Tax activates the caveolin-1 promoter. Effect of overexpression of Tax or HBZ on caveolin-1 promoter. Jurkat cells were transfected with increasing amounts of expression plasmid for HTLV-1 Tax (A) or HBZ (B) along with pGL2-cav1 (5 μg). Jurkat cells were transfected with either (C) pGL2-cav1 (5 μg), (D) κB-LUC (5 μg), or (E) LTR-LUC (5 μg) together with expression vector for HTLV-1 Tax (Tax WT), Tax M22, Tax 703, Tax SH-2, Tax Δ3, Tax 410, or empty vector (5 μg) alone or the combination of Tax M22 and Tax 703 with the use of electroporation. Cells were harvested 24 hours after transfection, and luciferase activity was measured with a luminometer. The results are expressed as fold induction by Tax, HBZ, or Tax mutants relative to the vector alone. Data are mean ± SD of 3 independent transfection experiments. (E) Western blot analysis showing the expression of Tax in Jurkat cells transfected with expression plasmid for Tax WT or mutants (bottom). (F) Subcellular localization of Tax mutants by immunofluorescence. Phase-contrast (right) and corresponding immunofluorescence (Hoechst 33342 and Tax) photomicrographs of fixed transfected Jurkat cells are presented.