Genetic regulation of phospholipid biosynthesis in Saccharomyces cerevisiae

Abstract

The synthesis of membrane phospholipids in Saccharomyces cerevisiae is a highly regulated process. The regulation of this essential metabolic pathway is exerted at the level of transcription, control of enzyme subunit levels, and allosteric modulation of enzyme activity. However, the major form of regulation, which accounts for the coordinated regulation of the system, is determined at the level of transcript abundance. This coordinated response to inositol requires a highly conserved cis-acting promoter element (5' CATGTGAAAT 3') designated the UAS(INO) element. The UAS(INO) element serves as binding site for a heterodimeric helix-loop-helix complex (Ino2p:Ino4p), which is required to activate transcription in the absence of inositol. In addition, a specific negative regulatory gene, OPII is required for repression of transcription in response to inositol supplementation. Although this regulatory cascade was initially defined for control of phospholipid biosynthetic gene expression, it also responsible for the regulation of several other unrelated yeast genes. Consequently, the presence of inositol in the growth medium appears to influence the expression of many yeast genes by a common regulatory pathway.