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  • The EMBO Journal (1997) 16, 2061 - 2071
  • doi:10.1093/emboj/16.8.2061

Mechanistic analysis of RNA polymerase III regulation by the retinoblastoma protein

Christopher G. C. Larminie1, Carol A. Cairns1, Renu Mital2, Klaus Martin3, Tony Kouzarides3, Stephen P. Jackson3 and Robert J. White1,3

  1. Institute of Biomedical and Life Sciences, Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, Glasgow, G12 8QQ, UK
  2. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
  3. Wellcome/CRC Institute, Tennis Court Road, Cambridge CB2 1QR, Departments of Zoology and Pathology, University of Cambridge, Cambridge, UK

Correspondence to:

Robert J. White,

Received 5 July 1996; Revised 7 January 1997

The tumour suppressor protein RB restricts cellular growth. This may involve inhibiting the synthesis of tRNA and 5S rRNA by RNA polymerase (pol) III. We have shown previously that RB can repress pol III transcription when overexpressed either in vitro or in vivo. We also demonstrated that pol III activity is elevated substantially in primary fibroblasts from RB-deficient mice. Here we address the molecular mechanism of this regulation. RB is shown to repress all types of pol III promoter. It can do this even if added after transcription complex assembly. Functional assays demonstrate that RB targets specifically the general pol III factor TFIIIB. A physical interaction between TFIIIB and RB is indicated by fractionation, pull-down and immunoprecipitation data. We show that TFIIIB activity is elevated in primary fibroblasts from RB-deficient mice. TFIIIB is a multisubunit complex that includes the TATA-binding protein (TBP) and a TFIIB-related factor called BRF. We show that RB itself contains regions of homology to both TBP and BRF and propose a model in which RB disrupts TFIIIB by mimicking these two components.

  • Keywords:

    • RB,
    • RNA polymerase III,
    • TBP,
    • TFIIIB,
    • transcription