Lysine residues 280 and 284 regulate UV-induced Tax localization. (A) Wild-type Tax or Tax mutants were transiently expressed in 293 cells. Localization of Tax mutants in the absence (black bars) or presence of 30 J/m2 UV irradiation (gray bars) is shown. Error bars represent the standard error in three independent experiments. (B) Western blot showing expression of each Tax mutant analyzed.