EFFECTS OF GAMMA-RAYS, ULTRAVIOLET-RADIATION, SUNLIGHT, MICROWAVES AND ELECTROMAGNETIC-FIELDS ON GENE-EXPRESSION MEDIATED BY HUMAN-IMMUNODEFICIENCY-VIRUS PROMOTER

Previous work by our group and others has shown the modulation of huma n immunodeficiency virus (HIV) promoter or long terminal repeat (LTR) after exposure to neutrons and ultraviolet radiations. Using HeLa cell s stably transfected with a construct containing the chloramphenicol a cetyl transferase (CAT) gene, the transcription of which is mediated b y the HIV-LTR, we designed experiments to examine the effects of expos ure to different types of radiation (such as gamma rays, ultraviolet a nd sunlight irradiations, electromagnetic fields and microwaves) on HI V-LTR-driven expression of CAT. These results demonstrated ultraviolet -light-induced transcription from the HIV promoter, as has been shown by others. Exposure to other DNA-damaging agents such as gamma rays an d sunlight (with limited exposures) had no significant effect on trans cription mediated by HIV-LTR, suggesting that induction of HIV is not mediated by just any type of DNA damage but rather may require specifi c types of DNA damage. Microwaves did not cause cell killing when cell s in culture were exposed in high volumes of medium, and the same cell s showed no changes in expression. When microwave exposure was carried out in low volumes of medium (so that excessive heat was generated) i nduction of HIV-LTR transcription (as assayed by CAT activity) was evi dent. Electromagnetic field exposures had no effect on expression of H IV-LTR. These results demonstrate that not all types of radiation and not all DNA-damaging agents are capable of inducing HIV. We hypothesiz e that induction of HIV transcription may be mediated by several diffe rent signals after exposure to radiation.