Point mutations of the AP-1–binding site within the PAI-1 promoter abolish its sensitivity to Tβ4-induced transcriptional activity. EA.hy 926 cells were transiently transfected either with p800LUC (•) or its mutated version (▪), in which the wild-type AP-1 consensus motif (TGAGTTCA) was substituted by its mutated version, TGTGTTTG. Eighteen hours following transfection, cells were washed and transferred to DMEM media containing 0.5% bovine serum albumin. After 24 hours, Tβ4 was added at the indicated concentration and the cells where harvested after an additional 7 hours. Luciferase and β-gal activities were assayed as described in “Materials and methods.” Values are expressed as relative light units (RLU) of luciferase normalized to β-gal activity with data of 2 experiments shown as the mean of 3 separate samples plus the SE. In addition, data obtained using EA.hy 926 cells transfected with the empty vector, pGL2, are shown (▴).