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Barchet C, Fréchin L, Holvec S, Hazemann I, von Loeffelholz O, Klaholz BP. Focused classifications and refinements in high-resolution single particle cryo-EM analysis. J Struct Biol 2023; 215:108015. [PMID: 37659578 DOI: 10.1016/j.jsb.2023.108015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 06/27/2023] [Accepted: 08/17/2023] [Indexed: 09/04/2023]
Abstract
Recent advances in cryo electron microscopy (cryo-EM) and image processing provide new opportunities to analyse drug targets at high resolution. However, structural heterogeneity limits resolution in many practical cases, hence restricting the level at which structural details can be analysed and drug design be performed. As structural disorder is not spread throughout the entire structure of a given macromolecular complex but instead is found in certain regions that move with respect to others and covering molecular scales from domain conformational changes up to the level of side chain conformations in ligand binding pockets, it is possible to focus the attention on those regions and the associated relative movements. Here we show how the usage of focused classifications and refinements provide insights into global conformational arrangements, exemplified on the human ribosome and on the cannabinoid G protein coupled receptor (GPCR), and how they can improve the local map resolution from an essentially disordered region to the 3-4 Å and finally to the 2 Å resolution range. A systematic analysis with variable spherical masks during focused refinement is presented showing that the choice of an optimal mask size helps refining to high resolution. This study covers several practical approaches on 4 examples illustrating how important mask size & shape and including neighbouring structural elements are for a focused analysis of a macromolecular complex. Such methods will be crucial for cryo-EM structure-based drug design of various medical targets and are applicable to single particle cryo-EM and electron tomography data.
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Affiliation(s)
- Charles Barchet
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Léo Fréchin
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Samuel Holvec
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Isabelle Hazemann
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Ottilie von Loeffelholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France
| | - Bruno P Klaholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 1 rue Laurent Fries, Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (Inserm) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France.
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Chiffi G, Grandgirard D, Leib SL, Chrdle A, Růžek D. Tick-borne encephalitis: A comprehensive review of the epidemiology, virology, and clinical picture. Rev Med Virol 2023; 33:e2470. [PMID: 37392370 DOI: 10.1002/rmv.2470] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 05/31/2023] [Accepted: 06/12/2023] [Indexed: 07/03/2023]
Abstract
Tick-borne encephalitis virus (TBEV) is a flavivirus commonly found in at least 27 European and Asian countries. It is an emerging public health problem, with steadily increasing case numbers over recent decades. Tick-borne encephalitis virus affects between 10,000 and 15,000 patients annually. Infection occurs through the bite of an infected tick and, much less commonly, through infected milk consumption or aerosols. The TBEV genome comprises a positive-sense single-stranded RNA molecule of ∼11 kilobases. The open reading frame is > 10,000 bases long, flanked by untranslated regions (UTR), and encodes a polyprotein that is co- and post-transcriptionally processed into three structural and seven non-structural proteins. Tick-borne encephalitis virus infection results in encephalitis, often with a characteristic biphasic disease course. After a short incubation time, the viraemic phase is characterised by non-specific influenza-like symptoms. After an asymptomatic period of 2-7 days, more than half of patients show progression to a neurological phase, usually characterised by central and, rarely, peripheral nervous system symptoms. Mortality is low-around 1% of confirmed cases, depending on the viral subtype. After acute tick-borne encephalitis (TBE), a minority of patients experience long-term neurological deficits. Additionally, 40%-50% of patients develop a post-encephalitic syndrome, which significantly impairs daily activities and quality of life. Although TBEV has been described for several decades, no specific treatment exists. Much remains unknown regarding the objective assessment of long-lasting sequelae. Additional research is needed to better understand, prevent, and treat TBE. In this review, we aim to provide a comprehensive overview of the epidemiology, virology, and clinical picture of TBE.
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Affiliation(s)
- Gabriele Chiffi
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Denis Grandgirard
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephen L Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Aleš Chrdle
- Department of Infectious Diseases, Hospital Ceske Budejovice, Ceske Budejovice, Czech Republic
- Faculty of Health and Social Sciences, University of South Bohemia, Ceske Budejovice, Czech Republic
- Royal Liverpool University Hospital, Liverpool, UK
| | - Daniel Růžek
- Veterinary Research Institute, Emerging Viral Diseases, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Ceske Budejovice, Czech Republic
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3
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DiIorio MC, Kulczyk AW. Exploring the Structural Variability of Dynamic Biological Complexes by Single-Particle Cryo-Electron Microscopy. MICROMACHINES 2022; 14:118. [PMID: 36677177 PMCID: PMC9866264 DOI: 10.3390/mi14010118] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/27/2022] [Accepted: 12/30/2022] [Indexed: 05/15/2023]
Abstract
Biological macromolecules and assemblies precisely rearrange their atomic 3D structures to execute cellular functions. Understanding the mechanisms by which these molecular machines operate requires insight into the ensemble of structural states they occupy during the functional cycle. Single-particle cryo-electron microscopy (cryo-EM) has become the preferred method to provide near-atomic resolution, structural information about dynamic biological macromolecules elusive to other structure determination methods. Recent advances in cryo-EM methodology have allowed structural biologists not only to probe the structural intermediates of biochemical reactions, but also to resolve different compositional and conformational states present within the same dataset. This article reviews newly developed sample preparation and single-particle analysis (SPA) techniques for high-resolution structure determination of intrinsically dynamic and heterogeneous samples, shedding light upon the intricate mechanisms employed by molecular machines and helping to guide drug discovery efforts.
