Protein synthesis shut-off induced by influenza virus infection is independent of PKR activity

The role of PKR activity in influenza virus-induced cell shut-off was studi ed by infection of PKR+ or PKR- cell cultures and metabolic labeling in viv o. No differences in the synthesis of viral proteins or the decay of cellul ar protein synthesis were observed. To investigate the relevance of the inh ibition of cellular pre-mRNA polyadenylation and nucleocytoplasmic transpor t in virus-induced shut-off, we carried out similar experiments with mutant viruses lacking C-terminal sequences of NS1 protein, No differences in the shut-off induced by mutant versus wild-type viruses were observed, indicat ing that these nuclear events are not relevant for shut-off. The analysis o f cytoplasmic mRNA stability indicated that the accumulation of viral mRNA during the infection correlated with the progressive decay of cellular mRNA , in both the wild type and an NS1 deletion mutant.