THE FISSION YEAST PROTEIN P73(RES2) IS AN ESSENTIAL COMPONENT OF THE MITOTIC MBF COMPLEX AND A MASTER REGULATOR OF MEIOSIS

Depending on environmental conditions, Schizosaccharomyces pombe can r emain in the stationary phase or enter into either premitotic or preme iotic DNA synthesis. This decision point is known as Start. In the mit otic cell cycle, regulation of G(1)/S-specific gene expression is depe ndent upon the MBF (Mlu1 binding factor) complex, known to contain p85 (cdc10) and p72(res1). Here we demonstrate that p73(res2) controls cel l cycle progression via its participation in the MBF complex, interact ing directly with both p85(cdc10) and p72(res1). In contrast, when cel ls enter into meiosis, the MBF complex is disrupted, and p73(res2) shi fts its regulatory function towards the transactivation of genes requi red for meiotic progression. These observations suggest that p73(res2) plays a pivotal role at Start and constitutes an example of a transcr iption factor involved in the central of both mitotic and meiotic prog ression.