Three other kinases activated upon cellular stress -Heme-regulated eIF2α kinase (HRI) upon heme depletion or mitochondrial dysfunction [236,237]; Protein Kinase R (PKR), upon viral infection; and General Control Nonderepressible 2 (GCN2), upon amino acid deprivation- can phosphorylate eIF2α [238]. This evidence concerns the gene EIF2AK4 and viral infectious disease.