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Adly AN, Bi M, Carlson CR, Syed AM, Ciling A, Doudna JA, Cheng Y, Morgan DO. Assembly of SARS-CoV-2 ribonucleosomes by truncated N ∗ variant of the nucleocapsid protein. J Biol Chem 2023; 299:105362. [PMID: 37863261 PMCID: PMC10665939 DOI: 10.1016/j.jbc.2023.105362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 10/05/2023] [Accepted: 10/11/2023] [Indexed: 10/22/2023] Open
Abstract
The nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) compacts the RNA genome into viral ribonucleoprotein (vRNP) complexes within virions. Assembly of vRNPs is inhibited by phosphorylation of the N protein serine/arginine (SR) region. Several SARS-CoV-2 variants of concern carry N protein mutations that reduce phosphorylation and enhance the efficiency of viral packaging. Variants of the dominant B.1.1 viral lineage also encode a truncated N protein, termed N∗ or Δ(1-209), that mediates genome packaging despite lacking the N-terminal RNA-binding domain and SR region. Here, we use mass photometry and negative stain electron microscopy to show that purified Δ(1-209) and viral RNA assemble into vRNPs that are remarkably similar in size and shape to those formed with full-length N protein. We show that assembly of Δ(1-209) vRNPs requires the leucine-rich helix of the central disordered region and that this helix promotes N protein oligomerization. We also find that fusion of a phosphomimetic SR region to Δ(1-209) inhibits RNA binding and vRNP assembly. Our results provide new insights into the mechanisms by which RNA binding promotes N protein self-association and vRNP assembly, and how this process is modulated by phosphorylation.
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Affiliation(s)
- Armin N Adly
- Department of Physiology, University of California, San Francisco, California, USA
| | - Maxine Bi
- Department of Biochemistry & Biophysics, University of California, San Francisco, California, USA
| | | | - Abdullah M Syed
- J. David Gladstone Institutes, San Francisco, California, USA
| | - Alison Ciling
- J. David Gladstone Institutes, San Francisco, California, USA
| | - Jennifer A Doudna
- J. David Gladstone Institutes, San Francisco, California, USA; Department of Molecular and Cell Biology, University of California, Berkeley, California, USA; Howard Hughes Medical Institute, University of California, Berkeley, California, USA; Innovative Genomics Institute, University of California, Berkeley, California, USA; California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California, USA; MBIB Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Yifan Cheng
- Department of Biochemistry & Biophysics, University of California, San Francisco, California, USA; Howard Hughes Medical Institute, University of California, San Francisco, California, USA
| | - David O Morgan
- Department of Physiology, University of California, San Francisco, California, USA.
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2
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Ker DS, Jenkins HT, Greive SJ, Antson AA. CryoEM structure of the Nipah virus nucleocapsid assembly. PLoS Pathog 2021; 17:e1009740. [PMID: 34270629 PMCID: PMC8318291 DOI: 10.1371/journal.ppat.1009740] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/28/2021] [Accepted: 06/22/2021] [Indexed: 11/18/2022] Open
Abstract
Nipah and its close relative Hendra are highly pathogenic zoonotic viruses, storing their ssRNA genome in a helical nucleocapsid assembly formed by the N protein, a major viral immunogen. Here, we report the first cryoEM structure for a Henipavirus RNA-bound nucleocapsid assembly, at 3.5 Å resolution. The helical assembly is stabilised by previously undefined N- and C-terminal segments, contributing to subunit-subunit interactions. RNA is wrapped around the nucleocapsid protein assembly with a periodicity of six nucleotides per protomer, in the “3-bases-in, 3-bases-out” conformation, with protein plasticity enabling non-sequence specific interactions. The structure reveals commonalities in RNA binding pockets and in the conformation of bound RNA, not only with members of the Paramyxoviridae family, but also with the evolutionarily distant Filoviridae Ebola virus. Significant structural differences with other Paramyxoviridae members are also observed, particularly in the position and length of the exposed α-helix, residues 123–139, which may serve as a valuable epitope for surveillance and diagnostics. Nipah virus is a highly pathogenic RNA virus which, along with the closely related Hendra virus, emerged relatively recently. Due to ~40% mortality rate and evidence of animal-to-human as well as human-to-human transmission, development of antivirals against the Nipah and henipaviral disease is particularly urgent. In common with other single-stranded RNA viruses, including Ebola and coronaviruses, the nucleocapsid assembly of the Nipah virus safeguards the viral genome, protecting it from degradation and facilitating its encapsidation and storage inside the virion. Here, we used cryo-electron microscopy to determine accurate three-dimensional structure for several different assemblies of the Nipah virus nucleocapsid protein, in particular a detailed structure for the complex of this protein with RNA. This structural information is important for understanding detailed molecular interactions driving and stabilizing the nucleocapsid assembly formation that are of fundamental importance for understanding similar processes in a large group of ssRNA viruses. Apart from highlighting structural similarities and differences with nucleocapsid proteins of other viruses of the Paramyxoviridae family, these data will inform the development of new antiviral approaches for the henipaviruses.
