Role of Signal Transduction Systems in Cell Proliferation in Yeast

Abstract

Publisher Summary This chapter discusses the major progress made in the genetic analysis of the mutants altered in the signal-transduction system and in the studies of the function of second messenger in yeast cells. The responses of yeast cells to external signals are commonly mediated by intracellular second messengers, such as cAMP, and the breakdown products of phosphoinositides. An important approach is to use mutants defective in the signal-transduction systems as the critical controls for the biochemical analyses of the cascade reactions related to the second messenger. The cAMP-requiring mutants are isolated from strains utilizing cAMP with the genetic background of P-28-24C. Strains indicating low cAMP levels have three distinct phenotypes: (1) they fail to grow efficiently on nonfermentable carbon sources, (2) they hyperaccumulate the storage carbohydrate glycogen and trehalose, and (3) diploid cells sporulate in rich medium. The mutant analysis on the cAMP-cascade system reveals that the cAMP-dependent protein kinase is involved in the phosphorylation events of specific proteins that need to regulate growth and differentiation of yeast. cAMP-dependent phosphorylation and dephosphorylation mechanisms in yeast regulate activities of various enzymes, such as trehalase, NAD-dependent glutamatedehydrogenase, glycogen phosphorylase, glycogen synthetase, and RNA polymerase.