FIG. 9.

PEK functionally substitutes for the eIF-2α kinase GCN2 in a yeast model system. (A) Strain H1894 (Δgcn2) was transformed with plasmid pC102-2, encoding GCN2 kinase (GCN2), p504, expressing PEK from a galactose-inducible promoter (PEK), or only vector pEBMLyex4 (Vector). Patches of transformed cells were replica printed onto agar plates containing SGal, SGal supplemented with 3-AT, or SGal supplemented with SM. GCN2-deficient strains are hypersensitive to the amino acid inhibitors 3-AT and SM. Replicated plates were grown for 4 days at 30°C and photographed. (B) PEK was similarly expressed in strains H1816 (Δgcn2 SUI2) and H1817 (Δgcn2 SUI2-S51A), which are related to H1894, and cells were replica printed onto SGal or galactose-inducing medium containing SM. Strain H1817 contains a mutant version of eIF-2α that has an alanine substituted for the phosphorylated residue serine-51. While expression of either GCN2 or PEK in H1816 facilitates growth of this strain in SGal medium containing SM, neither eIF-2α kinase mediated growth when expressed in H1817 cells.