FIGURE 6.

Increased GCN4 translation by the alternate nitrogen source GABA is dependent on Gcn2p and Sit4p. Wild-type (GCN2) and gcn2Δ (A) or sit4Δ (B) strains were cultured in synthetic medium lacking amino acids and containing ammonia (NH₄⁺) as the nitrogen source and then switched to synthetic medium containing GABA as the nitrogen source and grown for 6 h as shown on the legend. β-Galactosidase activity was measured from the GCN2 and gcn2Δ cells containing a GCN4-lacZ reporter plasmid with uORFs (GCN4-uORFs-lacZ). The average β-galactosidase activity from three independent cultures ± S.E. is shown. In B, the fold change for the different medium conditions as compared with the synthetic medium containing ammonia and all amino acids (NH₄⁺ + AA) is indicated above each histogram.