NS3/4A protein is an effective antagonist for cytokine/chemokine promoters. (A) IFN-β, IFN-λ1/IL-29, IFN-λ3/IL-28B and IFN-α1 gene promoter activities were studied in the presence of HCV core, NS3/4A-wt or NS3/4A-S139A after Sendai virus infection. (B) Cytokine/chemokine gene promoter activities were studied in the presence of HCV core or NS3/4A protein. The activities of IFN-β, CCL5/RANTES, CXCL8/IL-8, CXCL10/IP-10, TNF-α and IFN-α4 promoters in HCV core or NS3/4A-expressing HEK293 cells were measured after Sendai virus infection. HEK293 cells were treated as described in the legend for Figure 1. The activity of the sample that was transfected with empty pcDNA3 plasmids and mock infected was assigned to value of 1.