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Journal of Virology, November 2003, p. 12373-12377, Vol. 77, No. 22
0022-538X/03/$08.00+0     DOI: 10.1128/JVI.77.22.12373-12377.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

A Bipartite Late-Budding Domain in Human Immunodeficiency Virus Type 1

Juan Martin-Serrano and Paul D. Bieniasz*

Aaron Diamond AIDS Research Center and the Rockefeller University, New York, New York

Received 9 May 2003/ Accepted 7 August 2003


   ABSTRACT
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Human immunodeficiency virus type 1 (HIV-1) encodes a PTAP motif within the p6 domain of Gag that recruits Tsg101 and associated factors to facilitate virion budding. In this study, we use trans-complementation assays to demonstrate that the PTAP motif acts synergistically with additional p6 sequences to mediate the formation of infectious extracellular HIV-1 virions. These studies suggest that Tsg101 recruitment is necessary but not sufficient to account for late-budding activity exhibited by HIV-1 p6.


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All retroviruses and some otherwise unrelated rhabdo- and filoviruses encode a so-called late-budding domain or "L-domain" whose disruption results in a specific defect in particle release (4, 9-13, 27, 28). Viral L-domains fall into three classes, based on the presence of characteristic PT/SAP, PPXY, or YPDL sequence motifs. In several cases, viral L-domains are functionally interchangeable, can exert their activity when positioned at different locations within a retroviral Gag protein, and can function in trans (4, 17, 20, 29). These observations strongly suggest that L-domains act by recruiting host cell factors to facilitate egress, rather than directly influencing virion morphogenesis. In fact, a variety of findings indicate that the human immunodeficiency virus type 1 (HIV-1) and Ebola virus PTAP-type L-domains act by recruiting Tsg101 (5, 8, 17, 18, 26), a component of "endosomal sorting complex required for transport-I" (ESCRT-I) that normally functions in the budding of vesicles into the endosomal lumen (14). Specifically, there is an almost perfect correlation between the abilities of HIV-1 p6 mutants to bind Tsg101 and to mediate virion production (8, 17, 26). In addition, depletion of Tsg101 with small interfering RNA results in an HIV-1 budding defect that recapitulates the phenotype of a PTAP-defective virus (8). Moreover, expression of HIV-1 Gag or Ebola virus VP40 results in PTAP-dependent recruitment of Tsg101 and VPS28, another ESCRT-I component, to sites of particle assembly at the plasma membrane (17, 18).

We have previously described constructs and assays that demonstrated that artificial tethering of Tsg101 to sites of HIV-1 particle assembly, by fusion to Gag, reverses the HIV-1 budding defect that results from mutational inactivation of the PTAP L-domain (17, 18). This type of assay is represented schematically in Fig. 1A and employs a Gag precursor protein lacking the p6 domain (Gag{delta}p6) that encodes a synthetic linker at its C terminus. Candidate L-domains or Tsg101 is fused to this truncated Gag protein and is expressed with an L-domain-defective proviral plasmid. Because HIV-1 Gag efficiently multimerizes at the plasma membrane (16, 25), expression of a Gag{delta}p6 protein that is fused to functional L-domain or is directly fused to Tsg101 can functionally complement a PTAP-defective proviral construct, resulting in infectious virion production (17, 18). A result from this type of assay is shown in Fig. 1B. For this experiment, 5 x 104 HOS cells seeded in 24-well plates were cotransfected with 300 ng of a PTAP-defective HIV-1 proviral construct (pNL[LTAL]) (17) and 200 ng of a pGag{delta}p6-Tsg101 expression plasmid by using Lipofectamine Plus, according to the manufacturer's instructions. Infectious virus production was measured by inoculating P4-R5 cells, with clarified supernatant from the transfected HOS cells. ß-Galactosidase expression resulting from activation of the integrated HIV-1 long terminal repeat-lacZ indicator gene in P4-R5 cells was measured 48 h later, as previously described (3, 17). As can be seen in Fig. 1B, coexpression of Gag{delta}p6-Tsg101 resulted in an enhancement of NL(LTAL) infectious virion production by 10- to 15-fold. Conversely, in an almost identical experiment also shown in Fig. 1B, but in which the HIV-1 provirus was rendered defective by the introduction of a translational termination codon in place of the N-terminal p6 codon (NL{delta}p6), the Gag{delta}p6-Tsg101 fusion protein was, surprisingly, unable to restore infectious virion production.



