Phosphorylation at Thr167 is required for Schizosaccharomyces pombe P34cdc2 function

Abstract

Eukaryotic cell cycle progression requires the periodic activation and inactivation of a protein-serine/threonine kinase which in fission yeast is encoded by the cdc2 + gene. The activity of this gene product, p34(cdc2) is controlled by numerous interactions with other proteins and by its phosphorylation state. In fission yeast, p34(cdc2) is phosphorylated on two sites, one of which has been identified as Tyr15. Dephosphorylation of Tyr15 regulates the initiation of mitosis. To understand more completely the regulation of p34(cdc2) kinase activity, we have identified the second site of phosphorylation as Thrl67, a residue conserved amongst all p34(cdc2) homologues. By analysing the phenotypes of cells expressing various position 167 mutations and performing in vitro experiments, we establish that Thrl67 phosphorylation is required for p34(cdc2) kinase activity at mitosis and is involved in the association of p34(cdc2) with cyclin B. Dephosphorylation of Thrl67 might also play a role in the exit from mitosis.