Genetic Control of the DNA Polymerase α-Primase complex in the Yeast Saccharomyces cerevisiae

Three major control points can be envisaged in the cell division cycle of eukaryotic organisms. The transition from a quiescent state to active cell proliferation, the initiation of DNA synthesis and the induction of mitosis. By combining genetic approaches in the yeast Saccharomyces cerevisiae and Schizosaccharomyces pombe with the biochemical characterization of proteins that induce the mitotic state in other eukaryotic cells, a molecular description of the series of events that regulate the onset of mitosis is beginning to emerge (Cross et al. 1989; Nurse 1990). The p34CDC28/cdc2+ protein kinase plays a major role in the induction of mitosis by associating with a subset of oscillating proteins (cyclins) and by recognizing and modifying a variety of mitotic substrates (Lewin 1990). It has been proposed that p34CDC28/cdc2+ would allow the phosphorylation of a different set of substrates involved in the Gl to S phase transition by associating with other cyclin-like proteins (Nurse 1990; Pines and Hunter 1990).