INTERACTION OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VPR PROTEIN WITH THE NUCLEAR-PORE COMPLEX

The Vpr protein of human immunodeficiency virus type 1 (HIV-1) perform s a number of functions that are associated with the nucleus. Vpr enha nces the nuclear import of postentry viral nucleoprotein complexes, ar rests proliferating cells in the G(2) phase of the cell cycle, and act s as a modest transcriptional activator. For this paper, we have inves tigated the nuclear import of Vpr, Although Vpr does not encode a sequ ence that is recognizable as a nuclear localization signal (NLS), Vpr functions as a transferable NLS both in somatic cells and in Xenopus l aevis oocytes. In certain contexts, Vpr also mediates substantial accu mulation at the nuclear envelope and, in particular, at nuclear pore c omplexes (NPCs), Consistent with this, Vpr is shown to interact specif ically with nucleoporin phenylalanine-glycine (FG)-repeat regions. The se findings not only demonstrate that Vpr harbors a bona fide NLS but also raise the possibility that one (or more) o: Vpr's functions may t ake place at the NPC.