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Affiliation(s)
- De-Sheng Ker
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, United Kingdom
| | - Huw T. Jenkins
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, United Kingdom
| | - Sandra J. Greive
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, United Kingdom
| | - Alfred A. Antson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, United Kingdom
- * E-mail:
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3
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Riedel C, Hennrich AA, Conzelmann KK. Components and Architecture of the Rhabdovirus Ribonucleoprotein Complex. Viruses 2020; 12:v12090959. [PMID: 32872471 PMCID: PMC7552012 DOI: 10.3390/v12090959] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/27/2020] [Accepted: 08/27/2020] [Indexed: 12/14/2022] Open
Abstract
Rhabdoviruses, as single-stranded, negative-sense RNA viruses within the order Mononegavirales, are characterised by bullet-shaped or bacteroid particles that contain a helical ribonucleoprotein complex (RNP). Here, we review the components of the RNP and its higher-order structural assembly.
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Affiliation(s)
- Christiane Riedel
- Institute of Virology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
- Correspondence:
| | - Alexandru A. Hennrich
- Max von Pettenkofer-Institute Virology, Faculty of Medicine, and Gene Center, LMU Munich, 81377 Munich, Germany; (A.A.H.); (K.-K.C.)
| | - Karl-Klaus Conzelmann
- Max von Pettenkofer-Institute Virology, Faculty of Medicine, and Gene Center, LMU Munich, 81377 Munich, Germany; (A.A.H.); (K.-K.C.)
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4
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Wan W, Kolesnikova L, Clarke M, Koehler A, Noda T, Becker S, Briggs JAG. Structure and assembly of the Ebola virus nucleocapsid. Nature 2017; 551:394-397. [PMID: 29144446 PMCID: PMC5714281 DOI: 10.1038/nature24490] [Citation(s) in RCA: 127] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 10/04/2017] [Indexed: 12/11/2022]
Abstract
Ebola and Marburg viruses are filoviruses: filamentous, enveloped viruses that cause haemorrhagic fever. Filoviruses are within the order Mononegavirales, which also includes rabies virus, measles virus, and respiratory syncytial virus. Mononegaviruses have non-segmented, single-stranded negative-sense RNA genomes that are encapsidated by nucleoprotein and other viral proteins to form a helical nucleocapsid. The nucleocapsid acts as a scaffold for virus assembly and as a template for genome transcription and replication. Insights into nucleoprotein-nucleoprotein interactions have been derived from structural studies of oligomerized, RNA-encapsidating nucleoprotein, and cryo-electron microscopy of nucleocapsid or nucleocapsid-like structures. There have been no high-resolution reconstructions of complete mononegavirus nucleocapsids. Here we apply cryo-electron tomography and subtomogram averaging to determine the structure of Ebola virus nucleocapsid within intact viruses and recombinant nucleocapsid-like assemblies. These structures reveal the identity and arrangement of the nucleocapsid components, and suggest that the formation of an extended α-helix from the disordered carboxy-terminal region of nucleoprotein-core links nucleoprotein oligomerization, nucleocapsid condensation, RNA encapsidation, and accessory protein recruitment.
