The APC/C Subunit Mnd2/Apc15 Promotes Cdc20 Autoubiquitination and Spindle Assembly Checkpoint Inactivation

• Published in: Molecular cell Vol. 47; no. 6; pp. 921 - 932
• Main Authors: Foster, Scott A., Morgan, David O.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 28.09.2012
• Subjects: anaphase; Anaphase-Promoting Complex-Cyclosome; Cdc20 Proteins; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Chromosome Segregation; kinetochores; M Phase Cell Cycle Checkpoints; Mad2 Proteins; Nuclear Proteins - metabolism; Saccharomyces cerevisiae Proteins - metabolism; Spindle Apparatus - genetics; Spindle Apparatus - metabolism; Ubiquitin-Protein Ligase Complexes - metabolism; Ubiquitination; yeasts
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2012.07.031

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. ► Spindle checkpoint proteins synergize to stimulate Cdc20 autoubiquitination ► Mnd2/Apc15 is required for Cdc20 autoubiquitination in the checkpoint ► Cdc20 stabilization throughout the cycle prevents spindle checkpoint establishment ► Cells lacking Mnd2 maintain a checkpoint arrest but delay checkpoint inactivation