Ultraviolet radiation increases HIV-long terminal repeat-directed expression in transgenic mice.

Previously described FVB/N mice harboring a human immunodeficiency virus (HIV) long terminal repeat (LTR)/chloramphenicol acetyl transferase (CAT) transgene were treated with varying amounts of 254 nm UV-C radiation or 312 nm UV-B radiation. At optimal exposure periods, a 20-fold increase in HIV-LTR-directed expression was observed in ear specimens collected 24 h following UV-C exposure; a fourfold increase in expression was induced by UV-B exposure. Investigation of the kinetics of UV-C induction in vivo revealed that LTR-directed gene expression began to increase 2 hours after exposure and reached a maximum on Day 3 following exposure (greater than 30-fold induction). In experiments examining the kinetics of UV-B activation, the maximum level of CAT activity in the ears of irradiated transgenic animals was fivefold above levels in unirradiated transgenic controls (Day 5). Furthermore, CAT activity was not induced in fur-bearing skin following UV exposure; however, a fourfold increase in HIV-LTR-directed expression could be elicited when hair was removed by shaving prior to UV-B treatment.