EIF2AK2 and viral infectious disease: PKR is a ubiquitously expressed double-stranded RNA (dsRNA)-activated protein kinase (Meurs et al., 1990; Garcia et al., 2007), active under cellular stress conditions such as viral infections, oxidative and endoplasmic reticulum (ER) stress, and serum or growth factor deprivation (Ito et al., 1999; Patel et al., 2000).