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Horns F, Martinez JA, Fan C, Haque M, Linton JM, Tobin V, Santat L, Maggiolo AO, Bjorkman PJ, Lois C, Elowitz MB. Engineering RNA export for measurement and manipulation of living cells. Cell 2023; 186:3642-3658.e32. [PMID: 37437570 PMCID: PMC10528933 DOI: 10.1016/j.cell.2023.06.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 05/08/2023] [Accepted: 06/19/2023] [Indexed: 07/14/2023]
Abstract
A system for programmable export of RNA molecules from living cells would enable both non-destructive monitoring of cell dynamics and engineering of cells capable of delivering executable RNA programs to other cells. We developed genetically encoded cellular RNA exporters, inspired by viruses, that efficiently package and secrete cargo RNA molecules from mammalian cells within protective nanoparticles. Exporting and sequencing RNA barcodes enabled non-destructive monitoring of cell population dynamics with clonal resolution. Further, by incorporating fusogens into the nanoparticles, we demonstrated the delivery, expression, and functional activity of exported mRNA in recipient cells. We term these systems COURIER (controlled output and uptake of RNA for interrogation, expression, and regulation). COURIER enables measurement of cell dynamics and establishes a foundation for hybrid cell and gene therapies based on cell-to-cell delivery of RNA.
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Affiliation(s)
- Felix Horns
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Joe A Martinez
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Chengcheng Fan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Mehernaz Haque
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - James M Linton
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Victoria Tobin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Leah Santat
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Ailiena O Maggiolo
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Pamela J Bjorkman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Carlos Lois
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Michael B Elowitz
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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2
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Subcellular localization of nucleocapsid protein of SFTSV and its assembly into the ribonucleoprotein complex with L protein and viral RNA. Sci Rep 2021; 11:22977. [PMID: 34836987 PMCID: PMC8626419 DOI: 10.1038/s41598-021-01985-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 10/29/2021] [Indexed: 11/08/2022] Open
Abstract
Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging bunyavirus that causes novel zoonotic diseases in Asian countries including China, Japan, South Korea, and Vietnam. In phleboviruses, viral proteins play a critical role in viral particle formation inside the host cells. Viral glycoproteins (GPs) and RNA-dependent RNA polymerase (RdRp) are colocalized in the Golgi apparatus and endoplasmic reticulum-Golgi intermediate compartment (ERGIC). The nucleocapsid (N) protein was widely expressed in the cytoplasm, even in cells coexpressing GP. However, the role of SFTSV N protein remains unclear. The subcellular localization of SFTSV structural proteins was investigated using a confocal microscope. Subsequently, minigenome and immunoprecipitation assays were carried out. The N protein interacts with viral RNA (vRNA) and further shows translational activity with RdRp which is L protein and localized in the ERGIC and Golgi apparatus when co-expressed with GP. On the other hand, mutant N protein did not interact with vRNA either localized in the ERGIC or Golgi apparatus. The interaction between the N protein of SFTSV and vRNA is important for the localization of viral proteins and viral assembly. This study provides useful insights into the life cycle of SFTSV, which will lead to the detection of antiviral targets.
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3
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Lyu P, Wang L, Lu B. Virus-Like Particle Mediated CRISPR/Cas9 Delivery for Efficient and Safe Genome Editing. Life (Basel) 2020; 10:366. [PMID: 33371215 PMCID: PMC7766694 DOI: 10.3390/life10120366] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 12/26/2022] Open
Abstract
The discovery of designer nucleases has made genome editing much more efficient than before. The designer nucleases have been widely used for mechanistic studies, animal model generation and gene therapy development. However, potential off-targets and host immune responses are issues still need to be addressed for in vivo uses, especially clinical applications. Short term expression of the designer nucleases is necessary to reduce both risks. Currently, various delivery methods are being developed for transient expression of designer nucleases including Zinc Finger Nuclease (ZNF), Transcription Activator-Like Effector Nuclease (TALEN) and Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated (CRISPR/Cas). Recently, virus-like particles are being used for gene editing. In this review, we will talk through commonly used genome editing nucleases, discuss gene editing delivery tools and review the latest literature using virus-like particles to deliver gene editing effectors.
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Affiliation(s)
- Pin Lyu
- School of Physical Education and Health, Hangzhou Normal University, Hangzhou 311121, China;
| | - Luxi Wang
- Department of Cancer Biology, Comprehensive Cancer Center of Wake Forest Baptist Medical Center, Winston-Salem, NC 27157, USA;
| | - Baisong Lu
- Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA
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4
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Monette A, Niu M, Chen L, Rao S, Gorelick RJ, Mouland AJ. Pan-retroviral Nucleocapsid-Mediated Phase Separation Regulates Genomic RNA Positioning and Trafficking. Cell Rep 2020; 31:107520. [PMID: 32320662 PMCID: PMC8965748 DOI: 10.1016/j.celrep.2020.03.084] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 02/12/2020] [Accepted: 03/24/2020] [Indexed: 02/07/2023] Open
Abstract
The duality of liquid-liquid phase separation (LLPS) of cellular components into membraneless organelles defines the nucleation of both normal and disease processes including stress granule (SG) assembly. From mounting evidence of LLPS utility by viruses, we discover that HIV-1 nucleocapsid (NC) protein condenses into zinc-finger (ZnF)-dependent LLPSs that are dynamically influenced by cytosolic factors. ZnF-dependent and Zinc (Zn2+)-chelation-sensitive NC-LLPS are formed in live cells. NC-Zn2+ ejection reverses the HIV-1 blockade on SG assembly, inhibits NC-SG assembly, disrupts NC/Gag-genomic RNA (vRNA) ribonucleoprotein complexes, and causes nuclear sequestration of NC and the vRNA, inhibiting Gag expression and virus release. NC ZnF mutagenesis eliminates the HIV-1 blockade of SG assembly and repositions vRNA to SGs. We find that NC-mediated, Zn2+-coordinated phase separation is conserved among diverse retrovirus subfamilies, illustrating that this exquisitely evolved Zn2+-dependent feature of virus replication represents a critical target for pan-antiretroviral therapies.
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Affiliation(s)
- Anne Monette
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada.
| | - Meijuan Niu
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
| | - Lois Chen
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada; Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
| | - Shringar Rao
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada; Department of Biochemistry, Erasmus University Medical Center, Ee634, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Robert James Gorelick
- AIDS and Cancer Virus Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21701, USA
| | - Andrew John Mouland
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada; Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada; Department of Medicine, McGill University, Montréal, QC H3G 2M1, Canada.
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5
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Lyu P, Javidi-Parsijani P, Atala A, Lu B. Delivering Cas9/sgRNA ribonucleoprotein (RNP) by lentiviral capsid-based bionanoparticles for efficient 'hit-and-run' genome editing. Nucleic Acids Res 2019; 47:e99. [PMID: 31299082 PMCID: PMC6753487 DOI: 10.1093/nar/gkz605] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/11/2019] [Accepted: 07/03/2019] [Indexed: 01/22/2023] Open
Abstract
Transient expression of the CRISPR/Cas9 machinery will not only reduce risks of mutagenesis from off-target activities, but also decrease possible immune response to Cas9 protein. Building on our recent developing of a system able to package up to 100 copies of Cas9 mRNA in each lentivirus-like particle (LVLP) via the specific interaction between aptamer and aptamer-binding proteins (ABP), here we develop a lentiviral capsid-based bionanoparticle system, which allows efficient packaging of Cas9/sgRNA ribonucleoprotein (RNP). We show that replacing the Tetraloop of sgRNA scaffold with a com aptamer preserves the functions of the guide RNA, and the com-modified sgRNA can package Cas9/sgRNA RNP into lentivirus-like particles via the specific interactions between ABP and aptamer, and sgRNA and Cas9 protein. These RNP bionanoparticles generated Indels on different targets in different cells with efficiencies similar to or better than our recently described Cas9 mRNA LVLPs. The new system showed fast action and reduced off-target rates, and makes it more convenient and efficient in delivering Cas9 RNPs for transient Cas9 expression and efficient genome editing.
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Affiliation(s)
- Pin Lyu
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui, 241000, China.,Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, 27101, USA
| | - Parisa Javidi-Parsijani
- Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, 27101, USA
| | - Anthony Atala
- Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, 27101, USA
| | - Baisong Lu
- Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, 27101, USA
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6
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Olson ED, Musier-Forsyth K. Retroviral Gag protein-RNA interactions: Implications for specific genomic RNA packaging and virion assembly. Semin Cell Dev Biol 2018; 86:129-139. [PMID: 29580971 DOI: 10.1016/j.semcdb.2018.03.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/09/2018] [Accepted: 03/22/2018] [Indexed: 02/04/2023]
Abstract
Retroviral Gag proteins are responsible for coordinating many aspects of virion assembly. Gag possesses two distinct nucleic acid binding domains, matrix (MA) and nucleocapsid (NC). One of the critical functions of Gag is to specifically recognize, bind, and package the retroviral genomic RNA (gRNA) into assembling virions. Gag interactions with cellular RNAs have also been shown to regulate aspects of assembly. Recent results have shed light on the role of MA and NC domain interactions with nucleic acids, and how they jointly function to ensure packaging of the retroviral gRNA. Here, we will review the literature regarding RNA interactions with NC, MA, as well as overall mechanisms employed by Gag to interact with RNA. The discussion focuses on human immunodeficiency virus type-1, but other retroviruses will also be discussed. A model is presented combining all of the available data summarizing the various factors and layers of selection Gag employs to ensure specific gRNA packaging and correct virion assembly.