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Affiliation(s)
- Megan C. DiIorio
- Institute for Quantitative Biomedicine, Rutgers University, 174 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Arkadiusz W. Kulczyk
- Institute for Quantitative Biomedicine, Rutgers University, 174 Frelinghuysen Road, Piscataway, NJ 08854, USA
- Department of Biochemistry and Microbiology, Rutgers University, 75 Lipman Drive, New Brunswick, NJ 08901, USA
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Kaufman F, Dostálková A, Pekárek L, Thanh TD, Kapisheva M, Hadravová R, Bednárová L, Novotný R, Křížová I, Černý J, Grubhoffer L, Ruml T, Hrabal R, Rumlová M. Characterization and in vitro assembly of tick-borne encephalitis virus C protein. FEBS Lett 2020; 594:1989-2004. [PMID: 32510601 DOI: 10.1002/1873-3468.13857] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 05/12/2020] [Accepted: 05/17/2020] [Indexed: 01/10/2023]
Abstract
Tick-borne encephalitis virus (TBEV), a member of flaviviruses, represents a serious health threat by causing human encephalitis mainly in central and eastern Europe, Russia, and northeastern Asia. As no specific therapy is available, there is an urgent need to understand all steps of the TBEV replication cycle at the molecular level. One of the critical events is the packaging of flaviviral genomic RNA by TBEV C protein to form a nucleocapsid. We purified recombinant TBEV C protein and used a combination of physical-chemical approaches, such as size-exclusion chromatography, circular dichroism, NMR spectroscopies, and transmission electron microscopy, to analyze its structural stability and its ability to dimerize/oligomerize. We compared the ability of TBEV C protein to assemble in vitro into a nucleocapsid-like structure with that of dengue C protein.
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Affiliation(s)
- Filip Kaufman
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Alžběta Dostálková
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Lukáš Pekárek
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Tung Dinh Thanh
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Marina Kapisheva
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Romana Hadravová
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic.,Institute of Organic Chemistry and Biochemistry (IOCB) Research Centre & Gilead Sciences, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Lucie Bednárová
- Institute of Organic Chemistry and Biochemistry (IOCB) Research Centre & Gilead Sciences, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Radim Novotný
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic.,NMR Laboratory, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Ivana Křížová
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Jiří Černý
- Faculty of Tropical AgriSciences, Czech University of Life Sciences, Prague, Prague, Czech Republic
| | - Libor Grubhoffer
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.,Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Tomáš Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Richard Hrabal
- NMR Laboratory, University of Chemistry and Technology, Prague, Prague, Czech Republic
| | - Michaela Rumlová
- Department of Biotechnology, University of Chemistry and Technology, Prague, Prague, Czech Republic
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Diosa-Toro M, Prasanth KR, Bradrick SS, Garcia Blanco MA. Role of RNA-binding proteins during the late stages of Flavivirus replication cycle. Virol J 2020; 17:60. [PMID: 32334603 PMCID: PMC7183730 DOI: 10.1186/s12985-020-01329-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 04/11/2020] [Indexed: 12/21/2022] Open
Abstract
The genus Flavivirus encompasses several worldwide-distributed arthropod-borne viruses including, dengue virus, Japanese encephalitis virus, West Nile virus, yellow fever virus, Zika virus, and tick-borne encephalitis virus. Infection with these viruses manifest with symptoms ranging from febrile illness to life- threatening hypotensive shock and encephalitis. Therefore, flaviviruses pose a great risk to public health. Currently, preventive measures are falling short to control epidemics and there are no antivirals against any Flavivirus.Flaviviruses carry a single stranded positive-sense RNA genome that plays multiple roles in infected cells: it is translated into viral proteins, used as template for genome replication, it is the precursor of the subgenomic flaviviral RNA and it is assembled into new virions. Furthermore, viral RNA genomes are also packaged into extracellular vesicles, e.g. exosomes, which represent an alternate mode of virus dissemination.Because RNA molecules are at the center of Flavivirus replication cycle, viral and host RNA-binding proteins (RBPs) are critical determinants of infection. Numerous studies have revealed the function of RBPs during Flavivirus infection, particularly at the level of RNA translation and replication. These proteins, however, are also critical participants at the late stages of the replication cycle. Here we revise the function of host RBPs and the viral proteins capsid, NS2A and NS3, during the packaging of viral RNA and the assembly of new virus particles. Furthermore, we go through the evidence pointing towards the importance of host RBPs in mediating cellular RNA export with the idea that the biogenesis of exosomes harboring Flavivirus RNA would follow an analogous pathway.
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Affiliation(s)
- Mayra Diosa-Toro
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore.
| | - K Reddisiva Prasanth
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Shelton S Bradrick
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Global Health, Surveillance & Diagnostics Group, MRIGlobal, Kansas City, MO, USA
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, USA
| | - Mariano A Garcia Blanco
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore.
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA.
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, USA.
