Affinage

TAF1B

TATA box-binding protein-associated factor RNA polymerase I subunit B · UniProt Q53T94

Length
588 aa
Mass
68.8 kDa
Annotated
2026-06-10
40 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TAF1B is a subunit of the human RNA Polymerase I promoter selectivity factor SL1, where it functions as a core component of the basal machinery that drives transcription of ribosomal RNA genes (PMID:7491500). Within SL1 it directly contacts rDNA promoter DNA, and the complex stably associates with rRNA gene sites independent of transcriptional state (PMID:7491500, PMID:8609157). TAF1B is structurally related to TFIIB/TFIIB-like initiation factors through predicted N-terminal zinc ribbon and cyclin-like fold domains, an architecture conserved through its yeast ortholog Rrn7, establishing TFIIB-like factors as common initiation components across all three eukaryotic RNA polymerase systems (PMID:21921199, PMID:21921198). Mechanistically, TAF1B interacts directly with the initiation-competent cofactor RRN3 to recruit transcriptionally active Pol I to the rDNA promoter, and it carries an additional essential role in preinitiation complex assembly that follows Pol I recruitment (PMID:11250903, PMID:21921199). SL1 function through TAF1B is also required for stable engagement of UBTF at rRNA gene promoters, generating promoter specificity through an induced-fit mechanism (PMID:35139074). Loss of TAF1B collapses the Pol I preinitiation complex, reduces pre-rRNA synthesis, and triggers nucleolar stress that activates p53- and c-MYC-dependent programs to induce apoptosis and block proliferation in cancer cells (PMID:37645431, PMID:38169774). Across model organisms, TAF1B is required for rRNA synthesis supporting germline stem cell proliferation and hematopoietic cell maintenance (PMID:24436420, PMID:31434704).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 1995 High

    Established TAF1B as a defined subunit of the Pol I selectivity factor SL1 that directly contacts rDNA promoter DNA, identifying its place in the basal rRNA transcription machinery.

    Evidence In vitro reconstitution of SL1 with transcription assays and protein-DNA contact mapping

    PMID:7491500

    Open questions at the time
    • Atomic structure of TAF1B within SL1 not resolved
    • Specific promoter DNA bases contacted by TAF1B versus TAFI110 not delineated
  2. 1996 Medium

    Showed SL1 (including TAF1B) remains stably bound to rRNA genes regardless of transcriptional activity, indicating constitutive promoter occupancy rather than activity-dependent recruitment.

    Evidence Immunofluorescence colocalization and anti-TBP Co-IP from active and actinomycin D-treated cell extracts

    PMID:8609157

    Open questions at the time
    • Single-lab observation
    • Does not address dynamics of complex turnover
  3. 2001 High

    Identified TAF1B as a direct binding partner of the initiation factor RRN3, linking SL1 to recruitment of the transcriptionally active form of Pol I.

    Evidence Co-IP, direct interaction assay, and in vitro transcription with interaction-blocking experiments

    PMID:11250903

    Open questions at the time
    • Interaction interface on TAF1B not mapped at residue level
    • How RRN3 binding is regulated remains unaddressed
  4. 2004 Medium

    Characterized TBP-contact and nuclear import surfaces within SL1 TAF subunits, defining how the complex containing TAF1B assembles and localizes, though the mapped determinants reside on the partner TAFI48.

    Evidence Yeast two-hybrid, GST pull-down, GFP localization, and site-directed mutagenesis of TBP and TAFI48

    PMID:15113842 PMID:15315821

    Open questions at the time
    • Determinants mapped on TAFI48, not TAF1B itself
    • TAF1B's own import and TBP-contact contributions not isolated
  5. 2007 Medium

    Reported a pathogen (Toxoplasma GRA10) interaction with nucleolar TAF1B, indicating TAF1B can be targeted at the nucleolus by exogenous factors.

    Evidence Yeast two-hybrid, GST pull-down, Co-IP, and immunofluorescence colocalization

    PMID:17876161

    Open questions at the time
    • Functional consequence for host rRNA transcription unknown
    • Single-lab, non-physiological co-transfection context
  6. 2011 High

    Resolved TAF1B as a TFIIB-like factor with zinc ribbon and cyclin-fold domains and an essential post-recruitment role in PIC assembly, unifying initiation mechanisms across the three RNA polymerase systems.

