Human embryonic kidneys (HEK) 293T (2x105) cells (ATCC, CRL-3216) were seeded into 24-well plates the day before transfection. Cells were cotransfected with the IFN-β or ISRE promoter luciferase reporter and Renilla luciferase internal control (pRL-TK) using Lipofectamine 2000 (Invitrogen) as previously described . Cells were stimulated with DHX29, RIG-I, or MDA5 ligand 24 h post-transfection. Empty pcDNA3.1 HA/Flag/Myc tagged vector was used to ensure equal amounts of DNA among the wells. Luciferase activity was determined using the Dual-Luciferase Assay (Promega) with the Luminoskan Ascent Luminometer (Thermo Scientific) as previously described . Reporter gene activity was normalized to the internal control.