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6
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Valente AP, Moraes AH. Zika virus proteins at an atomic scale: how does structural biology help us to understand and develop vaccines and drugs against Zika virus infection? J Venom Anim Toxins Incl Trop Dis 2019; 25:e20190013. [PMID: 31523227 PMCID: PMC6727858 DOI: 10.1590/1678-9199-jvatitd-2019-0013] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In Brazil and in other tropical areas Zika virus infection was directly associated with clinical complications as microcephaly in newborn children whose mothers were infected during pregnancy and the Guillain-Barré syndrome in adults. Recently, research has been focused on developing new vaccines and drug candidates against Zika virus infection since none of those are available. In order to contribute to vaccine and drug development efforts, it becomes important the understanding of the molecular basis of the Zika virus recognition, infection and blockade. To this purpose, it is essential the structural determination of the Zika virus proteins. The genome sequencing of the Zika virus identified ten proteins, being three structural (protein E, protein C and protein prM) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5). Together, these proteins are the main targets for drugs and antibody recognition. Here we examine new discoveries on high-resolution structural biology of Zika virus, observing the interactions and functions of its proteins identified via state-of-art structural methodologies as X-ray crystallography, nuclear magnetic resonance spectroscopy and cryogenic electronic microscopy. The aim of the present study is to contribute to the understanding of the structural basis of Zika virus infection at an atomic level and to point out similarities and differences to others flaviviruses.
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Affiliation(s)
- Ana Paula Valente
- National Center of Magnetic Resonance, Leopoldo de Meis Institute of Medical Biochemistry, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil
| | - Adolfo Henrique Moraes
- Department of Chemistry, Institute of Exact Sciences, Federal University of Minas Gerais (UFMG), Belo Horizonte, MG, Brazil
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Abstract
Flaviviruses assemble initially in an immature, noninfectious state and undergo extensive conformational rearrangements to generate mature virus. Previous cryo-electron microscopy (cryo-EM) structural studies of flaviviruses assumed icosahedral symmetry and showed the concentric organization of the external glycoprotein shell, the lipid membrane, and the internal nucleocapsid core. We show here that when icosahedral symmetry constraints were excluded in calculating the cryo-EM reconstruction of an immature flavivirus, the nucleocapsid core was positioned asymmetrically with respect to the glycoprotein shell. The core was positioned closer to the lipid membrane at the proximal pole, and at the distal pole, the outer glycoprotein spikes and inner membrane leaflet were either perturbed or missing. In contrast, in the asymmetric reconstruction of a mature flavivirus, the core was positioned concentric with the glycoprotein shell. The deviations from icosahedral symmetry demonstrated that the core and glycoproteins have varied interactions, which likely promotes viral assembly and budding.
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8
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Pulkkinen LIA, Butcher SJ, Anastasina M. Tick-Borne Encephalitis Virus: A Structural View. Viruses 2018; 10:v10070350. [PMID: 29958443 PMCID: PMC6071267 DOI: 10.3390/v10070350] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 06/25/2018] [Accepted: 06/27/2018] [Indexed: 12/11/2022] Open
Abstract
Tick-borne encephalitis virus (TBEV) is a growing health concern. It causes a severe disease that can lead to permanent neurological complications or death and the incidence of TBEV infections is constantly rising. Our understanding of TBEV’s structure lags behind that of other flaviviruses, but has advanced recently with the publication of a high-resolution structure of the TBEV virion. The gaps in our knowledge include: aspects of receptor binding, replication and virus assembly. Furthermore, TBEV has mostly been studied in mammalian systems, even though the virus’ interaction with its tick hosts is a central part of its life cycle. Elucidating these aspects of TBEV biology are crucial for the development of TBEV antivirals, as well as the improvement of diagnostics. In this review, we summarise the current structural knowledge on TBEV, bringing attention to the current gaps in our understanding, and propose further research that is needed to truly understand the structural-functional relationship of the virus and its hosts.
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Affiliation(s)
- Lauri I A Pulkkinen
- HiLIFE-Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland.
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland.
| | - Sarah J Butcher
- HiLIFE-Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland.
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland.
| | - Maria Anastasina
- HiLIFE-Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland.
- Faculty of Biological and Environmental Sciences, University of Helsinki, 00790 Helsinki, Finland.
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Jiang W, Tang L. Atomic cryo-EM structures of viruses. Curr Opin Struct Biol 2017; 46:122-129. [PMID: 28787658 PMCID: PMC5683926 DOI: 10.1016/j.sbi.2017.07.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/12/2017] [Accepted: 07/19/2017] [Indexed: 01/30/2023]
Abstract
During the development of single particle cryo-EM in past five decades, icosahedral viruses have led the resolution progress owing to their large mass and high symmetry. Many technical advances in cryo-EM were first established with viruses. Since reaching ∼4Å resolution in 2008, it has become a relatively routine task to solve the atomic structure of isolated viruses. The future of structural virology will be increasingly focused on remaining challenges including solving structures of jumbo viruses, intermediate functional states during assembly, maturation, and infection, and in situ structures. Recent demonstrations of near-atomic resolution structure with electron tomography and sub-tomogram averaging opens a new direction for high resolution studies of pleomorphic viruses and the pleomorphic states of icosahedral viruses that have defied past efforts using the single particle cryo-EM approach.
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Affiliation(s)
- Wen Jiang
- Department of Biological Sciences, Immunology and Infectious Disease, Purdue University, 240 S. Martin Jischke Drive, West Lafayette, IN 47907, USA; Department of Chemistry, Immunology and Infectious Disease, Purdue University, 240 S. Martin Jischke Drive, West Lafayette, IN 47907, USA; Markey Center for Structural Biology, Immunology and Infectious Disease, Purdue University, 240 S. Martin Jischke Drive, West Lafayette, IN 47907, USA; Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, 240 S. Martin Jischke Drive, West Lafayette, IN 47907, USA.
| | - Liang Tang
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA.