    Evidence Structural homology prediction, domain swaps, and functional complementation; corroborated by yeast Rrn7 ortholog analysis

    PMID:21921198 PMID:21921199

    Open questions at the time
    • Precise step in PIC assembly executed by TAF1B not defined
    • No experimental high-resolution structure of human TAF1B
  7. 2014 High

    Demonstrated through genetic loss-of-function that TAF1B is required for rRNA synthesis supporting germline stem cell proliferation, linking the molecular function to a developmental cellular output.

    Evidence Drosophila loss-of-function genetics, rRNA transcription measurement, GSC proliferation assay

    PMID:24436420

    Open questions at the time
    • Drosophila complex composition may differ from human SL1
    • Tissue-specific requirements in mammals not addressed here
  8. 2017 Medium

    Placed TAF1B downstream of Piwi and upstream of Udd in nucleolar recruitment, ordering the SL1-like complex assembly pathway in germline cells.

    Evidence RNAi knockdown, immunofluorescence localization, and genetic epistasis in Drosophila

    PMID:29116069

    Open questions at the time
    • Molecular basis of TAF1B-dependent Udd recruitment unknown
    • Conservation of this hierarchy in mammals untested
  9. 2019 Medium

    Showed Taf1b expression is epigenetically controlled by KDM4 demethylases and is essential for hematopoietic cell maintenance, connecting TAF1B regulation to stem cell homeostasis.

    Evidence Conditional triple-knockout mice, H3K9me3 ChIP at the Taf1b TSS, expression and rescue analysis

    PMID:31434704

    Open questions at the time
    • Direct demonstration that rRNA loss mediates the hematopoietic phenotype not provided
    • Single-lab finding
  10. 2022 High

    Established that TAF1B/SL1 is required for stable UBTF engagement specifically at rRNA gene promoters, defining an induced-fit mechanism generating rDNA promoter specificity.

    Evidence Conditional TAF1B deletion with ChIP-seq for UBTF across rDNA

    PMID:35139074

    Open questions at the time
    • Structural basis of induced-fit cooperation not resolved
    • Order of UBTF versus SL1 binding events not fully established
  11. 2022 Medium

    Implicated the TAF1B-containing complex in selective activation of intact rDNA units in competition with heterochromatin, linking SL1 to rDNA copy-number/chromatin regulation.

    Evidence Drosophila RNAi knockdown, ChIP for H3K9me3/HP1a, qRT-PCR of R2 retrotransposon elements

    PMID:35037046

    Open questions at the time
    • Direct role of TAF1B in chromatin mark deposition versus indirect effect unclear
    • Mammalian relevance untested
  12. 2023 Medium

    Connected TAF1B-dependent PIC integrity to tumor cell viability, showing depletion collapses Pol I transcription and triggers nucleolar-stress apoptosis via p53/c-MYC pathways.

    Evidence Lentiviral/RNAi knockdown, ChIP, Co-IP, FISH, xenograft models, and apoptosis/proliferation readouts in hepatocellular and stomach carcinoma cells

    PMID:37645431 PMID:38169774

    Open questions at the time
    • Some pathway steps (p53-miR-101 feedback) are inferred rather than directly demonstrated
    • Single-lab studies per tumor type

Open questions

Synthesis pass · forward-looking unresolved questions
  • How TAF1B coordinates its sequential RRN3-mediated Pol I recruitment and post-recruitment PIC assembly roles at atomic resolution, and how these are regulated to control rRNA output, remains unresolved.
  • No experimental high-resolution structure of human SL1 with TAF1B
  • Regulatory inputs governing TAF1B activity in human cells undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 3 GO:0140223 general transcription initiation factor activity 2 GO:0003677 DNA binding 1
Localization
GO:0005730 nucleolus 3 GO:0005634 nucleus 1
Pathway
R-HSA-74160 Gene expression (Transcription) 4 R-HSA-8953854 Metabolism of RNA 2 R-HSA-5357801 Programmed Cell Death 1
Partners
RRN3TAF1ATAF1CTBPUBTF
Complex memberships
RNA Pol I core factor (yeast Rrn7)SL1 (Selectivity Factor 1)

