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Rauddi ML, Donald CLM, Affranchino JL, González SA. Mapping of the self-interaction domains in the simian immunodeficiency virus Gag polyprotein. AIDS Res Hum Retroviruses 2011; 27:303-16. [PMID: 20969459 DOI: 10.1089/aid.2010.0137] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
To gain a better understanding of the assembly process in simian immunodeficiency virus (SIV), we first established the conditions under which recombinant SIV Gag lacking the C-terminal p6 domain (SIV GagΔp6) assembled in vitro into spherical particles. Based on the full multimerization capacity of SIV GagΔp6, and to identify the Gag sequences involved in homotypic interactions, we next developed a pull-down assay in which a panel of histidine-tagged SIV Gag truncation mutants was tested for its ability to associate in vitro with GST-SIVGagΔp6. Removal of the nucleocapsid (NC) domain from Gag impaired its ability to interact with GST-SIVGagΔp6. However, this Gag mutant consisting of the matrix (MA) and capsid (CA) domains still retained 50% of the wild-type binding activity. Truncation of SIV Gag from its N-terminus yielded markedly different results. The Gag region consisting of the CA and NC was significantly more efficient than wild-type Gag at interacting in vitro with GST-SIVGagΔp6. Notably, a small Gag subdomain containing the C-terminal third of the CA and the entire NC not only bound to GST-SIVGagΔp6 in vitro at wild-type levels, but also associated in vivo with full-length Gag and was recruited into extracellular particles. Interestingly, when the mature Gag products were analyzed, the MA and NC interacted with GST-SIVGagΔp6 with efficiencies representing 20% and 40%, respectively, of the wild-type value, whereas the CA failed to bind to GST-SIVGagΔp6, despite being capable of self-associating into multimeric complexes.
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Affiliation(s)
- María L. Rauddi
- Laboratorio de Virología, CONICET-Facultad de Ciencias Exactas y Naturales, Universidad de Belgrano (UB), C1426BMJ Buenos Aires, Argentina
| | - Cecilia L. Mac Donald
- Laboratorio de Virología, CONICET-Facultad de Ciencias Exactas y Naturales, Universidad de Belgrano (UB), C1426BMJ Buenos Aires, Argentina
| | - José L. Affranchino
- Laboratorio de Virología, CONICET-Facultad de Ciencias Exactas y Naturales, Universidad de Belgrano (UB), C1426BMJ Buenos Aires, Argentina
| | - Silvia A. González
- Laboratorio de Virología, CONICET-Facultad de Ciencias Exactas y Naturales, Universidad de Belgrano (UB), C1426BMJ Buenos Aires, Argentina
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2
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Chen P, Hübner W, Riviere K, Liu YX, Chen BK. Chimeric HIV-1 containing SIV matrix exhibit enhanced assembly in murine cells and replicate in a cell-type-dependent manner in human T cells. Virology 2006; 349:1-12. [PMID: 16563454 DOI: 10.1016/j.virol.2006.02.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2005] [Revised: 10/26/2005] [Accepted: 02/08/2006] [Indexed: 02/03/2023]
Abstract
Murine fibroblasts expressing viral receptors and human cyclin T1 allow HIV-1 entry and viral gene expression but do not support efficient assembly. A chimeric HIV-1 carrying a non-homologous matrix (MA) from murine leukemia virus in place of HIV-1 MA can assemble efficiently in murine cells, yet has poor infectivity. Here, we assess the ability of a homologous MA from SIV MAC239 to complement assembly and infection in chimeric viruses designated SHIV(MA). The resulting SHIV(MA) chimeras produce more virus than native HIV-1 when transfected into murine cells. SHIV(MA) exhibits cell-type-specific replication in human T cell lines, replicating well in MT4 cells and poorly in Jurkat cells due to an incompatibility with the HIV-1 Env. The infectivity defects of SHIV(MA) are rescued by pseudotyping with VSV-G but not by truncation of the cytoplasmic tail of Env. Passage of SHIV(MA) in Jurkat cells produces variants with improved Env incorporation and improved replication in Jurkat but not in 3T3 TXC cells. The results indicate that cell-type-specific, or species-specific, host factors interact with MA to modulate the efficiency of assembly and its compatibility with Env. With additional selection, SIV/HIV-1 chimeras may be useful for the development of murine models of lentiviral infection.
