(A) HTLV-I–infected T-cell lines express a constitutive NF-κB–related activity. Various cell lines were transfected with 10 μg of a reporter plasmid containing the luciferase gene fused to five repeats of the κB motif of the IL-2R gene and enhancerless promoter of HTLV-I (κB-LUC). After 24 hours of incubation, lysates were prepared and assayed for luciferase activity. Ratio of luciferase activity in extracts of κB-LUC–transfected cells is expressed to that for dN-LUC–transfected cells. The results represent the mean of three experiments. (B) Northern blot analysis of Tax in various cell lines. Total RNA (20 μg of each) was isolated from various cell lines. Jurkat, MOLT-4, and H-9 are HTLV-I–uninfected T-cell lines. MT-2, HUT-102, SLB-1, TL-Om1, and C5/MJ are HTLV-I–infected T-cell lines. Blots were sequentially hybridized, exposed, stripped, and rehybridized with Tax and GAPDH probes.