The HIV-1 assembly and release pathway.  Virus particle production takes place as a series of steps driven by the Gag precursor protein, Pr55Gag.  Gag rapidly and specifically targets raft-rich regions of the plasma membrane.  Gag multimerization proceeds at the membrane, giving rise to budding structures that eventually pinch off from the cell surface as nascent virions.  The viral Env glycoproteins are incorporated during the budding process.  Virus release requires the host factor TSG101 and other components of the cellular endosomal sorting pathway.  Insets show by electron microscopy the inhibition of virus release upon coexpression of HIV-1 with a transdominant form of TSG101 (left inset; note the particles tethered to the plasma membrane) and wild-type virions released from the cell surface (right inset).