Cyclin-dependent kinase 1–dependent activation of APC/C ubiquitin ligase

Abstract

Phosphorylation cues exit from mitosis The entry and exit from the cell cycle are controlled by waves of protein phosphorylation and degradation events. Fujimitsu et al. describe the precise mechanism by which the cell cycle machinery controls exit from mitosis. The critical event is activation of a ubiquitin ligase, the anaphase-promoting complex or cyclosome (APC/C). The authors used purified components and the Xenopus egg extract system to show that two subunits of APC/C were directly phosphorylated by cyclin-dependent kinase 1 (CDK1). Phosphorylation of one subunit helped recruit CDK1 for further phosphorylation of another subunit. The second subunit interacted with the APC/C activator and target of anticancer therapy known as Cdc20. Science , this issue p. 1121