Regulation of p34CDC28 tyrosine phosphorylation is not required for entryinto mitosis in S. cerevisiae

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摘要：

PROGRESSION from G2 to M phase in eukaryotes requires activation of a protein kinase composed of p34 cdc2/CDC28 associated with Gl-specific cyclins (reviewed in ref. 1). In some organisms the activation of the kinase at the G2/M boundary is due to dephosphorylation of a highly conserved tyrosine residue at posi-tion 15 (Y15) of the cdc2 protein 2–6 . Here we report that in the budding yeast Saccharomyces cervisiae , p 34 CDC28 also undergoes cell-cycle regulated dephosphorylation on an equivalent tyrosine residue (Y19). However, in contrast to previous observations in S. pombe 6 , Xenopus 2,3 and mammalian cells 4,5 , dephosphorylation of Y19 is not required for the activation of the CDC28/cyclin kinase. Furthermore, mutation of this tyrosine residue does not affect dependence of mitosis on DNA synthesis nor does it abolish G2 arrest induced by DNA damage. Our data imply that regulated phosphorylation of this tyrosine residue is not the 'universal' means by which the onset of mitosis is determined. We propose that there are other unidentified controls that regulate entry into mitosis.

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关键词：

Saccharomyces cerevisiae Tyrosine Phosphopeptides Protein Kinases CDC2 Protein Kinase Phosphorylation Kinetics Mitosis Mutagenesis Peptide Fragments