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Affiliation(s)
- Ping Chen
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029, USA
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3
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Abstract
The assembly of HIV is relatively poorly investigated when compared with the process of virus entry. Yet a detailed understanding of the mechanism of assembly is fundamental to our knowledge of the complete life cycle of this virus and also has the potential to inform the development of new antiviral strategies. The repeated multiple interaction of the basic structural unit, Gag, might first appear to be little more than concentration dependent self-assembly but the precise mechanisms emerging for HIV are far from simple. Gag interacts not only with itself but also with host cell lipids and proteins in an ordered and stepwise manner. It binds both the genomic RNA and the virus envelope protein and must do this at an appropriate time and place within the infected cell. The assembled virus particle must successfully release from the cell surface and, whilst being robust enough for transmission between hosts, must nonetheless be primed for rapid disassembly when infection occurs. Our current understanding of these processes and the domains of Gag involved at each stage is the subject of this review.
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Affiliation(s)
- Catherine S Adamson
- School of Animal and Microbial Sciences, The University of Reading, Reading RG6 6AJ, UK.
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4
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Adamson CS, Nermut M, Jones IM. Control of human immunodeficiency virus type-1 protease activity in insect cells expressing Gag-Pol rescues assembly of immature but not mature virus-like particles. Virology 2003; 308:157-65. [PMID: 12706099 DOI: 10.1016/s0042-6822(02)00141-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Expression of human immunodeficiency virus type 1 (HIV-1) Gag protein in insect cells using baculovirus vectors leads to the abundant production of virus-like particles (VLPs) that represent the immature form of the virus. When Gag-Pol is included, however, VLP production is abolished, a result attributed to premature protease activation degrading the intracellular pool of Gag precursor before particle assembly can occur. As large-scale synthesis of mature noninfectious VLPs would be useful, we have sought to control HIV protease activity in insect cells to give a balance of Gag and Gag-Pol that is compatible with mature particle formation. We show here that intermediate levels of protease activity in insect cells can be attained through site-directed mutagenesis of the protease and through antiprotease drug treatment. However, despite Gag cleavage patterns that mimicked those seen in mammalian cells, VLP synthesis exhibited an essentially all-or-none response in which VLP synthesis occurred but was immature or failed completely. Our data are consistent with a requirement for specific cellular factors in addition to the correct ratio of Gag and Gag-Pol for assembly of mature retrovirus particles in heterologous cell types.
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Affiliation(s)
- Catherine S Adamson
- School of Animal and Microbial Sciences, The University of Reading, Reading RG6 6AJ, UK.
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5
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Wang SW, Aldovini A. RNA incorporation is critical for retroviral particle integrity after cell membrane assembly of Gag complexes. J Virol 2002; 76:11853-65. [PMID: 12414928 PMCID: PMC136867 DOI: 10.1128/jvi.76.23.11853-11865.2002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nucleocapsid (NC) domain of retroviruses plays a critical role in specific viral RNA packaging and virus assembly. RNA is thought to facilitate viral particle assembly, but the results described here with NC mutants indicate that it also plays a critical role in particle integrity. We investigated the assembly and integrity of particles produced by the human immunodeficiency virus type 1 M1-2/BR mutant virus, in which 10 of the 13 positive residues of NC have been replaced with alanines and incorporation of viral genomic RNA is virtually abolished. We found that the mutations in the basic residues of NC did not disrupt Gag assembly at the cell membrane. The mutant Gag protein can assemble efficiently at the cell membrane, and viral proteins are detected outside the cell as efficiently as they are for the wild type. However, only approximately 10% of the Gag molecules present in the supernatant of this mutant sediment at the correct density for a retroviral particle. The reduction of positive charge in the NC basic domain of the M1-2/BR virus adversely affects both the specific and nonspecific RNA binding properties of NC, and thus the assembled Gag polyprotein does not bind significant amounts of viral or cellular RNA. We found a direct correlation between the percentage of Gag associated with sedimented particles and the amount of incorporated RNA. We conclude that RNA binding by Gag, whether the RNA is viral or not, is critical to retroviral particle integrity after cell membrane assembly and is less important for Gag-Gag interactions during particle assembly and release.
