1
|
Abstract
The retroviral Gag polyprotein directs virus particle assembly, resulting in the release of virions from the plasma membranes of infected cells. The earliest steps in assembly, those immediately following Gag synthesis, are very poorly understood. For Rous sarcoma virus (RSV), Gag proteins are synthesized in the cytoplasm and then undergo transient nuclear trafficking before returning to the cytoplasm for transport to the plasma membrane. Thus, RSV provides a useful model to study the initial steps in assembly because the early and later stages are spatially separated by the nuclear envelope. We previously described mutants of RSV Gag that are defective in nuclear export, thereby isolating these "trapped" Gag proteins at an early assembly step. Using the nuclear export mutants, we asked whether Gag protein-protein interactions occur within the nucleus. Complementation experiments revealed that the wild-type Gag protein could partially rescue export-defective Gag mutants into virus-like particles (VLPs). Additionally, the export mutants had a trans-dominant negative effect on wild-type Gag, interfering with its release into VLPs. Confocal imaging of wild-type and mutant Gag proteins bearing different fluorescent tags suggested that complementation between Gag proteins occurred in the nucleus. Additional evidence for nuclear Gag-Gag interactions was obtained using fluorescence resonance energy transfer, and we found that the formation of intranuclear Gag complexes was dependent on the NC domain. Bimolecular fluorescence complementation allowed the direct visualization of intranuclear Gag-Gag dimers. Together, these experimental results strongly suggest that RSV Gag proteins are capable of interacting within the nucleus.
Collapse
|
2
|
Bouamr F, Houck-Loomis BR, De Los Santos M, Casaday RJ, Johnson MC, Goff SP. The C-terminal portion of the Hrs protein interacts with Tsg101 and interferes with human immunodeficiency virus type 1 Gag particle production. J Virol 2006; 81:2909-22. [PMID: 17182674 PMCID: PMC1865988 DOI: 10.1128/jvi.01413-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag protein recruits Tsg101 to facilitate HIV-1 particle budding and release. In uninfected cells, the Hrs protein recruits the ESCRT-I complex to the endosome, also through an interaction with Tsg101, to promote the sorting of host proteins into endosomal vesicles and multivesicular bodies. Here, we show that the overexpression of the C-terminal fragment of Hrs (residues 391 to 777) or Hrs mutants lacking either the N-terminal FYVE domain (mutant dFYVE) or the PSAP (residues 348 to 351) motif (mutant ASAA) all efficiently inhibit HIV-1 Gag particle production. Expression of the dFYVE or ASAA mutants of Hrs had no effect on the release of Moloney murine leukemia virus. Coimmunoprecipitation analysis showed that the expression of Hrs mutant dFYVE or ASAA significantly reduced or abolished the HIV-1 Gag-Tsg101 interaction. Yeast-two hybrid assays were used to identify two new and independent Tsg101 binding sites, one in the Hrs coiled-coil domain and one in the proline/glutamic acid-rich domain. Scanning electron microscopy of HeLa cells expressing HIV-1 Gag and the Hrs ASAA mutant showed viral particles arrested in "lump-like" structures that remained attached to the cell surface. Together, these data indicate that fragments of Hrs containing the C-terminal portion of the protein can potently inhibit HIV-1 particle release by efficiently sequestering Tsg101 away from the Gag polyprotein.
