title: Shugoshin prevents cohesin cleavage by PP2A(Cdc55)-dependent inhibition of separase.
abstract: Chromosome segregation is triggered by separase, an enzyme that cleaves cohesin, the protein complex that holds sister chromatids together. Separase activation requires the destruction of its inhibitor, securin, which occurs only upon the correct attachment of chromosomes to the spindle. However, other mechanisms restrict separase activity to the appropriate window in the cell cycle because cohesin is cleaved in a timely manner in securin-deficient cells. We investigated the mechanism by which the protector protein Shugoshin counteracts cohesin cleavage in budding yeast. We show that Shugoshin can prevent separase activation independently of securin. Instead, PP2A(Cdc55) is essential for Shugoshin-mediated inhibition of separase. Loss of both securin and Cdc55 leads to premature sister chromatid separation, resulting in aneuploidy. We propose that Cdc55 is a separase inhibitor that acts downstream from Shugoshin under conditions where sister chromatids are not under tension.
authors.affiliation: The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Dean
authors.initials: D
authors.lastname: Clift
authors.forename: Farid
authors.initials: F
authors.lastname: Bizzari
authors.forename: Adele L
authors.initials: AL
authors.lastname: Marston
mesh_terms: D000782:Aneuploidy; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000502:physiology; D010450:Endopeptidases / Q000235:genetics / Q000502:physiology*; D008540:Meiosis / Q000502:physiology; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D064249:Securin; D064247:Separase; D012854:Sister Chromatid Exchange; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D010450:Endopeptidases; D009687:Nuclear Proteins; D054648:Protein Phosphatase 2; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; D064247:Separase; D000097722:Cohesins; C071246:CDC55 protein, S cerevisiae; C578004:PDS1 protein, S cerevisiae; C482640:Sgo1 protein, S cerevisiae; C577986:ESP1 protein, S cerevisiae