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Affiliation(s)
- Shainn-Wei Wang
- Department of Medicine, Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA
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6
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Lenz O, ter Meulen J, Klenk HD, Seidah NG, Garten W. The Lassa virus glycoprotein precursor GP-C is proteolytically processed by subtilase SKI-1/S1P. Proc Natl Acad Sci U S A 2001; 98:12701-5. [PMID: 11606739 PMCID: PMC60117 DOI: 10.1073/pnas.221447598] [Citation(s) in RCA: 266] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The surface glycoprotein of the Lassa virus, a member of the arenaviridae family, is synthesized as a 76-kDa precursor (GP-C) that is posttranslationally cleaved into an N-terminal 44-kDa subunit and a C-terminal membrane-anchored 36-kDa subunit. Cleavage occurs at the C-terminal end of the unusual recognition motif R-R-L-L. We show here that GP-C is cleaved in the endoplasmic reticulum by the cellular subtilase SKI-1/S1P, an enzyme that has so far been observed to be involved in cholesterol metabolism. Furthermore, we present evidence that only cleaved glycoprotein is incorporated into virions and that this is necessary for the formation of infectious virus. To our knowledge, there have been no previous reports of this type of viral glycoprotein processing, one that may be an interesting target for antiviral therapy.
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Affiliation(s)
- O Lenz
- Institute of Virology, Philipps University, Robert-Koch-Strasse 17, 35037 Marburg, Germany
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7
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Manrique ML, Celma CC, González SA, Affranchino JL. Mutational analysis of the feline immunodeficiency virus matrix protein. Virus Res 2001; 76:103-13. [PMID: 11376850 DOI: 10.1016/s0168-1702(01)00249-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To study the process of feline immunodeficiency virus (FIV) assembly, we examined the suitability of the vaccinia vector system to reproduce FIV particle formation. To this end, we constructed a recombinant vaccinia virus carrying the FIV gag gene. Biochemical and electron microscopy analyses of cells infected with this recombinant virus showed that the FIV Gag polyprotein self-assembled into lentivirus-like particles that were released into the culture medium. As a first step in the identification of molecular determinants in FIV Gag that are involved in virus assembly, we performed a site-directed mutagenesis analysis of the N-terminal matrix (MA) domain of the FIV Gag precursor. To this end, a series of amino acid substitutions and small in-frame deletions were introduced into the FIV MA and the mutated FIV gag gene constructs were expressed by means of the vaccinia system. Characterization of the assembly phenotype of these FIV Gag mutants led to the identification of amino acidic regions within the MA domain that are necessary for efficient transport of the Gag precursor to the plasma membrane and particle assembly. Our results reveal the role that the FIV MA plays in virus morphogenesis and contribute to the understanding of the assembly process in non-primate lentiviruses.
