Phosphorylation Regulates the p31Comet-Mitotic Arrest-deficient 2 (Mad2) Interaction to Promote Spindle Assembly Checkpoint (SAC) Activity

The spindle assembly checkpoint (SAC) ensures the faithful segregation of the genome during mitosis by ensuring that sister chromosomes form bipolar attachments with microtubules of the mitotic spindle. p31Comet is an antagonist of the SAC effector Mad2 and promotes silencing of the SAC and mitotic progression. However, p31Comet interacts with Mad2 throughout the cell cycle. We show that p31Comet binds Mad2 solely in an inhibitory manner. We demonstrate that attenuating the affinity of p31Comet for Mad2 by phosphorylation promotes SAC activity in mitosis. Specifically, phosphorylation of Ser-102 weakens p31Comet-Mad2 binding and enhances p31Comet-mediated bypass of the SAC. Our results provide the first evidence for regulation of p31Comet and demonstrate a previously unknown event controlling SAC activity.Background: p31Comet antagonizes the SAC effector Mad2 to promote mitotic progression.Results: p31Comet phosphorylation modulates binding to Mad2.Conclusion: Phosphorylation attenuates binding of Mad2 by p31Comet to promote SAC activity.Significance: Our study provides the first description of p31Comet regulation and new insight into the control of SAC activity. The spindle assembly checkpoint (SAC) ensures the faithful segregation of the genome during mitosis by ensuring that sister chromosomes form bipolar attachments with microtubules of the mitotic spindle. p31Comet is an antagonist of the SAC effector Mad2 and promotes silencing of the SAC and mitotic progression. However, p31Comet interacts with Mad2 throughout the cell cycle. We show that p31Comet binds Mad2 solely in an inhibitory manner. We demonstrate that attenuating the affinity of p31Comet for Mad2 by phosphorylation promotes SAC activity in mitosis. Specifically, phosphorylation of Ser-102 weakens p31Comet-Mad2 binding and enhances p31Comet-mediated bypass of the SAC. Our results provide the first evidence for regulation of p31Comet and demonstrate a previously unknown event controlling SAC activity. Background: p31Comet antagonizes the SAC effector Mad2 to promote mitotic progression. Results: p31Comet phosphorylation modulates binding to Mad2. Conclusion: Phosphorylation attenuates binding of Mad2 by p31Comet to promote SAC activity. Significance: Our study provides the first description of p31Comet regulation and new insight into the control of SAC activity.