Article
- The EMBO Journal (2006) 25, 3310 - 3322
- doi:10.1038/sj.emboj.7601221
Published online: 6 July 2006
Subject Category:
UBF activates RNA polymerase I transcription by stimulating promoter escape
Kostya I Panov, J Karsten Friedricha, Jackie Russell and Joost C B M Zomerdijk
- Division of Gene Regulation and Expression, School of Life Sciences, Wellcome Trust Biocentre, University of Dundee, Dundee, UK
Correspondence to:
Joost C B M Zomerdijk, Division of Gene Regulation and Expression, School of Life Sciences, Wellcome Trust Biocentre, University of Dundee, Dundee DD1 5EH, UK. Tel.: +44 1382 384242; Fax: +44 1382 388072; E-mail: j.zomerdijk@dundee.ac.uk
aPresent address: Cancer Research UK Molecular Oncology Unit, Barts and The London School of Medicine and Dentistry, John Vane Science Centre, Charterhouse Square, London EC1M 6BQ, UK
Received 27 January 2006; Accepted 9 June 2006
Abstract
Ribosomal RNA gene transcription by RNA polymerase I (Pol I) is the driving force behind ribosome biogenesis, vital to cell growth and proliferation. The key activator of Pol I transcription, UBF, has been proposed to act by facilitating recruitment of Pol I and essential basal factor SL1 to rDNA promoters. However, we found no evidence that UBF could stimulate recruitment or stabilization of the pre-initiation complex (PIC) in reconstituted transcription assays. In this, UBF is fundamentally different from archetypal activators of transcription. Our data imply that UBF exerts its stimulatory effect on RNA synthesis, after PIC formation, promoter opening and first phosphodiester bond formation and before elongation. We provide evidence to suggest that UBF activates transcription in the transition between initiation and elongation, at promoter escape by Pol I. This novel role for UBF in promoter escape would allow control of rRNA synthesis at active rDNA repeats, independent of and complementary to the promoter-specific targeting of SL1 and Pol I during PIC assembly. We posit that stimulation of promoter escape could be a general mechanism of activator function.
Keywords:
- promoter escape,
- recruitment,
- RNA polymerase I,
- transcription activation,
- UBF