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MESH Headings
- Amino Acid Sequence
- Animals
- Cell Line
- DNA, Recombinant/genetics
- Fibroblasts
- Gene Products, gag/chemistry
- Gene Products, gag/genetics
- Gene Products, gag/metabolism
- Genes, gag/genetics
- Genetic Vectors/genetics
- Immunodeficiency Virus, Feline/genetics
- Immunodeficiency Virus, Feline/metabolism
- Immunodeficiency Virus, Feline/ultrastructure
- Microscopy, Electron
- Molecular Sequence Data
- Mutation/genetics
- Protein Structure, Tertiary
- Thymidine Kinase/genetics
- Transfection
- Vaccinia virus/genetics
- Viral Matrix Proteins/chemistry
- Viral Matrix Proteins/genetics
- Viral Matrix Proteins/metabolism
- Virus Assembly
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Affiliation(s)
- M L Manrique
- Centro de Virología Animal (CEVAN-CONICET), Serrano 669, C1414DEM, Buenos Aires, Argentina
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8
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Jasenosky LD, Neumann G, Lukashevich I, Kawaoka Y. Ebola virus VP40-induced particle formation and association with the lipid bilayer. J Virol 2001; 75:5205-14. [PMID: 11333902 PMCID: PMC114926 DOI: 10.1128/jvi.75.11.5205-5214.2001] [Citation(s) in RCA: 233] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Viral protein 40 (VP40) of Ebola virus appears equivalent to matrix proteins of other viruses, yet little is known about its role in the viral life cycle. To elucidate the functions of VP40, we investigated its ability to induce the formation of membrane-bound particles when it was expressed apart from other viral proteins. We found that VP40 is indeed able to induce particle formation when it is expressed in mammalian cells, and this process appeared to rely on a conserved N-terminal PPXY motif, as mutation or loss of this motif resulted in markedly reduced particle formation. These findings demonstrate that VP40 alone possesses the information necessary to induce particle formation, and this process most likely requires cellular WW domain-containing proteins that interact with the PPXY motif of VP40. The ability of VP40 to bind cellular membranes was also studied. Flotation gradient analysis indicated that VP40 binds to membranes in a hydrophobic manner, as NaCl at 1 M did not release the protein from the lipid bilayer. Triton X-114 phase-partitioning analysis suggested that VP40 possesses only minor features of an integral membrane protein. We confirmed previous findings that truncation of the 50 C-terminal amino acids of VP40 results in decreased association with cellular membranes and demonstrated that this deletion disrupts hydrophobic interactions of VP40 with the lipid bilayer, as well as abolishing particle formation. Truncation of the 150 C-terminal amino acids or 100 N-terminal amino acids of VP40 enhanced the protein's hydrophobic association with cellular membranes. These data suggest that VP40 binds the lipid bilayer in an efficient yet structurally complex fashion.
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Affiliation(s)
- L D Jasenosky
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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9
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Morikawa Y, Kinoshita A, Goto T, Tomoda H, Sano K. Membrane relocation but not tight binding of human immunodeficiency virus type 1 Gag particles myristoylated in Escherichia coli. Virology 2001; 283:343-52. [PMID: 11336559 DOI: 10.1006/viro.2001.0886] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Expression of human immunodeficiency virus Gag protein and the N-terminal matrix (MA) domain in Escherichia coli yielded spherical structures in the cytoplasm. When human N-myristoyltransferase was coexpressed, both Gag and MA were fully myristoylated and spherical structures were relocated in close proximity to the cytoplasmic membrane. However, neither myristoylated Gag nor MA exhibited tight binding to E. coli membrane, suggesting that myristoylation in E. coli did not confer membrane affinity on Gag despite the relocation. Our data also suggest that the morphogenetic pathway of Gag particles in prokaryotic cells differs from that in eukaryotic cells despite biochemical similarities of in the form of Gag expressed.
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Affiliation(s)
- Y Morikawa
- The Kitasato Institute, Shirokane 5-9-1, Minato-ku, Tokyo 108-8642, Japan.
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10
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Ono A, Demirov D, Freed EO. Relationship between human immunodeficiency virus type 1 Gag multimerization and membrane binding. J Virol 2000; 74:5142-50. [PMID: 10799589 PMCID: PMC110867 DOI: 10.1128/jvi.74.11.5142-5150.2000] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag precursor, Pr55(Gag), is necessary and sufficient for the assembly and release of viruslike particles. Binding of Gag to membrane and Gag multimerization are both essential steps in virus assembly, yet the domains responsible for these events have not been fully defined. In addition, the relationship between membrane binding and Gag-Gag interaction remains to be elucidated. To investigate these issues, we analyzed, in vivo, the membrane-binding and assembly properties of a series of C-terminally truncated Gag mutants. Pr55(Gag) was truncated at the C terminus of matrix (MAstop), between the N- and C-terminal domains of capsid (CA146stop), at the C terminus of capsid (p41stop), at the C terminus of p2 (p43stop), and after the N-terminal 35 amino acids of nucleocapsid (NC35stop). The ability of these truncated Gag molecules to assemble and release viruslike particles and their capacity to copackage into particles when coexpressed with full-length Gag were determined. We demonstrate that the amount of truncated Gag incorporated into particles is incrementally increased by extension from CA146 to NC35, suggesting that multiple sites in this region are involved in Gag multimerization. Using membrane flotation centrifugation, we observe that MA shows significantly reduced membrane binding relative to full-length Gag but that CA146 displays steady-state membrane-binding properties comparable to those of Pr55(Gag). The finding that the CA146 mutant, which contains only matrix and the N-terminal domain of capsid, exhibits levels of steady-state membrane binding equivalent to those of full-length Gag indicates that strong Gag-Gag interaction domains are not required for the efficient binding of HIV-1 Gag to membrane.
