While yeast have only one eIF2α kinase (GCN2, activated by amino acid shortage), mammals have three additional eIF2α kinases sensing diverse signals: PKR, activated by viral infections; HRI, activated by heme deficiency; and PERK (or PEK), activated by misfolded proteins in the ER (Sonenberg and Hinnebusch, 2009). This evidence concerns the gene EIF2AK3 and viral infectious disease.