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 TAF1B (TAFI63) is a subunit of the RNA Pol I promoter selectivity factor SL1 (composed of TBP, TAFI110, TAFI63/TAF1B, and TAFI48). Both TAFI110 and TAFI63 contact the rRNA gene promoter DNA directly, while TAFI48 (not TAF1B) serves as the target for UBF interaction and class-specific promoter selectivity. In vitro transcription assay, protein-DNA contact analysis, reconstitution of SL1 complex Science High 7491500
1996 TBP colocalizes with TAF(I)s (including TAF(I)63/TAF1B), UBF, and RNA Pol I at rRNA gene sites in both actively transcribing and mitotically silenced nucleoli; anti-TBP antibodies co-immunoprecipitate TAF(I)63 from both untreated and actinomycin D-treated cell extracts, demonstrating stable SL1 complex association with rRNA genes regardless of transcriptional activity. Immunofluorescence colocalization, co-immunoprecipitation from mammalian cell extracts The Journal of cell biology Medium 8609157
2001 hRRN3 (the initiation-competent Pol I co-factor) interacts directly with TAF(I)110 and TAF(I)63/TAF1B within SL1; blocking this RRN3–TAF1B/TAF(I)63 interaction prevents recruitment of the transcriptionally active Pol I (Pol I-beta) to the rDNA promoter. Co-immunoprecipitation, direct protein interaction assay, in vitro transcription with blocking experiments The EMBO journal High 11250903
2004 The carboxyl-terminal 51 residues of TAF(I)48 (a binding partner of TAF1B within SL1) are necessary and sufficient for nucleolar/nuclear localization and associate with multiple beta-karyopherin import receptors (importin beta, transportin, RanBP5) in a Ran-dependent manner, identifying the first nuclear import sequence within SL1 TAF subunits. Domain deletion analysis, GFP localization assay, GST pull-down with karyopherins, Ran-dependent binding assay Journal of biochemistry Medium 15113842
2004 TAF1B (TAF(I)63) directly binds TBP within SL1; a TBP-binding domain was identified in the carboxyl-terminus of the SL1 partner TAF(I)48, and residues within helix 2 of TBP (shared with TFIID and TFIIIB interactions) are required for this interaction, indicating conserved TBP-contact surfaces across Pol I, II, and III complexes. Yeast two-hybrid, GST pull-down, site-directed mutagenesis of TBP and TAF(I)48 Gene Medium 15315821
2007 Toxoplasma gondii GRA10 protein interacts with human TAF1B in the nucleolus; the interaction was confirmed by GST pull-down and co-immunoprecipitation, and both proteins co-localize in the nucleolus after co-transfection, with GRA10's nucleolar localization being actinomycin D-sensitive (consistent with dependence on active rRNA transcription). Yeast two-hybrid, GST pull-down, co-immunoprecipitation, immunofluorescence colocalization The Korean journal of parasitology Medium 17876161
2011 TAF1B, a subunit of human SL1, is structurally related to TFIIB/TFIIB-like proteins through predicted N-terminal zinc ribbon and cyclin-like fold domains. TAF1B has an essential post-Pol I recruitment role in preinitiation complex assembly at the rRNA gene promoter, in addition to SL1's established role in Pol I recruitment. Structural homology prediction, domain swap experiments, functional rescue assays for Pol I transcription Science High 21921199
2011 Yeast Rrn7 (ortholog of human TAF1B) is a TFIIB-like factor and a subunit of the yeast Pol I core factor; domain swaps between TFIIB-related factors show Rrn7 is most closely related to the Pol III factor Brf1, establishing evolutionary conservation of TFIIB-like initiation factors across all three eukaryotic RNA polymerase systems. Sequence analysis, structural domain comparison, TFIIB-related domain swapping functional assays Science High 21921198
