Cell, Vol 114, 701-713, 19 September 2003

The Protein Network of HIV Budding
Uta K. von Schwedler 1, Melissa Stuchell 1, Barbara Müller 3, Diane M. Ward 2, Hyo-Young Chung 1, Eiji Morita 1, Hubert E. Wang 4, Thaylon Davis 4, Gong-Ping He 4, Daniel M. Cimbora 4, Anna Scott 1, Hans-Georg Kräusslich 3, Jerry Kaplan 2, Scott G. Morham 4, and Wesley I. Sundquist *1

HIV release requires TSG101, a cellular factor that sorts proteins into vesicles that bud into multivesicular bodies (MVB). To test whether other proteins involved in MVB biogenesis (the class E proteins) also participate in HIV release, we identified 22 candidate human class E proteins. These proteins were connected into a coherent network by 43 different protein-protein interactions, with AIP1 playing a key role in linking complexes that act early (TSG101/ESCRT-I) and late (CHMP4/ESCRT-III) in the pathway. AIP1 also binds the HIV-1 p6Gag and EIAV p9Gag proteins, indicating that it can function directly in virus budding. Human class E proteins were found in HIV-1 particles, and dominant-negative mutants of late-acting human class E proteins arrested HIV-1 budding through plasmal and endosomal membranes. These studies define a protein network required for human MVB biogenesis and indicate that the entire network participates in the release of HIV and probably many other viruses.

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Cell, Vol 114, 689-699, 19 September 2003

AIP1/ALIX Is a Binding Partner for HIV-1 p6 and EIAV p9 Functioning in Virus Budding
Bettina Strack , Arianna Calistri , Stewart Craig , Elena Popova , and Heinrich G. Göttlinger *

HIV-1 and other retroviruses exit infected cells by budding from the plasma membrane, a process requiring membrane fission. The primary late assembly (L) domain in the p6 region of HIV-1 Gag mediates the detachment of the virion by recruiting host Tsg101, a component of the class E vacuolar protein sorting (Vps) machinery. We now show that HIV Gag p6 contains a second region involved in L domain function that binds AIP1, a homolog of the yeast class E Vps protein Bro1. Further, AIP1 interacts with Tsg101 and homologs of a subunit of the yeast class E Vps protein complex ESCRT-III. AIP1 also binds to the L domain in EIAV p9, and this binding correlates perfectly with L domain function. These observations identify AIP1 as a component of the viral budding machinery, which serves to link a distinct region in the L domain of HIV-1 p6 and EIAV p9 to ESCRT-III.

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