The function and regulation of budding yeast Swe1 in response to interrupted DNA synthesis.
Periodically regulated cyclin-dependent kinase (Cdk) is required for DNA synthesis and mitosis. Hydroxyurea (HU) inhibits DNA synthesis by depleting dNTPs, the basic unit for DNA synthesis. HU treatment triggers the S-phase checkpoint, which arrests cells at S-phase, inhibits late origin firing and stabilizes replication forks. Using budding yeast as a model system, we found that Swe1, a negative regulator of Cdk, appears at S-phase and accumulates in HU treatment cells. Interestingly, this accumulation is not dependent on S-phase checkpoint. Deltahsl1, Deltahsl7, and cdc5-2 mutants, which have defects in Swe1 degradation, show HU sensitivity because of high Swe1 protein levels. We further demonstrated that their HU sensitivity is not a result of DNA damage accumulation or incomplete DNA synthesis; instead the sensitivity is due to their dramatically delayed recovery from HU-induced S-phase arrest. Strikingly, our in vivo data indicate that Swe1 inhibits the kinase activity of Clb2-Cdk1, but not that of Clb5-Cdk1. Therefore, S-phase accumulated Swe1 prevents Clb2-Cdk1-mediated mitotic activities, but has little effects on Clb5-Cdk1-associated S-phase progression.
Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA.
Hong
H
Liu
Yanchang
Y
Wang
D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects / Q000502:physiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D006918:Hydroxyurea / Q000494:pharmacology; D007700:Kinetics; D008938:Mitosis; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D016213:Cyclins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D016203:CDC2 Protein Kinase; D018844:Cyclin-Dependent Kinases; D006918:Hydroxyurea