Control of Cell Type in Saccharomyces cerevisiae: Mating Type and Mating-type Interconversion

Abstract

INTRODUCTION The study of yeast mating and mating-type interconversion has attracted considerable interest for several reasons. (1) The mating process involves oligopeptide pheromones, specific for each haploid cell type (mating types a and α ), which act specifically to arrest the cells of opposite mating types in the G 1 phase of the cell cycle. Studies of the action of these pheromones may well shed light on the mechanism of growth control. Such studies are described elsewhere in this volume. (2) The mating type of a cell is determined by alleles of the mating-type locus MAT a or MATα , which in some manner controls a variety of cellular processes: pheromone production and response, agglutination, mating, and sporulation. A working hypothesis is that the mating-type locus codes for regulatory proteins that control expression of unlinked genes. Regulatory proteins are well known in prokaryotes as agents for controlling protein synthesis and act in many cases to control transcription initiation and termination. One of the central questions in gene control and in eukaryotic development is to understand the mechanism by which differentiated cells express a distinctive set of proteins. Analysis of how the mating-type locus determines cell type in yeast should provide information on gene control in yeast, e.g., on the nature of regulatory proteins, and provide an intellectual model for analogous processes in higher eukaryotes. Yeast regulatory proteins are also discussed by Jones and Fink (1982), Fraenkel (1982), Oshima (1982), and Sherman (1982). (3) Yeast cells can exhibit either a heterothallic life cycle, in which...