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Affiliation(s)
- Erik D Olson
- Department of Chemistry and Biochemistry, Center for RNA Biology, and Center for Retrovirus Research, Ohio State University, Columbus, OH, 43210, USA
| | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, Center for RNA Biology, and Center for Retrovirus Research, Ohio State University, Columbus, OH, 43210, USA.
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7
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Qu N, Ma Z, Zhang M, Rushdi MN, Krueger CJ, Chen AK. Inhibition of retroviral Gag assembly by non-silencing miRNAs promotes autophagic viral degradation. Protein Cell 2017; 9:640-651. [PMID: 28884441 PMCID: PMC6019656 DOI: 10.1007/s13238-017-0461-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 08/07/2017] [Indexed: 12/29/2022] Open
Abstract
We recently reported an unconventional mechanism by which miRNAs inhibit HIV-1 viral production. This occurs when miRNAs bind nonspecifically to the viral structural protein Gag, interfering with viral RNA-mediated Gag assembly at the plasma membrane. Consequently, misassembled viral complexes are redirected into the endocytic pathway where they are delivered to lysosomes for degradation. In this study, we demonstrate that autophagy is a critical mediator of the viral degradation pathway and that this pathway is not HIV-1 specific. Misassembled viral complexes were found to colocalize extensively with LC3 and p62 in late endosomes/lysosomes, demonstrating a convergence of autophagy with functional degradative compartments. Knocking down autophagosome formation machineries reduced this convergence, while treatment with autophagy-inducer rapamycin enhanced the convergence. Furthermore, similar autophagy-dependent nonspecific miRNA inhibition of murine leukemia virus (MLV) assembly was shown. Overall, these results reveal autophagy as a crucial regulator of the retroviral degradation pathway in host cells initiated by nonspecific miRNA-Gag interactions. These findings could have significant implications for understanding how cells may regulate retroviral complex assembly by miRNA expression and autophagy, and raise the possibility that similar regulations can occur in other biological contexts.
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Affiliation(s)
- Na Qu
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Zhao Ma
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Mengrao Zhang
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Muaz N Rushdi
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Christopher J Krueger
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Antony K Chen
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China.
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8
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Subcellular Localization of HIV-1 gag-pol mRNAs Regulates Sites of Virion Assembly. J Virol 2017; 91:JVI.02315-16. [PMID: 28053097 DOI: 10.1128/jvi.02315-16] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 12/23/2016] [Indexed: 02/07/2023] Open
Abstract
Full-length unspliced human immunodeficiency virus type 1 (HIV-1) RNAs serve dual roles in the cytoplasm as mRNAs encoding the Gag and Gag-Pol capsid proteins as well as genomic RNAs (gRNAs) packaged by Gag into virions undergoing assembly at the plasma membrane (PM). Because Gag is sufficient to drive the assembly of virus-like particles even in the absence of gRNA binding, whether viral RNA trafficking plays an active role in the native assembly pathway is unknown. In this study, we tested the effects of modulating the cytoplasmic abundance or distribution of full-length viral RNAs on Gag trafficking and assembly in the context of single cells. Increasing full-length viral RNA abundance or distribution had little-to-no net effect on Gag assembly competency when provided in trans In contrast, artificially tethering full-length viral RNAs or surrogate gag-pol mRNAs competent for Gag synthesis to non-PM membranes or the actin cytoskeleton severely reduced net virus particle production. These effects were explained, in large part, by RNA-directed changes to Gag's distribution in the cytoplasm, yielding aberrant subcellular sites of virion assembly. Interestingly, RNA-dependent disruption of Gag trafficking required either of two cis-acting RNA regulatory elements: the 5' packaging signal (Psi) bound by Gag during genome encapsidation or, unexpectedly, the Rev response element (RRE), which regulates the nuclear export of gRNAs and other intron-retaining viral RNAs. Taken together, these data support a model for native infection wherein structural features of the gag-pol mRNA actively compartmentalize Gag to preferred sites within the cytoplasm and/or PM.IMPORTANCE The spatial distribution of viral mRNAs within the cytoplasm can be a crucial determinant of efficient translation and successful virion production. Here we provide direct evidence that mRNA subcellular trafficking plays an important role in regulating the assembly of human immunodeficiency virus type 1 (HIV-1) virus particles at the plasma membrane (PM). Artificially tethering viral mRNAs encoding Gag capsid proteins (gag-pol mRNAs) to distinct non-PM subcellular locales, such as cytoplasmic vesicles or the actin cytoskeleton, markedly alters Gag subcellular distribution, relocates sites of assembly, and reduces net virus particle production. These observations support a model for native HIV-1 assembly wherein HIV-1 gag-pol mRNA localization helps to confine interactions between Gag, viral RNAs, and host determinants in order to ensure virion production at the right place and right time. Direct perturbation of HIV-1 mRNA subcellular localization may represent a novel antiviral strategy.
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9
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Evolutionary characterization of Ty3/gypsy-like LTR retrotransposons in the parasitic cestode Echinococcus granulosus. Parasitology 2016; 143:1691-1702. [PMID: 27571603 DOI: 10.1017/s0031182016001499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cyclophyllidean cestodes including Echinococcus granulosus have a smaller genome and show characteristics such as loss of the gut, a segmented body plan, and accelerated growth rate in hosts compared with other tissue-invading helminths. In an effort to address the molecular mechanism relevant to genome shrinkage, the evolutionary status of long-terminal-repeat (LTR) retrotransposons, which are known as the most potent genomic modulators, was investigated in the E. granulosus draft genome. A majority of the E. granulosus LTR retrotransposons were classified into a novel characteristic clade, named Saci-2, of the Ty3/gypsy family, while the remaining elements belonged to the CsRn1 clade of identical family. Their nucleotide sequences were heavily corrupted by frequent base substitutions and segmental losses. The ceased mobile activity of the major retrotransposons and the following intrinsic DNA loss in their inactive progenies might have contributed to decrease in genome size. Apart from the degenerate copies, a gag gene originating from a CsRn1-like element exhibited substantial evidences suggesting its domestication including a preserved coding profile and transcriptional activity, the presence of syntenic orthologues in cestodes, and selective pressure acting on the gene. To my knowledge, the endogenized gag gene is reported for the first time in invertebrates, though its biological function remains elusive.
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10
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Hamann MV, Müllers E, Reh J, Stanke N, Effantin G, Weissenhorn W, Lindemann D. The cooperative function of arginine residues in the Prototype Foamy Virus Gag C-terminus mediates viral and cellular RNA encapsidation. Retrovirology 2014; 11:87. [PMID: 25292281 PMCID: PMC4198681 DOI: 10.1186/s12977-014-0087-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 09/23/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND One unique feature of the foamy virus (FV) capsid protein Gag is the absence of Cys-His motifs, which in orthoretroviruses are irreplaceable for multitude functions including viral RNA genome recognition and packaging. Instead, FV Gag contains glycine-arginine-rich (GR) sequences at its C-terminus. In case of prototype FV (PFV) these are historically grouped in three boxes, which have been shown to play essential functions in genome reverse transcription, virion infectivity and particle morphogenesis. Additional functions for RNA packaging and Pol encapsidation were suggested, but have not been conclusively addressed. RESULTS Here we show that released wild type PFV particles, like orthoretroviruses, contain various cellular RNAs in addition to viral genome. Unlike orthoretroviruses, the content of selected cellular RNAs in capsids of PFV vector particles was not altered by viral genome encapsidation. Deletion of individual GR boxes had only minor negative effects (2 to 4-fold) on viral and cellular RNA encapsidation over a wide range of cellular Gag to viral genome ratios examined. Only the concurrent deletion of all three PFV Gag GR boxes, or the substitution of multiple arginine residues residing in the C-terminal GR box region by alanine, abolished both viral and cellular RNA encapsidation (>50 to >3,000-fold reduced), independent of the viral production system used. Consequently, those mutants also lacked detectable amounts of encapsidated Pol and were non-infectious. In contrast, particle release was reduced to a much lower extent (3 to 20-fold). CONCLUSIONS Taken together, our data provides the first identification of a full-length PFV Gag mutant devoid in genome packaging and the first report of cellular RNA encapsidation into PFV particles. Our results suggest that the cooperative action of C-terminal clustered positively charged residues, present in all FV Gag proteins, is the main viral protein determinant for viral and cellular RNA encapsidation. The viral genome independent efficiency of cellular RNA encapsidation suggests differential packaging mechanisms for both types of RNAs. Finally, this study indicates that analogous to orthoretroviruses, Gag - nucleic acid interactions are required for FV capsid assembly and efficient particle release.