Collapse
Affiliation(s)
- Fadila Bouamr
- Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | | | | | | | | | | |
Collapse
|
3
|
Angelopoulou K, Karanikolaou K, Papanastasopoulou M, Koumpati-Artopiou M, Vlemmas I, Papadopoulos O, Koptopoulos G. First partial characterisation of small ruminant lentiviruses from Greece. Vet Microbiol 2005; 109:1-9. [PMID: 15964721 DOI: 10.1016/j.vetmic.2005.04.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2004] [Revised: 01/25/2005] [Accepted: 04/13/2005] [Indexed: 11/24/2022]
Abstract
Small ruminant lentivirus (SRLV) infections are widespread in Greece, but SRLVs have never been isolated and characterized. In this study, we present the sequence of a 574-nucleotide (191-amino acid) region of the gag gene of SRLV strains from four sheep and one goat from a single geographic area of Greece. All five sequences appeared to be closely related at both nucleotide (2.1-14.2% variation) and deduced amino acid (1.6-4.2% variation) level. Greek SRLV strains were closer to ovine prototypic strains (average divergence 16.8%) than to the caprine strain CAEV-Co (21% divergence). By amino acid composition, the Greek SRLVs were on the average more than twice as distant from CAEV-Co as from other ovine strains. Phylogenetic analysis suggested that Greek strains segregate into a unique group, separate from, but related to, other ovine prototype sequences.
Collapse
Affiliation(s)
- K Angelopoulou
- Laboratory of Biochemistry and Toxicology, School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | | | | | | | | | | | | |
Collapse
|
4
|
Zábranský A, Sakalian M, Pichová I. Localization of self-interacting domains within betaretrovirus Gag polyproteins. Virology 2005; 332:659-66. [PMID: 15680431 DOI: 10.1016/j.virol.2004.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 11/13/2004] [Accepted: 12/11/2004] [Indexed: 11/18/2022]
Abstract
The Betaretrovirus genus is characterized by the ability to preassemble immature capsids within the cytoplasm. For Mason-Pfizer monkey virus (M-PMV) this ability depends in part upon the unique Internal Scaffold Domain (ISD) within the p12 region of Gag. In this study, we have further characterized the ability of M-PMV p12 to promote Gag-Gag interaction and have examined the Gag polyprotein of the related mouse mammary tumor virus (MMTV) to potentially identify a region with equivalent function. Using the yeast two-hybrid system, we confirmed that both Gag polyproteins strongly interact, primarily through the CA-NC regions, but also through additional domains N-terminal to CA. For M-PMV, this auxiliary interaction domain was p12. For MMTV, no single strongly self-interacting protein was identified. Instead, MMTV Gag appears to utilize the weak contributions of several protein domains to support the main interaction of its CA-NC. Our findings suggest that, in addition to the canonical NC "I-domain" interaction, MMTV Gag self-association results from the concerted action of multiple regions of the polyprotein while M-PMV Gag relies mainly on its p12 domain.
Collapse
Affiliation(s)
- Ales Zábranský
- Department of Protein Biochemistry, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo n.2, Prague 6, 16610, Czech Republic.
| | | | | |
Collapse
|
5
|
Lee EG, Linial ML. Basic residues of the retroviral nucleocapsid play different roles in gag-gag and Gag-Psi RNA interactions. J Virol 2004; 78:8486-95. [PMID: 15280457 PMCID: PMC479049 DOI: 10.1128/jvi.78.16.8486-8495.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 04/05/2004] [Indexed: 01/02/2023] Open
Abstract
The Orthoretrovirus Gag interaction (I) domain maps to the nucleocapsid (NC) domain in the Gag polyprotein. We used the yeast two-hybrid system to analyze the role of Alpharetrovirus NC in Gag-Gag interactions and also examined the efficiency of viral assembly and release in vivo. We could delete either or both of the two Cys-His (CH) boxes without abrogating Gag-Gag interactions. We found that as few as eight clustered basic residues, attached to the C terminus of the spacer peptide separating the capsid (CA) and NC domains in the absence of NC, was sufficient for Gag-Gag interactions. Our results support the idea that a sufficient number of basic residues, rather than the CH boxes, play the important role in Gag multimerization. We also examined the requirement for basic residues in Gag for packaging of specific packaging signal (Psi)-containing RNA. Using a yeast three-hybrid RNA-protein interaction assay, second-site suppressors of a packaging-defective Gag mutant were isolated, which restored Psi RNA binding. These suppressors mapped to the p10 or CA domains in Gag and resulted in either introduction of a positively charged residue or elimination of a negatively charged one. These results imply that the structural interactions of NC with other domains of Gag are necessary for Psi RNA binding. Taken together, our results show that while Gag assembly only requires a certain number of positively charged amino acids, Gag binding to genomic RNA for packaging requires more complex interactions inherent in the protein tertiary structure.
