Characterization of G1 and Mitotic Cyclins of Budding Yeast

Abstract

It has been known for a decade that in yeast, the CDC28 gene of Saccharomyces cerevisiae and the cdc2+ gene of Schizosaccharomyces pombe are needed at two points in their host's cell cycles: once in G1 phase, for commitment to division, and once again in mitosis (Nurse and Bissett 1981; Piggott et al. 1982). These two genes encode highly homologous proteins, which have proven to be the catalytic subunits of protein kinases (Reed et al. 1985; Simanis and Nurse 1986). The active protein kinase is a complex containing the Cdc28/cdc2 protein and a protein called a cyclin (Draetta et al. 1989). Other subunits may also be present (Brizuela et al. 1987.