Luciferase reporter assays

293T (2 × 10⁵) cells were seeded in 24‐well plates and transfected with plasmids encoding an IFN‐β or ISRE luciferase reporter (firefly luciferase; 100 ng) and pRL‐TK (renilla luciferase plasmid; 10 ng), together with various amounts of the appropriate control or protein‐expressing plasmid(s). An empty vector (pcDNA3.1) was used to maintain equal amounts of DNA among wells. Cells were collected at 24–36 h after transfection, and luciferase activity was measured with a dual‐luciferase assay (Promega) with a Luminoskan Ascent luminometer (Thermo Scientific) according to the manufacturer's protocol. Reporter gene activity was determined by normalizing to renilla luciferase activity as previously described 16.