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Affiliation(s)
- William Wan
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Larissa Kolesnikova
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Mairi Clarke
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Alexander Koehler
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Takeshi Noda
- Laboratory of Ultrastructural virology, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan; PRESTO, Japan Science and Technology Agency, Saitama, Japan
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - John A. G. Briggs
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Structural Studies Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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5
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Dong H, Li P, Böttcher B, Elliott RM, Dong C. Crystal structure of Schmallenberg orthobunyavirus nucleoprotein-RNA complex reveals a novel RNA sequestration mechanism. RNA 2013; 19:1129-1136. [PMID: 23798666 PMCID: PMC3708532 DOI: 10.1261/rna.039057.113] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 05/31/2013] [Indexed: 06/02/2023]
Abstract
Schmallenberg virus (SBV) is a newly emerged orthobunyavirus (family Bunyaviridae) that has caused severe disease in the offspring of farm animals across Europe. Like all orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that is encapsidated by the viral nucleocapsid (N) protein in the form of a ribonucleoprotein complex (RNP). We recently reported the three-dimensional structure of SBV N that revealed a novel fold. Here we report the crystal structure of the SBV N protein in complex with a 42-nt-long RNA to 2.16 Å resolution. The complex comprises a tetramer of N that encapsidates the RNA as a cross-shape inside the protein ring structure, with each protomer bound to 11 ribonucleotides. Eight bases are bound in the positively charged cleft between the N- and C-terminal domains of N, and three bases are shielded by the extended N-terminal arm. SBV N appears to sequester RNA using a different mechanism compared with the nucleoproteins of other negative-sense RNA viruses. Furthermore, the structure suggests that RNA binding results in conformational changes of some residues in the RNA-binding cleft and the N- and C-terminal arms. Our results provide new insights into the novel mechanism of RNA encapsidation by orthobunyaviruses.
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Affiliation(s)
- Haohao Dong
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park NR4 7TJ, United Kingdom
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Ping Li
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Bettina Böttcher
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
| | - Richard M. Elliott
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Changjiang Dong
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park NR4 7TJ, United Kingdom
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6
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Abstract
Respiratory syncytial virus (RSV), a nonsegmented, negative-sense RNA-containing virus, is a common cause of lower respiratory tract disease. Expression of RSV nucleocapsid protein (N) in insect cells using the baculovirus expression system leads to the formation of N-RNA complexes that are morphologically indistinguishable from viral nucleocapsids. When imaged in an electron microscope, three distinct types of structures were observed: tightly wound short-pitch helices, highly extended helices, and rings. Negative stain images of N-RNA rings were used to calculate a three-dimensional reconstruction at 24 A resolution, revealing features similar to those observed in nucleocapsids from other viruses of the order Mononegavirales. The reconstructed N-RNA rings comprise 10 N monomers and have an external radius of 83 A and an internal radius of 40 A. Comparison of this structure with crystallographic data from rabies virus and vesicular stomatitis virus N-RNA rings reveals striking morphological similarities.
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Affiliation(s)
- Kirsty Maclellan
- Medical Research Council Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, United Kingdom
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7
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Albertini AAV, Clapier CR, Wernimont AK, Schoehn G, Weissenhorn W, Ruigrok RWH. Isolation and crystallization of a unique size category of recombinant Rabies virus Nucleoprotein-RNA rings. J Struct Biol 2006; 158:129-33. [PMID: 17126031 DOI: 10.1016/j.jsb.2006.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 10/10/2006] [Accepted: 10/15/2006] [Indexed: 11/21/2022]
Abstract
In order to study the packaging of rabies virus RNA inside the viral nucleocapsid, rabies nucleoprotein was expressed in insect cells. In the cells, it binds to cellular RNA to form long, helical or short circular complexes, depending on the length of the bound RNA. The circular complexes contained from 9 up to 13 N-protomers per ring. Separation of the rings into defined size classes was impossible through regular column chromatographies or gradient centrifugation. The size classes could be separated by native polyacrylamide gel electrophoresis. A large-scale separation was achieved with a 4% native gel using a preparative electrophoresis apparatus. Crystallization trials were set up with N-RNA rings from three size classes and crystals were obtained in all cases. The best diffracting crystals, diffracting up to 6A, contained rings with 11 N-protomers plus an RNA molecule of 99 nucleotides. The diffraction limit was improved to 3.5A by air dehydration prior to flash freezing.
