Effect of FBXO3 on p62 degradation by RVFV NSs. (A) Western blot analysis of knockdown cells. Human A549 cells were treated with siRNA directed against the FBXO3 mRNA or with a control siRNA. Cells were then infected with wt RVFV (rZH548) or Clone 13 (Cl13) at an MOI of 10 and 6 h later analyzed for the presence of PKR, p62, RVFV N, and β-actin using Western blot analysis. (B) Immunofluorescence analysis. siRNA knockdown of FBXO3 mRNA was achieved in HeLa cells as described for panel A. Cells were infected for 6 h with a recombinant RVFV expressing Flag-tagged NSs (rZH-CF-NSs), and the presence of p62 and Flag-RVFV NSs was analyzed 6 h later using appropriate antibodies. DAPI was used for counterstaining the nuclei. (C) Real-time RT-PCR of the knockdown cells shown in panel A. Cells were treated and infected as described for panel A and analyzed for the presence of RNAs for FBXO3 (left panel) and RVFV L (right panel) at 3 and 6 h postinfection. Mean values and standard deviations of 3 independent experiments are shown. A two-tailed, paired t test using log-transformed data was used to compare the siRNA pairs.