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  		FIG. 1. Tsg101 recruitment is not sufficient to account for the L-domain activity exhibited by HIV-1 p6. (A) The complementation assay. A schematic representation of the complementing Gag{delta}p6 protein is shown. It contains MA, CA, and NC domains and the N-terminal 4 residues of p6 (LQSR) to permit cleavage by the HIV-1 protease. The synthetic linker sequence (LEFGGRLE) also encodes EcoRI, NotI, and XhoI restriction sites (underlined) for reinsertion of full-length or truncated versions of p6, the PTAP sequence, or Tsg101. For the assay itself, Gag-Pol and mutant Gag proteins are expressed by the defective proviral construct and are depicted in black; the complementing fusion protein, in this case Gag{delta}p6-Tsg101, is shown in white. Tsg101 is recruited to sites of virion production by virtue of Gag multimerization. (B) Infectious virus production by defective provirus (NL[LTAL], black bars; or NL{delta}p6, white bars) complemented by Gag{delta}p6-Tsg101. The chart shows ß-galactosidase activity in HeLa P4/R5 cells following inoculation with supernatant harvested from HOS cells transfected with defective provirus constructs and the indicated complementing expression plasmid. RLU, relative light units. (C) Same information as that given for panel B applies, except that only the pNL{delta}p6 proviral plasmid was used, complemented with either pGag{delta}p6-p6 or pGag{delta}p6-Tsg101, as indicated. (D) Western blot analysis, with an anti-CA monoclonal antibody, of cell lysates and virion pellets following transfection of HOS cells with the pNL{delta}p6 provirus plus either pGag{delta}p6 (lane 1), pGag{delta}p6-p6 (lane 2), or pGag{delta}p6-Tsg101 (lane 3).

 
As is shown in Fig. 1C, the inability of Gag{delta}p6-Tsg101 to complement NL{delta}p6 was not due to any cis-acting defect in the NL{delta}p6 provirus. Indeed, this defective virus was efficiently complemented in trans by coexpression of a Gag{delta}p6-p6 fusion protein. Moreover, as shown in Fig. 1D, the overall particle release and cell-associated Gag processing defect exhibited by NL{delta}p6, which are characteristic of L-domain defective HIV-1 constructs, were reversed by coexpression of Gag{delta}p6-p6 but not by coexpression of Gag{delta}p6-Tsg101. In contrast, we have previously shown that similar defects induced by point mutations in the PTAP motif could be reversed by Gag{delta}p6-Tsg101 coexpression (17, 18). Thus, these results indicate that recruitment of Tsg101 is sufficient to account for the activity exhibited by the HIV-1 PTAP motif but does not account for the entire effect on virion morphogenesis that is exerted by HIV-1 p6.

To test whether p6 sequences outside the PTAP motif could exhibit L-domain activity, either alone or in conjunction with PTAP, we again used a complementation approach. This strategy, shown schematically in Fig. 2A, was elaborated to include two complementing Gag{delta}p6-fusion proteins, coexpressed with the defective pNL{delta}p6 proviral construct. First, we compared the ability of a 10-residue HIV-1 p6-derived peptide containing the PTAP motif (P5EPTAPPEES14) versus the entire p6 domain to function in trans in the context of a Gag{delta}p6-fusion protein to restore infectious virion production by NL{delta}p6. For these experiments, 5 x 104 293T cells seeded in 24-well plates were cotransfected with 300 ng of NL{delta}p6 along with 100 ng of pGag{delta}p6 and 100 ng of either pGag{delta}p6-p6, pGag{delta}p6-PTAP, or pGag{delta}p6-p6 (15-51) expression plasmids by using Lipofectamine Plus. Analysis of infectious virion production revealed that the intact p6 domain functioned substantially more efficiently than did the PTAP-containing peptide sequence. Indeed, as shown in Fig. 2B, expression of Gag{delta}p6-p6 increased infectious virion production by NL{delta}p6 approximately 270-fold. In contrast, Gag{delta}p6-PTAP was less than 10% as active as Gag{delta}p6-p6 and enhanced infectious virion formation by only 24-fold.



