Mutation of the Tax affects the Tax-mediated repression of the transactivation functions of Smad3.

(A) HepG2 cells were cotransfected with 10 ng HTLV-I LTR-LUC, 100 ng κB-LUC, or 100 ng p3TP-Lux reporter plasmids, together with 100 ng Smad3 expression plasmid, or 3 μg plasmid expressing wild-type Tax—pβMT-2Tax (WT), a mutant Tax, pβTax (703), or pβTax (M22). The luciferase assay was performed 24 hours later. (B) CBP/p300-binding domain in Tax is essential for the Tax-mediated repression of Smad3 transactivation functions. HepG2 cells were cotransfected, as in Figure6, panel A. All transfections were equalized for total DNA by addition of the empty vector. Luciferase activity is presented as fold induction relative to the basal level measured in cells transfected with the reporter plasmid alone. Data represent the mean ± SD from 3 separate experiments.