Affinage

BRF2

Transcription factor IIIB 50 kDa subunit · UniProt Q9HAW0

Length
419 aa
Mass
46.5 kDa
Annotated
2026-06-09
22 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

BRF2 (TFIIIB50) is a TFIIB-like core transcription factor that assembles human TFIIIB-alpha activity required for RNA Polymerase III transcription at gene-external (type III) promoters, including U6 snRNA, RNase P, and 7SK (PMID:11121026, PMID:40781771). It is recruited to the TATA-box of Pol III snRNA gene promoters through a direct, TBP-dependent interaction in which BRF2 stabilizes TBP on TATA-containing templates and extends its DNA footprint, with the core domain of TBP sufficient for ternary BRF2·TBP·DNA complex formation (PMID:11564744). Crystallographic and structure-guided functional work resolved BRF2·TBP bound to natural promoters and defined a redox-sensing module within BRF2 that couples cellular oxidative stress to Pol III transcriptional output (PMID:26638071), and within the assembled pre-initiation complex BRF2-containing TFIIIB cooperates with SNAPc to form a transcriptionally competent Pol III PIC on the U6 promoter [PMID:bio_10.1101_2024.09.10.612236]. BRF2 confers promoter selectivity within the TFIIIB family, driving gene-external U6 transcription while BRF1 governs gene-internal templates (PMID:18700021), and its activity is negatively regulated by human Maf1 acting through TFIIIB (PMID:17505538). BRF2 functions as an oncogenic driver in lung squamous cell carcinoma, where its overexpression transforms bronchial epithelial cells and increases Pol III-mediated snRNA transcription (PMID:20668658). Biallelic loss-of-function variants in BRF2 that disrupt the TBP interaction impair Pol III transcription of the redox-regulating genes GPX1 and GPX4, disturbing redox homeostasis and causing primary immunodeficiency, craniofacial malformations, and neurodevelopmental disorders, with zebrafish defects rescued by wild-type but not mutant human BRF2 (PMID:40781771, PMID:40229899).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2000 High

    Established the molecular identity of the factor providing TFIIIB-alpha activity, answering which protein enables Pol III transcription of upstream-promoter genes.

    Evidence Cloning and biochemical reconstitution of TFIIIB50 with TBP and TFIIIB150 plus in vitro transcription

    PMID:11121026

    Open questions at the time
    • Did not resolve atomic-level promoter contacts
    • Did not address regulation of the complex
  2. 2001 High

    Defined how BRF2 is recruited to promoters, showing TBP-dependent targeting to the TATA-box and stabilization of TBP on DNA.

    Evidence Gel footprinting, EMSA, domain mapping and in vitro transcription on snRNA promoters

    PMID:11564744

    Open questions at the time
    • Did not capture the full PIC including other Pol III machinery
    • No structural model of the interaction surfaces at the time
  3. 2007 Medium

    Identified a negative regulator of BRF2-dependent transcription, placing Maf1 upstream of TFIIIB repression.

    Evidence Pol III luciferase and in vivo repression assays implicating Maf1 acting via Brf1 and Brf2

    PMID:17505538

    Open questions at the time
    • Direct physical interaction of Maf1 with BRF2 not biochemically dissected
    • Conditions triggering Maf1 repression of BRF2 not defined
  4. 2008 Medium

    Demonstrated functional promoter selectivity within the TFIIIB family, separating BRF2-driven gene-external transcription from BRF1-driven gene-internal transcription.

    Evidence Promoter activity assays, western blot and qRT-PCR across breast, cervical and prostate cancer lines

    PMID:18700021

    Open questions at the time
    • Correlation with cancer phenotype not mechanistically established here
    • Determinants of selectivity not mapped structurally
  5. 2010 High

    Established BRF2 as a tissue-specific oncogenic driver, linking its Pol III activity to lung squamous cell carcinoma transformation.

    Evidence Reciprocal overexpression and RNAi, colony/growth assays, and copy number/expression analysis across >330 clinical samples

    PMID:20668658

    Open questions at the time
    • Specific snRNA targets driving transformation not enumerated
    • Why oncogenic effect is restricted to SqCC unresolved
  6. 2015 High

    Resolved the BRF2-TBP-promoter structure and discovered a redox-sensing module, answering how Pol III output is coupled to oxidative stress.

    Evidence X-ray crystallography with structure-guided mutagenesis and functional transcription assays in cells

    PMID:26638071

    Open questions at the time
    • Full PIC architecture not captured in the crystal
    • Physiological oxidant species sensed not exhaustively defined
  7. 2015 Medium

    Showed BRF2 expression is regulated by estrogen receptor signaling, identifying an upstream control of BRF2 levels in breast cancer.

