Enhanced replication of mouse adenovirus type 1 following virus-induced degradation of protein kinase R (PKR)

Danielle E. Goodman; Carla D. Pretto; Tomas A. Krepostman; Kelly E. Carnahan; Katherine R. Spindler

Protein kinase R (PKR) plays a major role in activating host immunity during infection 25 by sensing dsRNA produced by viruses. Once activated by dsRNA, PKR phosphorylates the 26 translation factor eIF2α, halting cellular translation. Many viruses have methods of inhibiting 27 PKR activation or its downstream effects, circumventing protein synthesis shutdown. These 28 include sequestering dsRNA or producing proteins that bind to and inhibit PKR activation. Here 29 we describe our finding that in multiple cell types, PKR was depleted during mouse adenovirus 30 type 1 (MAV-1) infection. MAV-1 did not appear to be targeting PKR at a transcriptional or 31 translational level because total PKR mRNA levels and levels of PKR mRNA bound to 32 polysomes were unchanged or increased during MAV-1 infection. However, inhibiting the 33 proteasome reduced the PKR depletion seen in MAV-1-infected cells, whereas inhibiting the 34 lysosome had no effect. This suggests that proteasomal degradation alone is responsible for PKR 35 degradation during MAV-1 infection. Time course experiments indicate that the degradation 36 occurs early after infection. Infecting cells with UV-inactivated virus prevented PKR 37 degradation, whereas inhibiting viral DNA replication did not. Together these results suggest that 38 an early viral gene is responsible. Degradation of PKR is a rare mechanism to oppose PKR 39 activity, and it has only been described in six RNA viruses. To our knowledge, this is the first 40 example of a DNA virus counteracting PKR by degrading it. 41 42 Importance 43