EIF2AK4 and viral infectious disease: Activation of four critical kinases by viral infection (protein kinase R; PKR), heme deprivation, and oxidative stress (heme-regulated eukaryotic initiation factor eIF-2-alpha kinase; HRI), ER stress (PRKR-like ER kinase; PERK), and amino acid starvation and UV irradiation (eIF-2-alpha kinase GCN2; GCN2) result in the phosphorylation and inhibition of eIF2α, a subunit of eIF2 (115).