HIV-1 Vpr promotes nuclear entry of viral nucleic acids in nondividing macrophages and also causes a G2 cell-cycle arrest. Consistent with its role in nuclear transport, we show Vpr localizes to the nuclear envelope in both human and yeast cells. Like the importin-β subunit of the nuclear import receptor, Vpr also interacts with the yeast importin-α subunit and nucleoporins. Moreover, overexpression of either Vpr or importin-β in yeast blocks nuclear transport of mRNAs. A mutant form of Vpr (Vpr F34I) that does not localize at the nuclear envelope, or bind to importin-α and nucleoporins, renders HIV-1 incapable of infecting macrophages efficiently. Vpr F34I, however, still causes a G2 arrest, demonstrating that the dual functions of Vpr are genetically separable. Our data suggest Vpr functionally resembles importin-β in nuclear import of the HIV-1 pre-integration complex and this function is essential for the role of Vpr in macrophage infection, but not G2 arrest.
- Nuclear envelope