Thecdr2+Gene Encodes a Regulator of G2/M Progression and Cytokinesis inSchizosaccharomyces pombe

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Abstract
Schizosaccharomyces pombe cells respond to nutrient deprivation by altering G2/M cell size control. The G2/M transition is controlled by activation of the cyclin-dependent kinase Cdc2p. Cdc2p activation is regulated both positively and negatively. cdr2+ was identified in a screen for regulators of mitotic control during nutrient deprivation. We have cloned cdr2+and have found that it encodes a putative serine-threonine protein kinase that is related to Saccharomyces cerevisiae Gin4p and S. pombe Cdr1p/Nim1p.cdr2+ is not essential for viability, but cells lacking cdr2+ are elongated relative to wild-type cells, spending a longer period of time in G2. Because of this property, upon nitrogen deprivationcdr2+ mutants do not arrest in G1, but rather undergo another round of S phase and arrest in G2 from which they are able to enter a state of quiescence. Genetic evidence suggests thatcdr2+ acts as a mitotic inducer, functioning through wee1+, and is also important for the completion of cytokinesis at 36°C. Defects in cytokinesis are also generated by the overproduction of Cdr2p, but these defects are independent of wee1+, suggesting thatcdr2+ encodes a second activity involved in cytokinesis.