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Affiliation(s)
- Aurélie A V Albertini
- Institut de Virologie Moléculaire et Structurale, FRE 2854 Université Joseph Fourier-CNRS, IVMS, c/o EMBL, BP 181, 38042 Grenoble cedex 9, France
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8
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Mirambeau G, Lyonnais S, Coulaud D, Hameau L, Lafosse S, Jeusset J, Justome A, Delain E, Gorelick RJ, Le Cam E. Transmission electron microscopy reveals an optimal HIV-1 nucleocapsid aggregation with single-stranded nucleic acids and the mature HIV-1 nucleocapsid protein. J Mol Biol 2006; 364:496-511. [PMID: 17020765 DOI: 10.1016/j.jmb.2006.08.065] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 08/14/2006] [Indexed: 11/19/2022]
Abstract
HIV-1 nucleocapsid protein (NCp7) condenses the viral RNA within the mature capsid. In a capsid-free system, NCp7 promotes an efficient mechanism of aggregation with both RNA and DNA. Here, we show an analysis of these macromolecular complexes by dark-field imaging using transmission electron microscopy. Thousands of mature NCp7 proteins co-aggregate with hundreds of single-stranded circular DNA molecules (ssDNA) within minutes, as observed with poly(rA). These co-aggregates are highly stable but dynamic structures, as they dissociate under harsh conditions, and after addition of potent ssDNA or NCp7 competitive ligands. The N-terminal domain and zinc fingers of NCp7 are both required for efficient association. Addition of magnesium slightly increases the avidity of NCp7 for ssDNA, while it strongly inhibits co-aggregation with relaxed circular double-stranded DNA (dsDNA). This DNA selectivity is restricted to mature NCp7, compared to its precursors NCp15 and NCp9. Moreover, for NCp15, the linkage of NCp7 with the Gag C-terminal p6-peptide provokes a deficiency in ssDNA aggregation, but results in DNA spreading similar to prototypical SSB proteins. Finally, this co-aggregation is discussed in a dynamic architectural context with regard to the mature HIV-1 nucleocapsid. On the basis of the present data, we propose that condensation of encapsidated RNA requires the C-terminal processing of NCp. Subsequently, disassembly of the nucleocapsid should be favoured once dsDNA is produced by HIV-1 reverse transcriptase.
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Affiliation(s)
- Gilles Mirambeau
- Laboratoire de Microscopie Moléculaire et Cellulaire, CNRS UMR 8126, Institut Gustave Roussy, 94805 Villejuif, France.
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Mukhopadhyay S, Zhang W, Gabler S, Chipman PR, Strauss EG, Strauss JH, Baker TS, Kuhn RJ, Rossmann MG. Mapping the structure and function of the E1 and E2 glycoproteins in alphaviruses. Structure 2006; 14:63-73. [PMID: 16407066 PMCID: PMC2757649 DOI: 10.1016/j.str.2005.07.025] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Revised: 07/11/2005] [Accepted: 07/16/2005] [Indexed: 11/25/2022]
Abstract
The 9 A resolution cryo-electron microscopy map of Sindbis virus presented here provides structural information on the polypeptide topology of the E2 protein, on the interactions between the E1 and E2 glycoproteins in the formation of a heterodimer, on the difference in conformation of the two types of trimeric spikes, on the interaction between the transmembrane helices of the E1 and E2 proteins, and on the conformational changes that occur when fusing with a host cell. The positions of various markers on the E2 protein established the approximate topology of the E2 structure. The largest conformational differences between the icosahedral surface spikes at icosahedral 3-fold and quasi-3-fold positions are associated with the monomers closest to the 5-fold axes. The long E2 monomers, containing the cell receptor recognition motif at their extremities, are shown to rotate by about 180 degrees and to move away from the center of the spikes during fusion.
