"method\": \"Promoter spacing mutagenesis, permanganate footprinting of transcription bubbles, quantitative elongation assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mechanistic dissection by footprinting and functional assay; defines TFIIB B-finger role in promoter clearance\",\n      \"pmids\": [\"15989968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TFIIB plays a transcription-independent role in gene looping: TFIIB crosslinks to both the promoter and the terminator of genes, and the TFIIB E62K mutation adversely affects looping at all genes tested. TFIIB association with the terminator depends on Ssu72 and is independent of TBP, while promoter association is unaffected.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), chromosome conformation capture (3C), gene looping analysis with TFIIB mutants\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and 3C on multiple loci with defined TFIIB mutant; two orthogonal methods establish terminator localization and looping function\",\n      \"pmids\": [\"17803944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Expansion of the TBP polyglutamine (polyQ) tract enhances the TBP–TFIIB interaction while reducing TBP dimerization; in SCA17 transgenic mice, increased TFIIB occupancy of the Hspb1 promoter is decreased, and overexpression of TFIIB alleviates mutant TBP-induced neuritic defects.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, transgenic mouse model, lentiviral TFIIB overexpression\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ChIP plus in vivo rescue; single lab, multiple methods\",\n      \"pmids\": [\"17994014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of the complete Pol II–TFIIB complex at 4.3 Å reveals the mechanism of transcription initiation: B-core domain binds the Pol II wall to position promoter DNA; B-linker binds the Pol II rudder/clamp to assist DNA opening; B-reader approaches the active site to scan for the start site; RNA synthesis and upstream DNA rewinding displace B-reader and B-linker respectively, triggering TFIIB release and elongation complex formation.\",\n      \"method\": \"X-ray crystallography at 4.3 Å, complementary functional analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with functional validation; consistent with independent Kornberg lab structure\",\n      \"pmids\": [\"19820686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A new Pol II–TFIIB crystal structure at 3.8 Å reveals the C-terminal domain of TFIIB located above the active center cleft and the linker snaking toward the active center; this structure is complementary to the prior 4.5 Å structure, together revealing how TFIIB positions promoter DNA over the Pol II cleft.\",\n      \"method\": \"X-ray crystallography at 3.8 Å under different solution conditions\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure complementary to prior structural work; two independent labs solved related structures\",\n      \"pmids\": [\"19965383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TFIIB is phosphorylated at serine 65 in vivo, and this modification is present in PICs. Serine 65 phosphorylation is required after RNA pol II CTD serine 5 phosphorylation but before productive initiation; it regulates TFIIB's interaction with the CstF-64 component of the 3′ cleavage/polyadenylation complex, directing CstF recruitment to terminators and CPSF/CstF recruitment to promoters.\",\n      \"method\": \"Phosphorylation site identification, phospho-specific antibody, co-immunoprecipitation, ChIP, functional transcription assay with phospho-mutants\",\n      \"journal\": \"Current biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphorylation identified in vivo, mapped to specific residue, with functional interaction analysis; multiple orthogonal methods\",\n      \"pmids\": [\"20226668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TFIIF is not required for initiation or promoter clearance by RNA pol II. However, TFIIF stabilizes TFIIB within early elongation complexes; in the absence of TFIIF, TFIIB is lost immediately after initiation rather than at the normal +12–13 position.\",\n      \"method\": \"TFIIF depletion/phosphorylation (casein kinase 2), PIC assembly assay, TFIIB retention analysis in elongation complexes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional dissection with biochemical reconstitution; separates initiation from TFIIB stabilization function of TFIIF\",\n      \"pmids\": [\"21896726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RAP74 (large subunit of TFIIF) directly and independently binds TFIIB via its C-terminal region; RAP74 blocks TFIIB-RAP30 binding both by binding TFIIB and by binding RAP30, indicating that in the intact TFIIF complex, TFIIB-TFIIF contact is maintained exclusively through RAP74.\",\n      \"method\": \"Deletion mutagenesis, direct binding assay, in vitro transcription\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding mapping with deletion mutants; functional transcription correlation\",\n      \"pmids\": [\"8662660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structures of the Pol II–TFIIB complex at 3.4 Å and of an initially transcribing complex with DNA template and 6-nt RNA reveal: (1) TFIIB partially closes the Pol II cleft to position DNA; (2) B-reader binds the DNA template strand upstream of the active site to assist start site selection; (3) TFIIB rearranges active-site residues and induces metal B binding; (4) TFIIB prevents DNA-RNA hybrid tilting during short RNA synthesis; (5) RNA beyond 12–13 nt clashes with TFIIB, triggering TFIIB displacement and elongation complex formation.