Like other enveloped viruses, HIV-1 uses cellular machinery to bud from infected cells. We now show that Tsg101 protein, which functions in vacuolar protein sorting (Vps), is required for HIV-1 ...budding. The UEV domain of Tsg101 binds to an essential tetrapeptide (PTAP) motif within the p6 domain of the structural Gag protein and also to ubiquitin. Depletion of cellular Tsg101 by small interfering RNA arrests HIV-1 budding at a late stage, and budding is rescued by reintroduction of Tsg101. Dominant negative mutant Vps4 proteins that inhibit vacuolar protein sorting also arrest HIV-1 and MLV budding. These observations suggest that retroviruses bud by appropriating cellular machinery normally used in the Vps pathway to form multivesicular bodies.
The carboxyl-terminal domain, residues 146 to 231, of the human immunodeficiency virus-1 (HIV-1) capsid protein CA(146-231) is required for capsid dimerization and viral assembly. This domain ...contains a stretch of 20 residues, called the major homology region (MHR), which is conserved across retroviruses and is essential for viral assembly, maturation, and infectivity. The crystal structures of CA(146-231) and CA(151-231) reveal that the globular domain is composed of four helices and an extended amino-terminal strand. CA(146-231) dimerizes through parallel packing of helix 2 across a dyad. The MHR is distinct from the dimer interface and instead forms an intricate hydrogen-bonding network that interconnects strand 1 and helices 1 and 2. Alignment of the CA(146-231) dimer with the crystal structure of the capsid amino-terminal domain provides a model for the intact protein and extends models for assembly of the central conical core of HIV-1.
The Protein Network of HIV Budding von Schwedler, Uta K.; Stuchell, Melissa; Müller, Barbara ...
Cell,
09/2003, Letnik:
114, Številka:
6
Journal Article
Recenzirano
Odprti dostop
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 p6
Gag and EIAV p9
Gag 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.
After budding, the human immunodeficiency virus (HIV) must ‘mature’ into an infectious viral particle. Viral maturation requires proteolytic processing of the Gag polyprotein at the matrix–capsid ...junction, which liberates the capsid (CA) domain to condense from the spherical protein coat of the immature virus into the conical core of the mature virus. We propose that upon proteolysis, the amino‐terminal end of the capsid refolds into a β‐hairpin/helix structure that is stabilized by formation of a salt bridge between the processed amino‐terminus (Pro1) and a highly conserved aspartate residue (Asp51). The refolded amino‐terminus then creates a new CA–CA interface that is essential for assembling the condensed conical core. Consistent with this model, we found that recombinant capsid proteins with as few as four matrix residues fused to their amino‐termini formed spheres in vitro, but that removing these residues refolded the capsid amino‐terminus and redirected protein assembly from spheres to cylinders. Moreover, point mutations throughout the putative CA–CA interface blocked capsid assembly in vitro, core assembly in vivo and viral infectivity. Disruption of the conserved amino‐terminal capsid salt bridge also abolished the infectivity of Moloney murine leukemia viral particles, suggesting that lenti‐ and oncoviruses mature via analogous pathways.
Background: Classical hormone replacement therapy for hot flashes is contraindicated in breast cancer especially in endocrine responsive disease. Patients and methods: In a double-blind, randomized ...phase III study, breast cancer patients suffering from hot flashes at least twice a day, who were not taking any medication against hypertension and depression received either clonidine 0.075 mg twice a day or venlafaxine 37.5 mg twice a day for 4 weeks. The primary end point was defined as the frequency of hot flashes after 4 weeks of treatment. A self-reported 1-week hot flash and other symptom questionnaire were kept before the start of treatment until the end of treatment course. Results: From April 2002 to October 2004, 80 patients were recruited of whom 64 were assessable for efficacy analyses. Thirty-three received clonidine and 31 venlafaxine, nine patients stopped early because of side-effects and seven withdrew consent. At the end of treatment week 4, the median hot flash frequency dropped by 7.6 hot flashes per day for patients receiving venlafaxine and 4.85 hot flashes per day for those receiving clonidine (P = 0.025). Conclusion: Venlafaxine is significantly more effective in reducing the frequency of hot flashes in breast cancer patients than clonidine.
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