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Affiliation(s)
- Martin V Hamann
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Erik Müllers
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany. .,Present address: Department of Cell and Molecular Biology, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Juliane Reh
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Nicole Stanke
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Gregory Effantin
- Univ. Grenoble Alpes, UVHCI, F-38000, Grenoble, France. .,CNRS, UVHCI, F-38000, Grenoble, France.
| | - Winfried Weissenhorn
- Univ. Grenoble Alpes, UVHCI, F-38000, Grenoble, France. .,CNRS, UVHCI, F-38000, Grenoble, France.
| | - Dirk Lindemann
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
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11
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Murine leukemia virus Gag localizes to the uropod of migrating primary lymphocytes. J Virol 2014; 88:10541-55. [PMID: 24965475 DOI: 10.1128/jvi.01104-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED B and CD4(+) T lymphocytes are natural targets of murine leukemia virus (MLV). Migrating lymphocytes adopt a polarized morphology with a trailing edge designated the uropod. Here, we demonstrate that MLV Gag localizes to the uropod in polarized B cells and CD4(+) T cells. The uropod localization of MLV Gag was dependent on plasma membrane (PM) association and multimerization of Gag but independent of the viral glycoprotein Env. Basic residues in MA that are required for MLV Gag recruitment to virological synapses between HEK293 and XC cells were dispensable for uropod localization in migrating B cells. Ultrastructural studies indicated that both wild-type and basic-residue mutant Gag localized to the outer surface of the PM at the uropod. Late-domain mutant virus particles were seen at the uropod in form of budding-arrested intermediates. Finally, uropods mediated contact between MLV-infected B cells and uninfected T cells to form virological synapses. Our results suggest that MLV, not unlike HIV, accumulates at the uropod of primary lymphocytes to facilitate viral spreading through the formation of uropod-mediated cell-cell contacts. IMPORTANCE Viruses have evolved mechanisms to coordinate their assembly and budding with cell polarity to facilitate their spreading. In this study, we demonstrated that the viral determinants for MLV Gag to localize to the uropod in polarized B cells are distinct from the requirements to localize to virological synapses in transformed cell lines. Basic residues in MA that are required for the Gag localization to virological synapses between HEK293 and XC cells are dispensable for Gag localization to the uropod in primary B cells. Rather, plasma membrane association and capsid-driven multimerization of Gag are sufficient to drive MLV Gag to the uropod. MLV-laden uropods also mediate contacts between MLV-infected B cells and uninfected T cells to form virological synapses. Our results indicate that MLV accumulates at the uropod of primary lymphocytes to facilitate viral spreading through the formation of uropod-mediated cell-cell contacts.
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12
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Maldonado JO, Martin JL, Mueller JD, Zhang W, Mansky LM. New insights into retroviral Gag-Gag and Gag-membrane interactions. Front Microbiol 2014; 5:302. [PMID: 25009535 PMCID: PMC4068372 DOI: 10.3389/fmicb.2014.00302] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 06/02/2014] [Indexed: 11/19/2022] Open
Abstract
A critical aspect of viral replication is the assembly of virus particles, which are subsequently released as progeny virus. While a great deal of attention has been focused on better understanding this phase of the viral life cycle, many aspects of the molecular details remain poorly understood. This is certainly true for retroviruses, including that of the human immunodeficiency virus type 1 (HIV-1; a lentivirus) as well as for human T-cell leukemia virus type 1 (HTLV-1; a deltaretrovirus). This review discusses the retroviral Gag protein and its interactions with itself, the plasma membrane and the role of lipids in targeting Gag to virus assembly sites. Recent progress using sophisticated biophysical approaches to investigate – in a comparative manner – retroviral Gag–Gag and Gag–membrane interactions are discussed. Differences among retroviruses in Gag–Gag and Gag–membrane interactions imply dissimilar molecular aspects of the viral assembly pathway, including the interactions of Gag with lipids at the membrane.
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Affiliation(s)
- José O Maldonado
- 1Institute for Molecular Virology, University of Minnesota Minneapolis, MN, USA ; 2Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota , Minneapolis, MN, USA
| | - Jessica L Martin
- 1Institute for Molecular Virology, University of Minnesota Minneapolis, MN, USA ; 3Pharmacology Graduate Program, University of Minnesota Minneapolis, MN, USA
| | - Joachim D Mueller
- 1Institute for Molecular Virology, University of Minnesota Minneapolis, MN, USA ; 4School of Physics and Astronomy, University of Minnesota Minneapolis, MN, USA
| | - Wei Zhang
- 1Institute for Molecular Virology, University of Minnesota Minneapolis, MN, USA ; 2Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota , Minneapolis, MN, USA ; 5Characterization Facility, University of Minnesota Minneapolis, MN, USA
| | - Louis M Mansky
- 1Institute for Molecular Virology, University of Minnesota Minneapolis, MN, USA ; 2Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota , Minneapolis, MN, USA ; 3Pharmacology Graduate Program, University of Minnesota Minneapolis, MN, USA ; 6Department of Microbiology, University of Minnesota Minneapolis, MN, USA
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Alfadhli A, Barklis E. The roles of lipids and nucleic acids in HIV-1 assembly. Front Microbiol 2014; 5:253. [PMID: 24917853 PMCID: PMC4042026 DOI: 10.3389/fmicb.2014.00253] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 05/08/2014] [Indexed: 11/23/2022] Open
Abstract
During HIV-1 assembly, precursor Gag (PrGag) proteins are delivered to plasma membrane (PM) assembly sites, where they are triggered to oligomerize and bud from cells as immature virus particles. The delivery and triggering processes are coordinated by the PrGag matrix (MA) and nucleocapsid (NC) domains. Targeting of PrGag proteins to membranes enriched in cholesterol and phosphatidylinositol-4,5-bisphosphate (PI[4,5]P2) is mediated by the MA domain, which also has been shown to bind both RNA and DNA. Evidence suggests that the nucleic-acid-binding function of MA serves to inhibit PrGag binding to inappropriate intracellular membranes, prior to delivery to the PM. At the PM, MA domains putatively trade RNA ligands for PI(4,5)P2 ligands, fostering high-affinity membrane binding. Triggering of oligomerization, budding, and virus particle release results when NC domains on adjacent PrGag proteins bind to viral RNA, leading to capsid (CA) domain oligomerization. This process leads to the assembly of immature virus shells in which hexamers of membrane-bound MA trimers appear to organize above interlinked CA hexamers. Here, we review the functions of retroviral MA proteins, with an emphasis on the nucleic-acid-binding capability of the HIV-1 MA protein, and its effects on membrane binding.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University Portland, OR, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University Portland, OR, USA
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Determinants of Moloney murine leukemia virus Gag-Pol and genomic RNA proportions. J Virol 2014; 88:7267-75. [PMID: 24741085 DOI: 10.1128/jvi.03513-13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The Moloney murine leukemia virus (MoMLV) ribonucleoprotein complex is composed of an approximately 20:1 mixture of Gag and Gag-Pol polyproteins plus a single genomic RNA (gRNA) dimer. The mechanisms that regulate these proportions are unknown. Here, we examined whether virion proportions of Gag, Gag-Pol, and gRNA were determined by sampling (that is, if they reflected expression ratios or intracellular concentrations) or more specific recruitment. To this end, MoMLV Gag, Gag-Pol, and gRNA were expressed separately or together in various ratios. Varying the expression ratios of Gag and Gag-Pol revealed that Gag-Pol incorporation was stochastic and that the conserved 20:1 Gag/Gag-Pol ratio coincided with maximal particle production. When skewed expression ratios resulted in excess Gag-Pol, the released virions maintained the intracellular Gag/Gag-Pol ratios and the infectivity per virion was largely maintained, but virion production decreased sharply with high levels of Gag-Pol. The determinants of gRNA proportions were addressed by manipulating the amounts and contexts of functional nucleocapsid (NC) and the ratios of Gag to gRNA. The results showed that the NC domain of either Gag or Gag-Pol could provide gRNA packaging functions equally well. Unlike Gag-Pol, gRNA incorporation was saturable. An upper limit of gRNA incorporation was observed, and particle production was not disrupted by excess gRNA expression. These results indicate that the determinants of Gag/Gag-Pol proportions differ from those for Gag/gRNA. On the basis of the assumption that MoMLV evolved to produce virion components in optimal proportions, these data provide a means of estimating the proportion of unspliced MoMLV RNA that serves as genomic RNA. IMPORTANCE Viruses assemble their progeny from within the cells that they parasitize, where they must sort through a rich milieu of host proteins and nucleic acids to gather together their own building blocks, which are also proteins and nucleic acids. The research described here addresses whether or not the proportions of viral proteins and nucleic acids that are brought together to form a retroviral particle are determined by random sampling from the cell-and thus dictated by the components' availabilities within the cell-or if the amounts of each molecule are specified by the virus replication process. The results indicated that protein components of the murine retrovirus studied here are recruited by chance but that a specific counting mechanism defines the amount of nucleic acid incorporated into each progeny virion.
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15
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The foamy virus Gag proteins: what makes them different? Viruses 2013; 5:1023-41. [PMID: 23531622 PMCID: PMC3705263 DOI: 10.3390/v5041023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/15/2013] [Accepted: 03/20/2013] [Indexed: 12/15/2022] Open
Abstract
Gag proteins play an important role in many stages of the retroviral replication cycle. They orchestrate viral assembly, interact with numerous host cell proteins, engage in regulation of viral gene expression, and provide the main driving force for virus intracellular trafficking and budding. Foamy Viruses (FV), also known as spumaviruses, display a number of unique features among retroviruses. Many of these features can be attributed to their Gag proteins. FV Gag proteins lack characteristic orthoretroviral domains like membrane-binding domains (M domains), the major homology region (MHR), and the hallmark Cys-His motifs. In contrast, they contain several distinct domains such as the essential Gag-Env interaction domain and the glycine and arginine rich boxes (GR boxes). Furthermore, FV Gag only undergoes limited maturation and follows an unusual pathway for nuclear translocation. This review summarizes the known FV Gag domains and motifs and their functions. In particular, it provides an overview of the unique structural and functional properties that distinguish FV Gag proteins from orthoretroviral Gag proteins.
