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Mol Cell Biol, March 1998, p. 1163-1171, Vol. 18, No. 3
Departments of Genetics and
Development1 and
Microbiology,2 Columbia University,
New York, New York 10032
Received 29 October 1997/Accepted 24 November 1997
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 srb10
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Copyright © 1998, American Society for Microbiology. All rights reserved.
Functional Relationships of Srb10-Srb11 Kinase, Carboxy-Terminal
Domain Kinase CTDK-I, and Transcriptional Corepressor
Ssn6-Tup1
and srb11
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 srb10
and ctk1
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.
*
Corresponding author. Mailing address: HHSC 922, Box
126, 701 W. 168th St., New York, NY 10032. Phone: (212) 305-6314. Fax: (212) 305-1741. E-mail: mbc1{at}columbia.edu.
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