Faculty Opinions recommendation of Redox Signaling by the RNA Polymerase III TFIIB-Related Factor Brf2.

SUMMARYRNA polymerase III (Pol III) synthesizes small RNA molecules that are essential for cell viability. Accurate initiation of transcription by Pol III requires general transcription factor TFIIIB, which is composed of three subunits: TFIIB-related factor BRF1, TATA-binding protein and BDP1. Here we report the molecular characterization of BRF1 in Trypanosoma brucei (TbBRF1), a parasitic protozoa that shows distinctive transcription characteristics. In silico analysis allowed the detection in TbBRF1 of the three conserved domains located in the N-terminal region of all BRF1 orthologues, namely a zinc ribbon motif and two cyclin repeats. Homology modelling suggested that, similarly to other BRF1 and TFIIB proteins, the TbBRF1 cyclin repeats show the characteristic structure of five α-helices per repeat, connected by a short random-coiled linker. As expected for a transcription factor, TbBRF1 was localized in the nucleus. Knock-down of TbBRF1 by RNA interference (RNAi) showed that this protein is essential for the viability of procyclic forms of T. brucei, since ablation of TbBRF1 led to growth arrest of the parasites. Nuclear run-on and quantitative real-time PCR analyses demonstrated that transcription of all the Pol III-dependent genes analysed was reduced, at different levels, after RNAi induction.

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Differential Utilization of TATA Box-binding Protein (TBP) and TBP-related Factor 1 (TRF1) at Different Classes of RNA Polymerase III Promoters

Journal of Biological Chemistry ◽

10.1074/jbc.c113.503094 ◽

2013 ◽

Vol 288 (38) ◽

pp. 27564-27570 ◽

Cited By ~ 8

Author(s):

Neha Verma ◽

Ko-Hsuan Hung ◽

Jin Joo Kang ◽

Nermeen H. Barakat ◽

William E. Stumph

Keyword(s):

Rna Polymerase ◽

Binding Protein ◽

Rna Polymerase Iii ◽

Tata Box ◽

Related Factor ◽

U6 Snrna ◽

Polymerase Iii ◽

Tata Box Binding Protein ◽

In Cells

In the fruit fly Drosophila melanogaster, RNA polymerase III transcription was found to be dependent not upon the canonical TATA box-binding protein (TBP) but instead upon the TBP-related factor 1 (TRF1) (Takada, S., Lis, J. T., Zhou, S., and Tjian, R. (2000) Cell 101, 459–469). Here we confirm that transcription of fly tRNA genes requires TRF1. However, we unexpectedly find that U6 snRNA gene promoters are occupied primarily by TBP in cells and that knockdown of TBP, but not TRF1, inhibits U6 transcription in cells. Moreover, U6 transcription in vitro effectively utilizes TBP, whereas TBP cannot substitute for TRF1 to promote tRNA transcription in vitro. Thus, in fruit flies, different classes of RNA polymerase III promoters differentially utilize TBP and TRF1 for the initiation of transcription.

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The fission yeast TFIIB-related factor limits RNA polymerase III to a TATA-dependent pathway of TBP recruitment

Nucleic Acids Research ◽

10.1093/nar/gkg301 ◽

2003 ◽

Vol 31 (8) ◽

pp. 2108-2116 ◽

Cited By ~ 9

Author(s):

Y. Huang

Keyword(s):

Rna Polymerase ◽

Fission Yeast ◽

Rna Polymerase Iii ◽

Related Factor ◽

Polymerase Iii ◽

Dependent Pathway

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The transcription factor Sp1 modulates RNA polymerase III gene transcription by controlling BRF1 and GTF3C2 expression in human cells

Journal of Biological Chemistry ◽

10.1074/jbc.ra119.011555 ◽

2020 ◽

Vol 295 (14) ◽

pp. 4617-4630

Author(s):

Feixia Peng ◽

Ying Zhou ◽

Juan Wang ◽

Baoqiang Guo ◽

Yun Wei ◽

...

Keyword(s):

Transcription Factor ◽

Rna Polymerase ◽

Gene Transcription ◽

Rna Polymerase Iii ◽

Human Cells ◽

Related Factor ◽

Filamin A ◽

Polymerase Iii ◽

C Subunit ◽

Pol Iii

Specificity protein 1 (Sp1) is an important transcription factor implicated in numerous cellular processes. However, whether Sp1 is involved in the regulation of RNA polymerase III (Pol III)-directed gene transcription in human cells remains unknown. Here, we first show that filamin A (FLNA) represses Sp1 expression as well as expression of TFIIB-related factor 1 (BRF1) and general transcription factor III C subunit 2 (GTF3C2) in HeLa, 293T, and SaOS2 cell lines stably expressing FLNA-silencing shRNAs. Both BRF1 promoter 4 (BRF1P4) and GTF3C2 promoter 2 (GTF3C2P2) contain putative Sp1-binding sites, suggesting that Sp1 affects Pol III gene transcription by regulating BRF1 and GTF3C2 expression. We demonstrate that Sp1 knockdown inhibits Pol III gene transcription, BRF1 and GTF3C2 expression, and the proliferation of 293T and HeLa cells, whereas Sp1 overexpression enhances these activities. We obtained a comparable result in a cell line in which both FLNA and Sp1 were depleted. These results indicate that Sp1 is involved in the regulation of Pol III gene transcription independently of FLNA expression. Reporter gene assays showed that alteration of Sp1 expression affects BRF1P4 and GTF3C2P2 activation, suggesting that Sp1 modulates Pol III–mediated gene transcription by controlling BRF1 and GTF3C2 gene expression. Further analysis revealed that Sp1 interacts with and thereby promotes the occupancies of TATA box–binding protein, TFIIAα, and p300 at both BRF1P4 and GTF3C2P2. These findings indicate that Sp1 controls Pol III–directed transcription and shed light on how Sp1 regulates cancer cell proliferation.

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