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XB-ART-20210
Nature January 5, 1995; 373 (6509): 78-81.
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Role of a ubiquitin-conjugating enzyme in degradation of S- and M-phase cyclins.

Seufert W , Futcher B , Jentsch S .


Abstract
Cell cycle progression in eukaryotes is controlled by the p34cdc2/CDC28 protein kinase and its short-lived, phase-specific regulatory subunits called cyclins. In Xenopus oocytes, degradation of M-phase (B-type) cyclins is required for exit from mitosis and is mediated by the ubiquitin-dependent proteolytic system. Here we show that B-type-cyclin degradation in yeast involves an essential nuclear ubiquitin-conjugating enzyme, UBC9. Repression of UBC9 synthesis prevents cell cycle progression at the G2 or early M phase, causing the accumulation of large budded cells with a single nucleus, a short spindle and replicated DNA. In ubc9 mutants both CLB5, an S-phase cyclin, and CLB2, an M-phase cyclin, are stabilized. In wild-type cells the CLB5 protein is unstable throughout the cell cycle, whereas CLB2 turnover occurs only at a specific cell-cycle stage. Thus distinct degradation signals or regulated interaction with the ubiquitin-protein ligase system may determine the cell-cycle specificity of cyclin proteolysis.

PubMed ID: 7800043
Article link: Nature


Species referenced: Xenopus
Genes referenced: cdk1 ube2i