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Affiliation(s)
- Suchetana Mukhopadhyay
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
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10
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Acosta-Rivero N, Rodriguez A, Musacchio A, Falcón V, Suarez VM, Chavez L, Morales-Grillo J, Duenas-Carrera S. Nucleic acid binding properties and intermediates of HCV core protein multimerization in Pichia pastoris. Biochem Biophys Res Commun 2004; 323:926-31. [PMID: 15381089 DOI: 10.1016/j.bbrc.2004.08.189] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Indexed: 11/21/2022]
Abstract
Little is known about the in vivo assembly pathway or structure of the hepatitis C virus nucleocapsid. In this work the intermediates of HCcAg multimerization in Pichia pastoris cells and the nucleic acid binding properties of structured nucleocapsid-like particles (NLPs) were studied. Extensive cross-linking was observed for HCcAg after glutaraldehyde treatment. Data suggest that HCcAg exists in dimeric forms probably representing P21-P21, P21-P23, and P23-P23 dimers. In addition, the presence of HCcAg species that might represent trimers and multimers was observed. After sucrose equilibrium density gradient purification and nuclease digestion, NLPs were shown to contain both RNA and DNA molecules. Finally, the analysis by electron microscopy indicated that native NLPs were resistant to nuclease treatment. These results indicated that HCcAg assembles through dimers, trimers, and multimers' intermediates into capsids in P. pastoris cells. Assembly of NLPs in its natural environment might confer stability to these particles by adopting a compact structure.
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Affiliation(s)
- Nelson Acosta-Rivero
- Division of Vaccines, Electron Microscopy Laboratory, Center for Genetic Engineering and Biotechnology, P.O. Box 6162, C.P. 10600, Cuba.
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Majumdar A, Bhattacharya R, Basak S, Shaila MS, Chattopadhyay D, Roy S. P-protein of Chandipura virus is an N-protein-specific chaperone that acts at the nucleation stage. Biochemistry 2004; 43:2863-70. [PMID: 15005621 DOI: 10.1021/bi035793r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nucleocapsid protein N of Chandipura virus is prone to aggregation in vitro. We have shown that this aggregation occurs in two phases in a nucleation-dependent manner. Electron microscopy suggests that the aggregated state may have a ring-like structure. Using a GFP fusion, we have shown that the N-protein also aggregates in vivo. The P-protein suppresses the N-protein aggregation efficiently, both in vitro and in vivo. Increased lag phase in the presence of the P-protein suggests that chaperone-like action of the P-protein occurs before the nucleation event. The P-protein, however, does not exert any chaperone-like action against other proteins, suggesting that it binds to the N-protein specifically. Surface plasmon resonance and fluorescence enhancement indeed suggest that the P-protein binds tightly to the native N-protein. The P-protein is thus an N-protein-specific chaperone which inhibits the nucleation phase of N-protein aggregation, thus keeping a pool of encapsidation-competent N-protein for viral maturation.
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Affiliation(s)
- Amitabha Majumdar
- Dr. B. C. Guha Centre for Genetic Engineering and Biotechnology, Department of Biochemistry, University College of Science, University of Calcutta, 35 Ballygunge Circular Road, Calcutta 700 019, India
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12
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Mukhopadhyay S, Chipman PR, Hong EM, Kuhn RJ, Rossmann MG. In vitro-assembled alphavirus core-like particles maintain a structure similar to that of nucleocapsid cores in mature virus. J Virol 2002; 76:11128-32. [PMID: 12368355 PMCID: PMC136650 DOI: 10.1128/jvi.76.21.11128-11132.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In vitro-assembled core-like particles produced from alphavirus capsid protein and nucleic acid were studied by cryoelectron microscopy. These particles were found to have a diameter of 420 A with 240 copies of the capsid protein arranged in a T=4 icosahedral surface lattice, similar to the nucleocapsid core in mature virions. However, when the particles were subjected to gentle purification procedures, they were damaged, preventing generation of reliable structural information. Similarly, purified nucleocapsid cores isolated from virus-infected cells or from mature virus particles were also of poor quality. This suggested that in the absence of membrane and glycoproteins, nucleocapsid core particles are fragile, lacking accurate icosahedral symmetry.
