REGULATION OF YEAST CHROMOSOME SEGREGATION BY IPL1 PROTEIN-KINASE ANDTYPE-1 PROTEIN PHOSPHATASE

Chromosome segregation is a complicated process that involves the coor dinated functioning of a large number of cellular components. In this process, many proteins are activated and inactivated in a strict tempo ral order. While much progress has been made recently in the identific ation of structural components that are involved in chromosome segrega tion, relatively little is known about their regulation. We have inves tigated the chromosome segregation process in the budding yeast Saccha romyces cerevisiae. Our results indicate that this process absolutely requires a functional Ipl1 protein kinase. Upon inactivation of this p rotein kinase, yeast cells missegregate chromosomes severely and die w ithin a single cell cycle. Furthermore, the inviability caused by a pa rtial reduction in Ipl1 function can be rescued by perturbations that reduce type 1 protein phosphatase activity, thus suggesting that type 1 protein phosphatase acts in opposition to the Ipl1 protein kinase to insure the high fidelity of chromosome segregation in yeast cells. Th e purpose of this article is to describe some of our ongoing efforts t o characterize Ipl1 and PP1 functions.