Collapse
Affiliation(s)
- Eun-Gyung Lee
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Seattle, WA 98109-1024, USA
| | | |
Collapse
|
6
|
Wang MQ, Kim W, Gao G, Torrey TA, Morse HC, De Camilli P, Goff SP. Endophilins interact with Moloney murine leukemia virus Gag and modulate virion production. J Biol 2003; 3:4. [PMID: 14659004 PMCID: PMC442166 DOI: 10.1186/1475-4924-3-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2003] [Revised: 07/23/2003] [Accepted: 09/30/2003] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The retroviral Gag protein is the central player in the process of virion assembly at the plasma membrane, and is sufficient to induce the formation and release of virus-like particles. Recent evidence suggests that Gag may co-opt the host cell's endocytic machinery to facilitate retroviral assembly and release. RESULTS A search for novel partners interacting with the Gag protein of the Moloney murine leukemia virus (Mo-MuLV) via the yeast two-hybrid protein-protein interaction assay resulted in the identification of endophilin 2, a component of the machinery involved in clathrin-mediated endocytosis. We demonstrate that endophilin interacts with the matrix or MA domain of the Gag protein of Mo-MuLV, but not of human immunodeficiency virus, HIV. Both exogenously expressed and endogenous endophilin are incorporated into Mo-MuLV viral particles. Titration experiments suggest that the binding sites for inclusion of endophilin into viral particles are limited and saturable. Knock-down of endophilin with small interfering RNA (siRNA) had no effect on virion production, but overexpression of endophilin and, to a lesser extent, of several fragments of the protein, result in inhibition of Mo-MuLV virion production, but not of HIV virion production. CONCLUSIONS This study shows that endophilins interact with Mo-MuLV Gag and affect virion production. The findings imply that endophilin is another component of the large complex that is hijacked by retroviruses to promote virion production.
Collapse
Affiliation(s)
- Margaret Q Wang
- Department of Microbiology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| | - Wankee Kim
- Institute for Medical Sciences, Ajou University, South Korea
| | - Guangxia Gao
- Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China
| | - Ted A Torrey
- Laboratory of Immunopathology, NIAID, NIH, Rockville, MD 20852, USA
| | - Herbert C Morse
- Laboratory of Immunopathology, NIAID, NIH, Rockville, MD 20852, USA
| | - Pietro De Camilli
- Howard Hughes Medical Institute and Department of Cell Biology, Yale University, New Haven, CT 06510, USA
| | - Stephen P Goff
- Department of Microbiology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
- Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| |
Collapse
|
7
|
Ravazzolo AP, Reischak D, Peterhans E, Zanoni R. Phylogenetic analysis of small ruminant lentiviruses from Southern Brazil. Virus Res 2001; 79:117-23. [PMID: 11551652 DOI: 10.1016/s0168-1702(01)00339-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The first lentivirus isolated from sheep in Brazil was analysed phylogenetically. Evolutionary trees of the proviral 597 nucleotide gag and 432 nucleotide pol sequences obtained by the maximum likelihood method demonstrated that the sheep isolate clustered with prototype Maedi Visna virus whereas three lentiviruses isolated from goats in the same geographic region were close to caprine arthritis encephalitis prototypes. A subsequent comparison of sequence data of these viruses with those contained in the EMBL sequence database revealed that, in contrast to caprine prototypic viruses, all prototypic Maedi Visna viruses contain a deletion of six nucleotides in the gag gene resulting in the deletion of two residues in the central region of capsid protein. This deletion may be a useful marker in the analysis of small ruminant lentiviruses, especially when considering possible transmission of lentiviruses between sheep and goats.
