Department of Biochemistry and Molecular Pharmacology
Amino Acids, Peptides, and Proteins | Cell Biology | Cells | Enzymes and Coenzymes
Commitment to mitosis is regulated by cyclin-dependent kinase (CDK) activity. In the fission yeast Schizosaccharomyces pombe, the major B-type cyclin, Cdc13, is necessary and sufficient to drive mitotic entry. Furthermore, Cdc13 is also sufficient to drive S phase, demonstrating that a single cyclin can regulate alternating rounds of replication and mitosis and providing the foundation of the quantitative model of CDK function. It has been assumed that Cig2, a B-type cyclin expressed only during S-phase and incapable of driving mitosis in wild-type cells, was specialized for S-phase regulation. Here, we show that Cig2 is capable of driving mitosis. Cig2/CDK activity drives mitotic catastrophe -- lethal mitosis in inviably small cells -- in cells that lack CDK inhibition by tyrosine-phosphorylation. Moreover, Cig2/CDK can drive mitosis in the absence of Cdc13/CDK activity. These results demonstrate that in fission yeast, not only can the presumptive M-phase cyclin drive S phase, but the presumptive S-phase cyclin can drive M phase, further supporting the quantitative model of CDK function. Furthermore, these results provide an explanation, previously proposed on the basis of computation analyses, for the surprising observation that cells expressing a single-chain Cdc13-Cdc2 CDK do not require Y15 phosphorylation for viability. Their viability is due to the fact that in such cells, which lack Cig2/CDK complexes, Cdc13/CDK activity is unable to drive mitotic catastrophe.
fission yeast, Schizosaccharomyces pombe, Cdc13, cyclin, cyclin-dependent kinase, Cig2, cell biology
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DOI of Published Version
bioRxiv 213330; doi: https://doi.org/10.1101/213330. Link to preprint on bioRxiv service.
Magner M, Keifenheim DL, Rhind NR. (2017). The Fission Yeast S-Phase Cyclin Cig2 Can Drive Mitosis [preprint]. University of Massachusetts Medical School Faculty Publications. https://doi.org/10.1101/213330. Retrieved from https://escholarship.umassmed.edu/faculty_pubs/1521
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