Isolation and characterization of WHI3, a size-control gene of Saccharomyces cerevisiae

WHI3 is a gene affecting size control and cell cycle in the yeast Saccharom yces cerevisiae. The whi3 mutant has small cells, while extra doses of WHI3 produce large cells, and a large excess of WHI3 produces a lethal arrest i n G1 phase. WHI3 seems to be a dose-dependent inhibitor os Start. WHi3 and its partially redundant homolog Whi4 have an RNA-binding domain, and mutage nesis experiments include that this RNA-binding domain is essential for WHi 3 function. CLN3-1 whi3 cells are extremely small, nearly sterile, and larg ely nonresponsive to mating factor. Fertility is restored by deletion of CL N2, suggesting that whi3 cells may have abnormally high levels of CLN2 func tion.