NFAT1 enhances HIV-1 gene expression in primary human CD4 T cells

Cyclosporin A (CsA) is a potent inhibitor of the NFAT family of transcripti on factors that enhance T cell activation, The observation that human immun odeficiency virus type 1 (HIV-1)-positive transplant recipients have a redu ced HIV-1 viral burden during treatment with CsA suggested that NFAT may pl ay a direct role in enhancing transcription of the HIV-1 viral genome, Two sets of NFAT binding sites were identified in the HIV-1 long terminal repea t (LTR) promoter by in vitro footprinting with full-length recombinant NFAT protein, and gel shift analysis of nuclear protein from polyclonally activ ated primary CD4 T cells revealed specific binding of NFAT1 to the NF kappa B binding sites of the HIV-1 LTR, Activation of primary CD4 T cells transi ently transfected with a HIV-1 LTR luciferase reporter plasmid, lacking the NFAT binding sites in the upstream putative negative regulatory element bu t maintaining the NF kappa B/NFAT sites, demonstrated increased HIV-1 gene expression when cotransfected with a NFAT1 expression vector. Moreover, CsA , FK506, and a dominant-negative NFAT1 protein independently inhibited HIV- 1 LTR promoter activity in CD4 T cells stimulated with phorbol ester and ca lcium ionophore, In primary human CD4 T cells, CsA also inhibited promoter activity directed by multimers of binding sites for NFAT, while having no e ffect on NF kappa B multimer-driven promoter activity, Increasing NFAT1 lev els in CD4 T cells transiently transfected with a HIV-1 provirus also incre ased p24 protein expression. Thus, NFAT may be a target for prevention of H IV-1 LTR-directed gene expression in human CD4 T cells. (C) 2000 Academic P ress.