Cdc2 tyrosine phosphorylation is not required for the S-phase DNA damage checkpoint in fission yeast
Biochemistry & Molecular Pharmacology
Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology
Medical Subject Headings
CDC2 Protein Kinase; Cell Cycle; Cell Cycle Proteins; Cell Nucleus; *DNA Damage; Flow Cytometry; *Gene Expression Regulation, Fungal; Genotype; Phosphorylation; *S Phase; Schizosaccharomyces; Time Factors; Tyrosine
Life Sciences | Medicine and Health Sciences
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.
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Citation: Cell Cycle. 2006 Nov 1;5(21):2495-500. Epub 2006 Sep 19.