The cdr2(+) gene encodes a regulator of G(2)/M progression and cytokinesisin Schizosaccharomyces pombe

Schizosaccharomyces pombe cells respond to nutrient deprivation by altering G(2)/M cell size control. The G(2)/M transition is controlled by activatio n of the cyclin-dependent kinase Cdc2p. Cdc2p activation is regulated both positively and negatively, cdr2(+) was identified in a screen for regulator s of mitotic control during nutrient deprivation. We have cloned cdr2(+) an d have found that it encodes a putative serine-threonine protein kinase tha t is related to Saccharomyces cerevisiae Gin4p and S, pombe Cdr1p/Nim1p. cd r2(+) is not essential for viability, but cells lacking cdr2(+) are elongat ed relative to wild-type cells, spending a longer period of time in G(2). B ecause of this property, upon nitrogen deprivation cdr2(+) mutants do not a rrest in G(1), but rather undergo another round of S phase and arrest in G( 2) from which they are able to enter a state of quiescence. Genetic evidenc e suggests that cdr2(+) acts as a mitotic inducer, functioning through wee1 (+), and is also important for the completion of cytokinesis at 36 degrees C. Defects in cytokinesis are also generated by the overproduction of Cdr2p , but these defects are independent of wee1(+), suggesting that cdr2(+) enc odes a second activity involved in cytokinesis.