β-catenin and LEF1 regulate IFN-β promoter activity via IRF-PRD. (A) Vero cells were transfected with the reporter gene plasmid containing the IRF3-responsive elements of the IFN-β enhanceosome along with indicated plasmids, and the reporter gene activity was measured 30 h later. The luciferase activity of β-catenin and LEF1-transfected cells was arbitrarily taken as unity. (B) A549 cells were transfected with empty vector or plasmids coding for β-catenin and LEF1 for 30 h, and the interaction of cellular proteins with the DNA was analyzed by ChIP assays. The amount of amplified DNA in IRF3- and β-catenin-specific immunoprecipitates was quantified by qRT-PCR using primers specific for the promoter region of the IFNB1 gene. Values represent n-folds of IgG controls. One of three independently repeated experiments is depicted as representative.