Cellular distribution and karyophilic properties of matrix, integrase, andVpr proteins from the human and simian immunodeficiency viruses

Infections by human and simian immunodeficiency viruses (HIV and SIV) are i ndependent of host cell division since the preintegration complex (P1C), co ntaining the viral DNA, is able to undergo active nuclear import after vira l entry. In order to clarify the mechanisms responsible for nuclear import of the PIG, we have analyzed the subcellular distribution and the karyophil ic properties of its viral components, matrix protein (MA), integrase (IN), Vpr, and Vpx, Although MA has been reported to contain a nuclear localizat ion signal, the MA/GFP fusions are excluded from the nucleus and associated with cellular membranes. In contrast, both HIV-1 and SIV IN and Vpr locali ze in the nucleus of transfected cells. Interestingly, only Vpx from SIVsm virus accumulate in the nucleus while SIVsm Vpr is uniformly distributed th roughout nucleus and cytoplasm, Coexpression of MA, Vpr, and IN does not in duce any change in their respective intracellular localizations. Finally, w e confirm the karyophilic properties of HIV-1 IN and Vpr using an in vitro nuclear import assay. These results indicate that the viral proteins IN and Vpr, which are strongly associated with the viral DNA within PIG, may part icipate in the nuclear import of the HIV PIC. (C) 2000 Academic Press.