IE1 induces activity of 4XTRE-Luc, four-copy AP-1 element-driven reporter construct, in NIH 3T3 cells. NIH 3T3 cells were transiently transfected, in triplicate, with the indicated dose of pON2205 vector expressing IE1 protein, 0.5 μg of 4XTRE-Luc vector, 0.5 μg of SV40 β-Gal expression vector, and pBluescript for a total of 3 μg of DNA. Relative luciferase units are presented ± the standard deviation. Activity of the control 4XTRE-Luc vector DNA was set at 1.