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  		FIG. 2. The PTAP motif and additional p6 sequences can act synergistically and in trans to mediate infectious HIV-1 virion production. (A) Schematic representation of the complementation assay. Gag-Pol and Gag{delta}p6 proteins expressed by the defective proviral construct (NL{delta}p6) are depicted in black; the complementing fusion proteins, in this case Gag{delta}p6-PTAP and Gag{delta}p6-p6 (15-51), are shown in white. (B) Infectious virion production measured as for Fig. 1 by using HeLa P4/R5 cells. Forty-eight hours of transfection of 293T cells with 300 ng of NL{delta}p6 was carried out, and the indicated quantities (in nanograms) of pGag{delta}p6, pGag{delta}p6-p6, pGag{delta}p6-PTAP and/or pGag{delta}p6-p6 (15-51) are indicated. RLU, relative light units. (C and D) The same information as that given for panel A applies, except that HOS (C) or TE671 (D) was transfected.

 
Previous observations have suggested that HIV-1 replication and particle release are partly defective when sequences C terminal to the PTAP motif are deleted from p6 (6, 9). Moreover, a PTAP motif cannot support particle budding in the context of an HIV-1-based artificial mini-Gag construct (24). These data and the findings depicted in Fig. 2B suggested that sequences outside the PTAP motif in HIV-1 p6 are required for efficient HIV-1 virion release. In principle, the additional (non-PTAP-encoding) p6 sequences could modulate PTAP function by influencing the structure or presentation of the PTAP motif. However, it has been previously shown that short PTAP-containing peptides and the entire p6 domain bind to Tsg101 with essentially identical affinity (8, 21). Alternatively, p6 sequences outside the PTAP motif might function independently, perhaps by recruiting additional cellular cofactors to facilitate HIV-1 budding. Nonetheless, Gag{delta}p6-p6 (15-51), which contains all p6 sequences C terminal to the PTAP-containing peptide described above, was inactive and did not detectably increase virion formation when coexpressed with NL{delta}p6 (Fig. 2B). Notably, however, when used in combination, Gag{delta}p6-PTAP and Gag{delta}p6-p6 (15-51) complemented NL{delta}p6 efficiently and supported infectious virion formation almost as efficiently as the intact Gag{delta}p6-p6 protein (Fig. 2B). These data indicate that the PTAP motif and p6 residues 15 to 51 can complement each other in trans to mediate the formation of infectious HIV-1 particles. This strongly suggests that p6 residues outside the PTAP motif do not accentuate HIV-1 budding by modulating PTAP structure but instead contribute an additional activity that synergizes with PTAP to induce HIV-1 virion morphogenesis. To confirm that the activity ascribed to p6 residues 15 to 51 was not simply a cell line-specific phenomenon, we performed experiments essentially identical to those depicted in Fig. 2A but used additional HIV-1-permissive cell lines. As is shown in Fig. 2B and C, a similar trans-complementing phenotype between PTAP and p6 (15-51) was observed in both HOS and TE671 cells. Similar results were also obtained with HeLa cells (data not shown).

