Spindle checkpoint regulates Cdc20p stability in Saccharomyces cerevisiae.
The spindle checkpoint arrests cells at the metaphase-to-anaphase transition until all chromosomes have properly attached to the mitotic spindle. Checkpoint proteins Mad2p and Mad3p/BubR1p bind and inhibit Cdc20p, an activator for the anaphase-promoting complex (APC). We find that upon spindle checkpoint activation by microtubule inhibitors benomyl or nocodazole, wild-type Saccharomyces cerevisiae contains less Cdc20p than spindle checkpoint mutants do, whereas their CDC20 mRNA levels are similar. The difference in Cdc20p levels correlates with their difference in the half-lives of Cdc20p, indicating that the spindle checkpoint destabilizes Cdc20p. This process requires the association between Cdc20p and Mad2p, and functional APC, but is independent of the known destruction boxes in Cdc20p and the other APC activator Cdh1p. Importantly, destabilization of Cdc20p is important for the spindle checkpoint, because a modest overexpression of Cdc20p causes benomyl sensitivity and premature Pds1p degradation in cells treated with nocodazole. Our study suggests that the spindle checkpoint reduces Cdc20p to below a certain threshold level to ensure a complete inhibition of Cdc20p before anaphase.
Pan
Jing
J
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
Chen
Rey-Huei
RH
D000705:Anaphase; D064173:Anaphase-Promoting Complex-Cyclosome; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism*; D015536:Down-Regulation; D006207:Half-Life; D064246:Mad2 Proteins; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins; D011485:Protein Binding; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000378:metabolism*; D008941:Spindle Apparatus; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
C577495:CDC20 protein, S cerevisiae; D002352:Carrier Proteins; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C577695:MAD2 protein, S cerevisiae; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D015739:Nocodazole