HIV-1 Vpr transactivates LTR-directed expression through sequences presentwithin-278 to-176 and increases virus replication in vitro

Human immunodeficiency virus type 1 (HIV-1) Vpr, a 14-kDa virion-associated protein, plays an important role in the viral life cycle. Using a panel of truncated HIV-1 LTR-CAT constructs and Vpr expression plasmid, we have ide ntified sequences from nucleotide -278 to -176 in LTR as Vpr-mediated trans activation domain. This region includes the glucocorticoid response element (GRE) in HIV-1 LTR. Transactivation by Vpr was noted with the HIV-1 LTR re porter constructs containing CAT or luciferase. A similar effect was also o bserved with a construct in which the GRE motif was linked to CAT. Studies involving Vpr mutants identified that helical domains I and III, and amino acid residues at G75 and C76, are responsible for GRE-mediated LTR transact ivation. The transactivation function of Vpr is independent of its cell cyc le arrest activity, Further, viral replication studies indicated that Vpr-m ediated increase in viral replication is directly correlated with the abili ty of Vpr to transactivate HIV-1 LTR. The results presented here demonstrat e that Vpr activates HIV-1 LTR through the host GR pathway and suggest that an intact GRE in the LTR is critical for Vpr activity. (C) 2001 Academic P ress.