We further examined Gag processing and particle production phenotypes in 293T cells by using the same complementation assay in conjunction with Western blot analysis. As shown in Fig. 3, cells expressing NL{delta}p6 and Gag{delta}p6 released undetectable levels of viral particles and analysis of cell-associated Gag revealed a profound processing defect with little mature p24 being present. A substantial reversion of this defect was observed when Gag{delta}p6-p6 was coexpressed. Although significant levels of partly processed p25 (CA-p2) were observed in these cell lysates, this is likely due to a suboptimal level of p6 and Pol expressed in these cells: because this elaboration of the trans-complementation assay requires cotransfection with three expression plasmids, only approximately one-fifth of the total Gag expressed encodes p6 and about three-fifths of the normal level of Pol is expressed. Nonetheless, this analysis clearly demonstrates the ability of Gag{delta}p6-p6 to enhance NL{delta}p6Gag processing and particle release. Gag{delta}p6-PTAP had marginal effects on Gag processing but did support particle release. However, while the total level of Gag{delta}p6-PTAP-induced particle release was only slightly reduced (<2-fold) compared to that induced by Gag{delta}p6-p6, approximately one-third of the particle-associated capsid protein was in an immature, p25CA-p2 form. This latter finding probably explains why Gag{delta}p6-PTAP-complemented virions appear significantly less infectious than do Gag{delta}p6-p6-complemented counterparts (Fig. 2A). The Gag{delta}p6-p6 (15-51) fusion protein appeared inactive when present as the sole complementing construct; however, its expression clearly enhanced the ability of Gag{delta}p6-PTAP to mediate fully processed virion formation. Indeed, the combination of Gag{delta}p6-PTAP and Gag{delta}p6-p6 (15-51) was as active as the intact Gag{delta}p6-p6 protein (Fig. 3). Thus, these results are similar to those obtained by use of the infectivity assay of virion production (Fig. 2A) and confirm that the PTAP motif and p6 residues 15 to 51 act synergistically and in trans to mediate the formation of mature HIV-1 virions. A further Western analysis of cell lysates and virion pellets derived from similarly transfected HOS cells revealed results essentially identical to those obtained with 293T cells (data not shown).



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  		FIG. 3. Western blot analysis of the effect of PTAP and p6 (15-51) on Gag processing and particle release. 293T cells were transfected with 300 ng of pNL{delta}p6 and the indicated complementing pGag{delta}p6-fusion protein expression plasmids, as was done for Fig. 2. Forty-eight hours after transfection, cell lysates and pelleted extracellular virions (harvested by ultracentrifugation through a 20% sucrose cushion) were analyzed by Western blotting with an anti-p24CA monoclonal antibody. The number(s) below each lane indicates the levels of mature p24 CA protein and the incompletely processed p25 CA-p2 intermediate in virion pellets, quantitated by analysis of the blots with NIH Image. ND, not detectable.

 
We next used electron microscopy to visualize HIV-1 budding by NL{delta}p6 virions complemented in trans by coexpression of either Gag{delta}p6-PTAP or Gag{delta}p6-p6. These experiments, shown in Fig. 4, revealed that pNL{delta}p6-transfected cells synthesized immature virions that largely remained tethered to each other and to cells (Fig. 4A). This phenotype was expected but was somewhat more dramatic than has been previously reported for PTAP point mutants. Conversely, NL{delta}p6 complemented with Gag{delta}p6-p6 did not exhibit this dramatic L-domain-defective phenotype. Budding structures as well as immature, and occasionally mature, extracellular virions were observed (Fig. 4B). Complementation with Gag{delta}p6-PTAP resulted in an apparently intermediate phenotype: while the late-budding defect appeared somewhat less severe than in the absence of a complementing Gag{delta}p6-fusion protein, immature cell-associated virions were observed and mature extracellular virions were only very rarely observed (Fig. 4C). These results suggest that the L-domain activity exhibited by the PTAP motif is accentuated by the presence of additional p6 sequences.



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  		FIG. 4. Electron microscopy analysis of p6- and PTAP-mediated virion budding. 293T cells were transfected with pNL{delta}p6 and pGag{delta}p6 (A), pNL{delta}p6 and pGag{delta}p6-p6 (B), or pNL{delta}p6 and pGag{delta}p6-PTAP (C), in each case in a 3:2 molar ratio. Cells were harvested and processed for microscopy 48 h after transfection. Each panel shows an overview of part of a transfected cell (left) as well as a higher magnification of budding structures and virions (right).

