SUBCELLULAR-LOCALIZATION OF THE VIF PROTEIN OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

The Vif (viral infectivity factor) protein of human immunodeficiency v irus type 1 (HIV-1) has been shown to dramatically enhance the infecti vity of HIV-1 virus particles during virus production. The subcellular localization of Vif was examined to elucidate cellular pathways which may be important far Vif function. Indirect immunofluorescence staini ng of Vif demonstrated a diffuse cytoplasmic distribution and showed t hat most Vif was not associated with the Golgi complex, a proposed sit e of localization (B. Guy, M. Geist, K. Dott, D. Spehner, M.-P. Kieny, and J.-P. Lecocq, J. Virol. 65:1325-1331, 1991). Subcellular fraction ation of transfected COS cells and HIV-1-infected Jurkat and CEM cells demonstrated that Vif is a cytoplasmic protein which exists in both a soluble cytosolic form and membrane-associated form. The membrane-ass ociated form of Vif is a peripheral membrane protein which is tightly associated with the cytoplasmic side of cellular membranes. The C term inus of Vif was required for the stable association of Vif with membra nes. The C terminus was also essential for Vif function, suggesting th at the association of Vif with membranes is likely to be important for its biological activity. The highly conserved regions at residues 103 to 115 and 142 to 150 were important for Vif function but did not aff ect membrane association, indicating that these regions are likely to be important for other, as-yet-unknown functions.