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At the onset of anaphase, a caspase-related protease (separase) destroys the link between sister chromatids by cleaving the cohesin subunit Scc1. During most of the cell cycle, separase is kept inactive by binding to an inhibitory protein called securin. Separase activation requires proteolysis of securin, which is mediated by an ubiquitin protein ligase called the anaphase-promoting complex. Cells regulate anaphase entry by delaying securin ubiquitination until all chromosomes have attached to the mitotic spindle. Though no longer regulated by this mitotic surveillance mechanism, sister separation remains tightly cell cycle regulated in yeast mutants lacking securin. We show here that the Polo/Cdc5 kinase phosphorylates serine residues adjacent to Scc1 cleavage sites and strongly enhances their cleavage. Phosphorylation of separase recognition sites may be highly conserved and regulates sister chromatid separation independently of securin.

Type

Journal article

Journal

Cell

Publication Date

18/05/2001

Volume

105

Pages

459 - 472

Keywords

Amino Acid Sequence, Anaphase, Anaphase-Promoting Complex-Cyclosome, CDC2 Protein Kinase, Cell Cycle Proteins, Centromere, Chromatin, Chromosomal Proteins, Non-Histone, Conserved Sequence, Drosophila Proteins, Endopeptidases, Fungal Proteins, Ligases, Metaphase, Molecular Sequence Data, Nuclear Proteins, Phosphoproteins, Phosphorylation, Protein Kinases, Protein-Serine-Threonine Kinases, Saccharomyces cerevisiae Proteins, Securin, Serine, Sister Chromatid Exchange, Telomere, Ubiquitin-Protein Ligase Complexes, Ubiquitin-Protein Ligases, Yeasts