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Affiliation(s)
- A Ono
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0460, USA
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11
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Deora A, Spearman P, Ratner L. The N-terminal matrix domain of HIV-1 Gag is sufficient but not necessary for viral protein U-mediated enhancement of particle release through a membrane-targeting mechanism. Virology 2000; 269:305-12. [PMID: 10753709 DOI: 10.1006/viro.1999.0094] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Viral protein U (Vpu) is an 81 amino acid phosphoprotein found in human immunodeficiency virus type 1 (HIV-1)-infected cells. One function of Vpu is to enhance the release of virus particles from the plasma membrane in infected cells. Using subcellular fractionation, we observed that Vpu promotes the targeting of Pr55 Gag to the plasma membrane, the site of viral assembly. Deletions of Pr55, which removed most of the N-terminal matrix domain (p39) or the C-terminal domains of nucleocapsid and p6 (p41), still allowed for virus-like particle production. Moreover, the release of these particles remained Vpu-responsive. The N-terminal matrix (MA) domain of Gag, which contains its membrane-binding domain, is sufficient for Vpu-mediated enhanced release into the supernatant. Furthermore, a MA-GFP fusion protein showed enhanced membrane binding in the presence of Vpu. This demonstrates that Vpu action may be mediated by allowing Gag, specifically the N-terminal matrix domain, to efficiently associate with the plasma membrane. Thus MA appears sufficient but not necessary for Vpu-mediated enhanced particle release.
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Affiliation(s)
- A Deora
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
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Kakker NK, Mikhailov MV, Nermut MV, Burny A, Roy P. Bovine leukemia virus Gag particle assembly in insect cells: formation of chimeric particles by domain-switched leukemia/lentivirus Gag polyprotein. Virology 1999; 265:308-18. [PMID: 10600602 DOI: 10.1006/viro.1999.0007] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A key stage in the life cycle of C-type retroviruses is the assembly of Gag precursor protein at the plasma membrane of infected cells. Here we report the assembly of bovine leukemia virus (BLV) gag gene product into virus-like particles (VLPs) using the baculovirus expression system. Expression of BLV Pr44(Gag) resulted in the assembly and release of VLPs, thereby confirming the ability of retroviral Gag polyprotein to assemble and bud from insect cells. Efficient particle formation required a myristoylation signal at the N-terminus of BLV Pr44(Gag). Recombinant baculoviruses expressing matrix (MA) or capsid-nucleocapsid (CA-NC) proteins of BLV were generated but neither of these domains was capable of assembling into particulate structures. To assess the compatibility of Gag domains between leukemia and lentivirus groups three different recombinant chimeras each expressing MA of one virus (e.g., simian immunodeficiency or BLV) and CA-NC of another (e.g., BLV or human T-cell leukemia virus type-I) were constructed. Each of the chimeric proteins assembled efficiently and budded as VLPs, suggesting that the MA and CA domains of these two evolutionary divergent retrovirus groups can be functionally exchanged without perturbation of Gag VLP formation. The lenti-leukemia chimeric Gag approach has potential for studying protein-protein interactions in other retroviruses.
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Affiliation(s)
- N K Kakker
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
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Wang JJ, Horton R, Varthakavi V, Spearman P, Ratner L. Formation and release of virus-like particles by HIV-1 matrix protein. AIDS 1999; 13:281-3. [PMID: 10202836 DOI: 10.1097/00002030-199902040-00018] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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