 
Taken together, these findings suggest that HIV-1 encodes a bipartite L-domain whose function is only partly due to the PTAP-Tsg101 interaction. While previous studies have documented that the late-budding defect is more profound when all of p6 is deleted, compared to when only PTAP is abolished (6, 9), this study explicitly indicates that p6 encodes an additional activity that can act synergistically with the PTAP/Tsg101 interaction to mediate HIV-1 particle formation. While p6 residues 15 to 51 did not exhibit detectable L-domain activity when present alone, the likeliest explanation for these results is that p6 (15-51) contributes to the overall L-domain activity exhibited by HIV-1 p6. Clearly, these sequences were required for full expression of the PTAP-induced phenotype. At present we cannot exclude a postbudding effect of p6 (15-51) on virion maturation, but the electron microscopy analysis (Fig. 4) suggested that the PTAP motif is only partly effective in inducing HIV-1 particle release, and previous findings indicate that PTAP is insufficient and that an intact p6 is essential for particle release in an artificial mini-Gag context (24). Moreover, maturation defects in extracellular particles (Fig. 3) are likely to be consequent to partially defective L-domain function. Indeed, in some contexts L-domain defects can result in the formation of extracellular virions that remained tethered to each other and, consequently, immature (6). In addition, late-budding defects induced by p6 deletion or PTAP mutation result in reduced incorporation of pol gene products into virions and deleterious effects on maturation (7, 9). Because neither PTAP nor p6 (15-51) appears sufficient for full L-domain activity, these findings strongly suggest that HIV-1 encodes a bipartite L-domain. Importantly, however, we show that these two p6 domains are not required to be present in cis to mediate virion formation. Thus, it seems likely that the two components of the HIV-1 L-domain act independently of each other, and it is therefore unlikely that p6 (15-51) acts by influencing the structure of the Tsg101 binding site. Moreover, because Gag{delta}p6-Tsg101 does not complement NL{delta}p6, it is also unlikely that p6 (15-51) acts by facilitating Tsg101 recruitment. This effectively excludes the possibility that p6 ubiqutination and consequent enhancement of Tsg101 binding (8) are the underlying mechanism by which p6 (12-51) enhances HIV-1 particle formation. Indeed, it has been previously shown that lysine residues in p6 are completely dispensable for HIV-1 budding and replication (19). While it is possible that ubiquitination at alternative HIV-1 Gag sites might facilitate Tsg101 recruitment (8, 23), the presence of this proven L-domain cofactor at sites of particle assembly appears insufficient to account for the virion morphogenesis activity exhibited by HIV-1 p6. One possibility, currently under investigation, is that p6 (12-51) acts by recruiting distinct cellular cofactors, perhaps additional ESCRT components or other class E VPS factors that are known to mediate the budding of vesicles within cells (1, 2, 15, 22).


   ACKNOWLEDGMENTS
 
We thank Eleana Sphicas of the Rockefeller Bioimaging Resource Center for electron microscopy.

This work was supported by grants from the NIH (RO1 AI52774) and AmFAR (02865-31). J.M.-S. is the recipient of a postdoctoral fellowship from Ministerio de Educacion, Cultura y Deporte (Spain). P.D.B. is an Elizabeth Glaser Scientist of the Elizabeth Glaser Pediatric AIDS Foundation.


   FOOTNOTES
 
* Corresponding author. Mailing address: Aaron Diamond AIDS Research Center, 455 First Ave., New York, NY 10021. Phone: (212) 448-5070. Fax: (212) 725-1126. E-mail: pbienias{at}adarc.org. Back


