Figure 2. MHV N protein antagonizes IFN-β production by targeting molecule(s) upstream of RIG-I/MDA5.

HEK-293T cells were co-transfected with IFN-β–Luc, pRL–TK plasmids, and plasmids encoding MHV-N (A–E) or SARS-N (F and G) proteins together with constructs expressing RIG-I, MDA5, IPS-1, IKKe, TBK1, IRF3 and IRF3-5D. Luciferase assays were performed at 28 h after transfection. The results represent the means and standard deviations of three independent experiments. (H and I). pCAGGS–HA-MHV-N and Flag-RIG-I or -MDA5 vectors were transfected into HEK-293T cells and immunoprecipitation was performed with an anti-Flag antibody, followed by immunoblotting analyses with antibodies against Flag, HA and β-actin, respectively.