title: Downregulation of PP2A(Cdc55) phosphatase by separase initiates mitotic exit in budding yeast.
abstract: After anaphase, the high mitotic cyclin-dependent kinase (Cdk) activity is downregulated to promote exit from mitosis. To this end, in the budding yeast S. cerevisiae, the Cdk counteracting phosphatase Cdc14 is activated. In metaphase, Cdc14 is kept inactive in the nucleolus by its inhibitor Net1. During anaphase, Cdk- and Polo-dependent phosphorylation of Net1 is thought to release active Cdc14. How Net1 is phosphorylated specifically in anaphase, when mitotic kinase activity starts to decline, has remained unexplained. Here, we show that PP2A(Cdc55) phosphatase keeps Net1 underphosphorylated in metaphase. The sister chromatid-separating protease separase, activated at anaphase onset, interacts with and downregulates PP2A(Cdc55), thereby facilitating Cdk-dependent Net1 phosphorylation. PP2A(Cdc55) downregulation also promotes phosphorylation of Bfa1, contributing to activation of the "mitotic exit network" that sustains Cdc14 as Cdk activity declines. These findings allow us to present a new quantitative model for mitotic exit in budding yeast.
authors.affiliation: Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.
authors.forename: Ethel
authors.initials: E
authors.lastname: Queralt
authors.forename: Chris
authors.initials: C
authors.lastname: Lehane
authors.forename: Bela
authors.initials: B
authors.lastname: Novak
authors.forename: Frank
authors.initials: F
authors.lastname: Uhlmann
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002466:Cell Nucleolus / Q000378:metabolism; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D008938:Mitosis / Q000502:physiology*; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D064247:Separase
chemical_list: C074860:CDC14 protein, S cerevisiae; C093749:CLB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; C119300:Net1 protein, S cerevisiae; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases; D010450:Endopeptidases; C577986:ESP1 protein, S cerevisiae; D064247:Separase