Fission yeast TORC1 prevents eIF2α phosphorylation in response to nitrogen and amino acids via Gcn2 kinase

Serine 51 phosphorylation of the eukaryotic initiation factor-2 alpha (eIF2 alpha) is an important mechanism involved in blocking general protein synthesis in response to diverse types of stress. In fission yeast, three kinases (Hri1, Hri2 and Gcn2) can phosphorylate eIF2 alpha at serine 51. In this study, we show that Tor2, as part of the TORC1 complex, prevents the phosphorylation of eIF2 alpha in cells growing in the presence of nitrogen and amino acids. Inhibition of TORC1, either by rapamycin treatment, mutation of Tor2 or nitrogen deprivation, induces Gcn2-dependent phosphorylation of eIF2 alpha.