The effect of the vaccinia K1 protein on the PKR-eIF2alpha pathway in RK13 and HeLa cells.
Activated PKR protein regulates downstream anti-viral effects, including inhibition of translation. Thus, many viruses encode proteins to inhibit PKR. Here, we provide evidence that the vaccinia virus K1 protein, a host-range protein, possesses this function. First, the expression of the wild-type K1 protein was necessary to inhibit virus-induced eIF2alpha phosphorylation, an indirect measure of PKR activation, in RK13 and HeLa cells. Second, virus-induced eIF2alpha phosphorylation no longer occurred in PKR-deficient HeLa cells, suggesting PKR was responsible for vaccinia virus-induced eIF2alpha modification. Third, in normal HeLa cells, K1 protein expression also prevented virus-mediated PKR phosphorylation (activation). Residues in the C-terminal portion of the ANK2 region of K1 were identified as necessary for this inhibitory phenotype. Interestingly, mutant viruses that failed to inhibit PKR activation, such as S2C#2, also did not replicate in HeLa cells, suggesting that K1's inhibition of PKR was required for a productive infection. In support of this theory, when PKR was absent from HeLa cells, there was a modest restoration of viral protein synthesis during S2C#2 infection. However, the increased protein synthesis was insufficient for a productive infection.
Willis
Kristen L
KL
Department of Microbiology, College of Medicine, University of Illinois at Urbana-Champaign, 601 S. Goodwin Avenue, Urbana, IL 61801, USA.
Patel
Samir
S
Xiang
Yan
Y
Shisler
Joanna L
JL
D000818:Animals; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D011817:Rabbits; D014616:Vaccinia virus / Q000254:growth & development / Q000472:pathogenicity*; D014764:Viral Proteins / Q000502:physiology*; D014779:Virus Replication; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors*
D015852:Eukaryotic Initiation Factor-2; C083205:K1L protein, Vaccinia virus; D014764:Viral Proteins; D019892:eIF-2 Kinase