Collapse
Affiliation(s)
- A P Ravazzolo
- Biotechnology Center and Veterinary Faculty, UFRGS-Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, CEP 91501-970, Porto Alegre, Brazil.
| | | | | | | |
Collapse
|
8
|
Bacharach E, Gonsky J, Alin K, Orlova M, Goff SP. The carboxy-terminal fragment of nucleolin interacts with the nucleocapsid domain of retroviral gag proteins and inhibits virion assembly. J Virol 2000; 74:11027-39. [PMID: 11069998 PMCID: PMC113183 DOI: 10.1128/jvi.74.23.11027-11039.2000] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2000] [Accepted: 09/12/2000] [Indexed: 11/20/2022] Open
Abstract
A yeast two-hybrid screen for cellular proteins that interact with the murine leukemia virus (MuLV) Gag protein resulted in the identification of nucleolin, a host protein known to function in ribosome assembly. The interacting fusions contained the carboxy-terminal 212 amino acids of nucleolin [Nuc(212)]. The nucleocapsid (NC) portion of Gag was necessary and sufficient to mediate the binding to Nuc(212). The interaction of Gag with Nuc(212) could be demonstrated in vitro and was manifested in vivo by the NC-dependent incorporation of Nuc(212) inside MuLV virions. Overexpression of Nuc(212), but not full-length nucleolin, potently and specifically blocked MuLV virion assembly and/or release. A mutant of MuLV, selected to specifically disrupt the binding to Nuc(212), was found to be severely defective for virion assembly. This mutant harbors a single point mutation in capsid (CA) adjacent to the CA-NC junction, suggesting a role for this region in Moloney MuLV assembly. These experiments demonstrate that selection for proteins that bind assembly domain(s) can yield potent inhibitors of virion assembly. These experiments also raise the possibility that a nucleolin-Gag interaction may be involved in virion assembly.
Collapse
Affiliation(s)
- E Bacharach
- Howard Hughes Medical Institute, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | | | | | | | | |
Collapse
|
9
|
Rumlova-Klikova M, Hunter E, Nermut MV, Pichova I, Ruml T. Analysis of Mason-Pfizer monkey virus Gag domains required for capsid assembly in bacteria: role of the N-terminal proline residue of CA in directing particle shape. J Virol 2000; 74:8452-9. [PMID: 10954545 PMCID: PMC116356 DOI: 10.1128/jvi.74.18.8452-8459.2000] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mason-Pfizer monkey virus (M-PMV) preassembles immature capsids in the cytoplasm prior to transporting them to the plasma membrane. Expression of the M-PMV Gag precursor in bacteria results in the assembly of capsids indistinguishable from those assembled in mammalian cells. We have used this system to investigate the structural requirements for the assembly of Gag precursors into procapsids. A series of C- and N-terminal deletion mutants progressively lacking each of the mature Gag domains (matrix protein [MA]-pp24/16-p12-capsid protein [CA]-nucleocapsid protein [NC]-p4) were constructed and expressed in bacteria. The results demonstrate that both the CA and the NC domains are necessary for the assembly of macromolecular arrays (sheets) but that amino acid residues at the N terminus of CA define the assembly of spherical capsids. The role of these N-terminal domains is not based on a specific amino acid sequence, since both MA-CA-NC and p12-CA-NC polyproteins efficiently assemble into capsids. Residues N terminal of CA appear to prevent a conformational change in which the N-terminal proline plays a key role, since the expression of a CA-NC protein lacking this proline results in the assembly of spherical capsids in place of the sheets assembled by the CA-NC protein.
