DOWN-MODULATION OF HIV-1 LTR ACTIVITY BY AN EXTRA-LTR NEF GENE FRAGMENT

The objective of this study was to assess the inhibitory effect of pot ential negative regulatory elements on human immunodeficiency virus (H IV)-1 long terminal repeat (LTR) activity. This was carried out by pai rwise comparisons of reporter gene activities of HIV-LTR-CAT construct s differing in the presence and absence of nef sequences in transient transfection assays. Parallel transfections were performed in two pers istently HIV-infected cell lines and the uninfected parental cell line s. The negative regulatory element (NRE) of the LTR did not suppress H IV LTR activity in any of the cell lines examined. However, a non-LTR- derived fragment of the nef gene had a distinct suppressive effect on activity of the full-length LTR in chronically infected astrocytoma ce lls. A weaker negative effect of this nef partial sequence (nps) was d etected in the other cell lines with constructs lacking the NRE. The n ps was capable of suppressing LTR activity in trans in chronically inf ected astrocytoma cells in a concentration-dependent manner. These res ults stress a negative role of a non-LTR nef partial sequence in a cel l-specific manner. In addition, our data indicate that nps functions i n trans with promoters unrelated to HIV LTR such as SV40 early and CMV immediate-early promoters. (C) 1996 Academic Press, Inc.