The model suggests how three different early-acting ESCRT-associated factors recruited by HIV-1 Gag -- NEDD4L (pink), ESCRT-I (red) and dimeric ALIX (dark blue) -- could work together in a stepwise fashion to facilitate virus budding. The three regions of HIV-1 Gag are depicted in yellow (MA), orange (CA) and red (NC, bound to blue RNA), the subunits of the trimeric viral Env protein are depicted in blue (SU/gp120) and pink (TM/gp41), and ESCRT-III proteins (light green) are depicted schematically as either polymeric filaments (central panel, light green ring) or soluble, autoinhibited subunits (right panel, discrete subunits). ESCRT-I is missing from the final panel because the ultimate fate of this complex is not yet clear.