Analysis of ISRE-luciferase promoter activation due to intracellular expression of IRF9-Stat fusion proteins. R15-3 cells were transfected with IRF9, IRF9-S1C or IRF9-S2C plasmid and cultured (-) and (+) IFN-α (1,000 IU/ml). At 48 hours FL and RL activity were measured. Values are expressed in RL normalized units and error bars represent the SEM from three experiments. The Student's t-test was used to compare IRF9 with and without IFN to IRF9-S1C, IRF9-S2C and IRF9-S1C plus IRF9-S2C with and without IFN. Values <.05 were considered significant.