    Evidence Daidzein treatment with promoter methylation, mRNA stability assays and in vivo mouse diet experiments in ER+ vs ER- cells

    PMID:26573593

    Open questions at the time
    • Direct ER binding to the BRF2 locus not demonstrated
    • Functional consequence for tumor biology not established
  8. 2021 Medium

    Linked BRF2 to MAPK/ERK signaling and identified let-7b-3p as a direct post-transcriptional regulator controlling proliferation and metastasis.

    Evidence Dual-luciferase reporter, transcriptome sequencing, western blot, siRNA and xenograft in lung cancer

    PMID:34012797

    Open questions at the time
    • Mechanism connecting BRF2 to MAPK/ERK not biochemically defined
    • Single-lab pathway placement
  9. 2021 Low

    Proposed a role for BRF2 in rescuing oxidative-stress-induced apoptosis within the DNA damage response.

    Evidence Virtual screening, molecular dynamics, proliferation and ROS assays with bexarotene treatment

    PMID:34359683

    Open questions at the time
    • Largely computational with no direct DNA damage mechanistic assay
    • Single drug, single lab
    • Direct DDR role of BRF2 not demonstrated
  10. 2023 Low

    Associated BRF2 with Wnt/beta-catenin-driven HCC metastasis and identified miR-409-3p as a direct regulator.

    Evidence Luciferase reporter, siRNA, invasion/migration assays and bioinformatic pathway analysis

    PMID:36927769

    Open questions at the time
    • Pathway placement is bioinformatic only without direct mechanistic validation
    • Single lab
  11. 2023 Low

    Connected BRF2 to LKB1/AMPK signaling in HCC through a MALAT1/miR-1-3p ceRNA axis.

    Evidence Dual-luciferase, siRNA, AMPK pathway western blot, xenograft and flow cytometry

    PMID:37653482

    Open questions at the time
    • BRF2-to-LKB1/AMPK link is indirect single-lab evidence
    • ceRNA mechanism not orthogonally confirmed
  12. 2024 High

    Resolved how BRF2-containing TFIIIB assembles with SNAPc into a transcriptionally competent Pol III PIC, defining the structural basis of selective SNAPc engagement.

    Evidence Cryo-EM of the full-length SNAPc-Pol III PIC on the U6 promoter in open and melting states with XL-MS (preprint)

    PMID:bio_10.1101_2024.09.10.612236

    Open questions at the time
    • Single-lab preprint
    • Dynamics of promoter melting not fully resolved kinetically
  13. 2025 Medium

    Established BRF2 as a Mendelian disease gene, showing biallelic loss-of-function impairs Pol III transcription of redox genes and causes a multisystem disorder.

    Evidence Whole-exome and single-cell RNA sequencing plus Pol III activity and expression assays in patient cells; zebrafish morpholino knockdown with wild-type but not mutant mRNA rescue

    PMID:40229899 PMID:40781771

    Open questions at the time
    • Causal chain from GPX1/GPX4 deficit to immunodeficiency not fully traced
    • Genotype-phenotype correlations from limited cases

Open questions

Synthesis pass · forward-looking unresolved questions
  • How BRF2-mediated Pol III output is mechanistically integrated with the diverse downstream signaling pathways (MAPK/ERK, Wnt, LKB1/AMPK) implicated in cancer remains unresolved.
  • No direct biochemical link between BRF2 transcriptional activity and these signaling pathways
  • Most pathway connections rest on single-lab correlative data

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 4 GO:0003677 DNA binding 2 GO:0140223 general transcription initiation factor activity 2 GO:0140299 molecular sensor activity 1
Localization
GO:0005634 nucleus 2
Pathway
R-HSA-74160 Gene expression (Transcription) 5 R-HSA-1643685 Disease 3 R-HSA-8953897 Cellular responses to stimuli 1
Partners
BDP1MAF1SNAPCTBP
Complex memberships
SNAPc-Pol III pre-initiation complexTFIIIB-alpha