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16
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Chamontin C, Yu B, Racine PJ, Darlix JL, Mougel M. MoMuLV and HIV-1 nucleocapsid proteins have a common role in genomic RNA packaging but different in late reverse transcription. PLoS One 2012; 7:e51534. [PMID: 23236513 PMCID: PMC3517543 DOI: 10.1371/journal.pone.0051534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/05/2012] [Indexed: 11/25/2022] Open
Abstract
Retroviral nucleocapsid proteins harbor nucleic acid chaperoning activities that mostly rely on the N-terminal basic residues and the CCHC zinc finger motif. Such chaperoning is essential for virus replication, notably for genomic RNA selection and packaging in virions, and for reverse transcription of genomic RNA into DNA. Recent data revealed that HIV-1 nucleocapsid restricts reverse transcription during virus assembly--a process called late reverse transcription--suggesting a regulation between RNA packaging and late reverse transcription. Indeed, mutating the HIV-1 nucleocapsid basic residues or the two zinc fingers caused a reduction in RNA incorporated and an increase in newly made viral DNA in the mutant virions. MoMuLV nucleocapsid has an N-terminal basic region similar to HIV-1 nucleocapsid but a unique zinc finger. This prompted us to investigate whether the N-terminal basic residues and the zinc finger of MoMuLV and HIV-1 nucleocapsids play a similar role in genomic RNA packaging and late reverse transcription. To this end, we analyzed the genomic RNA and viral DNA contents of virions produced by cells transfected with MoMuLV molecular clones where the zinc finger was mutated or completely deleted or with a deletion of the N-terminal basic residues of nucleocapsid. All mutant virions showed a strong defect in genomic RNA content indicating that the basic residues and zinc finger are important for genomic RNA packaging. In contrast to HIV-1 nucleocapsid-mutants, the level of viral DNA in mutant MoMuLV virions was only slightly increased. These results confirm that the N-terminal basic residues and zinc finger of MoMuLV nucleocapsid are critical for genomic RNA packaging but, in contrast to HIV-1 nucleocapsid, they most probably do not play a role in the control of late reverse transcription. In addition, these results suggest that virus formation and late reverse transcription proceed according to distinct mechanisms for MuLV and HIV-1.
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Affiliation(s)
| | - Bing Yu
- UMR5236 CNRS, UM1,UM2, CPBS, Montpellier, France
| | | | - Jena-Luc Darlix
- UMR 7213 CNRS, Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, Illkirch, France
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17
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Abstract
Expression of a retroviral Gag protein in mammalian cells leads to the assembly of virus particles. In vitro, recombinant Gag proteins are soluble but assemble into virus-like particles (VLPs) upon addition of nucleic acid. We have proposed that Gag undergoes a conformational change when it is at a high local concentration and that this change is an essential prerequisite for particle assembly; perhaps one way that this condition can be fulfilled is by the cooperative binding of Gag molecules to nucleic acid. We have now characterized the assembly in human cells of HIV-1 Gag molecules with a variety of defects, including (i) inability to bind to the plasma membrane, (ii) near-total inability of their capsid domains to engage in dimeric interaction, and (iii) drastically compromised ability to bind RNA. We find that Gag molecules with any one of these defects still retain some ability to assemble into roughly spherical objects with roughly correct radius of curvature. However, combination of any two of the defects completely destroys this capability. The results suggest that these three functions are somewhat redundant with respect to their contribution to particle assembly. We suggest that they are alternative mechanisms for the initial concentration of Gag molecules; under our experimental conditions, any two of the three is sufficient to lead to some semblance of correct assembly.
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Virus assembly and plasma membrane domains: which came first? Virus Res 2012; 171:332-40. [PMID: 22989508 DOI: 10.1016/j.virusres.2012.08.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 08/21/2012] [Accepted: 08/21/2012] [Indexed: 11/23/2022]
Abstract
Viral assembly is a key step in the virus life cycle. In this review, we focus mainly on the ability of retroviruses, especially HIV-1, to assemble at the plasma membrane of their host cells. The assembly process of RNA enveloped viruses necessitates a fine orchestration between the different viral components and specific interactions between viral proteins and lipids of the host cell membrane. Searching for a comparison with another RNA enveloped virus, we refer to influenza virus to show how it could share (or not) some common features with HIV-1 assembly since both viruses are believed to assemble mainly in raft microdomains. We also discuss the role of RNA and the cellular actin cytoskeleton in enhancing these viral assembly processes. Finally, based on the literature and on new results we have obtained by molecular docking, we propose another mechanism for HIV-1 assembly in membrane domains. This mechanism involves the trapping of acidic lipids by the viral Gag protein by means of ionic protein-lipid interactions, inducing thereby formation of acidic lipid-enriched microdomains (ALEM).
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Johnson SF, Garcia EL, Summers MF, Telesnitsky A. Moloney murine leukemia virus genomic RNA packaged in the absence of a full complement of wild type nucleocapsid protein. Virology 2012; 430:100-9. [PMID: 22633243 DOI: 10.1016/j.virol.2012.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 03/26/2012] [Accepted: 05/07/2012] [Indexed: 11/17/2022]
Abstract
The current model for MLV genomic RNA (gRNA) packaging predicts that of the thousands of Gag proteins in a budding virion, only a small number (≤1%) may be necessary to recruit gRNA. Here, we examined the threshold limits of functional Gag required to package gRNA using wild-type (WT) and packaging deficient mutant nucleocapsid (NC) phenotypically mixed virions. Although gRNA packaging was severely diminished for the NC mutant, the residual encapsidated RNA dimer displayed motility on gels, thermostability, and integrity that was indistinguishable from that of WT. In phenotypically mixed virions, gRNA encapsidation recovered to within approximately two-fold of WT levels when the amount of WT NC was 5-10% of the total. Our results demonstrate that NC's roles in gRNA dimerization and packaging are genetically separable. Additionally, MLV gRNA packaging does not require 100% WT NC, but the amount of functional NC required is greater than the predicted minimum.
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Affiliation(s)
- Silas F Johnson
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
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20
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Solution properties of murine leukemia virus gag protein: differences from HIV-1 gag. J Virol 2011; 85:12733-41. [PMID: 21917964 DOI: 10.1128/jvi.05889-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Immature retrovirus particles are assembled from the multidomain Gag protein. In these particles, the Gag proteins are arranged radially as elongated rods. We have previously characterized the properties of HIV-1 Gag in solution. In the absence of nucleic acid, HIV-1 Gag displays moderately weak interprotein interactions, existing in monomer-dimer equilibrium. Neutron scattering and hydrodynamic studies suggest that the protein is compact, and biochemical studies indicate that the two ends can approach close in three-dimensional space, implying the need for a significant conformational change during assembly. We now describe the properties of the Gag protein of Moloney murine leukemia virus (MLV), a gammaretrovirus. We found that this protein is very different from HIV-1 Gag: it has much weaker protein-protein interaction and is predominantly monomeric in solution. This has allowed us to study the protein by small-angle X-ray scattering and to build a low-resolution molecular envelope for the protein. We found that MLV Gag is extended in solution, with an axial ratio of ∼7, comparable to its dimensions in immature particles. Mutational analysis suggests that runs of prolines in its matrix and p12 domains and the highly charged stretch at the C terminus of its capsid domain all contribute to this extended conformation. These differences between MLV Gag and HIV-1 Gag and their implications for retroviral assembly are discussed.
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21
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Rein A, Datta SAK, Jones CP, Musier-Forsyth K. Diverse interactions of retroviral Gag proteins with RNAs. Trends Biochem Sci 2011; 36:373-80. [PMID: 21550256 PMCID: PMC3130074 DOI: 10.1016/j.tibs.2011.04.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 03/31/2011] [Accepted: 04/04/2011] [Indexed: 10/18/2022]
Abstract
Retrovirus particles are constructed from a single virus-encoded protein, termed Gag. Given that assembly is an essential step in the viral replication cycle, it is a potential target for antiviral therapy. However, such an approach has not yet been exploited because of the lack of fundamental knowledge concerning the structures and interactions responsible for assembly. Assembling an infectious particle entails a remarkably diverse array of interactions, both specific and nonspecific, between Gag proteins and RNAs. These interactions are essential for the construction of the particle, for packaging of the viral RNA into the particle, and for placement of the primer for viral DNA synthesis. Recent results have provided some new insights into each of these interactions. In the case of HIV-1 Gag, it is clear that more than one domain of the protein contributes to Gag-RNA interaction.
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Affiliation(s)
- Alan Rein
- HIV Drug Resistance Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA.
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Jouvenet N, Lainé S, Pessel-Vivares L, Mougel M. Cell biology of retroviral RNA packaging. RNA Biol 2011; 8:572-80. [PMID: 21691151 DOI: 10.4161/rna.8.4.16030] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Generation of infectious retroviral particles rely on the targeting of all structural components to the correct cellular sites at the correct time. Gag, the main structural protein, orchestrates the assembly process and the mechanisms that trigger its targeting to assembly sites are well described. Gag is also responsible for the packaging of the viral genome and the molecular details of the Gag/RNA interaction are well characterized. Until recently, much less was understood about the cell biology of retrovirus RNA packaging. However, novel biochemical and live-cell microscopic approaches have identified where in the cell the initial events of genome recognition by Gag occur. These recent developments have shed light on the role played by the viral genome during virion assembly. Other central issues of the cell biology of RNA packaging, such as how the Gag-RNA complex traffics through the cytoplasm towards assembly sites, await characterization.
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Muriaux D, Darlix JL. Properties and functions of the nucleocapsid protein in virus assembly. RNA Biol 2010; 7:744-53. [PMID: 21157181 DOI: 10.4161/rna.7.6.14065] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
HIV-1 nucleocapsid protein (NC) is a small basic protein generated by the cleavage of the Gag structural polyprotein precusor by the viral protease during virus assembly in the infected cell. HIV-1 NC possesses two copies of a highly conserved CCHC zinc finger (ZnF), flanked by basic residues. HIV-1 NC and more generally retroviral NC proteins are nucleic acid binding proteins possessing potent nucleic acid condensing and chaperoning activities. As such NC protein drives critical structural rearrangements of the genomic RNA, notably RNA dimerization in the course of virus assembly and viral nucleic acid annealing required for genomic RNA replication by the viral reverse transcriptase (RT). Here we review the relationships between the 3D structure of HIV-1 NC, notably the central globular domain encompassing the two zinc fingers and the basic linker and NC functions in the early and late phases of virus replication. One of the salient feature of the NC central globular domain is an hydrophobic plateau which appears to orchestrate the NC functions, such as chaperoning the conversion of the genomic RNA into viral DNA by RT during the early phase, and driving the selection and dimerization of the genomic RNA at the initial stage of viral particle assembly. This ensures a bona fide trafficking of early GagNC-genomic RNA complexes to the plasma membrane of the infected cell and ultimately virion formation and budding.
