Flp1, a fission yeast orthologue of the S-cerevisiae CDC14 gene, is not required for cyclin degradation or rum1p stabilisation at the end of mitosis

In Saccharomyces cerevisiae, the phosphoprotein phosphatase Cdc14p plays a central role in exit from mitosis, by promoting B-type cyclin degradation a nd allowing accumulation of the cyclin-dependent kinase inhibitor Sic1p. Cd c14p is sequestered in the nucleolus during interphase, from where it is re leased at the end of mitosis, dependent upon mitotic exit network function. The CDC14 gene is essential and loss-of-function mutants arrest at the end of mitosis. We have identified a fission yeast orthologue of CDC14 through database searches. A Schizosaccharomyces pombe flp1 (cdc (f) under bar our teen-(l) under bar ike-(p) under bar hosphatase) null mutant is viable, div ides at a reduced size and shows defects in septation. flp1p is not the ess ential effector of the S. pombe septation initiation network, but may poten tiate signalling of the onset of septation. In contrast to S. cerevisiae Cd c14p, flp1p is not required for the accumulation or destruction of the B-ty pe cyclin cdc13p, the cyclin-dependent kinase inhibitor rum1p, or for depho sphorylation of the APC/C specificity factor ste9p in G(1). Like its buddin g yeast counterpart, flp1p is restricted to the nucleolus until mitosis, wh en it is dispersed through the nucleus. In contrast to S. cerevisiae Cdc14p , ftp1p is also present on the mitotic spindle and contractile ring. The po tential roles of flp1p in cell cycle control are discussed.