Activation of HIV-1 enhancer sequence by vaccinia virus

To investigate whether vaccinia virus (VV) can augment gene expression of h uman immunodeficiency virus type 1 (HIV-l), co-transfection experiments wer e carried out in which recombinant plasmids containing various portions of the HIV-1 long terminal repeat (LTR) linked to the chloramphenicol acetyltr ansferase (CAT) gene were transfected into cultured cells. A high level of enhancement in CAT activity directed by the HIV-I LTRs containing the enhan cer sequence was observed in cells infected with VV, as in the cells infect ed with type 1 herpes simplex virus (HSV-1). The sequence responsible for t his augmentation of CAT activity was different from that recognized by HIV- 1 Tat. These data clearly demonstrated that VV transactivates HIV-1 LTR thr ough a mechanism distinct from that of activation by HIV-1 Tat.