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Conserved and variable features of Gag structure and arrangement in immature retrovirus particles. J Virol 2010; 84:11729-36. [PMID: 20810738 DOI: 10.1128/jvi.01423-10] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The assembly of retroviruses is driven by oligomerization of the Gag polyprotein. We have used cryo-electron tomography together with subtomogram averaging to describe the three-dimensional structure of in vitro-assembled Gag particles from human immunodeficiency virus, Mason-Pfizer monkey virus, and Rous sarcoma virus. These represent three different retroviral genera: the lentiviruses, betaretroviruses and alpharetroviruses. Comparison of the three structures reveals the features of the supramolecular organization of Gag that are conserved between genera and therefore reflect general principles of Gag-Gag interactions and the features that are specific to certain genera. All three Gag proteins assemble to form approximately spherical hexameric lattices with irregular defects. In all three genera, the N-terminal domain of CA is arranged in hexameric rings around large holes. Where the rings meet, 2-fold densities, assigned to the C-terminal domain of CA, extend between adjacent rings, and link together at the 6-fold symmetry axis with a density, which extends toward the center of the particle into the nucleic acid layer. Although this general arrangement is conserved, differences can be seen throughout the CA and spacer peptide regions. These differences can be related to sequence differences among the genera. We conclude that the arrangement of the structural domains of CA is well conserved across genera, whereas the relationship between CA, the spacer peptide region, and the nucleic acid is more specific to each genus.
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Targeting of murine leukemia virus gag to the plasma membrane is mediated by PI(4,5)P2/PS and a polybasic region in the matrix. J Virol 2010; 84:503-15. [PMID: 19828619 DOI: 10.1128/jvi.01134-09] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Membrane targeting of the human immunodeficiency virus Gag proteins is dependent on phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)] located in the plasma membrane. In order to determine if evolutionarily distant retroviral Gag proteins are targeted by a similar mechanism, we generated mutants of the matrix (MA) domain of murine leukemia virus (MuLV) Gag, examined their binding to membrane models in vitro, and analyzed their phenotypes in cell culture. In vitro, we showed that MA bound all the phosphatidylinositol phosphates with significant affinity but displayed a strong specificity for PI(4,5)P(2) only if enhanced by phosphatidylserine. Mutations in the polybasic region in MA dramatically reduced this affinity. In cells, virus production was strongly impaired by PI(4,5)P(2) depletion under conditions of 5ptaseIV overexpression, and mutations in the MA polybasic region altered Gag localization, membrane binding, and virion production. Our results suggest that the N-terminal polybasic cluster of MA is essential for Gag targeting to the plasma membrane. The binding of the MA domain to PI(4,5)P(2) appears to be a conserved feature among retroviruses despite the fact that the MuLV-MA domain is structurally different from that of human immunodeficiency virus types 1 and 2 and lacks a readily identifiable PI(4,5)P(2) binding cleft.
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Assembly properties of human immunodeficiency virus type 1 Gag-leucine zipper chimeras: implications for retrovirus assembly. J Virol 2008; 83:2216-25. [PMID: 19073719 DOI: 10.1128/jvi.02031-08] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of the retroviral Gag protein leads to formation of virus-like particles in mammalian cells. In vitro and in vivo experiments show that nucleic acid is also required for particle assembly. However, several studies have demonstrated that chimeric proteins in which the nucleocapsid domain of Gag is replaced by a leucine zipper motif can also assemble efficiently in mammalian cells. We have now analyzed assembly by chimeric proteins in which nucleocapsid of human immunodeficiency virus type 1 (HIV-1) Gag is replaced by either a dimerizing or a trimerizing zipper. Both proteins assemble well in human 293T cells; the released particles lack detectable RNA. The proteins can coassemble into particles together with full-length, wild-type Gag. We purified these proteins from bacterial lysates. These recombinant "Gag-Zipper" proteins are oligomeric in solution and do not assemble unless cofactors are added; either nucleic acid or inositol phosphates (IPs) can promote particle assembly. When mixed with one equivalent of IPs (which do not support assembly of wild-type Gag), the "dimerizing" Gag-Zipper protein misassembles into very small particles, while the "trimerizing" protein assembles correctly. However, addition of both IPs and nucleic acid leads to correct assembly of all three proteins; the "dimerizing" Gag-Zipper protein also assembles correctly if inositol hexakisphosphate is supplemented with other polyanions. We suggest that correct assembly requires both oligomeric association at the C terminus of Gag and neutralization of positive charges near its N terminus.
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Nucleocapsid protein function in early infection processes. Virus Res 2008; 134:39-63. [PMID: 18279991 DOI: 10.1016/j.virusres.2007.12.006] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 12/13/2007] [Accepted: 12/13/2007] [Indexed: 01/15/2023]
Abstract
The role of nucleocapsid protein (NC) in the early steps of retroviral replication appears largely that of a facilitator for reverse transcription and integration. Using a wide variety of cell-free assay systems, the properties of mature NC proteins (e.g. HIV-1 p7(NC) or MLV p10(NC)) as nucleic acid chaperones have been extensively investigated. The effect of NC on tRNA annealing, reverse transcription initiation, minus-strand-transfer, processivity of reverse transcription, plus-strand-transfer, strand-displacement synthesis, 3' processing of viral DNA by integrase, and integrase-mediated strand-transfer has been determined by a large number of laboratories. Interestingly, these reactions can all be accomplished to varying degrees in the absence of NC; some are facilitated by both viral and non-viral proteins and peptides that may or may not be involved in vivo. What is one to conclude from the observation that NC is not strictly required for these necessary reactions to occur? NC likely enhances the efficiency of each of these steps, thereby vastly improving the productivity of infection. In other words, one of the major roles of NC is to enhance the effectiveness of early infection, thereby increasing the probability of productive replication and ultimately of retrovirus survival.
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Abstract
Expression of the budding yeast retrotransposon Ty3 results in production of viruslike particles (VLPs) and retrotransposition. The Ty3 major structural protein, Gag3, similar to retrovirus Gag, is processed into capsid, spacer, and nucleocapsid (NC) during VLP maturation. The 57-amino-acid Ty3 NC protein has 17 basic amino acids and contains one copy of the CX(2)CX(4)HX(4)C zinc-binding motif found in retrovirus NC proteins. Ty3 RNA, protein, and VLPs accumulate in clusters associated with RNA processing bodies (P bodies). This study investigated the role of the NC domain in Ty3-P body clustering and VLP assembly. Fifteen Ty3 NC Ala substitution and deletion mutants were examined using transposition, immunoblot, RNA protection, cDNA synthesis, and multimerization assays. Localization of Ty3 proteins and VLPs was characterized microscopically. Substitutions of each of the conserved residues of the zinc-binding motif resulted in the loss of Ty3 RNA packaging. Substitution of the first two of four conserved residues in this motif caused the loss of Ty3 RNA and protein clustering with P bodies and disrupted particle formation. NC was shown to be a mediator of formation of Ty3 RNA foci and association of Ty3 RNA and protein with P bodies. Mutations that disrupted these NC functions resulted in various degrees of Gag3 nuclear localization and a spectrum of different particle states. Our findings are consistent with the model that Ty3 assembly is associated with P-body components. We hypothesize that the NC domain acts as a molecular switch to control Gag3 conformational states that affect both assembly and localization.
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Human immunodeficiency virus type 1 Gag engages the Bro1 domain of ALIX/AIP1 through the nucleocapsid. J Virol 2007; 82:1389-98. [PMID: 18032513 DOI: 10.1128/jvi.01912-07] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) and other retroviruses harbor short peptide motifs in Gag that promote the release of infectious virions. These motifs, known as late assembly (L) domains, recruit a cellular budding machinery that is required for the formation of multivesicular bodies (MVBs). The primary L domain of HIV-1 maps to a PTAP motif in the p6 region of Gag and engages the MVB pathway by binding to Tsg101. Additionally, HIV-1 p6 harbors an auxiliary L domain that binds to the V domain of ALIX, another component of the MVB pathway. We now show that ALIX also binds to the nucleocapsid (NC) domain of HIV-1 Gag and that ALIX and its isolated Bro1 domain can be specifically packaged into viral particles via NC. The interaction with ALIX depended on the zinc fingers of NC, which mediate the specific packaging of genomic viral RNA, but was not disrupted by nuclease treatment. We also observed that HIV-1 zinc finger mutants were defective for particle production and exhibited a similar defect in Gag processing as a PTAP deletion mutant. The effects of the zinc finger and PTAP mutations were not additive, suggesting a functional relationship between NC and p6. However, in contrast to the PTAP deletion mutant, the double mutants could not be rescued by overexpressing ALIX, further supporting the notion that NC plays a role in virus release.
