A novel TBP-associated factor of SL1 functions in RNA polymerase I transcription.
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.
Gorski
Julia J
JJ
Division of Gene Regulation and Expression, College of Life Sciences, Wellcome Trust Biocentre, University of Dundee, Dundee, UK.
Pathak
Shalini
S
Panov
Kostya
K
Kasciukovic
Taciana
T
Panova
Tanya
T
Russell
Jackie
J
Zomerdijk
Joost C B M
JC
D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism*; D012318:RNA Polymerase I / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D035381:TATA-Binding Protein Associated Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
D017931:DNA Primers; D035463:Pol1 Transcription Initiation Complex Proteins; C091129:TAF1B protein, human; C521196:TAF1D protein, human; D035381:TATA-Binding Protein Associated Factors; D012318:RNA Polymerase I