A gene family homologous to the S-phase specific gene in higher plants is essential for cell proliferation in Saccharomyces cerevisiae.

Previously we reported the isolation and characterization of the gene, cyc07, which was specifically expressed in the S phase during the cell cycle in synchronous cell division cultures of the higher plant, Catharanthus roseus. We found that the yeast Saccharomyces cerevisiae contains two closely related genes which show a high degree of similarity (about 64% at the amino acid level) to cyc07 of C. roseus. Site-directed disruption mutations demonstrated that the two yeast genes, homologous to cyc07, constitute an essential gene family for cell proliferation in yeast cells. Furthermore, the rate of cell proliferation varied with the gene copy number.