title: The APC/C subunit Mnd2/Apc15 promotes Cdc20 autoubiquitination and spindle assembly checkpoint inactivation.
abstract: The fidelity of chromosome segregation depends on the spindle assembly checkpoint (SAC). In the presence of unattached kinetochores, anaphase is delayed when three SAC components (Mad2, Mad3/BubR1, and Bub3) inhibit Cdc20, the activating subunit of the anaphase-promoting complex (APC/C). We analyzed the role of Cdc20 autoubiquitination in the SAC of budding yeast. Reconstitution with purified components revealed that a Mad3-Bub3 complex synergizes with Mad2 to lock Cdc20 on the APC/C and stimulate Cdc20 autoubiquitination, while inhibiting ubiquitination of substrates. SAC-dependent Cdc20 autoubiquitination required the Mnd2/Apc15 subunit of the APC/C. General inhibition of Cdc20 ubiquitination in vivo resulted in high Cdc20 levels and a failure to establish a SAC arrest, suggesting that SAC establishment depends on low Cdc20 levels. Specific inhibition of SAC-dependent ubiquitination, by deletion of Mnd2, allowed establishment of a SAC arrest but delayed release from the arrest, suggesting that Cdc20 ubiquitination is also required for SAC inactivation.
authors.affiliation: Department of Physiology and Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Foster
authors.forename: David O
authors.initials: DO
authors.lastname: Morgan
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D020090:Chromosome Segregation; D059566:M Phase Cell Cycle Checkpoints; D064246:Mad2 Proteins; D009687:Nuclear Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: C070352:BUB3 protein, S cerevisiae; C577495:CDC20 protein, S cerevisiae; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C577695:MAD2 protein, S cerevisiae; C406764:MAD3 protein, S cerevisiae; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome