Section 10
Chapter 9,531

The Cak1p protein kinase is required at G1/S and G2/M in the budding yeast cell cycle

Sutton, A.; Freiman, R.

Genetics 147(1): 57-71


ISSN/ISBN: 0016-6731
PMID: 9286668
Accession: 009530595

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The CAK1 gene encodes the major CDK-activating kinase (CAK) in budding yeast and is required for activation of Cdc28p for cell cycle progression from G-2 to M phase. Here we describe the isolation of a mutant allele of CAK1 in a synthetic lethal screen with the Sit4 protein phosphatase. Analysis of several different cak1 mutants shows that although the G-2 to M transition appears most sensitive to loss of Cak1p function, Cak1p is also required for activation of Cdc28p for progression from G-1 into S phase. Further characterization of these mutants suggests that, unlike the CAK identified from higher eukaryotes, Cak1p of budding yeast may not play a role in general transcription. Finally, although Cak1 protein levels and in vitro protein kinase activity do not fluctuate during the cell cycle, at least a fraction of Cak1p associates with higher molecular weight proteins, which may be important for its in vivo function.

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