HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VIF PROTEIN BINDS TO THE PR55(GAG) PRECURSOR

The Vif protein of human immunodeficiency virus type 1 is required for productive replication in peripheral blood lymphocytes. Previous repo rts suggest that vif-deleted viruses are limited in replication becaus e of a defect in the late steps of the virus life cycle. One of the re maining questions is to determine whether the functional role of Vif i nvolves a specific interaction with virus core proteins. In this study , we demonstrate a direct interaction between Vif and the pr55(Gag) pr ecursor in vitro as well as in infected cells. No interaction is obser ved between Vif and the mature capsid protein. The pr55(Gag)-Vif inter action is detected (i) in the glutathione S-transferase system, with i n vitro-translated proteins demonstrating a critical role of the NC p7 domain of the Gag precursor; (ii) with proteins expressed in infected cells; and (iii) by coimmunoprecipitation experiments. Deletion of th e C-terminal 22 amino acids of Vif abolishes its interaction with the Pr55(Gag) precursor. Furthermore, point mutations in the C-terminal do main of Vif which have been previously shown to abolish virus infectiv ity and binding to cell membranes dramatically decrease the Gag-Vif in teraction. These results suggest that the interaction between Vif and the Pr55(Gag) precursor is a critical determinant of Vif function.