Protein Kinase R (PKR) Plays a Pro-viral Role in Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Replication by Modulating Viral Gene Transcription

Protein kinase R (PKR) is involved in apoptotic cell death and antiviral activities in response to many virus infections. To reveal the role of PKR in the replication of porcine reproductive and respiratory syndrome virus (PRRSV), we first examined the kinetics of PKR phosphorylation during PRRSV infection. The results showed that PRRSV transiently activates PKR at 12 and 24 h postinfection. Surprisingly, eIF-2α, the well-known downstream target of PKR, was significantly phosphorylated compared to mock-infected cells only at 48 and 72 h postinfection. Reduced viral gene transcription, viral protein synthesis, and virus titer were detected in cells transfected with PKR silencing RNA prior to PRRSV infection compared to control silencing RNA transfected cells, indicating a role of PKR in facilitating virus replication. Overall, our data suggest that PKR is not a major contributor to the phosphorylation of eIF-2α during PRRSV infection, but it plays a pro-viral role in PRRSV replication by modulating primarily viral gene transcription