Two nuclear localization signals in the HIV-1 matrix protein regulate nuclear import of the HIV-1 pre-integration complex

Replication of HIV-1 in non-dividing and slowly proliferating cell populati ons depends on active import of the viral pre-integration complex (PIC) int o the cell nucleus. While it is commonly accepted that this :process is med iated by an interaction between the HIV-1 PIC and the cellular nuclear impo rt machinery, controversial results have been reported concerning the mecha nisms of this interaction. Here, we demonstrate that a recently identified nuclear localization signal within the HIV-1 matrix protein (MA), MA NLS-2, together with previously described MA NLS-1, mediates nuclear import of th e HIV-1 PEG. Inactivation of both MA NLSs precluded nuclear translocation o f MA and rendered the virus defective in nuclear import and replication in non-dividing macrophage cultures, even when functional Vpr and integrase (I N), two more viral proteins implicated in HIV-1 nuclear import, were presen t. Taken together, these results indicate that Vpr does not function as an independent nuclear import factor and demonstrate that HIV-1 MA, by virtue of its two nuclear localization signals, regulates HIV-1 nuclear import. (C) 2000 Academic Press.