NIH3T3 cells were transfected with the minimal promoter, -151Tnk Luc (2μg) along with either the control, pCDNA, CMV-Sp1, CMVSp3 or CMV-AP2. CMV-βGal was co-transfected in all cases for normalizing transfection efficiency. The transfected cells were deprived of serum for 24 hours prior to the determination of luciferase activity. The data represent the average of triplicate (± S. D.) determinations normalized to β-galactosidase activity. Inset shows the ectopic expression of Sp1, Sp3 and AP2 in the transfected cells. The endogenous expression level of Tnk1/Kos1 in the transfected cells is indicated. The level of Actin served as the loading control.