Collapse
Affiliation(s)
- M Rumlova-Klikova
- Department of Biochemistry, Institute of Organic Chemistry and Biochemistry, Academy of Sciences, 166 10 Prague, Czech Republic
| | | | | | | | | |
Collapse
|
10
|
Todd S, Laboissière MC, Craik CS. Yeast two-hybrid assay for examining human immunodeficiency virus protease heterodimer formation with dominant-negative inhibitors and multidrug-resistant variants. Anal Biochem 2000; 277:247-53. [PMID: 10625514 DOI: 10.1006/abio.1999.4388] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The yeast two-hybrid assay was used to study the dimerization of engineered and naturally occurring variants of human immunodeficiency virus (HIV) protease (PR) monomers. Defective monomers that were previously shown to exhibit a dominant-negative (D-N) effect in cultured mammalian cells were tested for their ability to interact in the two-hybrid assay. Similarly, monomers with dimer-interface substitutions and monomers harboring in vivo selected mutations that confer multidrug resistance (mdr) in an AIDS patient were tested for interaction in yeast. Dimer formation between wt monomers with catalytic aspartates was not detected in yeast, whereas the dimerization of PR monomers harboring the acid active site substitution D25N was readily demonstrated. The use of inactive monomers harboring the D25N substitution as a genetic background for studying additional HIV PR mutations allowed for the probing of interactions between monomers with mdr-associated mutations with those based on the HIV-1 HXB2R sequence. The HTLVIII/HIV-1 HXB2R clone has been the basis for a large number of HIV-related plasmids, primers, antibodies, and other specific reagents throughout the HIV research community. The results of our assay suggest that HXB2R-based D-N PR inhibitors associate with variant monomers based on the recently obtained nucleotide sequence from an AIDS patient with a multidrug-resistant virus. These results further encourage the use of D-N PR inhibitors as antiviral agents which may complement existing small-molecule combination therapies.
Collapse
Affiliation(s)
- S Todd
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446, USA
| | | | | |
Collapse
|
11
|
Tang Y, Winkler U, Freed EO, Torrey TA, Kim W, Li H, Goff SP, Morse HC. Cellular motor protein KIF-4 associates with retroviral Gag. J Virol 1999; 73:10508-13. [PMID: 10559369 PMCID: PMC113106 DOI: 10.1128/jvi.73.12.10508-10513.1999] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously we demonstrated that murine retroviral Gag proteins associate with a cellular motor protein, KIF-4. Using the yeast two-hybrid assay, we also found an association of KIF-4 with Gag proteins of Mason-Pfizer monkey virus (MPMV), simian immunodeficiency virus (SIV), and human immunodeficiency virus type 1 (HIV-1). Studies performed with mammalian cell systems confirmed that the HIV-1 Gag protein associates with KIF-4. Soluble cytoplasmic proteins from cells infected with recombinant vaccinia virus expressing the entire Gag-Pol precursor protein of HIV-1 or transfected with HIV-1 molecular clone pNL4-3 were fractionated by sucrose gradient centrifugation and further separated by size-exclusion and anion-exchange chromatographies. KIF-4 and HIV-1 Gag cofractionated in both chromatographic separations. Immunoprecipitation assays have also verified the KIF-4-Gag association. KIF-4 binds mainly to the Gag precursor (Pr55 Gag) and a matrix-capsid processing intermediate (Pr42) but not to other processed Gag products. The binding of Gag is mediated by a domain of KIF-4 proximal to the C terminus. These results, and our previous studies, raise the possibility that KIF-4 may play an important role in retrovirus Gag protein transport.
