TGF-β activation of Smad-responsive reporters is inhibited by Tax.

■, −Tax; ▪, +Tax. (A) Tax inhibits transcriptional activation induced by the constitutively active TβRI. Three micrograms pH2Rneo (−Tax) or pH2R40M (+Tax) was transfected with 5 μg TβRI-WT or TβRI-T204D into HepG2 cells. Luciferase activity derived from the cotransfected p3TP-Lux reporter construct is depicted. Luciferase activity is presented as fold induction relative to the basal level measured in cells transfected with p3TP-Lux alone. (B) TGF-β–dependent induction of the ARE is inhibited by Tax. HepG2 cells were transfected with the ARE-Lux reporter construct (1 μg), FAST-1 (1 μg), Smad2 (2 μg), Smad4 (2 μg), and 3 μg of either pH2Rneo (−Tax) or pH2R40M (+Tax), as indicated. Cells were incubated in the absence or presence of 10 ng/mL TGF-β, and the luciferase activity was analyzed. Luciferase activity is presented as in Figures 1and 3, except that the control was based on untreated Smad2/4.