   REFERENCES
Top
 Abstract
 Text
 References
 

  1. Babst, M., D. J. Katzmann, E. J. Estepa-Sabal, T. Meerloo, and S. D. Emr. 2002. Escrt-III: an endosome-associated heterooligomeric protein complex required for mvb sorting. Dev. Cell 3:271-282.[CrossRef][Medline]
  2. Babst, M., D. J. Katzmann, W. B. Snyder, B. Wendland, and S. D. Emr. 2002. Endosome-associated complex, ESCRT-II, recruits transport machinery for protein sorting at the multivesicular body. Dev. Cell 3:283-289.[CrossRef][Medline]
  3. Bieniasz, P. D., T. A. Grdina, H. P. Bogerd, and B. R. Cullen. 1998. Recruitment of a protein complex containing Tat and cyclin T1 to TAR governs the species specificity of HIV-1 Tat. EMBO J. 17:7056-7065.[CrossRef][Medline]
  4. Craven, R. C., R. N. Harty, J. Paragas, P. Palese, and J. W. Wills. 1999. Late domain function identified in the vesicular stomatitis virus M protein by use of rhabdovirus-retrovirus chimeras. J. Virol. 73:3359-3365.[Abstract/Free Full Text]
  5. Demirov, D. G., A. Ono, J. M. Orenstein, and E. O. Freed. 2002. Overexpression of the N-terminal domain of TSG101 inhibits HIV-1 budding by blocking late domain function. Proc. Natl. Acad. Sci. USA 99:955-960.[Abstract/Free Full Text]
  6. Demirov, D. G., J. M. Orenstein, and E. O. Freed. 2002. The late domain of human immunodeficiency virus type 1 p6 promotes virus release in a cell type-dependent manner. J. Virol. 76:105-117.[Abstract/Free Full Text]
  7. Dettenhofer, M., and X.-F. Yu. 1999. Proline residues in human immunodeficiency virus type 1 p6Gag exert a cell type-dependent effect on viral replication and virion incorporation of Pol proteins. J. Virol. 73:4696-4704.[Abstract/Free Full Text]
  8. Garrus, J. E., U. K. von Schwedler, O. W. Pornillos, S. G. Morham, K. H. Zavitz, H. E. Wang, D. A. Wettstein, K. M. Stray, M. Cote, R. L. Rich, D. G. Myszka, and W. I. Sundquist. 2001. Tsg101 and the vacuolar protein sorting pathway are essential for HIV-1 budding. Cell 107:55-65.[CrossRef][Medline]
  9. Gottlinger, H. G., T. Dorfman, J. G. Sodroski, and W. A. Haseltine. 1991. Effect of mutations affecting the p6 gag protein on human immunodeficiency virus particle release. Proc. Natl. Acad. Sci. USA 88:3195-3199.[Abstract/Free Full Text]
  10. Harty, R. N., M. E. Brown, G. Wang, J. Huibregtse, and F. P. Hayes. 2000. A PPxY motif within the VP40 protein of Ebola virus interacts physically and functionally with a ubiquitin ligase: implications for filovirus budding. Proc. Natl. Acad. Sci. USA 97:13871-13876.[Abstract/Free Full Text]
  11. Harty, R. N., J. Paragas, M. Sudol, and P. Palese. 1999. A proline-rich motif within the matrix protein of vesicular stomatitis virus and rabies virus interacts with WW domains of cellular proteins: implications for viral budding. J. Virol. 73:2921-2929.[Abstract/Free Full Text]
  12. Huang, M., J. M. Orenstein, M. A. Martin, and E. O. Freed. 1995. p6Gag is required for particle production from full-length human immunodeficiency virus type 1 molecular clones expressing protease. J. Virol. 69:6810-6818.[Abstract]
  13. Jayakar, H. R., K. G. Murti, and M. A. Whitt. 2000. Mutations in the PPPY motif of vesicular stomatitis virus matrix protein reduce virus budding by inhibiting a late step in virion release. J. Virol. 74:9818-9827.[Abstract/Free Full Text]
  14. Katzmann, D. J., M. Babst, and S. D. Emr. 2001. Ubiquitin-dependent sorting into the multivesicular body pathway requires the function of a conserved endosomal protein sorting complex, ESCRT-I. Cell 106:145-155.[CrossRef][Medline]