\",\n      \"method\": \"X-ray crystallography at 3.4 Å (apo complex) and initially transcribing complex; functional mutational analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution structures of multiple states with functional validation; provides complete mechanistic model for TFIIB function in initiation through elongation transition\",\n      \"pmids\": [\"23151482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Single-molecule imaging reveals that TFIIB binding to the promoter is highly transient (average residence time ~1.5 sec), whereas TFIID and TFIIA bind stably. Stable TFIIB association and PIC progression occur only in the presence of Pol II–TFIIF, defining a checkpoint where transient-to-stable TFIIB binding requires downstream factor recruitment.\",\n      \"method\": \"Single-molecule fluorescence imaging, live-cell imaging, reconstituted in vitro single-molecule transcription platform\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule reconstitution with purified factors complemented by live-cell imaging; novel mechanistic insight on PIC dynamics\",\n      \"pmids\": [\"27798851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rapid acute depletion of TFIIB in human cells (PRO-Seq) shows that TFIIB depletion has the largest general effect on Pol II promoter activity compared to TBP, TAF1, and XPB depletions; TFIIB depletion also correlates with apparent transcription termination defects downstream of genes, consistent with TFIIB's role in linking initiation and termination.\",\n      \"method\": \"Rapid acute protein depletion (auxin-inducible degron), precision nuclear run-on sequencing (PRO-Seq) at >70,000 promoters\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide quantitative measurement after acute depletion; large-scale dataset with specific TFIIB-dependent termination phenotype\",\n      \"pmids\": [\"35947745\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TFIIB (GTF2B) is an essential RNA polymerase II general transcription factor that bridges promoter-bound TBP (via its C-terminal cyclin-like core domain) and Pol II (via its N-terminal zinc ribbon binding the Pol II Dock domain); its B-linker assists DNA opening, its B-reader positions the template strand to scan for the transcription start site and allosterically stimulates initial RNA synthesis, and the growing RNA chain (beyond ~12–13 nt) sterically displaces TFIIB to trigger promoter clearance; TFIIB also recognizes two flanking core promoter elements (upstream and downstream BREs) through independent DNA-binding motifs, undergoes serine 65 phosphorylation that links the promoter to 3′ cleavage/polyadenylation machinery, and participates in gene looping by associating with both promoter and terminator regions in an Ssu72-dependent manner; in addition, TFIIB is a direct target of numerous transcriptional activators (VP16, nuclear hormone receptors, and others) that stimulate preinitiation complex assembly by enhancing TFIIB recruitment or inducing productive conformational changes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GTF2B encodes TFIIB, an essential general transcription factor for RNA polymerase II that nucleates preinitiation complex assembly and governs the transition from promoter recognition to productive initiation [#0, #48]. TFIIB is organized into two functionally separable modules: a C-terminal core of two cyclin A–like direct repeats that recognizes the preformed TBP–TATA complex and extends contacts to promoter DNA, and an N-terminal zinc-ribbon region that recruits RNA polymerase II–TFIIF; mutation of the core abolishes Pol II recruitment without disrupting TBP binding, while the zinc ribbon is dispensable for TBP contact [#4, #5, #6, #12, #13]. Within the assembled complex, TFIIB sits beneath the concave face of TBP and surrounds promoter DNA, and its zinc ribbon contacts the Pol II Dock domain near the RNA exit path while its linker, reader, and core elements reach over the active-center cleft to position template DNA, assist DNA opening, and scan for the transcription start site [#14, #21, #34, #35, #41, #46]. Accordingly, TFIIB and TATA-box mutations impair transcription after recruitment, and TFIIB determines start-site selection through genetic and functional interactions with the Pol II Rpb1, Rpb2, and Rpb9 subunits and with TFIIF [#2, #11, #22, #23, #28, #32, #37]. As RNA synthesis proceeds beyond ~12–13 nt the growing transcript and upstream DNA rewinding sterically displace the B-reader and B-linker, triggering TFIIB release and promoter clearance, with TFIIF stabilizing TFIIB in early elongation until that point [#38, #41, #44, #46]. TFIIB additionally recognizes flanking core-promoter BRE elements through distinct DNA-binding modules, links initiation to 3′ processing via serine-65 phosphorylation that controls CstF/CPSF recruitment, and participates in Ssu72-dependent gene looping by associating with both promoters and terminators [#33, #36, #39, #43, #48]. TFIIB is also a direct convergence point for transcriptional regulators, contacting the acidic activator VP16 and nuclear hormone receptors among others to enhance its recruitment or induce productive conformational changes [#1, #3, #7, #15, #20, #31]. Single-molecule imaging shows TFIIB promoter binding is highly transient and is stabilized only upon Pol II–TFIIF recruitment, defining a kinetic checkpoint in PIC progression [#47].