2014 In Drosophila, TAF1B is part of an RNA Pol I regulatory complex with Udd (Under-developed) and a TAF1C-like factor. Disruption of TAF1B reduces rRNA transcription and causes reduced ovarian germline stem cell (GSC) proliferation, demonstrating TAF1B is required for rRNA synthesis and GSC maintenance. Genetic disruption (Drosophila loss-of-function), rRNA transcription measurement, GSC proliferation assay Science High 24436420
2017 In Drosophila germline cells, TAF1B (component of the SL1-like complex) is required for nucleolar localization of Udd (another SL1-like complex subunit); knockdown of TAF1B in germline cells leads to accumulation of late-stage egg chambers due to reduced rRNA transcription. Knockdown of TAF1B does not disrupt Piwi nucleolar localization, placing TAF1B downstream of Piwi in the nucleolar recruitment pathway. RNAi knockdown in Drosophila, immunofluorescence localization, genetic epistasis Molekuliarnaia biologiia Medium 29116069
2019 KDM4 histone demethylases (KDM4A/B/C) are required for expression of Taf1b in hematopoietic stem cells; conditional triple knockout of KDM4 demethylases leads to H3K9me3 accumulation at the Taf1b transcription start site and downregulation of Taf1b expression, and Taf1b is shown to be essential for maintenance of hematopoietic cells. Conditional triple-knockout mice, ChIP for H3K9me3, gene expression analysis, functional rescue Blood Medium 31434704
2022 Conditional deletion of the TAF1B subunit of SL1 causes striking depletion of UBTF specifically at both rRNA gene promoters (but not elsewhere across the rDNA), demonstrating that TAF1B/SL1 is required for stable UBTF1 engagement at rDNA promoters and that UBTF1–SL1 cooperation generates rDNA promoter specificity in an induced-fit mechanism. Conditional TAF1B deletion, ChIP-seq for UBTF at rDNA promoters, quantitative genomic analysis PLoS genetics High 35139074
2022 In Drosophila, impaired function of TAF1B (a subunit of the SL1-like complex) leads to derepression of R2-retrotransposon-containing rDNA units, accompanied by reduction of H3K9me3 and HP1a marks at those loci, suggesting the SL1-like complex participates in selective activation of intact rDNA units in competition with heterochromatin formation. RNAi knockdown of TAF1B in Drosophila ovaries, ChIP for H3K9me3/HP1a, quantitative RT-PCR of R2 elements Nucleic acids research Medium 35037046
2023 TAF1B depletion in hepatocellular carcinoma cells disrupts the pre-initiation complex (PIC) at rDNA, reduces Pol I binding to rDNA (validated by ChIP), decreases pre-rRNA levels, induces nucleolar stress, and triggers apoptosis via a p53–miR-101 feedback circuit in which Pol I transcription repression activates p53, which induces miR-101, and miR-101 negatively feeds back by inhibiting the p53-mediated PARP pathway. Lentiviral knockdown, Co-IP, ChIP, FISH for rDNA activity, immunofluorescence, xenograft tumor model, Western blot for apoptosis markers Frontiers in oncology Medium 37645431
2023 TAF1B knockdown in stomach adenocarcinoma cells disrupts the Pol I pre-initiation complex, impairs rRNA gene transcription and ribosome biogenesis, induces nucleolar stress, and promotes c-MYC mRNA degradation, resulting in inhibition of cell proliferation and survival in vitro and in vivo. RNAi knockdown, in vitro proliferation assay, xenograft model, qRT-PCR for pre-rRNA, Western blot for c-MYC Heliyon Medium 38169774

