EIF2AK3 and viral infectious disease: Four eIF2α kinases are responsible for the phosphorylation of this factor in response to various stress stimuli: protein kinase double-stranded RNA-dependent (PKR) was initially found to directly react to viral infection, PKR-like ER kinase (PERK) is activated upon ER-stress, haeme-regulated inhibitor (HRI) responds to haeme deprivation, and amino acid deprivation induces the activation of general control non-derepressible-2 (GCN2) kinase.