Negative regulation of mitosis by the fission yeast protein phosphatase ppa2.

To understand the role of the type 2A-like protein phosphatase in the cell division cycle, we investigated the mutant phenotypes obtained when the fission yeast ppa1 + and ppa2 + phosphatase genes (which encode polypeptides with ∼80% identity to mammalian type 2A phosphatases) were either deleted or overexpressed. We also investigated the in vivo effect of okadaic acid, an inhibitor of protein serine/threonine phosphatases, on cell division. We show that ppa2 + interacts genetically with the cell cycle regulators cdc 25+ and wee1 + , as a ppa2 deletion is lethal when combined with wee1-50 but partially suppresses the conditional lethality of cdc25-22 mutation