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10
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The core protein of a pestivirus protects the incoming virus against IFN-induced effectors. Sci Rep 2017; 7:44459. [PMID: 28290554 PMCID: PMC5349576 DOI: 10.1038/srep44459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 02/08/2017] [Indexed: 01/21/2023] Open
Abstract
A multitude of viral factors - either inhibiting the induction of the IFN-system or its effectors – have been described to date. However, little is known about the role of structural components of the incoming virus particle in protecting against IFN-induced antiviral factors during or immediately after entry. In this study, we take advantage of the previously reported property of Classical swine fever virus (family Flaviviridae, genus Pestivirus) to tolerate a deletion of the core protein if a compensatory mutation is present in the NS3-helicase-domain (Vp447∆c). In contrast to the parental virus (Vp447), which causes a hemorrhagic-fever-like disease in pigs, Vp447∆c is avirulent in vivo. In comparison to Vp447, growth of Vp447∆c in primary porcine cells and IFN-treated porcine cell lines was reduced >20-fold. Also, primary porcine endothelial cells and IFN-pretreated porcine cell lines were 8–24 times less susceptible to Vp447∆c. This reduction of susceptibility could be partially reversed by loading Vp447∆c particles with different levels of core protein. In contrast, expression of core protein in the recipient cell did not have any beneficial effect. Therefore, a protective effect of core protein in the incoming virus particle against the products of IFN-stimulated genes could be demonstrated.
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Viktorovskaya OV, Greco TM, Cristea IM, Thompson SR. Identification of RNA Binding Proteins Associated with Dengue Virus RNA in Infected Cells Reveals Temporally Distinct Host Factor Requirements. PLoS Negl Trop Dis 2016; 10:e0004921. [PMID: 27556644 PMCID: PMC4996428 DOI: 10.1371/journal.pntd.0004921] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 07/22/2016] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND There are currently no vaccines or antivirals available for dengue virus infection, which can cause dengue hemorrhagic fever and death. A better understanding of the host pathogen interaction is required to develop effective therapies to treat DENV. In particular, very little is known about how cellular RNA binding proteins interact with viral RNAs. RNAs within cells are not naked; rather they are coated with proteins that affect localization, stability, translation and (for viruses) replication. METHODOLOGY/PRINCIPAL FINDINGS Seventy-nine novel RNA binding proteins for dengue virus (DENV) were identified by cross-linking proteins to dengue viral RNA during a live infection in human cells. These cellular proteins were specific and distinct from those previously identified for poliovirus, suggesting a specialized role for these factors in DENV amplification. Knockdown of these proteins demonstrated their function as viral host factors, with evidence for some factors acting early, while others late in infection. Their requirement by DENV for efficient amplification is likely specific, since protein knockdown did not impair the cell fitness for viral amplification of an unrelated virus. The protein abundances of these host factors were not significantly altered during DENV infection, suggesting their interaction with DENV RNA was due to specific recruitment mechanisms. However, at the global proteome level, DENV altered the abundances of proteins in particular classes, including transporter proteins, which were down regulated, and proteins in the ubiquitin proteasome pathway, which were up regulated. CONCLUSIONS/SIGNIFICANCE The method for identification of host factors described here is robust and broadly applicable to all RNA viruses, providing an avenue to determine the conserved or distinct mechanisms through which diverse viruses manage the viral RNA within cells. This study significantly increases the number of cellular factors known to interact with DENV and reveals how DENV modulates and usurps cellular proteins for efficient amplification.
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Affiliation(s)
- Olga V. Viktorovskaya
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Todd M. Greco
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Ileana M. Cristea
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Sunnie R. Thompson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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Abstract
Dengue virus affects hundreds of millions of people each year around the world, causing a tremendous social and economic impact on affected countries. The aim of this review is to summarize our current knowledge of the functions, structure, and interactions of the viral capsid protein. The primary role of capsid is to package the viral genome. There are two processes linked to this function: the recruitment of the viral RNA during assembly and the release of the genome during infection. Although particle assembly takes place on endoplasmic reticulum membranes, capsid localizes in nucleoli and lipid droplets. Why capsid accumulates in these locations during infection remains unknown. In this review, we describe available data and discuss new ideas on dengue virus capsid functions and interactions. We believe that a deeper understanding of how the capsid protein works during infection will create opportunities for novel antiviral strategies, which are urgently needed to control dengue virus infections.
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Affiliation(s)
- Laura A Byk
- Fundación Instituto Leloir-National Research Council for Science and Technology (CONICET), Buenos Aires 1405, Argentina;
| | - Andrea V Gamarnik
- Fundación Instituto Leloir-National Research Council for Science and Technology (CONICET), Buenos Aires 1405, Argentina;
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13
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Abstract
This chapter describes algorithmic advances in the RELION software, and how these are used in high-resolution cryo-electron microscopy (cryo-EM) structure determination. Since the presence of projections of different three-dimensional structures in the dataset probably represents the biggest challenge in cryo-EM data processing, special emphasis is placed on how to deal with structurally heterogeneous datasets. As such, this chapter aims to be of practical help to those who wish to use RELION in their cryo-EM structure determination efforts.