Collapse
Affiliation(s)
- Y Tang
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Burniston MT, Cimarelli A, Colgan J, Curtis SP, Luban J. Human immunodeficiency virus type 1 Gag polyprotein multimerization requires the nucleocapsid domain and RNA and is promoted by the capsid-dimer interface and the basic region of matrix protein. J Virol 1999; 73:8527-40. [PMID: 10482606 PMCID: PMC112873 DOI: 10.1128/jvi.73.10.8527-8540.1999] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag polyprotein directs the formation of virions from productively infected cells. Many gag mutations disrupt virion assembly, but little is known about the biochemical effects of many of these mutations. Protein-protein interactions among Gag monomers are believed to be necessary for virion assembly, and data suggest that RNA may modify protein-protein interactions or even serve as a bridge linking Gag polyprotein monomers. To evaluate the primary sequence requirements for HIV-1 Gag homomeric interactions, a panel of HIV-1 Gag deletion mutants was expressed in bacteria and evaluated for the ability to associate with full-length Gag in vitro. The nucleocapsid protein, the major RNA-binding domain of Gag, exhibited activity comparable to that of the complete polyprotein. In the absence of the nucleocapsid protein, relatively weak activity was observed that was dependent upon both the capsid-dimer interface and basic residues within the matrix domain. The relevance of the in vitro findings was confirmed with an assay in which nonmyristylated mutant Gags were assessed for the ability to be incorporated into virions produced by wild-type Gag expressed in trans. Evidence of the importance of RNA for Gag-Gag interaction was provided by the demonstration that RNase impairs the Gag-Gag interaction and that HIV-1 Gag interacts efficiently with Gags encoded by distantly related retroviruses and with structurally unrelated RNA-binding proteins. These results are consistent with models in which Gag multimerization involves indirect contacts via an RNA bridge as well as direct protein-protein interactions.
Collapse
Affiliation(s)
- M T Burniston
- Departments of Microbiology, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA
| | | | | | | | | |
Collapse
|
13
|
Bachand F, Yao XJ, Hrimech M, Rougeau N, Cohen EA. Incorporation of Vpr into human immunodeficiency virus type 1 requires a direct interaction with the p6 domain of the p55 gag precursor. J Biol Chem 1999; 274:9083-91. [PMID: 10085158 DOI: 10.1074/jbc.274.13.9083] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 96-amino acid Vpr protein is the major virion-associated accessory protein of the human immunodeficiency virus type 1 (HIV-1). As Vpr is not part of the p55 Gag polyprotein precursor (Pr55(gag)), its incorporation requires an anchor to associate with the assembling viral particles. Although the molecular mechanism is presently unclear, the C-terminal region of the Pr55(gag) corresponding to the p6 domain appears to constitute such an anchor essential for the incorporation of the Vpr protein. In order to clarify the mechanism by which the Vpr accessory protein is trans-incorporated into progeny virion particles, we tested whether HIV-1 Vpr interacted with the Pr55(gag) using the yeast two-hybrid system and the maltose-binding protein pull-down assay. The present study provides genetic and biochemical evidence indicating that the Pr55(gag) can physically interact with the Vpr protein. Furthermore, point mutations affecting the integrity of the conserved L-X-S-L-F-G motif of p6(gag) completely abolish the interaction between Vpr and the Pr55(gag) and, as a consequence, prevent Vpr virion incorporation. In contrast to other studies, mutations affecting the integrity of the NCp7 zinc fingers impaired neither Vpr virion incorporation nor the binding between Vpr and the Pr55(gag). Conversely, amino acid substitutions in Vpr demonstrate that an intact N-terminal alpha-helical structure is essential for the Vpr-Pr55(gag) interaction. Vpr and the Pr55(gag) demonstrate a strong interaction in vitro as salt concentrations as high as 900 mM could not disrupt the interaction. Finally, the interaction is efficiently competed using anti-Vpr sera. Together, these results strongly suggest that Vpr trans-incorporation into HIV-1 particles requires a direct interaction between its N-terminal region and the C-terminal region of p6(gag). The development of Pr55(gag)-Vpr interaction assays may allow the screening of molecules that can prevent the incorporation of the Vpr accessory protein into HIV-1 virions, and thus inhibit its early functions.
Collapse
Affiliation(s)
- F Bachand
- Laboratoire de rétrovirologie humaine, Département de Microbiologie et Immunologie, Faculté de Médecine, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | | | | | | | | |
Collapse
|