(A and B) Luciferase assay analysis of IFN-β (A) or IRF-mediated ISRE (B) promoter activity in HEK293 cells transfected with scrambled control or HIPK2 siRNA and the indicated expression plasmids for 24 hours. Data (top) with means ± SEM are from three experiments. Blots confirming expression of the indicated proteins (lower) are representative of all experiments. (C) Bioassay of type I IFN production by wild-type, Irf3−/−, or Irf7−/− iBMDMs transfected with Vec control or HIPK2 expression plasmids and infected with SeV for 24 hours. Data with means ± SEM are from three experiments. (D) Enzyme-linked immunosorbent assay (ELISA) analysis of type I IFNs secreted from wild-type, Irf3−/−, Irf7−/−, and p65−/− iBMDMs transfected with Vec control or HIPK2 expression plasmids and infected with SeV for 6 hours. Data with means ± SEM are from three experiments. (E and F) Bioassay of IFN production by wild-type or p65−/− iBMDMs transfected with Vec or HIPK2 expression plasmids and infected with VSV (E) or SeV (F) for 6 hours. Data with means ± SEM are from three experiments. *P < 0.05, **P < 0.01, and ***P < 0.001 by Student’s t test.