Functional relationships of Srb10-Srb11 kinase, carboxy-terminal domain kinase CTDK-I, and transcriptional corepressor Ssn6-Tup1.
The Srb10-Srb11 protein kinase of Saccharomyces cerevisiae is a cyclin-dependent kinase (cdk)-cyclin pair which has been found associated with the carboxy-terminal domain (CTD) of RNA polymerase II holoenzyme forms. Previous genetic findings implicated the Srb10-Srb11 kinase in transcriptional repression. Here we use synthetic promoters and LexA fusion proteins to test the requirement for Srb10-Srb11 in repression by Ssn6-Tup1, a global corepressor. We show that srb10delta and srb11delta mutations reduce repression by DNA-bound LexA-Ssn6 and LexA-Tup1. A point mutation in a conserved subdomain of the kinase similarly reduced repression, indicating that the catalytic activity is required. These findings establish a functional link between Ssn6-Tup1 and the Srb10-Srb11 kinase in vivo. We also explored the relationship between Srb10-Srb11 and CTD kinase I (CTDK-I), another member of the cdk-cyclin family that has been implicated in CTD phosphorylation. We show that mutation of CTK1, encoding the cdk subunit, causes defects in transcriptional repression by LexA-Tup1 and in transcriptional activation. Analysis of the mutant phenotypes and the genetic interactions of srb10delta and ctk1A suggests that the two kinases have related but distinct roles in transcriptional control. These genetic findings, together with previous biochemical evidence, suggest that one mechanism of repression by Ssn6-Tup1 involves functional interaction with RNA polymerase II holoenzyme.
Kuchin
S
S
Department of Genetics and Development, Columbia University, New York, New York 10032, USA.
Carlson
M
M
D001426:Bacterial Proteins / Q000235:genetics; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D006026:Glycoside Hydrolases / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics; D007763:Lac Operon; D009687:Nuclear Proteins; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D043324:beta-Fructofuranosidase; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases; D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006026:Glycoside Hydrolases; D006836:Hydro-Lyases; D009687:Nuclear Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases; D014157:Transcription Factors; D043324:beta-Fructofuranosidase; D000099160:LexA Repressor Protein; C065455:CYC8 protein, S cerevisiae; C066502:TUP1 protein, S cerevisiae; C060137:carboxy-terminal domain kinase; C093345:SSN8 protein, S cerevisiae; C498309:SSN3 protein, S cerevisiae; C021434:imidazoleglycerolphosphate dehydratase