Protein kinase A regulates RNA polymerase III transcription through the nuclear localization of Maf1.
Maf1 is an essential and specific mediator of transcriptional repression in the RNA polymerase (pol) III system. Maf1-dependent repression occurs in response to a wide range of conditions, suggesting that the protein itself is targeted by the major nutritional and stress-signaling pathways. We show that Maf1 is a substrate for cAMP-dependent PKA in vitro and is differentially phosphorylated on PKA sites in vivo under normal versus repressing conditions. PKA activity negatively regulates Maf1 function because strains with unregulated high PKA activity block repression of pol III transcription in vivo, and strains lacking all PKA activity are hyperrepressible. Nuclear accumulation of Maf1 is required for transcriptional repression and is regulated by two nuclear localization sequences in the protein. An analysis of PKA phosphosite mutants shows that the localization of Maf1 is affected via the N-terminal nuclear localization sequence. In particular, mutations that prevent phosphorylation at PKA consensus sites promote nuclear accumulation of Maf1 without inducing repression. These results indicate that negative regulation of Maf1 by PKA is achieved by inhibiting its nuclear import and suggest that a PKA-independent activation step is required for nuclear Maf1 to function in the repression of pol III transcription. Finally, we report a previously undescribed phenotype for Maf1 in tRNA gene-mediated silencing of nearby RNA pol II transcription.
Moir
Robyn D
RD
Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Lee
JaeHoon
J
Haeusler
Rebecca A
RA
Desai
Neelam
N
Engelke
David R
DR
Willis
Ian M
IM
D021581:Active Transport, Cell Nucleus / Q000235:genetics; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000502:physiology; D004794:Enzyme Repression / Q000235:genetics; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics; D012320:RNA Polymerase III / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
C104954:MAF1 protein, S cerevisiae; D019913:Nuclear Localization Signals; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D017868:Cyclic AMP-Dependent Protein Kinases; D012320:RNA Polymerase III