Target cells were transiently co-transfected using appropriate pGL3 and internal control pRL-TK contructs (Promega) and pcDNA3.1(+) vectors (Invitrogen). The total amount of DNA used per sample was approximately 2 mg. Following 48 h post-transfection, cells were harvested and Firefly and Renilla luciferase activities were analyzed using the dual luciferase system (Promega). Luciferase activity was monitored using a Turner Systems Luminometer (Sunnyvale, CA) as per earlier protocols [6] . The relative luciferase activity was calculated by normalizing ORF50P luciferase activity to control Renilla luciferase activity. The results were plotted as a percentage of the activity of the empty pGL3 vector.