A. The region deleted in each HTLV-I LTR mutant, with respect to the wild type (CR-CAT) is illustrated schematically. Basal and Tax-trans-activated promoter activity for each mutant is shown compared to the wild type. Absolute CAT acetylation values are given. B. The activities of the wild type HTLV-I LTR and the deletion mutant HTLV-I LTRs in the presence and absence of rapamycin are illustrated. CAT acetylation values are given as the percentage of the rapamycin-negative control for each construct. Mean values of three independent assays are illustrated ± SEM.