EIF2AK4 and viral infectious disease: GCN2 (the protein encoded by EIF2AK4) represents one arm of the Integrated Stress Response (ISR) pathway, whereby cells adapt to various stresses such as viral infection, heme deprivation, unfolded protein response (UPR) and, in the case of GCN2, amino acid deprivation42 (Supplementary Fig. 6c).