title: Preferential cleavage of chromatin-bound cohesin after targeted phosphorylation by Polo-like kinase.
abstract: The final irreversible step in the duplication and dissemination of eukaryotic genomes takes place when sister chromatid pairs split and separate in anaphase. This is triggered by the protease separase that cleaves the Scc1 subunit of 'cohesin', the protein complex responsible for holding sister chromatids together in metaphase. Only part of cellular cohesin is bound to chromosomes in metaphase, and it is unclear whether and how separase specifically targets this fraction for cleavage. We established an assay to compare cleavage of chromatin-bound versus soluble budding yeast cohesin. Scc1 in chromosomal cohesin is significantly preferred by separase over Scc1 in soluble cohesin. The difference is most likely due to preferential phosphorylation of chromatin-bound Scc1 by Polo-like kinase. Site-directed mutagenesis of 10 Polo phosphorylation sites in Scc1 slowed cleavage of chromatin-bound cohesin, and hyperphosphorylation of soluble Scc1 by Polo overexpression accelerated its cleavage to levels of chromosomal cohesin. Polo is bound to chromosomes independently of cohesin's presence, providing a possible explanation for chromosome-specific cohesin modification and targeting of separase cleavage.
authors.affiliation: Chromosome Segregation Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London, UK.
authors.forename: Nadine C D
authors.initials: NC
authors.lastname: Hornig
authors.forename: Frank
authors.initials: F
authors.lastname: Uhlmann
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D043171:Chromosomal Instability; D002868:Chromosomal Proteins, Non-Histone; D010450:Endopeptidases / Q000378:metabolism; D005656:Fungal Proteins; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D064247:Separase; D012995:Solubility; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D010450:Endopeptidases; D005656:Fungal Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D029701:Saccharomyces cerevisiae Proteins; D064247:Separase; D000097722:Cohesins; C490529:MCD1 protein, S cerevisiae; C081927:CDC5 protein, S cerevisiae; C577986:ESP1 protein, S cerevisiae