Retinoblastoma protein disrupts interactions required for RNA polymerase III transcription.
The retinoblastoma protein (RB) has been shown to suppress RNA polymerase (Pol) III transcription in vivo (R. J. White, D. Trouche, K. Martin, S. P. Jackson, and T. Kouzarides, Nature 382:88-90, 1996). This regulation involves interaction with TFIIIB, a multisubunit factor that is required for the expression of all Pol III templates (C. G. C. Larminie, C. A. Cairns, R. Mital, K. Martin, T. Kouzarides, S. P. Jackson, and R. J. White, EMBO J. 16:2061-2071, 1997; W.-M. Chu, Z. Wang, R. G. Roeder, and C. W. Schmid, J. Biol. Chem. 272:14755-14761, 1997). However, it has not been established why RB binding to TFIIIB results in transcriptional repression. For several Pol II-transcribed genes, RB has been shown to inhibit expression by recruiting histone deacetylases, which are thought to decrease promoter accessibility. We present evidence that histone deacetylases exert a negative effect on Pol III activity in vivo. However, RB remains able to regulate Pol III transcription in the presence of the histone deacetylase inhibitor trichostatin A. Instead, RB represses by disrupting interactions between TFIIIB and other components of the basal Pol III transcription apparatus. Recruitment of TFIIIB to most class III genes requires its binding to TFIIIC2, but this can be blocked by RB. In addition, RB disrupts the interaction between TFIIIB and Pol III that is essential for transcription. The ability of RB to inhibit these key interactions can explain its action as a potent repressor of class III gene expression.
Sutcliffe
J E
JE
Institute of Biomedical and Life Sciences, Division of Biochemistry and Molecular Biology, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Brown
T R
TR
Allison
S J
SJ
Scott
P H
PH
White
R J
RJ
D000818:Animals; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D051379:Mice; D008957:Models, Genetic; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D012320:RNA Polymerase III / Q000235:genetics / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019474:Transcription Factors, TFIII / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection; D000098832:Transcription Factor TFIIIC
D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; D019474:Transcription Factors, TFIII; C405486:U6 small nuclear RNA; D000098832:Transcription Factor TFIIIC; C012589:trichostatin A; D012320:RNA Polymerase III; D006655:Histone Deacetylases