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 remain in the stationary phase or enter into either premitotic or premeiotic DNA synthesis. This decision point is known as Start. In the mitotic cell cycle, regulation of G₁S-specific gene expression is dependent upon the MBF (Mlu1 binding factor) complex, known to contain p85(cdc10) and p72(res1). Here we demonstrate that p73(res2) controls cell cycle progression via its participation in the MBF complex, interacting directly with both p85(cdc10) and p72(res1). In contrast, when cells enter into meiosis, the MBF complex is disrupted, and p73(res2) shifts its regulatory function towards the transactivation of genes required for meiotic progression. These observations suggest that p73(res2) plays a pivotal role at Start and constitutes an example of a transcription factor involved in the control of both mitotic and meiotic progression.