title: Cdk1 and SUMO regulate Swe1 stability.
abstract: The Swe1/Wee1 kinase phosphorylates and inhibits Cdk1-Clb2 and is a major mitotic switch. Swe1 levels are controlled by ubiquitin mediated degradation, which is regulated by interactions with various mitotic kinases. We have recently reported that Swe1 levels are capable of sensing the progress of the cell cycle by measuring the levels of Cdk1-Clb2, Cdc5 and Hsl1. We report here a novel mechanism that regulates the levels of Swe1. We show that S. cerevisiae Swe1 is modified by Smt3/SUMO on residue K594 in a Cdk1 dependant manner. A degradation of the swe1(K594R) mutant that cannot be modified by Smt3 is considerably delayed in comparison to wild type Swe1. Swe1(K594R) cells express elevated levels of Swe1 protein and demonstrate higher levels of Swe1 activity as manifested by Cdk1-Y19 phosphorylation. Interestingly this mutant is not targeted, like wild type Swe1, to the bud neck where Swe1 degradation takes place. We show that Swe1 is SUMOylated by the Siz1 SUMO ligase, and consequently siz1Δ cells express elevated levels of Swe1 protein and activity. Finally we show that swe1(K594R) cells are sensitive to osmotic stress, which is in line with their compromised regulation of Swe1 degradation.
authors.affiliation: The Department of Genetics, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Kobi J
authors.initials: KJ
authors.lastname: Simpson-Lavy
authors.forename: Michael
authors.initials: M
authors.lastname: Brandeis
mesh_terms: D000595:Amino Acid Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins / Q000737:chemistry; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation; D009995:Osmosis; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; C099362:SMT3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D025801:Ubiquitin; D049452:Green Fluorescent Proteins; D044767:Ubiquitin-Protein Ligases; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D016203:CDC2 Protein Kinase; C436837:Siz1 protein, S cerevisiae