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 TFIIIB50 (BRF2) was identified, cloned, and shown to form a stable complex with TBP, TFIIIB150, and tightly associated factors that reconstitutes human TFIIIB-alpha activity, which is specifically required for RNA Pol III transcription of genes with upstream (gene-external) promoter elements. Biochemical reconstitution, cloning, and in vitro transcription assay Proceedings of the National Academy of Sciences of the United States of America High 11121026
2001 BRFU (BRF2) is directly recruited to the TATA-box of Pol III snRNA gene promoters through TBP-dependent interaction; BRFU stabilizes TBP on TATA-containing templates and extends the TBP footprint both upstream and downstream of the TATA element. The core domain of TBP is sufficient for BRFU·TBP·DNA complex formation. Specific amino acid residues in TBP and domains of BRFU mediating the interaction were mapped. Gel footprinting, gel mobility shift assay, domain mapping, in vitro transcription The Journal of biological chemistry High 11564744
2015 Crystal structures of a human Brf2–TBP complex bound to natural promoters revealed molecular interactions at Brf2-dependent Pol III promoters and a redox-sensing module within Brf2. Structural and functional studies demonstrated that this module specifically regulates Pol III transcriptional output in response to oxidative stress in living cells, establishing Brf2 as a central redox-sensing transcription factor. X-ray crystallography, structure-guided mutagenesis, functional transcription assays in cells Cell High 26638071
2007 Human Maf1 represses RNA Pol III transcription via the TFIIB family members Brf1 and Brf2, acting through TFIIIB in vivo. RNA Pol III luciferase assay, in vivo repression assays International journal of biological sciences Medium 17505538
2008 Brf2 protein expression levels correlate with U6 snRNA promoter activity in breast, cervical, and prostate cancer cells, and Brf2-dependent U6 transcription is specifically driven by Brf2 (gene-external promoter), whereas Brf1 governs gene-internal (VAI) transcription, demonstrating functional promoter selectivity between the two TFIIIB factors. Promoter activity assays, western blotting, qRT-PCR in multiple cancer cell lines BMC molecular biology Medium 18700021
2010 Ectopic expression of BRF2 in human bronchial epithelial cells induced a transformed phenotype; RNAi-mediated knockdown suppressed growth and colony formation of squamous cell carcinoma (SqCC) cells overexpressing BRF2 but not adenocarcinoma cells, establishing BRF2 as an oncogenic driver specifically in lung SqCC through increased Pol III-mediated transcription of snRNAs involved in RNA splicing. Ectopic overexpression, RNAi knockdown, colony formation and growth assays, genomic copy number and expression analysis across >330 clinical samples PLoS medicine High 20668658
2015 The soy isoflavone daidzein induces BRF2 expression in ER-positive breast cancer cells through promoter demethylation and mRNA stabilization, leading to increased Pol III-regulated non-coding RNAs; this effect is absent in ER-negative cells, indicating estrogen receptor-dependent regulation of BRF2. qRT-PCR, western blotting, promoter methylation assay, mRNA stability assay, 5-azacytidine treatment, in vivo mouse diet experiment BMC cancer Medium 26573593
2021 BRF2 knockdown in lung cancer cells inhibited the MAPK/ERK signaling pathway, as shown by transcriptome sequencing and western blot; let-7b-3p directly targets BRF2 (confirmed by dual-luciferase reporter assay) and suppresses cell proliferation and metastasis both in vitro and in vivo through this BRF2-MAPK/ERK axis. Dual-luciferase reporter assay, transcriptome sequencing, western blot, siRNA knockdown, in vivo xenograft Translational lung cancer research Medium 34012797
2021 BRF2 plays a novel role in the DNA damage response; bexarotene treatment reduces oxidative stress-induced BRF2 levels and cellular proliferation in cancer cells, suggesting BRF2 functions in rescuing oxidative stress-induced apoptosis linked to the DNA damage response pathway. Virtual screening, molecular dynamics simulation, cell proliferation assays, ROS measurement with bexarotene treatment Cancers Low 34359683
2023 BRF2 promotes HCC invasion and metastasis via the Wnt/β-catenin signaling pathway; miR-409-3p directly targets the 3′ UTR of BRF2 mRNA (validated by luciferase reporter assay) to downregulate BRF2 expression, and BRF2 depletion suppressed HCC metastasis and invasion. Luciferase reporter assay, siRNA knockdown, invasion/migration assays, bioinformatic pathway analysis Cancer cell international Low 36927769
2023 BRF2 knockdown in HCC cells activated the LKB1/AMPK signaling pathway, inhibiting HCC progression; MALAT1 acts as a competitive endogenous RNA sponging miR-1-3p to upregulate BRF2, forming a MALAT1/miR-1-3p/BRF2/LKB1/AMPK axis. Dual-luciferase reporter assay, siRNA knockdown, western blotting (AMPK pathway), xenograft tumor model, flow cytometry Cancer cell international Low 37653482
2025 Biallelic loss-of-function variants in BRF2 cause defective RNA Pol III transcription specifically at type III promoters (U6, RNase P, 7SK); compound heterozygous variants predicted to disrupt interaction with TBP lead to defective BRF2-dependent transcription of redox-regulating genes GPX1 and GPX4, disrupting redox homeostasis and resulting in primary immunodeficiency and developmental anomalies. Whole-exome sequencing, single-cell RNA sequencing, functional assays in human cells expressing BRF2 variants (RNA Pol III activity, gene expression profiling) Molecular therapy Medium 40781771
2025 Biallelic BRF2 variants in humans and brf2 morpholino knockdown in zebrafish cause craniofacial malformations and neurodevelopmental defects; in silico 3D modelling and functional analyses showed differences in target loci occupancy for disease-associated variants; zebrafish defects were rescued by wild-type but not mutant human BRF2 mRNA, confirming variant deleteriousness. Human genetics (sequencing), zebrafish morpholino knockdown, in silico 3D modelling, mRNA rescue experiments, functional occupancy assays Genome medicine Medium 40229899
2024 Cryo-EM structures of the full-length SNAPc-containing Pol III pre-initiation complex (PIC) assembled on the U6 snRNA promoter in open and melting states (3.2–4.2 Å) revealed how a Brf2-containing TFIIIB complex assembles with SNAPc to form a transcriptionally competent PIC; comparative analysis revealed the molecular basis of selective and structurally distinct SNAPc engagement within Pol III versus Pol II PICs. Cryo-EM structure determination, crosslinking mass spectrometry, comparative structural analysis bioRxivpreprint High bio_10.1101_2024.09.10.612236

