HCV NS2 and NS3/4A inhibit IFN-β gene expression. (A) The effect of expressed 11 HCV polypeptides on IFN-β promoter activity was studied in HEK293 cells by Luc reporter driven assay. The cells were transfected in triplicates with 1.0 μg HCV protein expression plasmids together with 0.1 μg firefly luciferase reporter under IFN-β promoter and 0.05 μg Renilla luciferase reporter (control) plasmids. Total DNA amount was balanced with the empty plasmid (pcDNA3.1(+)-FLAG). At 18 h after transfection the cells were infected with Sendai virus (MOI 5) or mock infected for 24 h, followed by collection of cells, preparation of cell lysates and measurement of luciferase activity. IFN-β promoter activities were normalized with Renilla luciferase activities. The activity of the sample that was transfected with empty pcDNA3 plasmids was assigned to 100%. Original values of IFN-β promoter (B) and Renilla luciferase (C) activities with HCV expression constructs are presented in the figures. Promoter activities were measured as triplicates and expressed as the means +/- standard deviations.