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Bai XC, Rajendra E, Yang G, Shi Y, Scheres SHW. Sampling the conformational space of the catalytic subunit of human γ-secretase. eLife 2015; 4. [PMID: 26623517 PMCID: PMC4718806 DOI: 10.7554/elife.11182] [Citation(s) in RCA: 456] [Impact Index Per Article: 50.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/30/2015] [Indexed: 12/12/2022] Open
Abstract
Human γ-secretase is an intra-membrane protease that cleaves many different substrates. Aberrant cleavage of Notch is implicated in cancer, while abnormalities in cutting amyloid precursor protein lead to Alzheimer's disease. Our previous cryo-EM structure of γ-secretase revealed considerable disorder in its catalytic subunit presenilin. Here, we describe an image classification procedure that characterizes molecular plasticity at the secondary structure level, and apply this method to identify three distinct conformations in our previous sample. In one of these conformations, an additional transmembrane helix is visible that cannot be attributed to the known components of γ-secretase. In addition, we present a γ-secretase structure in complex with the dipeptidic inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT). Our results reveal how conformational mobility in the second and sixth transmembrane helices of presenilin is greatly reduced upon binding of DAPT or the additional helix, and form the basis for a new model of how substrate enters the transmembrane domain. DOI:http://dx.doi.org/10.7554/eLife.11182.001 An enzyme called gamma-secretase cuts other proteins in cells into smaller pieces. Like most enzymes, gamma-secretase is expected to move through several different three-dimensional shapes to perform its role, and identifying these structures could help us to understand how the enzyme works. One of the proteins that is targeted by gamma-secretase is called amyloid precursor protein, and cutting this protein results in the formation of so-called amyloid-beta peptides. When gamma-secretase doesn't work properly, these amyloid-beta peptides can accumulate in the brain and large accumulations of these peptides have been observed in the brains of patients with Alzheimer's disease. Earlier in 2015, a group of researchers used a technique called cryo-electron microscopy (cryo-EM) to produce a three-dimensional model of gamma-secretase. This revealed that the active site of the enzyme, that is, the region that is used to cut the other proteins, is particularly flexible. Now, Bai et al. – including many of the researchers from the earlier work – studied this flexibility in more detail. For the experiments, gamma-secretase was exposed to an inhibitor molecule that stopped it from cutting other proteins. This meant that the structure of gamma-secretase became more rigid than normal, which made it possible to collect more detailed structural information using cryo-EM. Bai et al. also developed new methods for processing images to separate the images of individual enzyme molecules based on the different shapes they had adopted at the time. These methods make it possible to view a mixture of very similar enzyme structures that differ only in a small region of the protein (in this case the active site). In the future, it would be useful to repeat these imaging experiments using a range of different molecules that alter the activity of gamma-secretase. Furthermore, the new image processing methods developed by Bai et al. could be used to study flexibility in the shapes of other proteins. DOI:http://dx.doi.org/10.7554/eLife.11182.002
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Affiliation(s)
- Xiao-chen Bai
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Eeson Rajendra
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Guanghui Yang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yigong Shi
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
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15
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Zhang X, Ding K, Yu X, Chang W, Sun J, Zhou ZH. In situ structures of the segmented genome and RNA polymerase complex inside a dsRNA virus. Nature 2015; 527:531-534. [PMID: 26503045 PMCID: PMC5086257 DOI: 10.1038/nature15767] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/07/2015] [Indexed: 01/15/2023]
Abstract
Viruses in the Reoviridae, like the triple-shelled human rotavirus and the single-shelled insect cytoplasmic polyhedrosis virus (CPV), all package a genome of segmented double-stranded RNAs (dsRNAs) inside the viral capsid and carry out endogenous messenger RNA synthesis through a transcriptional enzyme complex (TEC). By direct electron-counting cryoelectron microscopy and asymmetric reconstruction, we have determined the organization of the dsRNA genome inside quiescent CPV (q-CPV) and the in situ atomic structures of TEC within CPV in both quiescent and transcribing (t-CPV) states. We show that the ten segmented dsRNAs in CPV are organized with ten TECs in a specific, non-symmetric manner, with each dsRNA segment attached directly to a TEC. The TEC consists of two extensively interacting subunits: an RNA-dependent RNA polymerase (RdRP) and an NTPase VP4. We find that the bracelet domain of RdRP undergoes marked conformational change when q-CPV is converted to t-CPV, leading to formation of the RNA template entry channel and access to the polymerase active site. An amino-terminal helix from each of two subunits of the capsid shell protein (CSP) interacts with VP4 and RdRP. These findings establish the link between sensing of environmental cues by the external proteins and activation of endogenous RNA transcription by the TEC inside the virus.