Source papers

Stage 0 corpus · 40 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2017 DNA Methylation Analysis Identifies Loci for Blood Pressure Regulation. American journal of human genetics 177 29198723
2014 Changes in rRNA transcription influence proliferation and cell fate within a stem cell lineage. Science (New York, N.Y.) 161 24436420
2001 hRRN3 is essential in the SL1-mediated recruitment of RNA Polymerase I to rRNA gene promoters. The EMBO journal 155 11250903
2009 Tumor-infiltrating lymphocytes in colorectal cancers with microsatellite instability are correlated with the number and spectrum of frameshift mutations. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 136 19503063
1996 In vivo evidence that TATA-binding protein/SL1 colocalizes with UBF and RNA polymerase I when rRNA synthesis is either active or inactive. The Journal of cell biology 129 8609157
2020 A Frameshift Peptide Neoantigen-Based Vaccine for Mismatch Repair-Deficient Cancers: A Phase I/IIa Clinical Trial. Clinical cancer research : an official journal of the American Association for Cancer Research 122 32540851
2004 Immunogenic peptides generated by frameshift mutations in DNA mismatch repair-deficient cancer cells. Cancer immunity 86 15563124
1995 Coactivator and promoter-selective properties of RNA polymerase I TAFs. Science (New York, N.Y.) 86 7491500
1996 RRN11 encodes the third subunit of the complex containing Rrn6p and Rrn7p that is essential for the initiation of rDNA transcription by yeast RNA polymerase I. The Journal of biological chemistry 70 8702872
2005 Microsatellite instability of selective target genes in HNPCC-associated colon adenomas. Oncogene 68 15735733
2011 Yeast Rrn7 and human TAF1B are TFIIB-related RNA polymerase I general transcription factors. Science (New York, N.Y.) 62 21921198
2019 The KDM4/JMJD2 histone demethylases are required for hematopoietic stem cell maintenance. Blood 59 31434704
2011 TAF1B is a TFIIB-like component of the basal transcription machinery for RNA polymerase I. Science (New York, N.Y.) 50 21921199
2002 Identification of MARCKS, FLJ11383 and TAF1B as putative novel target genes in colorectal carcinomas with microsatellite instability. Oncogene 47 12140758
2010 Serum antibodies against frameshift peptides in microsatellite unstable colorectal cancer patients with Lynch syndrome. Familial cancer 44 19957108
1987 Differential susceptibility to actively induced experimental allergic encephalomyelitis and experimental allergic orchitis among BALB/c substrains. Cellular immunology 41 2446778
2013 14-3-3 proteins are essential signalling hubs for beta cell survival. Diabetologia 37 23354124
2012 Effects of multikinase inhibitors on pressure overload-induced right ventricular remodeling. International journal of cardiology 35 22854298
2014 Oligogenic germline mutations identified in early non-smokers lung adenocarcinoma patients. Lung cancer (Amsterdam, Netherlands) 33 24954872
2022 The transcription factor Xrp1 orchestrates both reduced translation and cell competition upon defective ribosome assembly or function. eLife 32 35179490
2008 Prediction of the immunogenic potential of frameshift-mutated antigens in microsatellite instable cancer. International journal of cancer 28 18506693
2013 Hepatocellular carcinoma as extracolonic manifestation of Lynch syndrome indicates SEC63 as potential target gene in hepatocarcinogenesis. Scandinavian journal of gastroenterology 22 23537056
2001 Isolation of expressed sequence tags of skeletal muscle of neonatal healthy and splay leg piglets and mapping by somatic cell hybrid analysis. Animal genetics 19 11683718
2022 Ribosomal DNA promoter recognition is determined in vivo by cooperation between UBTF1 and SL1 and is compromised in the UBTF-E210K neuroregression syndrome. PLoS genetics 18 35139074
2022 Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon. Nucleic acids research 16 35037046
2013 Emergence and expansion of TFIIB-like factors in the plant kingdom. Gene 13 23608173
2016 The mutational profile and infiltration pattern of murine MLH1-/- tumors: concurrences, disparities and cell line establishment for functional analysis. Oncotarget 11 27447752
2015 Frameshift mutations of TAF1C gene, a core component for transcription by RNA polymerase I, and its regional heterogeneity in gastric and colorectal cancers. Pathology 11 25551296
2007 Nucleolar translocalization of GRA10 of Toxoplasma gondii transfectionally expressed in HeLa cells. The Korean journal of parasitology 9 17876161
2016 The Effect of Sorafenib, Tadalafil and Macitentan Treatments on Thyroxin-Induced Hemodynamic Changes and Cardiac Abnormalities. PloS one 7 27082116
2004 The carboxyl-terminus directs TAF(I)48 to the nucleus and nucleolus and associates with multiple nuclear import receptors. Journal of biochemistry 7 15113842
2000 Genomic localization of the human genes TAF1A, TAF1B and TAF1C, encoding TAF(I)48, TAF(I)63 and TAF(I)110 subunits of class I general transcription initiation factor SL1. Cytogenetics and cell genetics 7 10894955
2022 Nucleolar GTPase Bms1 displaces Ttf1 from RFB-sites to balance progression of rDNA transcription and replication. Journal of molecular cell biology 6 34791311
2023 Whole Exome-Trio Analysis Reveals Rare Variants Associated with Congenital Pouch Colon. Children (Basel, Switzerland) 5 37238450
2017 [Participation of the piRNA pathway in recruiting a component of RNA polymerase I transcription initiation complex to germline cell nucleoli]. Molekuliarnaia biologiia 5 29116069
2004 Identification of a domain within human TAF(I)48, a subunit of Selectivity Factor 1, that interacts with helix 2 of TBP. Gene 4 15315821
2023 TAF1B depletion leads to apoptotic cell death by inducing nucleolar stress and activating p53-miR-101 circuit in hepatocellular carcinoma. Frontiers in oncology 3 37645431
2023 Inhibition of TAF1B impairs ribosome biosynthesis and suppresses cell proliferation in stomach adenocarcinoma through promoting c-MYC mRNA degradation. Heliyon 1 38169774
2024 Genetic landscape of congenital pouch colon: systematic review and functional enrichment study. Pediatric surgery international 0 39557707
2013 Meeting report for Odd Pols 2012. Gene 0 23608169

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