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established TFIIB as a discrete, essential basal factor required for Pol II transcription initiation, defining the molecular entity itself.\",\n      \"evidence\": \"protein purification to homogeneity, cDNA cloning, and in vitro transcription reconstitution\",\n      \"pmids\": [\"1946368\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of how TFIIB engages the initiation machinery\", \"Molecular basis of essentiality not defined\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Showed that an acidic activator directly contacts TFIIB to accelerate a rate-limiting recruitment step, establishing TFIIB as a target of transcriptional activation.\",\n      \"evidence\": \"affinity chromatography with recombinant VP16 and TFIIB plus in vitro transcription rate measurement\",\n      \"pmids\": [\"1922364\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Surface on TFIIB contacted by VP16 not mapped\", \"Whether all activators use this route unknown\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Demonstrated in vivo that TFIIB is a determinant of transcription start-site selection, extending its role beyond simple assembly.\",\n      \"evidence\": \"yeast SUA7 suppressor genetics and primer-extension start-site mapping at cyc1 and ADH1\",\n      \"pmids\": [\"1547497\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which TFIIB sets the start site not resolved\", \"Pol II partners in selection not yet identified\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Resolved TFIIB into separable N-terminal (Pol II recruitment) and C-terminal (TBP binding) functional domains, defining its bridging architecture.\",\n      \"evidence\": \"site-directed and deletion mutagenesis, limited proteolysis, footprinting, and in vitro transcription/TBP-binding assays\",\n      \"pmids\": [\"8516312\", \"8516311\", \"8413225\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the domains not yet known\", \"How the two domains coordinate during assembly unclear\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Identified nuclear hormone receptors as direct TFIIB-binding regulators, showing receptor transactivation and hormone-modulated silencing operate through TFIIB.\",\n      \"evidence\": \"recombinant binding/GST pulldown and reporter cotransfection for COUP-TF, ER, PR, thyroid and vitamin D receptors\",\n      \"pmids\": [\"1517211\", \"8415616\", \"7878015\", \"7623841\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding surfaces partially mapped\", \"Functional consequence for PIC kinetics not quantified in all cases\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showed TFIIB can support minimal initiation and that its start-site function is tied to specific Pol II subunits, placing it in a defined functional network with the polymerase.\",\n      \"evidence\": \"reconstituted YY1/TFIIB/Pol II transcription and sua7–sua8(RPB1) synthetic lethality with start-site mapping\",\n      \"pmids\": [\"8137426\", \"8264591\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical basis of the TFIIB–Rpb1 interaction not defined\", \"TBP-independent route physiological relevance unclear\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Provided the structural basis for TFIIB recognition of the TBP–TATA complex, revealing a cyclin A–like fold and DNA contacts flanking the TATA box.\",\n      \"evidence\": \"2.7 Å crystal structure of TFIIB–TBP–TATA, solution NMR of the core domain, and hydroxyl-radical footprinting\",\n      \"pmids\": [\"7675079\", \"7671313\", \"7637813\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Pol II-bound conformation not captured\", \"Position of the N-terminal zinc ribbon relative to Pol II unresolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Mapped TFIIB as part of a DNA-encircling clamp and defined its genetic partners in TFIIF, refining the geometry and network of the early complex.\",\n      \"evidence\": \"site-specific protein–DNA photocrosslinking of the TBP–TFIIA–TFIIB–DNA complex and SSU71/TFG1 suppressor genetics\",\n      \"pmids\": [\"8855228\", \"7724527\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct TFIIB–TFIIF contact surface not yet defined\", \"Order of clamp assembly steps unclear\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Distinguished post-recruitment functions of TFIIB and separated its zinc-ribbon (Pol II binding) from an adjacent start-site-selection homology block.\",\n      \"evidence\": \"immobilized-template PIC assays with E62G mutant and mutagenesis dissecting yeast TFIIB N-terminal domains\",\n      \"pmids\": [\"9887099\", \"9651390\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural correlate of the start-site homology block lacking\", \"Catalytic contribution to initiation not yet visualized\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined TFIIB recognition of core-promoter BRE elements and showed activators can modulate this DNA recognition, linking TFIIB to promoter-strength control.\",\n      \"evidence\": \"transcription assays with BRE-mutant promoters and protein–DNA footprinting\",\n      \"pmids\": [\"11711430\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream BRE recognition module not yet identified\", \"Generality across promoter classes untested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Delivered the Pol II–TFIIB structure showing the zinc ribbon at the Dock domain and the B-finger reaching into the active center, plus a second BRE-binding module, unifying the assembly and initiation roles.