Cyclic AMP regulates cell size of Schizosaccharomyces pombe through Cdc25 mitotic inducer

Nutritional state modulates the cell size of the fission yeast Schizosaccharomyces pombe, such that cells grown in rich medium are larger in size than those in poor medium. This signal is transduced partly through the cyclic AMP-dependent protein kinase cascade. However, little is known about how cyclic AMP interacts with the central cell cycle machinery, Cdc2, the cyclin-dependent kinase that induces mitosis. We show here that cyclic AMP regulates mitosis and cell size, in part, through regulation of protein stability of the Cdc2-activating phosphatase, Cdc25. However, our analysis demonstrates that cyclic AMP can negatively regulate mitosis independently of dephosphorylation of Cdc2 at Tyr(15).