Background:  HIV-1 budding requires a membrane fission event to release the nascent virion. This membrane fission event is promoted by the p6 domain of Gag, which recruits Tsg101, a component of the class E vacuolar protein sorting (Vps) machinery.  We find that HIV-1 p6 contains a second region involved in budding that interacts with the class E Vps protein AIP1.

Methods:  We used protein microsequencing, GST pull-down, yeast 2-hybrid, and co-immunoprecipitation assays to identify AIP1 as a host protein that interacts with HIV-1 and SIV p6, as well as with other class E Vps proteins.

Results:  AIP1 interacts with a conserved C-terminal region of HIV-1 p6 that is critical for viral budding in a minimal Gag context. AIP1 also interacts with Tsg101 and with components of ESCRT-III, a complex required for the budding of cellular vesicles into late endosomes. Dominant-negative versions of AIP1 and of ESCRT-III components potently arrest HIV-1 budding at the cell surface. Our results also indicate that the ESCRT machinery is tightly regulated via autoinhibitory interactions.

Conclusions:  Our results identify AIP1 as a component of the HIV-1 budding machinery that couples HIV-1 p6 to the late-acting endosomal sorting complex ESCRT-III.

Keywords: Assembly; Gag; Host factors