TIRAP/Mal is required in HSV-1–induced up-regulation of IL-15 gene expression. (A) THP-1 cells were transfected with TIRAP/Mal siRNA or control siRNA for a total period of 48 hours, and protein lysates were analyzed for TIRAP and β-actin expression levels by immunoblotting. (B) TIRAP/Mal-deficient THP-1 cells were treated with HSV-1, and IL-15 gene expression was determined by RT-PCR. IL-15 mRNA (top panel) and 18S rRNA (bottom panel) are shown and are representative of 3 independent experiments. (C) IL-15 gene expression was also analyzed by real-time RT-PCR. Data are expressed as the ratio of IL-15 mRNA in treated samples to the untreated sample (after normalization with reference dye and housekeeping gene). (D) TIRAP/Mal-deficient THP1 cells were incubated with HSV-1 for 1 hour. Nuclear extracts were subjected to EMSA analysis with radiolabeled NF-κB consensus oligonucleotide in the presence of unlabeled competitor (a lanes) or nonspecific competitor (b lanes). NF-κB binding was visible by autoradiography.