Plasma membrane rafts play a critical role in HIV-1 assembly and release

HIV-1 particle production occurs in a series of steps promoted by the viral Gag protein. Although it is well established that assembly and release tak e place at the plasma membrane, the nature of membrane assembly sites remai ns poorly understood. We show here that Gag specifically associates with ch olesterol-enriched microdomains ("rafts") at the plasma membrane. Kinetic s tudies demonstrate that raft association follows membrane binding, and the analysis of Gag mutants reveals that, whereas the N terminus of Gag mediate s raft binding, this association is greatly enhanced by Gag-Gag interaction domains. We observe that depletion of cellular cholesterol markedly and sp ecifically reduces HIV-1 particle production. Furthermore, treatment of vir us-producing cells or virus particles with raft-disrupting agents significa ntly impairs virus infectivity. These results identify the association of G ag with plasma membrane rafts as an important step in HIV-1 replication. Th ese findings may lead to novel strategies for suppressing HIV-1 replication in vivo.