title: Inefficient degradation of cyclin B1 re-activates the spindle checkpoint right after sister chromatid disjunction.
abstract: Sister chromatid separation creates a sudden loss of tension on kinetochores, which could, in principle, re-activate the spindle checkpoint in anaphase. This so-called "anaphase problem" is probably avoided by timely inactivation of cyclin B1-Cdk1, which may prevent the spindle tension sensing Aurora B kinase from destabilizing kinetochore-microtubule interactions as they lose tension in anaphase. However, exactly how spindle checkpoint re-activation is prevented remains unclear. Here, we investigated how different degrees of cyclin B1 stabilization affected the spindle checkpoint in metaphase and anaphase. Cells expressing a strongly stabilized (R42A) mutant of cyclin B1 degraded APC/C(Cdc20) substrates normally, showing that checkpoint release was not inhibited by high cyclin B1-Cdk1 activity. However, after this initial wave of APC/C(Cdc20) activity, the spindle checkpoint returned in cells with uncohesed sister chromatids. Expression of a lysine mutant of cyclin B1 that is degraded only slightly inefficiently allowed a normal metaphase-to-anaphase transition. Strikingly, however, the spindle checkpoint returned in cells that had not degraded the cyclin B1 mutant 10-15 min after anaphase onset. When cyclin B1 remained in late anaphase, cytokinesis stalled, and translocation of INCENP from separated sister chromatids to the spindle midzone was blocked. This late anaphase arrest required the activity of Aurora B and Mps1. In conclusion, our results reveal that complete removal of cyclin B1 is essential to prevent the return of the spindle checkpoint following sister chromatid disjunction. Speculatively, increasing activity of APC/C(Cdc20) in late anaphase helps to keep cyclin B1 levels low.
authors.affiliation: a Division of Cell Biology I (B5) and Division of Molecular Carcinogenesis (B7); The Netherlands Cancer Institute (NKI-AvL); Amsterdam, The Netherlands.
authors.forename: Linda
authors.initials: L
authors.lastname: Clijsters
authors.forename: Wouter
authors.initials: W
authors.lastname: van Zon
authors.forename: Bas Ter
authors.initials: BT
authors.lastname: Riet
authors.forename: Erik
authors.initials: E
authors.lastname: Voets
authors.forename: Michiel
authors.initials: M
authors.lastname: Boekhout
authors.forename: Janneke
authors.initials: J
authors.lastname: Ogink
authors.forename: Cornelia
authors.initials: C
authors.lastname: Rumpf-Kienzl
authors.forename: Rob M F
authors.initials: RM
authors.lastname: Wolthuis
mesh_terms: D064107:Aurora Kinase B / Q000378:metabolism; D016203:CDC2 Protein Kinase; D064199:Cdc20 Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D056744:Cyclin B1 / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000502:physiology*; D020066:Merozoite Surface Protein 1 / Q000378:metabolism; D009154:Mutation; D059748:Proteolysis; D012854:Sister Chromatid Exchange / Q000502:physiology*
chemical_list: D064199:Cdc20 Proteins; D056744:Cyclin B1; D020066:Merozoite Surface Protein 1; C576921:AURKB protein, human; D064107:Aurora Kinase B; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases; D008239:Lysine
keywords: APC/C; Cdc20; Cdk1; anaphase; cyclin B1; metaphase; spindle checkpoint