A novel TBP-associated factor of SL1 functions in RNA polymerase I transcription

EMBO J. 2007 Mar 21;26(6):1560-8. doi: 10.1038/sj.emboj.7601601. Epub 2007 Feb 22.

Abstract

In mammalian RNA polymerase I transcription, SL1, an assembly of TBP and associated factors (TAFs), is essential for preinitiation complex formation at ribosomal RNA gene promoters in vitro. We provide evidence for a novel component of SL1, TAF(I)41 (MGC5306), which functions in Pol I transcription. TAF(I)41 resides at the rDNA promoter in the nucleolus and co-purifies and co-immunoprecipitates with SL1. TAF(I)41 immunodepletion from nuclear extracts dramatically reduces Pol I transcription; addition of SL1 restores the ability of these extracts to support Pol I transcription. In cells, siRNA-mediated decreased expression of TAF(I)41 leads to loss of SL1 from the rDNA promoter in vivo, with concomitant loss of Pol I from the rDNA and reduced synthesis of the pre-rRNA. Extracts from these cells support reduced levels of Pol I transcription; addition of SL1 to the extracts raises the level of Pol I transcription. These data suggest that TAF(I)41 is integral to transcriptionally active SL1 and imply a role for SL1, including the TAF(I)41 subunit, in Pol I recruitment and, therefore, preinitiation complex formation in vivo.

Publication types

  • Comparative Study

MeSH terms

  • Chromatin Immunoprecipitation
  • DNA Primers
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Pol1 Transcription Initiation Complex Proteins / metabolism*
  • RNA Polymerase I / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • TATA-Binding Protein Associated Factors / metabolism*
  • Transcription, Genetic / physiology*

Substances

  • DNA Primers
  • Pol1 Transcription Initiation Complex Proteins
  • TAF1B protein, human
  • TAF1D protein, human
  • TATA-Binding Protein Associated Factors
  • RNA Polymerase I