\",\n      \"evidence\": \"X-ray crystallography of Pol II–TFIIB, crosslinking/hydroxyl-radical probing, B-finger/Rpb2 genetics, and downstream-BRE DNA-binding assays\",\n      \"pmids\": [\"14963322\", \"14536083\", \"15082791\", \"16230532\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Resolution insufficient to model template-strand path fully\", \"How the B-finger times initiation not resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Linked B-finger displacement to transcription-bubble collapse and promoter clearance, establishing TFIIB's role in the initiation-to-elongation transition.\",\n      \"evidence\": \"permanganate footprinting of bubbles across promoter-spacing mutants with quantitative elongation assays\",\n      \"pmids\": [\"15989968\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact RNA length triggering displacement defined only functionally here\", \"Coupling to TFIIH release mechanistically incomplete\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Revealed a transcription-architectural role for TFIIB in Ssu72-dependent gene looping by bridging promoters and terminators.\",\n      \"evidence\": \"ChIP and 3C across multiple loci with the looping-defective E62K mutant\",\n      \"pmids\": [\"17803944\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct TFIIB–terminator contacts not biochemically reconstituted\", \"Functional output of looping for re-initiation not quantified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Completed the structural mechanism of initiation, defining B-linker (DNA opening), B-reader (start-site scanning), and the displacement logic that triggers TFIIB release.\",\n      \"evidence\": \"Pol II–TFIIB crystal structures at 4.3 and 3.8 Å with functional analysis\",\n      \"pmids\": [\"19820686\", \"19965383\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"State with nascent RNA not yet captured\", \"Allosteric activation of synthesis only inferred\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected TFIIB to 3′-end processing through serine-65 phosphorylation that controls CstF/CPSF recruitment, mechanistically coupling initiation and termination.\",\n      \"evidence\": \"phospho-site mapping, phospho-specific antibody, Co-IP, ChIP, and phospho-mutant transcription assays\",\n      \"pmids\": [\"20226668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for S65 phosphorylation not identified\", \"Stoichiometry across the transcription cycle unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Provided the definitive multi-state structural model of TFIIB action from cleft closure and start-site scanning through RNA-driven displacement at ~12–13 nt.\",\n      \"evidence\": \"crystal structures of apo Pol II–TFIIB at 3.4 Å and an initially transcribing complex with 6-nt RNA, plus functional mutagenesis\",\n      \"pmids\": [\"23151482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Activator-induced conformational states not captured in this framework\", \"Human-specific differences from yeast model not addressed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed TFIIB promoter binding is highly transient and stabilized only by Pol II–TFIIF, defining a kinetic checkpoint in PIC formation.\",\n      \"evidence\": \"single-molecule fluorescence imaging in reconstituted and live-cell systems\",\n      \"pmids\": [\"27798851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo determinants of residence time not fully defined\", \"Relationship of transient binding to bursting unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Quantified the genome-wide requirement for TFIIB in human cells, confirming it is the dominant determinant of Pol II promoter activity and revealing termination defects upon depletion.\",\n      \"evidence\": \"auxin-inducible acute depletion with PRO-Seq across >70,000 promoters\",\n      \"pmids\": [\"35947745\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect termination effects not separated\", \"Promoter features dictating differential sensitivity not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How activator-induced conformational changes in TFIIB are coupled to the kinetic stabilization checkpoint and to TFIIB's roles in looping and 3′ processing remains unresolved.\",\n      \"evidence\": \"no single study in the corpus integrates activator-driven TFIIB conformational change with single-molecule PIC dynamics and the initiation–termination coupling\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the activator-primed TFIIB state lacking\", \"Mechanistic link between S65 phosphorylation, looping, and termination not unified\", \"Kinase and regulatory inputs to TFIIB in human cells uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 25, 33]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [14, 33, 36, 21]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 5, 35, 41]},\n      {\"term_id\": \"GO:0140223\", \"supporting_discovery_ids\": [0, 32, 48]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [26, 39, 40]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 41, 46, 48]}\n    ],\n    \"complexes\": [\"RNA polymerase II preinitiation complex\"],\n    \"partners\": [\"TBP\", \"POLR2A\", \"GTF2F1\", \"GTF2A1\", \"SSU72\", \"SUB1\", \"FCP1\", \"VP16\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}