Two steps in Maf1-dependent repression of transcription by RNA polymerase III.
In Saccharomyces cerevisiae, Maf1 is essential for mediating the repression of transcription by RNA polymerase (pol) III in response to diverse cellular conditions. These conditions activate distinct signaling pathways that converge at or above Maf1. Thus, Maf1-dependent repression is thought to involve a common set of downstream inhibitory effects on the pol III machinery. Here we provide support for this view and define two steps in Maf1-dependent transcriptional repression. We show that chlorpromazine (CPZ)-induced repression of pol III transcription is achieved by inhibiting de novo assembly of transcription factor (TF) IIIB onto DNA as well as the recruitment of pol III to preassembled TFIIIB.DNA complexes. Additionally Brf1 was identified as a target of repression in extracts of CPZ-treated cells. Maf1-Brf1 and Maf1-pol III interactions were implicated in the inhibition of TFIIIB.DNA complex assembly and polymerase recruitment by recombinant Maf1. Co-immunoprecipitation experiments confirmed these interactions in yeast extracts and demonstrated that Maf1 does not differentially sequester Brf1 or pol III under repressing conditions. The results suggest that Maf1 functions by a non-stoichiometric mechanism to repress pol III transcription.
Desai
Neelam
N
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Lee
Jaehoon
J
Upadhya
Rajendra
R
Chu
Yaya
Y
Moir
Robyn D
RD
Willis
Ian M
IM
D002746:Chlorpromazine / Q000494:pharmacology; D015536:Down-Regulation; D046911:Macromolecular Substances; D011485:Protein Binding; D012320:RNA Polymerase III / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction; D035361:Transcription Factor TFIIIB / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic
C090956:BRF1 protein, S cerevisiae; C104954:MAF1 protein, S cerevisiae; D046911:Macromolecular Substances; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; D012320:RNA Polymerase III; D002746:Chlorpromazine