EIF2A and viral infectious disease: Of the four kinases which phosphorylate eIF2α (general control non-derepressible 2, GCN2; protein kinase R, PKR; PKR-like endoplasmic reticulum kinase, PERK and heme regulated inhibitory kinase, HRI), PKR can be phosphorylated by viral infection [20,58] and alternatively by SA [44,59].