Objective:Because of the important medical consequences of human cytomegalovirus (HCMV) infection in human immunodeficiency virus (HIV)-infected individuals, we wanted to understand the molecular interactions that occur during coinfection. Specifically, in this study, we wanted to identify the transactivating target sequences on the HIV long terminal repeat (LTR) that responded to HCMV infection.Study Design/Methods:In this study, we transfected the HIV-LTR into human fibroblasts and then mapped the regulation of this promoter following HCMV infection and cotransfection with the HCMV immediate-early (IE) gene product IE2-86. In addition, we examined IE2-86 binding to specific sequences in the HIV-LTR by electrophoretic mobility shift assay.Results:Our results documented that HCMV and IE2-86 could transactivate the HIV-LTR. In mapping the regions of the HIV-LTR that IE2-86 transactivates, we identified discrete target sequences between -120 and -20 that are the major transactivating regions for the IE2-86-mediated effects and determined that IE2-86 could specifically bind to several discrete sequences within this region of the HIV-LTR.Conclusions:Our discovery of the binding of IE2-86 to the HIV-LTR, coupled with its ability to transactivate the HIV-LTR and induce cellular transcription factors, points to potential molecular mechanisms used by HCMV to upregulate the HIV life cycle and, consequently, exacerbate the conditions observed in individuals co-infected with HCMV and HIV.Journal of Human Virology 1999;2:81-90 © Lippincott Williams & Wilkins, Inc.