  15. Katzmann, D. J., G. Odorizzi, and S. D. Emr. 2002. Receptor downregulation and multivesicular-body sorting. Nat. Rev. Mol. Cell Biol. 3:893-905.[CrossRef][Medline]
  16. Luban, J., K. B. Alin, K. L. Bossolt, T. Humaran, and S. P. Goff. 1992. Genetic assay for multimerization of retroviral gag polyproteins. J. Virol. 66:5157-5160.[Abstract/Free Full Text]
  17. Martin-Serrano, J., T. Zang, and P. D. Bieniasz. 2001. HIV-1 and Ebola virus encode small peptide motifs that recruit Tsg101 to sites of particle assembly to facilitate egress. Nat. Med. 7:1313-1319.[CrossRef][Medline]
  18. Martin-Serrano, J., T. Zang, and P. D. Bieniasz. 2003. Role of ESCRT-I in retroviral budding. J. Virol. 77:4794-4804.[Abstract/Free Full Text]
  19. Ott, D. E., L. V. Coren, E. N. Chertova, T. D. Gagliardi, and U. Schubert. 2000. Ubiquitination of HIV-1 and MuLV Gag. Virology 278:111-121.[CrossRef][Medline]
  20. Parent, L. J., R. P. Bennett, R. C. Craven, T. D. Nelle, N. K. Krishna, J. B. Bowzard, C. B. Wilson, B. A. Puffer, R. C. Montelaro, and J. W. Wills. 1995. Positionally independent and exchangeable late budding functions of the Rous sarcoma virus and human immunodeficiency virus Gag proteins. J. Virol. 69:5455-5460.[Abstract]
  21. Pornillos, O., S. L. Alam, D. R. Davis, and W. I. Sundquist. 2002. Structure of the Tsg101 UEV domain in complex with the PTAP motif of the HIV-1 p6 protein. Nat. Struct. Biol. 9:812-817.[Medline]
  22. Pornillos, O., J. E. Garrus, and W. I. Sundquist. 2002. Mechanisms of enveloped RNA virus budding. Trends Cell Biol. 12:569-579.[CrossRef][Medline]
  23. Strack, B., A. Calistri, M. A. Accola, G. Palu, and H. G. Gottlinger. 2000. A role for ubiquitin ligase recruitment in retrovirus release. Proc. Natl. Acad. Sci. USA 97:13063-13068.[Abstract/Free Full Text]
  24. Strack, B., A. Calistri, and H. G. Göttlinger. 2002. Late assembly domain function can exhibit context dependence and involves ubiquitin residues implicated in endocytosis. J. Virol. 76:5472-5479.[Abstract/Free Full Text]
  25. Tritel, M., and M. D. Resh. 2000. Kinetic analysis of human immunodeficiency virus type 1 assembly reveals the presence of sequential intermediates. J. Virol. 74:5845-5855.[Abstract/Free Full Text]
  26. VerPlank, L., F. Bouamr, T. J. LaGrassa, B. Agresta, A. Kikonyogo, J. Leis, and C. A. Carter. 2001. Tsg101, a homologue of ubiquitin-conjugating (E2) enzymes, binds the L domain in HIV type 1 Pr55(Gag). Proc. Natl. Acad. Sci. USA 98:7724-7729.[Abstract/Free Full Text]
  27. Wills, J. W., C. E. Cameron, C. B. Wilson, Y. Xiang, R. P. Bennett, and J. Leis. 1994. An assembly domain of the Rous sarcoma virus Gag protein required late in budding. J. Virol. 68:6605-6618.[Abstract/Free Full Text]
  28. Yasuda, J., and E. Hunter. 1998. A proline-rich motif (PPPY) in the Gag polyprotein of Mason-Pfizer monkey virus plays a maturation-independent role in virion release. J. Virol. 72:4095-4103.[Abstract/Free Full Text]
  29. Yuan, B., S. Campbell, E. Bacharach, A. Rein, and S. P. Goff. 2000. Infectivity of Moloney murine leukemia virus defective in late assembly events is restored by late assembly domains of other retroviruses. J. Virol. 74:7250-7260.[Abstract/Free Full Text]

Journal of Virology, November 2003, p. 12373-12377, Vol. 77, No. 22
0022-538X/03/$08.00+0     DOI: 10.1128/JVI.77.22.12373-12377.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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