Evolution of Ime2 phosphorylation sites on Cdk1 substrates provides a mechanism to limit the effects of the phosphatase Cdc14 in meiosis.

Progression through meiosis in yeast is governed by the cyclin-dependent kinase Cdk1, in concert with a related kinase called Ime2. It remains unclear how these kinases collaborate to meet the unique demands of meiotic progression. We demonstrate that Ime2 and Cdk1 phosphorylate an overlapping substrate set and that the two kinases overlap functionally as inhibitors of the ubiquitin ligase APC(Cdh1) and replication origin licensing. Surprisingly, Ime2 phosphorylates Cdk1 substrates at distinct phosphorylation sites that are highly resistant to dephosphorylation by the phosphatase Cdc14. We propose that Ime2-dependent phosphorylation of a subset of cell-cycle proteins limits the effects of Cdc14 in meiosis.