Mutations in the yeast cyclin-dependent kinase Cdc28 reveal a role in the spindle assembly checkpoint
Anaphase onset and mitotic exit are regulated by the spindle assembly or kinetochore checkpoint, which inhibits the anaphase-promoting complex (APC), preventing the degradation of anaphase inhibitors and mitotic cyclins. As a result, cells arrest with high cyclin-dependent kinase (CDK) activity due to the accumulation of cyclins. Aside from this, a clear-cut demonstration of a direct role for CDKs in the spindle checkpoint response has been elusive. Cdc28 is the main CDK driving the cell cycle in budding yeast. In this report, mutations in cdc28 are described that confer specific checkpoint defects, supersensitivity towards microtubule poisons and chromosome loss. Two alleles encode single mutations in the N and C terminal regions, respectively (R10G and R288G), and one allele specifies two mutations near the C terminus (F245L, I284T). These cdc28 mutants are unable to arrest or efficiently prevent sister chromatid separation during treatment with nocodazole. Genetic interactions with checkpoint and apc mutants suggest Cdc28 may regulate checkpoint arrest downstream of the MAD2 and BUB2 pathways. These studies identify a C-terminal domain of Cdc28 required for checkpoint arrest upon spindle damage that mediates chromosome stability during vegetative growth, suggesting that it has an essential surveillance function in the unperturbed cell cycle.
KeywordsAnaphase Cell cycle Chromosome segregation Mitosis
- Baumer M, Braus GH, Irniger S (2000) Two different modes of cyclin Clb2 proteolysis during mitosis in Saccharomyces cerevisiae. FEBS Lett 468:14–28Google Scholar
- Cahill DP, Lengauer C, Yu J, Riggins GJ, Willson JK, Markowitz SD, Kinzler KW, Vogelstein B (1998) Mutations of mitotic checkpoint genes in human cancers. Nature 392:300–303Google Scholar
- Morgan DO (1997) Cyclin-dependent kinases: engines, clocks, and microprocessors. Annu Rev Cell Dev Biol 13:261–291Google Scholar
- Morgan DO (1999) Regulation of the APC and the exit from mitosis. Nat Cell Biol 1: E47–53Google Scholar
- Tennyson CMV, Andrews BJ (1998) In vitro assay for cyclin-dependent kinase activity in yeast. Technical Tips Online 1:P01174Google Scholar