GENETIC-EVIDENCE FOR FUNCTIONAL SPECIFICITY OF THE YEAST GCN2 KINASE

In yeast the GCN2 kinase mediates translational control of GCN4 by pho sphorylating the alpha subunit of eIF-2 in response to extracellular a mino acid limitation. Although phosphorylation of eIF-2 alpha has been shown to inhibit global protein synthesis, amino acid starvation resu lts in a specific activation effect on GCN4 mRNA translation. Under th e same conditions, translation of other mRNAs appears only slightly af fected. The mechanism responsible for the observed selectivity of the GCN2 kinase is not clear. Here, we present genetic evidence that sugge sts that locally restricted action of the GCN2 kinase facilitates GCN4 -specific translational regulation.