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2015 Redox Signaling by the RNA Polymerase III TFIIB-Related Factor Brf2. Cell 87 26638071
2010 Integrative genomic analyses identify BRF2 as a novel lineage-specific oncogene in lung squamous cell carcinoma. PLoS medicine 84 20668658
2000 A stable complex of a novel transcription factor IIB- related factor, human TFIIIB50, and associated proteins mediate selective transcription by RNA polymerase III of genes with upstream promoter elements. Proceedings of the National Academy of Sciences of the United States of America 70 11121026
2011 RNA polymerase III transcription in cancer: the BRF2 connection. Molecular cancer 62 21518452
2019 Long noncoding RNA MNX1-AS1 contributes to lung cancer progression through the miR-527/BRF2 pathway. Journal of cellular physiology 54 30618167
2007 Human Maf1 negatively regulates RNA polymerase III transcription via the TFIIB family members Brf1 and Brf2. International journal of biological sciences 54 17505538
2015 Induction of proto-oncogene BRF2 in breast cancer cells by the dietary soybean isoflavone daidzein. BMC cancer 31 26573593
2017 MicroRNA-373 Inhibits Cell Proliferation and Invasion via Targeting BRF2 in Human Non-small Cell Lung Cancer A549 Cell Line. Cancer research and treatment 29 29025258
2021 Let-7b-3p inhibits tumor growth and metastasis by targeting the BRF2-mediated MAPK/ERK pathway in human lung adenocarcinoma. Translational lung cancer research 25 34012797
2008 Differential expression of the TFIIIB subunits Brf1 and Brf2 in cancer cells. BMC molecular biology 25 18700021
2001 BRFU, a TFIIB-like factor, is directly recruited to the TATA-box of polymerase III small nuclear RNA gene promoters through its interaction with TATA-binding protein. The Journal of biological chemistry 25 11564744
1997 Apolipoprotein B gene regulatory factor-2 (BRF-2) is structurally and immunologically highly related to hepatitis B virus X associated protein-1 (XAP-1). Biochemistry 25 9020796
2023 MALAT1/ mir-1-3p mediated BRF2 expression promotes HCC progression via inhibiting the LKB1/AMPK signaling pathway. Cancer cell international 18 37653482
2021 Targeting BRF2 in Cancer Using Repurposed Drugs. Cancers 11 34359683
2023 BRF2 is mediated by microRNA-409-3p and promotes invasion and metastasis of HCC through the Wnt/β-catenin pathway. Cancer cell international 10 36927769
2020 Silencing of BRF2 inhibits the growth and metastasis of lung cancer cells. Molecular medicine reports 9 32705258
2018 BRF2 as a promising indicator for radical lymph-node dissection surgery in patients with cN0 squamous cell carcinoma of the middle thoracic esophagus. Surgery today 8 30182305
2017 New tricks for an old dog: Brf2-dependent RNA Polymerase III transcription in oxidative stress and cancer. Transcription 8 28854119
1992 Transcriptional regulation of the apolipoprotein B100 gene: purification and characterization of trans-acting factor BRF-2. Molecular and cellular biology 8 1620125
2025 Bi-allelic variants in BRF2 are associated with perinatal death and craniofacial anomalies. Genome medicine 1 40229899
2025 Biallelic BRF2 mutations disrupt redox homeostasis as etiological factors in syndromic immunodeficiency and developmental disorders. Molecular therapy : the journal of the American Society of Gene Therapy 0 40781771
2023 Targeting BRF2: insights from in silico screening and molecular dynamic simulations. Journal of biomolecular structure & dynamics 0 37705251

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