CHARACTERIZATION OF HIV-1 VPR NUCLEAR IMPORT - ANALYSIS OF SIGNALS AND PATHWAYS

While the Vpr protein of HIV-1 has been implicated in import of the vi ral preintegration complex across the nuclear pore complex (NPC) of no ndividing cellular hosts, the mechanism by which Vpr enters the nucleu s remains unknown. We now demonstrate that Vpr contains two discrete n uclear targeting signals that use two different import pathways, both of which are distinct from the classical nuclear localization signal ( NLS)- and the M9-dependent pathways. Vpr import does not appear to req uire Ran-mediated GTP hydrolysis and persists under conditions of low energy. Competition experiments further suggest that Vpr directly enga ges the NPC at two discrete sites. These sites appear to form distal c omponents of a common import pathway used by NLS- and M9-containing pr oteins. Together, our data suggest that Vpr bypasses many of the solub le receptors involved in import of cellular cargoes. Rather, this vira l protein appears to directly access the NPC, a property that may help to ensure the capacity of HIV to replicate in nondividing cellular ho sts.