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MESH Headings
- Capsid Proteins/chemistry
- Capsid Proteins/metabolism
- Capsid Proteins/ultrastructure
- Catalytic Domain
- Cryoelectron Microscopy
- Genome, Viral/genetics
- Models, Molecular
- Multienzyme Complexes/chemistry
- Multienzyme Complexes/metabolism
- Multienzyme Complexes/ultrastructure
- Nucleoside-Triphosphatase/metabolism
- Nucleoside-Triphosphatase/ultrastructure
- Protein Subunits/chemistry
- Protein Subunits/metabolism
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/ultrastructure
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/ultrastructure
- RNA, Viral/biosynthesis
- RNA, Viral/genetics
- RNA, Viral/ultrastructure
- RNA-Dependent RNA Polymerase/chemistry
- RNA-Dependent RNA Polymerase/metabolism
- RNA-Dependent RNA Polymerase/ultrastructure
- Reoviridae/enzymology
- Reoviridae/genetics
- Reoviridae/ultrastructure
- Templates, Genetic
- Transcription, Genetic
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Affiliation(s)
- Xing Zhang
- California Nanosystems Institute, Los Angeles, CA 90095, USA
| | - Ke Ding
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Bioengineering, University of California, Los Angeles, CA 90095, USA
| | - Xuekui Yu
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Winston Chang
- California Nanosystems Institute, Los Angeles, CA 90095, USA
| | - Jingchen Sun
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Subtropical Sericulture and Mulberry Resources Protection and Safety Engineering Research Center, Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China
| | - Z. Hong Zhou
- California Nanosystems Institute, Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Bioengineering, University of California, Los Angeles, CA 90095, USA
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16
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Veesler D, Kearney BM, Johnson JE. Integration of X-ray crystallography and electron cryo-microscopy in the analysis of virus structure and function. CRYSTALLOGR REV 2015. [DOI: 10.1080/0889311x.2015.1038530] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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San Martín C. Transmission electron microscopy and the molecular structure of icosahedral viruses. Arch Biochem Biophys 2015; 581:59-67. [PMID: 26072114 DOI: 10.1016/j.abb.2015.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/01/2015] [Accepted: 06/04/2015] [Indexed: 11/16/2022]
Abstract
The field of structural virology developed in parallel with methodological advances in X-ray crystallography and cryo-electron microscopy. At the end of the 1970s, crystallography yielded the first high resolution structure of an icosahedral virus, the T=3 tomato bushy stunt virus at 2.9Å. It took longer to reach near-atomic resolution in three-dimensional virus maps derived from electron microscopy data, but this was finally achieved, with the solution of complex icosahedral capsids such as the T=25 human adenovirus at ∼3.5Å. Both techniques now work hand-in-hand to determine those aspects of virus assembly and biology that remain unclear. This review examines the trajectory followed by EM imaging techniques in showing the molecular structure of icosahedral viruses, from the first two-dimensional negative staining images of capsids to the latest sophisticated techniques that provide high resolution three-dimensional data, or snapshots of the conformational changes necessary to complete the infectious cycle.
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Affiliation(s)
- Carmen San Martín
- Department of Macromolecular Structure and NanoBioMedicine Initiative, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, 28049 Madrid, Spain.
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18
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Roby JA, Setoh YX, Hall RA, Khromykh AA. Post-translational regulation and modifications of flavivirus structural proteins. J Gen Virol 2015; 96:1551-69. [PMID: 25711963 DOI: 10.1099/vir.0.000097] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Flaviviruses are a group of single-stranded, positive-sense RNA viruses that generally circulate between arthropod vectors and susceptible vertebrate hosts, producing significant human and veterinary disease burdens. Intensive research efforts have broadened our scientific understanding of the replication cycles of these viruses and have revealed several elegant and tightly co-ordinated post-translational modifications that regulate the activity of viral proteins. The three structural proteins in particular - capsid (C), pre-membrane (prM) and envelope (E) - are subjected to strict regulatory modifications as they progress from translation through virus particle assembly and egress. The timing of proteolytic cleavage events at the C-prM junction directly influences the degree of genomic RNA packaging into nascent virions. Proteolytic maturation of prM by host furin during Golgi transit facilitates rearrangement of the E proteins at the virion surface, exposing the fusion loop and thus increasing particle infectivity. Specific interactions between the prM and E proteins are also important for particle assembly, as prM acts as a chaperone, facilitating correct conformational folding of E. It is only once prM/E heterodimers form that these proteins can be secreted efficiently. The addition of branched glycans to the prM and E proteins during virion transit also plays a key role in modulating the rate of secretion, pH sensitivity and infectivity of flavivirus particles. The insights gained from research into post-translational regulation of structural proteins are beginning to be applied in the rational design of improved flavivirus vaccine candidates and make attractive targets for the development of novel therapeutics.
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Affiliation(s)
- Justin A Roby
- 1Australian Infectious Diseases Research Centre, The University of Queensland, Australia 2School of Chemistry and Molecular Biosciences, The University of Queensland, Australia
| | - Yin Xiang Setoh
- 1Australian Infectious Diseases Research Centre, The University of Queensland, Australia 2School of Chemistry and Molecular Biosciences, The University of Queensland, Australia
| | - Roy A Hall
- 1Australian Infectious Diseases Research Centre, The University of Queensland, Australia 2School of Chemistry and Molecular Biosciences, The University of Queensland, Australia
| | - Alexander A Khromykh
- 1Australian Infectious Diseases Research Centre, The University of Queensland, Australia 2School of Chemistry and Molecular Biosciences, The University of Queensland, Australia
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19
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Abstract
Dengue virus (DENV) is an emerging mosquito-borne human pathogen that affects millions of individuals each year by causing severe and potentially fatal syndromes. Despite intense research efforts, no approved vaccine or antiviral therapy is yet available. Overcoming this limitation requires detailed understanding of the intimate relationship between the virus and its host cell, providing the basis to devise optimal prophylactic and therapeutic treatment options. With the advent of novel high-throughput technologies including functional genomics, transcriptomics, proteomics, and lipidomics, new important insights into the DENV replication cycle and the interaction of this virus with its host cell have been obtained. In this chapter, we provide a comprehensive overview on the current status of the DENV research field, covering every step of the viral replication cycle with a particular focus on virus-host cell interaction. We will also review specific chemical inhibitors targeting cellular factors and processes of relevance for the DENV replication cycle and their possible exploitation for the development of next generation antivirals.
