ACTIVATION OF HIV TYPE-1 LONG TERMINAL REPEAT BY ULTRAVIOLET-LIGHT ISSERUM AND STRAIN-SPECIFIC

We have studied the UV responsiveness of xeroderma pigmentosum (XP) an d HeLa cell lines transfected with a CAT reporter gene under the contr ol of the HIV-1 LTR promoter. XP fibroblasts grown in 10% newborn bovi ne serum (NBS) were three times more responsive to UV radiation than c ells grown in 10% fetal calf serum (FCS). Moreover, cocultivation of U V-irradiated XP cells with XP cells containing stable integrants of HI V-LTR CAT was found to be more than four times more effective in induc ing the CAT activity when cells were maintained in 10% NBS than in 10% FCS. The level of induction was also dependent on the serum concentra tion. These data indicate that a serum component, possibly a cytokine( s), can enhance the UV response of both irradiated cells and unirradia ted cells cocultivated with irradiated cells. The magnitude of UV resp onsiveness seemed also to be strain dependent. CAT activity for the HI V LTR promoter from the HTLV-IIIB (HN-IIIB) strain was induced more th an 30-fold by UV irradiation whereas activity from the LAV-1(BRU) Stra in was less than 2-fold. In contrast, both constructs were strongly in duced by Tat expression. This indicates that there are differences in the induction mechanism for these two stimuli, even though UV radiatio n has been pre- viously reported to induce a cellular Tat-like factor (Valerie K, et al., Nature [London] 1988;333:78-81).