title: Cdc2 tyrosine phosphorylation is not required for the S-phase DNA damage checkpoint in fission yeast.
abstract: The S-phase DNA damage checkpoint slows replication when damage occurs during S phase. Cdc25, which activates Cdc2 by dephosphorylating tyrosine-15, has been shown to be a downstream target of the checkpoint in metazoans, but its role is not clear in fission yeast. The dephosphorylation of Cdc2 has been assumed not to play a role in S-phase regulation because cells replicate in the absence of Cdc25, demonstrating that tyrosine-15 phosphorylated dc2 is sufficient for S phase. However, it has been reported recently that Cdc25 is involved in the slowing of S phase in response to damage in fission yeast, suggesting a modulatory role for Cdc2 dephosphorylation in S phase. We have investigated the role of Cdc25 and the tyrosine phosphorylation of Cdc2 in the S-phase damage checkpoint, and our results show that Cdc2 phosphorylation is not a target of the checkpoint. The checkpoint was not compromised in a Cdc25 overexpressing strain, a strain carrying nonphosphorylatable form of Cdc2, or in a strain lacking Cdc25. Our results are consistent with a strictly Cdc2-Y15 phosphorylation-independent mechanism of the fission yeast S-phase DNA damage checkpoint.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01609, USA.
authors.forename: Naveen
authors.initials: N
authors.lastname: Kommajosyula
authors.forename: Nicholas
authors.initials: N
authors.lastname: Rhind
mesh_terms: D016203:CDC2 Protein Kinase / Q000737:chemistry* / Q000502:physiology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D004249:DNA Damage; D005434:Flow Cytometry; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D010766:Phosphorylation; D016196:S Phase; D012568:Schizosaccharomyces / Q000235:genetics* / Q000502:physiology*; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D018797:Cell Cycle Proteins; D014443:Tyrosine; D016203:CDC2 Protein Kinase