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20
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Zhang W, Kaufmann B, Chipman PR, Kuhn RJ, Rossmann MG. Membrane curvature in flaviviruses. J Struct Biol 2013; 183:86-94. [PMID: 23602814 DOI: 10.1016/j.jsb.2013.04.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 04/03/2013] [Accepted: 04/09/2013] [Indexed: 11/26/2022]
Abstract
Coordinated interplay between membrane proteins and the lipid bilayer is required for such processes as transporter function and the entrance of enveloped viruses into host cells. In this study, three-dimensional cryo-electron microscopy density maps of mature and immature flaviviruses were analyzed to assess the curvature of the membrane leaflets and its relation to membrane-bound viral glycoproteins. The overall morphology of the viral membrane is determined by the icosahedral scaffold composed of envelope (E) and membrane (M) proteins through interaction of the proteins' stem-anchor regions with the membrane. In localized regions, small membrane areas exhibit convex, concave, flat or saddle-shaped surfaces that are constrained by the specific protein organization within each membrane leaflet. These results suggest that the organization of membrane proteins in small enveloped viruses mediate the formation of membrane curvature.
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Affiliation(s)
- Wei Zhang
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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21
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A novel coding-region RNA element modulates infectious dengue virus particle production in both mammalian and mosquito cells and regulates viral replication in Aedes aegypti mosquitoes. Virology 2012; 432:511-26. [PMID: 22840606 DOI: 10.1016/j.virol.2012.06.028] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2012] [Revised: 04/17/2012] [Accepted: 06/21/2012] [Indexed: 12/20/2022]
Abstract
Dengue virus (DENV) is an enveloped flavivirus with a positive-sense RNA genome transmitted by Aedes mosquitoes, causing the most important arthropod-borne viral disease affecting humans. Relatively few cis-acting RNA regulatory elements have been described in the DENV coding-region. Here, by introducing silent mutations into a DENV-2 infectious clone, we identify the conserved capsid-coding region 1 (CCR1), an RNA sequence element that regulates viral replication in mammalian cells and to a greater extent in Ae. albopictus mosquito cells. These defects were confirmed in vivo, resulting in decreased replication in Ae. aegypti mosquito bodies and dissemination to the salivary glands. Furthermore, CCR1 does not regulate translation, RNA synthesis or virion retention but likely modulates assembly, as mutations resulted in the release of non-infectious viral particles from both cell types. Understanding the role of CCR1 could help characterize the poorly-defined stage of assembly in the DENV life cycle and uncover novel anti-viral targets.
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22
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Fischl W, Bartenschlager R. Exploitation of cellular pathways by Dengue virus. Curr Opin Microbiol 2011; 14:470-5. [DOI: 10.1016/j.mib.2011.07.012] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 06/29/2011] [Accepted: 07/05/2011] [Indexed: 01/11/2023]
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23
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Pong WL, Huang ZS, Teoh PG, Wang CC, Wu HN. RNA binding property and RNA chaperone activity of dengue virus core protein and other viral RNA-interacting proteins. FEBS Lett 2011; 585:2575-81. [PMID: 21771593 PMCID: PMC7164067 DOI: 10.1016/j.febslet.2011.06.038] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 06/29/2011] [Accepted: 06/30/2011] [Indexed: 11/30/2022]
Abstract
In this study we showed that the dengue virus (DENV) core protein forms a dimer with an α-helix-rich structure, binds RNA and facilitates the strand annealing process. To assess the RNA chaperone activity of this core protein and other dengue viral RNA-interacting proteins, such as NS3 helicase and NS5 proteins, we engineered cis- and trans-cleavage hammerhead ribozyme constructs carrying DENV genomic RNA elements. Our results indicate that DENV core protein facilitates typical hammerhead structure formation by acting as an RNA chaperone and DENV NS5 has a weak RNA chaperone activity, while DENV NS3 helicase failed to refold RNA with a complex secondary structure.
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Affiliation(s)
- Wen-Li Pong
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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24
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Kaufmann B, Plevka P, Kuhn RJ, Rossmann MG. Crystallization and preliminary X-ray diffraction analysis of West Nile virus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:558-62. [PMID: 20445259 DOI: 10.1107/s1744309110009899] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 03/16/2010] [Indexed: 11/10/2022]
Abstract
West Nile virus, a human pathogen, is closely related to other medically important flaviviruses of global impact such as dengue virus. The infectious virus was purified from cell culture using polyethylene glycol (PEG) precipitation and density-gradient centrifugation. Thin amorphously shaped crystals of the lipid-enveloped virus were grown in quartz capillaries equilibrated by vapor diffusion. Crystal diffraction extended at best to a resolution of about 25 A using synchrotron radiation. A preliminary analysis of the diffraction images indicated that the crystals had unit-cell parameters a approximately b approximately 480 A, gamma = 120 degrees , suggesting a tight hexagonal packing of one virus particle per unit cell.
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Affiliation(s)
- Bärbel Kaufmann
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA
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25
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Association of the pr peptides with dengue virus at acidic pH blocks membrane fusion. J Virol 2009; 83:12101-7. [PMID: 19759134 DOI: 10.1128/jvi.01637-09] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational change at low pH that renders it accessible to furin (I. M. Yu, W. Zhang, H. A. Holdaway, L. Li, V. A. Kostyuchenko, P. R. Chipman, R. J. Kuhn, M. G. Rossmann, and J. Chen, Science 319:1834-1837, 2008). Here we show, using cryoelectron microscopy, that the structure of immature dengue virus at pH 6.0 is essentially the same before and after the cleavage of prM. The structure shows that after cleavage, the proteolytic product pr remains associated with the virion at acidic pH, and that furin cleavage by itself does not induce any major conformational changes. We also show by liposome cofloatation experiments that pr retention prevents membrane insertion, suggesting that pr is present on the virion in the trans-Golgi network to protect the progeny virus from fusion within the host cell.
