EIF2AK2 and viral infectious disease: Remarkably, SUMO1 and SUMO3 expression exert a differential effect on PKR activation SUMO1 expression alone results in PKR and eIF-2α phosphorylation, whereas SUMO3 reduces PKR and eIF-2α phosphorylation upon viral infection or dsRNA transfection (Maarifi et al., 2018).