A peptide derived from the N-terminal region of HIV-1 Vpr promotes nuclear import in permeabilized cells: Elucidation of the NLS region of the Vpr

Viral protein r (Vpr), a HIV-1 auxiliary protein which mediates nuclear import of the viral preintegration complex (PIC), contains two regions, N- and C-terminal, which have been proposed to function as a nuclear localization signal (NLS). We have synthesized peptides corresponding to both regions (designated as VprN and VprC), conjugated them to bovine serum albumin (BSA), and tested their ability to mediate nuclear import in permeabilized cells. Only VprN, and not VprC, functioned as an active NLS and promoted translocation of the conjugate into nuclei. Nuclear import of the conjugate was found to be energy and temperature dependent and was inhibited by wheat germ agglutinin (WGA). However, it did not require the addition of cytosolic factors and was not inhibited by the prototypic SV40 large T- antigen NLS peptide. Our results show that Vpr harbours a non-conventional negatively charged NLS and therefore suggest that Vpr may use a distinct nuclear import pathway.