Genes which control cell proliferation in the yeast Saccharomyces cerevisiae

Abstract

Cell proliferation is regulated at a point in G1 close to the initiation of DNA synthesis. This point is called start and for cells to proceed beyond start, to initiate DNA synthesis and produce a bud, various conditions must be met. Two of these conditions are the presence of adequate nutrients in the medium and the attainment of a critical size. Some of the genes controlling start were identified by isolating mutants, altered with respect to the conditions in which start occurs. Two types of mutant were isolated. One resulted in bud initiation when the parent cell is only half the size at which bud initiation occurs in wild-type cells. Such mutants define a single gene, whi-1. A 2nd type of mutation affects a 2nd gene, whi-2, which is involved in the mechanism whereby cells arrest in G1 in stationary phase. whi-2- cells growing exponentially initiate buds at the same size as wild-type cells. In stationary phase, however, whi-2- cells, unlike wild-type cells, are predominantly budded and are smaller than wild-type cells.