Effect of p53 on HTLV-I promoter in cells containing Tax protein. Jurkat-Tax and MT-2 cells were transfected with HTLV-I LTR CAT reporter construct (5 μg), together with increasing amounts of an expression vector encoding wild-type p53 as indicated. In all cases, the total amount of DNA transfected was maintained at 15 μg by addition of control plasmid (pCMV-NeoBam). Values for CAT activity are expressed as a percentage of levels seen in the absence of p53. Data are the mean ± SEM for 3 independent transfections.