Transcriptional and Translational Regulation of Gene Expression in the General Control of Amino-Acid Biosynthesis in Saccharomyces cerevisiae

Abstract

This chapter describes the transcriptional and translational regulatory events that involve in the general amino-acid control of S. cerevisiae. General-control-mediated derepression of certain lysine biosynthetic enzymes is also partially over-ridden by a lysine-specific repression mechanism when lysine is not limiting. The same phenomenon may apply to certain leucine biosynthetic enzymes that are subject to leucine-specific repression. By contrast, multivalent repression of enzymes in the isoleucine-valine pathway by a mixture of isoleucine, valine, and leucine does not interfere with their derepression by the general control system in response to starvation for other amino acids. Smaller increases have been observed for the leucine and glutamate pools. It is not obvious why S. cerevisiae responds to limitation for a single amino acid by increasing the size of many different amino-acid pools. Perhaps single amino-acid limitation occurs rarely in nature, such that multiple-pathway derepression is generally a simple and effective response to starvation conditions, with specific repression mechanisms operating to over-ride derepression of those pathways for which no amino-acid limitation exists.