FIG 2 .

pH1N1 NP is more resistant to TRIM22-mediated inhibition than sH1N1 NP in a polymerase activity assay. Expression plasmids for the polymerase subunits PB2, PB1, and PA from the pH1N1 virus and NP expression plasmids from either the pH1N1 or sH1N1 strains were cotransfected with a plasmid carrying a pseudoviral genome, harboring a Renilla reporter, into HEK293T cells either without (Nil) or with increasing concentrations of TRIM22-expressing plasmid. The reporter gene activity was measured 24 h later. (A) Increasing amounts of exogenous beta interferon (IFN-β) were added to the polymerase activity assay. The sH1N1 NP-dependent polymerase activity was more sensitivity to the IFN-β stimulation than that of pH1N1 NP. Means ± standard deviations (SD) from 3 independent experiments in triplicates are reported. P values were determined using one-way ANOVA with Bonferroni’s multiple-comparison test of Nil versus each treatment (****, P < 0.0001). (B) Forty nanograms of TRIM22-expressing plasmid reduced the polymerase activity driven by the sH1N1 NP by 50% but not the polymerase activity driven by the pH1N1 NP. Means ± SEM from 3 independent experiments in triplicate are reported. P values were determined using one-way ANOVA with the Bonferroni’s multiple-comparison test of nil versus each treatment (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001). Western blot analysis was performed to determine the expression levels of TRIM22 and both pH1N1 and sH1N1 NPs.