Mutual inhibition of separase and Cdk1 by two-step complex formation.
Stable maintenance of genetic information requires chromosome segregation to occur with high accuracy. Anaphase is triggered when ring-shaped cohesin is cleaved by separase, a protease regulated by association with its inhibitor securin. Dispensability of vertebrate securin strongly suggests additional means of separase regulation. Indeed, sister chromatid separation but not securin degradation is inhibited by constitutively active cyclin-dependent kinase 1 (Cdk1) and can be rescued solely by preventing phosphorylation of separase. We demonstrate that Cdk1-dependent phosphorylation of separase is not sufficient for inhibition. In a second step, Cdk1 stably binds phosphorylated separase via its regulatory cyclin B1 subunit. Complex formation results in inhibition of both protease and kinase, and we show that vertebrate separase is a direct inhibitor of Cdk1. This unanticipated function of separase is negatively regulated by securin but independent of separase's proteolytic activity.
Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Ingo H
IH
Gorr
Dominik
D
Boos
Olaf
O
Stemmann
D000818:Animals; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000302:isolation & purification; D002457:Cell Extracts; D002474:Cell-Free System / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics / Q000302:isolation & purification; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D009154:Mutation; D009865:Oocytes / Q000737:chemistry; D010766:Phosphorylation; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D064247:Separase; D014981:Xenopus
D018797:Cell Cycle Proteins; D002457:Cell Extracts; D004791:Enzyme Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D016203:CDC2 Protein Kinase; D010450:Endopeptidases; C577986:ESP1 protein, S cerevisiae; C577987:ESPL1 protein, human; D064247:Separase