TAT and viral infectious disease: Although PKR is well-known for its antiviral function by sensing viral RNA and phosphorylating the host translation initiation factor eIF2α (72), it has also been implicated in the phosphorylation and regulation of the HIV trans-acting protein Tat, which binds to the transactivation-responsive element (TAR) in the HIV genome, in the context of viral infection (73, 74).