Identification of AAS genes and their regulatory role in general control of amino acid biosynthesis in yeast.

In yeast, most amino acid biosynthetic pathways are coregulated: starvation for a single amino acid results in derepression of enzyme activities for many different biosynthetic pathways. This phenomenon is referred to as "general control of amino acid biosynthesis." In this paper we describe the isolation and characterization of 43 amino acid analog-sensitive (aas-) mutants that are perturbed in this general regulatory system. These 43 mutations define four unlinked complementation groups, AAS101, AAS102, AAS103, and AAS104, two of which identify previously unreported genes involved in general control. These aas mutants are unable to derepress a number of amino acid biosynthetic genes, resulting in increased sensitivity to amino acid analogs, reduced growth rates, and reduced enzyme activity levels under amino acid starvation conditions. Thus, the AAS+ gene products function as positive regulatory elements for this system. We show that the AAS genes mediate these effects by regulating the mRNA levels of genes under their control.