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Affiliation(s)
- Suchetana Mukhopadhyay
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
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13
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Abstract
Nucleocapsid (N) proteins from representative viruses of three genera within the Paramyxoviridae were expressed in insect cells using recombinant baculoviruses. RNA-containing structures, which appear morphologically identical to viral nucleocapsids, were isolated and subsequently imaged under a transmission electron microscope. Analysis of these images revealed marked differences in nucleocapsid morphology among the genera investigated, most notably between viruses of the Paramyxovirinae and the Pneumovirinae subfamilies. Helical pitch measurements were made, revealing that measles virus (MV, a Morbillivirus within the subfamily Paramyxovirinae) N protein produces helices that adopt multiple conformations with varying degrees of flexibility, while that of the Rubulavirus simian virus type 5 (SV5, subfamily Paramyxovirinae) produces more rigid structures with a less heterogeneous pitch distribution. Nucleocapsids produced by respiratory syncytial virus (RSV, subfamily Pneumovirinae) appear significantly narrower than those of MV and SV5 and have a longer pitch than the most extended form of MV. In addition to helical nucleocapsids, ring structures were also produced, image analysis of which has demonstrated that rings assembled from MV N protein consist of 13 subunits. This is consistent with previous reports that Sendai virus nucleocapsids have 13.07 subunits per turn. It was determined, however, that SV5 subnucleocapsid rings have 14 subunits, while rings derived from the radically different RSV nucleocapsid have been found to contain predominantly 10 subunits.
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Affiliation(s)
- David Bhella
- Medical Research Council Virology Unit, Church Street, Glasgow G11 5JR, UK1
| | - Adam Ralph
- Medical Research Council Virology Unit, Church Street, Glasgow G11 5JR, UK1
| | - Lindsay B Murphy
- Medical Research Council Virology Unit, Church Street, Glasgow G11 5JR, UK1
| | - Robert P Yeo
- Medical Research Council Virology Unit, Church Street, Glasgow G11 5JR, UK1
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14
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Acosta-Rivero N, Alvarez-Obregón JC, Musacchio A, Falcón V, Dueñas-Carrera S, Marante J, Menéndez I, Morales J. In vitro self-assembled HCV core virus-like particles induce a strong antibody immune response in sheep. Biochem Biophys Res Commun 2002; 290:300-4. [PMID: 11779169 DOI: 10.1006/bbrc.2001.6177] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The in vitro self-assembly properties of the entire hepatitis C virus core protein (HCcAg) obtained from Pichia pastoris cells and the induction of specific antibody immune response were studied. HCcAg was purified as a low-molecular-weight species by electroelution under denaturing conditions for confirmation of its self-assembly properties. After renaturalization, electron microscopy showed that HCcAg assembled into spherical particles of 30 nm. HCcAg also showed homogeneity and was specifically recognized by serum from a chronic HCV carrier patient. The data indicated that in vitro assembly of HCcAg, into virus-like particles resembling HCV nucleocapsid particles at a mature stage, is an intrinsic quality of this protein. Finally, HCcAg generated a strong antibody immune response in sheep, suggesting its usefulness for stimulating the host immune response against HCV.
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Affiliation(s)
- Nelson Acosta-Rivero
- Division of Vaccines, Center for Genetic Engineering and Biotechnology, Ave. 31 e/158 y 190, P.O. Box 61562, C.P. 10 600, Havana City, Cuba.
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15
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Tellinghuisen TL, Hamburger AE, Fisher BR, Ostendorp R, Kuhn RJ. In vitro assembly of alphavirus cores by using nucleocapsid protein expressed in Escherichia coli. J Virol 1999; 73:5309-19. [PMID: 10364277 PMCID: PMC112586 DOI: 10.1128/jvi.73.7.5309-5319.1999] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of the alphavirus virion is a multistep event requiring the assembly of the nucleocapsid core in the cytoplasm and the maturation of the glycoproteins in the endoplasmic reticulum and the Golgi apparatus. These components associate during the budding process to produce the mature virion. The nucleocapsid proteins of Sindbis virus and Ross River virus have been produced in a T7-based Escherichia coli expression system and purified. In the presence of single-stranded but not double-stranded nucleic acid, the proteins oligomerize in vitro into core-like particles which resemble the native viral nucleocapsid cores. Despite their similarities, Sindbis virus and Ross River virus capsid proteins do not form mixed core-like particles. Truncated forms of the Sindbis capsid protein were used to establish amino acid requirements for assembly. A capsid protein starting at residue 19 [CP(19-264)] was fully competent for in vitro assembly, whereas proteins with further N-terminal truncations could not support assembly. However, a capsid protein starting at residue 32 or 81 was able to incorporate into particles in the presence of CP(19-264) or could inhibit assembly if its molar ratio relative to CP(19-264) was greater than 1:1. This system provides a basis for the molecular dissection of alphavirus core assembly.
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Affiliation(s)
- T L Tellinghuisen
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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