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Grigorov B, Décimo D, Smagulova F, Péchoux C, Mougel M, Muriaux D, Darlix JL. Intracellular HIV-1 Gag localization is impaired by mutations in the nucleocapsid zinc fingers. Retrovirology 2007; 4:54. [PMID: 17683545 PMCID: PMC1976323 DOI: 10.1186/1742-4690-4-54] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Accepted: 08/03/2007] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The HIV-1 nucleocapsid protein (NC) is formed of two CCHC zinc fingers flanked by highly basic regions. HIV-1 NC plays key roles in virus structure and replication via its nucleic acid binding and chaperoning properties. In fact, NC controls proviral DNA synthesis by reverse transcriptase (RT), gRNA dimerization and packaging, and virion assembly. RESULTS We previously reported a role for the first NC zinc finger in virion structure and replication 1. To investigate the role of both NC zinc fingers in intracellular Gag trafficking, and in virion assembly, we generated series of NC zinc fingers mutations. Results show that all Zinc finger mutations have a negative impact on virion biogenesis and maturation and rendered defective the mutant viruses. The NC zinc finger mutations caused an intracellular accumulation of Gag, which was found either diffuse in the cytoplasm or at the plasma membrane but not associated with endosomal membranes as for wild type Gag. Evidences are also provided showing that the intracellular interactions between NC-mutated Gag and the gRNA were impaired. CONCLUSION These results show that Gag oligomerization mediated by gRNA-NC interactions is required for correct Gag trafficking, and assembly in HIV-1 producing cells and the release of infectious viruses.
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Affiliation(s)
- Boyan Grigorov
- LaboRetro, Unité de virologie humaine INSERM U758, IFR128, ENS, 46 allée d'Italie, 69 364 Lyon, France
| | - Didier Décimo
- LaboRetro, Unité de virologie humaine INSERM U758, IFR128, ENS, 46 allée d'Italie, 69 364 Lyon, France
| | | | - Christine Péchoux
- LaboRetro, Unité de virologie humaine INSERM U758, IFR128, ENS, 46 allée d'Italie, 69 364 Lyon, France
| | | | - Delphine Muriaux
- LaboRetro, Unité de virologie humaine INSERM U758, IFR128, ENS, 46 allée d'Italie, 69 364 Lyon, France
| | - Jean-Luc Darlix
- LaboRetro, Unité de virologie humaine INSERM U758, IFR128, ENS, 46 allée d'Italie, 69 364 Lyon, France
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31
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Whitney JB, Wainberg MA. Recovery of fitness of a live attenuated simian immunodeficiency virus through compensation in both the coding and non-coding regions of the viral genome. Retrovirology 2007; 4:44. [PMID: 17608929 PMCID: PMC1934378 DOI: 10.1186/1742-4690-4-44] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 07/03/2007] [Indexed: 12/23/2022] Open
Abstract
We have analyzed a SIV deletion mutant that was compromised both in viral replication and RNA packaging. Serial passage of this variant in two different T-cell lines resulted in compensatory reversion and the generation of independent groups of point mutations within each cell line. Within each group, single point mutations were shown to contribute to increased viral infectivity and the rescue of wild-type replication kinetics. The complete recovery of viral fitness ultimately correlated with the restoration of viral RNA packaging. Consistent with the latter finding was the rescue of Pr55 Gag processing, also restoring proper virus core morphology in mature virions. These seemingly independently arising groups of compensatory mutations were functionally interchangeable in regard to the recovery of wild type replication in rhesus PBMCs. These findings indicate that viral reversion that overcomes a genetic bottleneck is not limited to a single pathway, and illustrates the remarkable adaptability of lentiviruses.
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Affiliation(s)
- James B Whitney
- McGill University AIDS Centre, Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, H3A 2B4, Canada
- Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
| | - Mark A Wainberg
- McGill University AIDS Centre, Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, H3A 2B4, Canada
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32
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Overby AK, Pettersson RF, Neve EPA. The glycoprotein cytoplasmic tail of Uukuniemi virus (Bunyaviridae) interacts with ribonucleoproteins and is critical for genome packaging. J Virol 2007; 81:3198-205. [PMID: 17229712 PMCID: PMC1866086 DOI: 10.1128/jvi.02655-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have analyzed the importance of specific amino acids in the cytoplasmic tail of the glycoprotein G(N) for packaging of ribonucleoproteins (RNPs) into virus-like particles (VLPs) of Uukuniemi virus (UUK virus), a member of the Bunyaviridae family. In order to study packaging, we added the G(N)/G(C) glycoprotein precursor (p110) to a polymerase I-driven minigenome rescue system to generate VLPs that are released into the supernatant. These particles can infect new cells, and reporter gene expression can be detected. To determine the role of UUK virus glycoproteins in RNP packaging, we performed an alanine scan of the glycoprotein G(N) cytoplasmic tail (amino acids 1 to 81). First, we discovered three regions in the tail (amino acids 21 to 25, 46 to 50, and 71 to 81) which are important for minigenome transfer by VLPs. Further mutational analysis identified four amino acids that were important for RNP packaging. These amino acids are essential for the binding of nucleoproteins and RNPs to the glycoprotein without affecting the morphology of the particles. No segment-specific interactions between the RNA and the cytoplasmic tail could be observed. We propose that VLP systems are useful tools for analyzing protein-protein interactions important for packaging of viral genome segments, assembly, and budding of other members of the Bunyaviridae family.
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Affiliation(s)
- Anna K Overby
- Ludwig Institute for Cancer Research, Stockholm Branch, Karolinska Institute, Box 240, SE-17177 Stockholm, Sweden
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33
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Bukrinskaya A. HIV-1 matrix protein: a mysterious regulator of the viral life cycle. Virus Res 2007; 124:1-11. [PMID: 17210199 DOI: 10.1016/j.virusres.2006.07.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 06/30/2006] [Accepted: 07/05/2006] [Indexed: 01/17/2023]
Abstract
Significant progress has been achieved in the last few years concerning the human immunodeficiency virus (HIV-1) life cycle, mostly in the fields of cellular receptors for the virus, virus assembly and budding of virus particles from the cell surface. Meanwhile, some aspects, such as postentry events, virus maturation and the regulatory role of individual viral proteins remain poorly defined. This review summarizes some recent findings concerning the role of Gag Pr55 and its proteolytic processing in the HIV-1 life cycle with particular emphasis on the functions of matrix protein p17 (MA), the protein which plays a key role in regulation of the early and late steps of viral morphogenesis. Based on our recent observations, the possibility is discussed that two subsets of MA exist, one cleaved from the Gag precursor in the host cell (cMA), and the other cleaved in the virions (vMA). It is suggested that two MA fractions possess diverse functions and are involved in different stages of virus morphogenesis as key regulators of the viral life cycle.
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Affiliation(s)
- Alissa Bukrinskaya
- D.I.Ivanovsky Institute of Virology, Russian Academy of Medical Sciences, Moscow 123098, RF, Russia.
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34
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Datta SAK, Curtis JE, Ratcliff W, Clark PK, Crist RM, Lebowitz J, Krueger S, Rein A. Conformation of the HIV-1 Gag protein in solution. J Mol Biol 2006; 365:812-24. [PMID: 17097677 PMCID: PMC1866279 DOI: 10.1016/j.jmb.2006.10.073] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 10/05/2006] [Accepted: 10/21/2006] [Indexed: 11/23/2022]
Abstract
A single multi-domain viral protein, termed Gag, is sufficient for assembly of retrovirus-like particles in mammalian cells. We have purified the human immunodeficiency virus type 1 (HIV-1) Gag protein (lacking myristate at its N terminus and the p6 domain at its C terminus) from bacteria. This protein is capable of assembly into virus-like particles in a defined in vitro system. We have reported that it is in monomer-dimer equilibrium in solution, and have described a mutant Gag protein that remains monomeric at high concentrations in solution. We report that the mutant protein retains several properties of wild-type Gag. This mutant enabled us to analyze solutions of monomeric protein. Hydrodynamic studies on the mutant protein showed that it is highly asymmetric, with a frictional ratio of 1.66. Small-angle neutron scattering (SANS) experiments confirmed its asymmetry and yielded an R(g) value of 34 A. Atomic-level structures of individual domains within Gag have previously been determined, but these domains are connected in Gag by flexible linkers. We constructed a series of models of the mutant Gag protein based on these domain structures, and tested each model computationally for its agreement with the experimental hydrodynamic and SANS data. The only models consistent with the data were those in which Gag was folded over, with its N-terminal matrix domain near its C-terminal nucleocapsid domain in three-dimensional space. Since Gag is a rod-shaped molecule in the assembled immature virion, these findings imply that Gag undergoes a major conformational change upon virus assembly.
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Affiliation(s)
- Siddhartha A K Datta
- HIV Drug Resistance Program, National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
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35
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Piver E, Collin C, Renault N, Bru T, Pagès JC. Mobilization of full-length Semliki Forest virus replicon by retrovirus particles. J Virol 2006; 80:9889-95. [PMID: 16973593 PMCID: PMC1617220 DOI: 10.1128/jvi.00664-06] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Conciliating biosafety with efficient gene transfer remains a constant concern in the development of retroviral vectors. Semliki Forest virus (SFV) replicons allow important retroviral vector production with interesting features. It is noteworthy that retroviruses have the ability to package Psi+ and, to some extent, Psi- cellular RNAs. Therefore, it was important to study the retroviral transfer of highly abundant SFV genomes expressing retroviral proteins. Here, we show that full-length SFV-vector replicons, with or without Psi, are efficiently packaged into retrovirus particles. Mechanistically, our data suggest that SFV packaging is the sum of its retroviral nucleocapsid-dependent recruitment together with a passive hijacking of membrane-anchored SFV replicon. A direct consequence of this phenomenon is the formation of particles harboring autonomous replicative abilities and contaminating vector preparations. Importantly, we confirm that retroviral SFV mobilization is not an exclusive feature of murine gamma retroviruses, since it is also observed using lentivectors.