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26
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Murray CL, Jones CT, Rice CM. Architects of assembly: roles of Flaviviridae non-structural proteins in virion morphogenesis. Nat Rev Microbiol 2009; 6:699-708. [PMID: 18587411 DOI: 10.1038/nrmicro1928] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Viruses of the Flaviviridae family, including hepatitis C, dengue and bovine viral diarrhoea, are responsible for considerable morbidity and mortality worldwide. Recent advances in our understanding of virion assembly have uncovered commonalities among distantly related members of this family. We discuss the emerging hypothesis that physical virion components are not alone in forming the infectious particle, but that non-structural proteins are intimately involved in orchestrating morphogenesis. Pinpointing the roles of Flaviviridae proteins in virion production could reveal new avenues for antiviral therapeutics.
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27
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Shreif Z, Adhangale P, Cheluvaraja S, Perera R, Kuhn R, Ortoleva P. Enveloped viruses understood via multiscale simulation: computer-aided vaccine design. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s10820-008-9101-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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28
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Bovine viral diarrhea virus core is an intrinsically disordered protein that binds RNA. J Virol 2007; 82:1294-304. [PMID: 18032507 DOI: 10.1128/jvi.01815-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Pestiviruses, including bovine viral diarrhea virus (BVDV), are important animal pathogens and close relatives of hepatitis C virus. Pestivirus particles are composed of an RNA genome, a host-derived lipid envelope, and four virion-encoded structural proteins, core (C), E(rns), E1, and E2. Core is a small, highly basic polypeptide that is processed by three enzymatic cleavages before its incorporation into virions. Little is known about its biological properties or its role in virion assembly and structure. We have purified BVDV core protein and characterized it biochemically. We have determined that the processed form of core lacks significant secondary structure and is instead intrinsically disordered. Consistent with its highly basic sequence, we observed that core binds to RNA, although with low affinity and little discernible specificity. We found that BVDV core protein was able to functionally replace the nonspecific RNA binding and condensing region of an unrelated viral capsid protein. Together these results suggest that the in vitro properties of core may reflect its mechanism of action in RNA packaging and virion morphogenesis.
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29
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Hafenstein S, Palermo LM, Kostyuchenko VA, Xiao C, Morais MC, Nelson CDS, Bowman VD, Battisti AJ, Chipman PR, Parrish CR, Rossmann MG. Asymmetric binding of transferrin receptor to parvovirus capsids. Proc Natl Acad Sci U S A 2007; 104:6585-9. [PMID: 17420467 PMCID: PMC1871829 DOI: 10.1073/pnas.0701574104] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2007] [Indexed: 12/11/2022] Open
Abstract
Although many viruses are icosahedral when they initially bind to one or more receptor molecules on the cell surface, such an interaction is asymmetric, probably causing a breakdown in the symmetry and conformation of the original infecting virion in preparation for membrane penetration and release of the viral genome. Cryoelectron microscopy and biochemical analyses show that transferrin receptor, the cellular receptor for canine parvovirus, can bind to only one or a few of the 60 icosahedrally equivalent sites on the virion, indicating that either canine parvovirus has inherent asymmetry or binding of receptor induces asymmetry. The asymmetry of receptor binding to canine parvovirus is reminiscent of the special portal in tailed bacteriophages and some large, icosahedral viruses. Asymmetric interactions of icosahedral viruses with their hosts might be a more common phenomenon than previously thought and may have been obscured by averaging in previous crystallographic and electron microscopic structure determinations.
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Affiliation(s)
- Susan Hafenstein
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Laura M. Palermo
- The James A. Baker Institute, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Victor A. Kostyuchenko
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Chuan Xiao
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Marc C. Morais
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Christian D. S. Nelson
- The James A. Baker Institute, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Valorie D. Bowman
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Anthony J. Battisti
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Paul R. Chipman
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
| | - Colin R. Parrish
- The James A. Baker Institute, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Michael G. Rossmann
- *Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054; and
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30
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Huiskonen JT, Butcher SJ. Membrane-containing viruses with icosahedrally symmetric capsids. Curr Opin Struct Biol 2007; 17:229-36. [PMID: 17387010 DOI: 10.1016/j.sbi.2007.03.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 02/07/2007] [Accepted: 03/14/2007] [Indexed: 11/19/2022]
Abstract
Viruses with an icosahedrally symmetric protein capsid and a membrane infect hosts from all three domains of life. Similar architectural principles are shared by different viral families, as exemplified by double-stranded DNA viruses such as PRD1 and STIV. During virus assembly, the membrane lipids are selectively acquired from the host cell. The X-ray structure of bacteriophage PRD1 revealed that the lipids are asymmetrically distributed between the two leaflets and facet length is controlled by a tape-measure protein. In most membrane-containing viruses, viral and host membranes fuse during viral entry. In the best-understood systems of the alphaviruses, flaviviruses and herpes viruses, fusion is mediated by viral glycoproteins. Recent structural advances reveal how very different protein architectures can be used to form trimeric extensions that extend into the target cell membrane and then fold back to mediate fusion of the target and viral membranes.
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Affiliation(s)
- Juha T Huiskonen
- Institute of Biotechnology and Department of Biological and Environmental Sciences, PO Box 65 (Viikinkaari 1), University of Helsinki, Finland
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