Knockout of the Host Resistance Gene Pkr Fully Restores Replication of Murine Cytomegalovirus m142 and m143 Mutants In Vivo.

Murine cytomegalovirus (MCMV) proteins m142 and m143 are essential for viral replication. They bind double-stranded RNA and prevent protein kinase R-induced protein synthesis shutoff. Whether the two viral proteins have additional functions such as their homologs in human cytomegalovirus do remained unknown. We show that MCMV m142 and m143 knockout mutants attain organ titers equivalent to those attained by wild-type MCMV in Pkr knockout mice, suggesting that these viral proteins do not encode additional PKR-independent functions relevant for pathogenesis in vivo.