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Affiliation(s)
- Eric Piver
- Université François Rabelais, INSERM ERI 19, EA 3856-IFR 136, Faculté de Médecine de Tours, 10 Bd Tonnellé, Tours, France
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36
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McCown MF, Pekosz A. Distinct domains of the influenza a virus M2 protein cytoplasmic tail mediate binding to the M1 protein and facilitate infectious virus production. J Virol 2006; 80:8178-89. [PMID: 16873274 PMCID: PMC1563831 DOI: 10.1128/jvi.00627-06] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cytoplasmic tail of the influenza A virus M2 protein is highly conserved among influenza A virus isolates. The cytoplasmic tail appears to be dispensable with respect to the ion channel activity associated with the protein but important for virus morphology and the production of infectious virus particles. Using reverse genetics and transcomplementation assays, we demonstrate that the M2 protein cytoplasmic tail is a crucial mediator of infectious virus production. Truncations of the M2 cytoplasmic tail result in a drastic decrease in infectious virus titers, a reduction in the amount of packaged viral RNA, a decrease in budding events, and a reduction in budding efficiency. The M1 protein binds to the M2 cytoplasmic tail, but the M1 binding site is distinct from the sequences that affect infectious virus particle formation. Influenza A virus strains A/Udorn/72 and A/WSN/33 differ in their requirements for M2 cytoplasmic tail sequences, and this requirement maps to the M1 protein. We conclude that the M2 protein is required for the formation of infectious virus particles, implicating the protein as important for influenza A virus assembly in addition to its well-documented role during virus entry and uncoating.
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Affiliation(s)
- Matthew F McCown
- Department of Molecular Microbiology, Washington University School of Medicine, Campus Box 8230, 660 S. Euclid Ave., St. Louis, MO 63110-1093, USA
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37
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Overby AK, Popov V, Neve EPA, Pettersson RF. Generation and analysis of infectious virus-like particles of uukuniemi virus (bunyaviridae): a useful system for studying bunyaviral packaging and budding. J Virol 2006; 80:10428-35. [PMID: 16928751 PMCID: PMC1641803 DOI: 10.1128/jvi.01362-06] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the present report we describe an infectious virus-like particle (VLP) system for the Uukuniemi (UUK) virus, a member of the Bunyaviridae family. It utilizes our recently developed reverse genetic system based on the RNA polymerase I minigenome system for UUK virus used to study replication, encapsidation, and transcription by monitoring reporter gene expression. Here, we have added the glycoprotein precursor expression plasmid together with the minigenome, nucleoprotein, and polymerase to generate VLPs, which incorporate the minigenome and are released into the supernatant. The particles are able to infect new cells, and reporter gene expression can be monitored if the trans-acting viral proteins (RNA polymerase and nucleoprotein) are also expressed in these cells. No minigenome transfer occurred in the absence of glycoproteins, demonstrating that the glycoproteins are absolutely required for the generation of infectious particles. Moreover, expression of glycoproteins alone was sufficient to produce and release VLPs. We show that the ribonucleoproteins (RNPs) are incorporated into VLPs but are not required for the generation of particles. Morphological analysis of the particles by electron microscopy revealed that VLPs, either with or without minigenomes, display a surface morphology indistinguishable from that of the authentic UUK virus and that they bud into Golgi vesicles in the same way as UUK virus does. This infectious VLP system will be very useful for studying the bunyaviral structural components required for budding and packaging of RNPs and receptor binding and may also be useful for the development of new vaccines for the human pathogens from this family.
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Affiliation(s)
- Anna K Overby
- Ludwig Institute for Cancer Research, Stockholm Branch, Karolinska Institute, Box 240, SE-17177 Stockholm, Sweden
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38
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Grigorov B, Arcanger F, Roingeard P, Darlix JL, Muriaux D. Assembly of Infectious HIV-1 in Human Epithelial and T-Lymphoblastic Cell Lines. J Mol Biol 2006; 359:848-62. [PMID: 16682056 DOI: 10.1016/j.jmb.2006.04.017] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 03/28/2006] [Accepted: 04/03/2006] [Indexed: 11/25/2022]
Abstract
The canonical view of the ultimate steps of HIV-1 replication is that virus assembly and budding are taking place at the plasma membrane of infected cells. Surprisingly, recent studies revealed that these steps also occur on endosomal membranes in the interior of infected cells, such as macrophages. This prompted us to revisit the site of HIV-1 assembly in human epithelial-like cells and in infected human T-lymphoblastic cells. To address this question, we investigated the intracellular location of the major viral structural components of HIV-1, namely Gag, Env and the genomic RNA. Using a sub-cellular fractionation method, as well as immuno-confocal and electron microscopy, we show that Gag, the Env glycoproteins and the genomic RNA accumulate in late endosomes that contain infectious HIV-1 particles. In epithelial-like 293T cells, HIV-1 assembles and buds both at the plasma membrane and in endosomes, while in chronically infected human T lymphocytes, viral assembly mostly occurs within the cell where large amounts of infectious virions accumulate in endosomal compartments. In addition, HIV-1 release could be enhanced by ionomycin, a drug stimulating calcium-dependent exocytosis. These results favour the view that newly made Gag molecules associate with the genomic RNA in the cytosol, then viral core complexes can be targeted to late endosomes together with Env, where infectious HIV-1 are made and subsequently released by exocytosis.
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Affiliation(s)
- Boyan Grigorov
- LaboRetro Unité de virologie humaine INSERM U758, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69 364 Lyon, France
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39
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Leblanc P, Alais S, Porto-Carreiro I, Lehmann S, Grassi J, Raposo G, Darlix JL. Retrovirus infection strongly enhances scrapie infectivity release in cell culture. EMBO J 2006; 25:2674-85. [PMID: 16724107 PMCID: PMC1500854 DOI: 10.1038/sj.emboj.7601162] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Accepted: 05/02/2006] [Indexed: 01/15/2023] Open
Abstract
Prion diseases are neurodegenerative disorders associated in most cases with the accumulation in the central nervous system of PrPSc (conformationally altered isoform of cellular prion protein (PrPC); Sc for scrapie), a partially protease-resistant isoform of the PrPC. PrPSc is thought to be the causative agent of transmissible spongiform encephalopathies. The mechanisms involved in the intercellular transfer of PrPSc are still enigmatic. Recently, small cellular vesicles of endosomal origin called exosomes have been proposed to contribute to the spread of prions in cell culture models. Retroviruses such as murine leukemia virus (MuLV) or human immunodeficiency virus type 1 (HIV-1) have been shown to assemble and bud into detergent-resistant microdomains and into intracellular compartments such as late endosomes/multivesicular bodies. Here we report that moloney murine leukemia virus (MoMuLV) infection strongly enhances the release of scrapie infectivity in the supernatant of coinfected cells. Under these conditions, we found that PrPC, PrPSc and scrapie infectivity are recruited by both MuLV virions and exosomes. We propose that retroviruses can be important cofactors involved in the spread of the pathological prion agent.
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Affiliation(s)
- Pascal Leblanc
- LaboRétro unité de virologie humaine INSERM U758, Ecole Normale Supérieure de Lyon, Lyon Cedex, France.
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40
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Ott DE, Coren LV, Gagliardi TD. Redundant roles for nucleocapsid and matrix RNA-binding sequences in human immunodeficiency virus type 1 assembly. J Virol 2006; 79:13839-47. [PMID: 16254319 PMCID: PMC1280203 DOI: 10.1128/jvi.79.22.13839-13847.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
RNA appears to be required for the assembly of retroviruses. This is likely due to binding of RNA by multiple Gags, which in turn organizes and stabilizes the Gag-Gag interactions that form the virion. While the nucleocapsid (NC) domain is the most conspicuous RNA-binding region of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein, we have previously shown that NC is not strictly required for efficient particle production. To determine if an RNA requirement for HIV-1 assembly exists, we analyzed virions produced by an NC deletion mutant for the presence of RNA. The results revealed that virions without NC still contained significant amounts of RNA. Since these packaged RNAs are probably incorporated by other RNA-binding sequences in Gag, an RNA-binding site in the matrix protein (MA) of Gag was mutated. While this mutation did not interfere with HIV-1 replication, a construct with both MA and NC mutations (MX/NX) failed to produce particles. The MX/NX mutant was rescued in trans by coassembly with several forms of Gag: wild-type Gag, either of the single-mutant Gags, or Gag truncations that contain MA or NC sequences. Addition of basic sequences to the MX/NX mutant partially restored particle production, consistent with a requirement for Gag-RNA binding in addition to Gag-Gag interactions. Together, these results support an RNA-binding requirement for Gag assembly, which relies on binding of RNA by MA or NC sequences to condense, organize, and stabilize the HIV-1 Gag-Gag interactions that form the virion.
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Affiliation(s)
- David E Ott
- Basic Research Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA.
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41
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Alfadhli A, Dhenub TC, Still A, Barklis E. Analysis of human immunodeficiency virus type 1 Gag dimerization-induced assembly. J Virol 2006; 79:14498-506. [PMID: 16282449 PMCID: PMC1287545 DOI: 10.1128/jvi.79.23.14498-14506.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nucleocapsid (NC) domains of retrovirus precursor Gag (PrGag) proteins play an essential role in virus assembly. Evidence suggests that NC binding to viral RNA promotes dimerization of PrGag capsid (CA) domains, which triggers assembly of CA N-terminal domains (NTDs) into hexamer rings that are interconnected by CA C-terminal domains. To examine the influence of dimerization on human immunodeficiency virus type 1 (HIV-1) Gag protein assembly in vitro, we analyzed the assembly properties of Gag proteins in which NC domains were replaced with cysteine residues that could be linked via chemical treatment. In accordance with the model that Gag protein pairing triggers assembly, we found that cysteine cross-linking or oxidation reagents induced the assembly of virus-like particles. However, efficient assembly also was observed to be temperature dependent or required the tethering of NTDs. Our results suggest a multistep pathway for HIV-1 Gag protein assembly. In the first step, Gag protein pairing through NC-RNA interactions or C-terminal cysteine linkage fosters dimerization. Next, a conformational change converts assembly-restricted dimers or small oligomers into assembly-competent ones. At the final stage, final particle assembly occurs, possibly through a set of larger intermediates.
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Affiliation(s)
- Ayna Alfadhli
- Vollum Institute and Department of Microbiology, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97201, USA
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42
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Lee EG, Linial ML. Deletion of a Cys-His motif from the Alpharetrovirus nucleocapsid domain reveals late domain mutant-like budding defects. Virology 2006; 347:226-33. [PMID: 16406458 DOI: 10.1016/j.virol.2005.11.048] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 11/08/2005] [Accepted: 11/30/2005] [Indexed: 10/25/2022]
Abstract
The Rous sarcoma virus (RSV) Gag polyprotein is the only protein required for virus assembly and release. We previously found that deletion of either one of the two Cys-His (CH) motifs in the RSV nucleocapsid (NC) protein did not abrogate Gag-Gag interactions, RNA binding, or packaging but greatly reduced virus production (E-G. Lee, A. Alidina et al., J. Virol. 77: 2010-2020, 2003). In this report, we have further investigated the effects of mutations in the CH motifs on virus assembly and release. Precise deletion of either CH motif, without affecting surrounding basic residues, reduced virus production by approximately 10-fold, similar to levels seen for late (L) domain mutants. Strikingly, transmission electron microscopy revealed that virions of both DeltaCH1 and DeltaCH2 mutants were assembled normally at the plasma membrane but were arrested in budding. Virus particles remained tethered to the membrane or to each other, reminiscent of L domain mutants, although the release defect appears to be independent of the L domain functions. Therefore, two CH motifs are likely to be required for budding independent of a requirement for either Gag-Gag interactions or RNA packaging.
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Affiliation(s)
- Eun-Gyung Lee
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Seattle, WA 98109-1024, USA
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43
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Ako-Adjei D, Johnson MC, Vogt VM. The retroviral capsid domain dictates virion size, morphology, and coassembly of gag into virus-like particles. J Virol 2005; 79:13463-72. [PMID: 16227267 PMCID: PMC1262573 DOI: 10.1128/jvi.79.21.13463-13472.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The retroviral structural protein, Gag, is capable of independently assembling into virus-like particles (VLPs) in living cells and in vitro. Immature VLPs of human immunodeficiency virus type 1 (HIV-1) and of Rous sarcoma virus (RSV) are morphologically distinct when viewed by transmission electron microscopy (TEM). To better understand the nature of the Gag-Gag interactions leading to these distinctions, we constructed vectors encoding several RSV/HIV-1 chimeric Gag proteins for expression in either insect cells or vertebrate cells. We used TEM, confocal fluorescence microscopy, and a novel correlative scanning EM (SEM)-confocal microscopy technique to study the assembly properties of these proteins. Most chimeric proteins assembled into regular VLPs, with the capsid (CA) domain being the primary determinant of overall particle diameter and morphology. The presence of domains between matrix and CA also influenced particle morphology by increasing the spacing between the inner electron-dense ring and the VLP membrane. Fluorescently tagged versions of wild-type RSV, HIV-1, or murine leukemia virus Gag did not colocalize in cells. However, wild-type Gag proteins colocalized extensively with chimeric Gag proteins bearing the same CA domain, implying that Gag interactions are mediated by CA. A dramatic example of this phenomenon was provided by a nuclear export-deficient chimera of RSV Gag carrying the HIV-1 CA domain, which by itself localized to the nucleus but relocalized to the cytoplasm in the presence of wild type HIV-1 Gag. Wild-type and chimeric Gag proteins were capable of coassembly into a single VLP as viewed by correlative fluorescence SEM if, and only if, the CA domain was derived from the same virus. These results imply that the primary selectivity of Gag-Gag interactions is determined by the CA domain.
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Affiliation(s)
- Danso Ako-Adjei
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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44
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Lingappa JR, Dooher JE, Newman MA, Kiser PK, Klein KC. Basic residues in the nucleocapsid domain of Gag are required for interaction of HIV-1 gag with ABCE1 (HP68), a cellular protein important for HIV-1 capsid assembly. J Biol Chem 2005; 281:3773-84. [PMID: 16275648 DOI: 10.1074/jbc.m507255200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During human immunodeficiency virus, type 1 (HIV-1) assembly, Gag polypeptides multimerize into immature HIV-1 capsids. The cellular ATP-binding protein ABCE1 (also called HP68 or RNase L inhibitor) appears to be critical for proper assembly of the HIV-1 capsid. In primate cells, ABCE1 associates with Gag polypeptides present in immature capsid assembly intermediates. Here we demonstrate that the NC domain of Gag is critical for interaction with endogenous primate ABCE1, whereas other domains in Gag can be deleted without eliminating the association of Gag with ABCE1. NC contains two Cys-His boxes that form zinc finger motifs and are responsible for encapsidation of HIV-1 genomic RNA. In addition, NC contains basic residues known to play a critical role in nonspecific RNA binding, Gag-Gag interactions, and particle formation. We demonstrate that basic residues in NC are needed for the Gag-ABCE1 interaction, whereas the cysteine and histidine residues in the zinc fingers are dispensable. Constructs that fail to interact with primate ABCE1 or interact poorly also fail to form capsids and are arrested at an early point in the immature capsid assembly pathway. Whereas others have shown that basic residues in NC bind nonspecifically to RNA, which in turn scaffolds or nucleates assembly, our data demonstrate that the same basic residues in NC act either directly or indirectly to recruit a cellular protein that also promotes capsid formation. Thus, in cells, basic residues in NC appear to act by two mechanisms, recruiting both RNA and a cellular ATPase in order to facilitate efficient assembly of HIV-1 capsids.
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Affiliation(s)
- Jaisri R Lingappa
- Department of Pathobiology, University of Washington, Seattle, 98195, USA.
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45
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Lorenzi HA, Robledo G, Levin MJ. The VIPER elements of trypanosomes constitute a novel group of tyrosine recombinase-enconding retrotransposons. Mol Biochem Parasitol 2005; 145:184-94. [PMID: 16297462 DOI: 10.1016/j.molbiopara.2005.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 10/02/2005] [Accepted: 10/04/2005] [Indexed: 11/29/2022]
Abstract
VIPER was initially characterized as a 2326bp LTR-like retroelement associated to SIRE, a short interspersed repetitive element specific of Trypanosoma cruzi. It carried a single ORF that coded for a putative reverse transcriptase-RNAse H protein, suggesting that it could be a truncated copy of a longer retroelement. Herein we report the identification and characterization of a complete 4480bp long VIPER in the T. cruzi genome. The complete VIPER harbored three non-overlapped domains encoding for a GAG-like, a tyrosine recombinase and a reverse transcriptase-RNAse H proteins. VIPER elements were also found in the genomes of Trypanosoma brucei and Trypanosoma vivax, but not in Leishmania sp. On the basis of its reverse transcriptase phylogeny, VIPER was classified as an LTR retroelement. However, VIPER was structurally related to the tyrosine recombinase encoding retroelements, DIRS and Ngaro. Phylogenetic analysis showed that VIPER's tyrosine recombinase grouped with the transposases RCI1 of Escherichia coli and Ye24 and Ye72 of Haemophilus influenzae within a major branch of prokaryotic recombinases. Taken together, VIPER's structure, the nature of its tyrosine recombinase, the unique features of its reverse transcriptase catalytic consensus motif and the fact that it was found in Trypanosomes, an early branching eukaryote, suggest that VIPER may be the closest relative of the founder element of the tyrosine recombinase encoding retrotransposons known up to date. Our analysis revealed that tyrosine recombinase-encoding retroelements were originated as early in evolution as non-LTR retroelements and suggests that VIPER, Ngaro and DIRS elements may constitute a third group of retrotransposons, distinct from both LTR and non-LTR retroelements.
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Affiliation(s)
- Hernan A Lorenzi
- Laboratorio de Biologia Molecular de la Enfermedad de Chagas (LaBMECh) INGEBI, National Research Council (CONICET), Centro de Genomica Aplicada (CeGA), University of Buenos Aires, Vuelta de Obligado 2490 2P, 1428, Buenos Aires, Argentina
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Li J, Bhuvanakantham R, Howe J, Ng ML. Identifying the region influencing the cis-mode of maturation of West Nile (Sarafend) virus using chimeric infectious clones. Biochem Biophys Res Commun 2005; 334:714-20. [PMID: 16018972 DOI: 10.1016/j.bbrc.2005.06.150] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Accepted: 06/09/2005] [Indexed: 11/26/2022]
Abstract
West Nile (Sarafend) virus [WN(S)V] has been shown to egress by budding at the plasma membrane of infected cells. However, the region influencing this mode of virus release remains to be deciphered. In this study, we have constructed three chimeric clones in which specific regions of West Nile (Wengler) virus [WN(W)V] were replaced for the corresponding regions of WN(S)V in the full-length infectious clone of WN(S)V to define the region responsible for the cis-mode of WN(S)V maturation. The WN(W)V matures by the trans-mode. All of the resulting chimeric viruses were found to be infective. Transmission electron microscopy analyses performed in Vero cells infected with these chimeric viruses disclosed that the 5' end of the WN(S)V genome plays a major role in influencing the process of maturation at the plasma membrane.
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Affiliation(s)
- J Li
- Flavivirology Laboratory, Department of Microbiology, National University of Singapore, Singapore 117597, Singapore
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Grigorov B, Muriaux D, Argirova R, Darlix JL. New Insights into Human Immunodeficiency Virus—Type 1 Replication. BIOTECHNOL BIOTEC EQ 2005. [DOI: 10.1080/13102818.2005.10817147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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