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den Boon JA, Nishikiori M, Zhan H, Ahlquist P. Positive-strand RNA virus genome replication organelles: structure, assembly, control. Trends Genet 2024; 40:681-693. [PMID: 38724328 DOI: 10.1016/j.tig.2024.04.003] [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: 02/27/2024] [Revised: 04/09/2024] [Accepted: 04/10/2024] [Indexed: 08/09/2024]
Abstract
Positive-strand RNA [(+)RNA] viruses include pandemic SARS-CoV-2, tumor-inducing hepatitis C virus, debilitating chikungunya virus (CHIKV), lethal encephalitis viruses, and many other major pathogens. (+)RNA viruses replicate their RNA genomes in virus-induced replication organelles (ROs) that also evolve new viral species and variants by recombination and mutation and are crucial virus control targets. Recent cryo-electron microscopy (cryo-EM) reveals that viral RNA replication proteins form striking ringed 'crowns' at RO vesicle junctions with the cytosol. These crowns direct RO vesicle formation, viral (-)RNA and (+)RNA synthesis and capping, innate immune escape, and transfer of progeny (+)RNA genomes into translation and encapsidation. Ongoing studies are illuminating crown assembly, sequential functions, host factor interactions, etc., with significant implications for control and beneficial uses of viruses.
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Affiliation(s)
- Johan A den Boon
- Rowe Center for Virology, Morgridge Institute for Research, Madison, WI, USA; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI
| | - Masaki Nishikiori
- Rowe Center for Virology, Morgridge Institute for Research, Madison, WI, USA; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI
| | - Hong Zhan
- Rowe Center for Virology, Morgridge Institute for Research, Madison, WI, USA; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI
| | - Paul Ahlquist
- Rowe Center for Virology, Morgridge Institute for Research, Madison, WI, USA; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI.
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2
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Lin S, Chang P, Tsao S, Aderinwale A, Sallapalli BT, He J, Zhang Y. Oxysterol binding protein (OSBP) contributes to hepatitis E virus replication. Virol J 2024; 21:161. [PMID: 39039546 PMCID: PMC11265327 DOI: 10.1186/s12985-024-02438-3] [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: 03/05/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024] Open
Abstract
Hepatitis E virus (HEV) is a positive-sense, single-stranded RNA virus and causes primarily acute self-limiting infections. The ORF1 of the HEV genome encodes a polyprotein around 190 kDa, which contains several putative domains, including helicase and RNA-dependent RNA polymerase. The HEV-encoded helicase is a member of the superfamily 1 helicase family and possesses multiple enzymatic functions, such as RNA 5'-triphosphatase, RNA unwinding, and NTPase, which are thought to contribute to viral RNA synthesis. However, the helicase interaction with cellular proteins remains less known. Oxysterol binding protein (OSBP) is a lipid regulator that shuffles between the Golgi apparatus and the endoplasmic reticulum for cholesterol and phosphatidylinositol-4-phosphate exchange and controls the efflux of cholesterol from cells. In this study, the RNAi-mediated silencing of OSBP significantly reduced HEV replication. Further studies indicate that the HEV helicase interacted with OSBP, shown by co-immunoprecipitation and co-localization in co-transfected cells. The presence of helicase blocked OSBP preferential translocation to the Golgi apparatus. These results demonstrate that OSBP contributes to HEV replication and enrich our understanding of the HEV-cell interactions.
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Affiliation(s)
- Shaoli Lin
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Peixi Chang
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Shane Tsao
- National Cancer Institute, National Institute of Health, Bethesda, MD, USA
| | - Abigail Aderinwale
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Bhargava Teja Sallapalli
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Jia He
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Yanjin Zhang
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
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3
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Paronetto O, Allioux C, Diméglio C, Lobjois L, Jeanne N, Ranger N, Boineau J, Pucelle M, Demmou S, Abravanel F, Chapuy-Regaud S, Izopet J, Lhomme S. Characterization of virus‒host recombinant variants of the hepatitis E virus. J Virol 2024; 98:e0029524. [PMID: 38712945 PMCID: PMC11237545 DOI: 10.1128/jvi.00295-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 04/09/2024] [Indexed: 05/08/2024] Open
Abstract
Hepatitis E virus is a single-strand, positive-sense RNA virus that can lead to chronic infection in immunocompromised patients. Virus-host recombinant variants (VHRVs) have been described in such patients. These variants integrate part of human genes into the polyproline-rich region that could introduce new post-translational modifications (PTMs), such as ubiquitination. The aim of this study was to characterize the replication capacity of different VHRVs, namely, RNF19A, ZNF787, KIF1B, EEF1A1, RNA18, RPS17, and RPL6. We used a plasmid encoding the Kernow strain, in which the fragment encoding the S17 insertion was deleted (Kernow p6 delS17) or replaced by fragments encoding the different insertions. The HEV RNA concentrations in the supernatants and the HepG2/C3A cell lysates were determined via RT-qPCR. The capsid protein ORF2 was immunostained. The effect of ribavirin was also assessed. The HEV RNA concentrations in the supernatants and the cell lysates were higher for the variants harboring the RNF19A, ZNF787, KIF1B, RPS17, and EEF1A1 insertions than for the Kernow p6 del S17, while it was not with RNA18 or RPL6 fragments. The number of ORF2 foci was higher for RNF19A, ZNF787, KIF1B, and RPS17 than for Kernow p6 del S17. VHRVs with replicative advantages were less sensitive to the antiviral effect of ribavirin. No difference in PTMs was found between VHRVs with a replicative advantage and those without. In conclusion, our study showed that insertions did not systematically confer a replicative advantage in vitro. Further studies are needed to determine the mechanisms underlying the differences in replicative capacity. IMPORTANCE Hepatitis E virus (HEV) is a major cause of viral hepatitis. HEV can lead to chronic infection in immunocompromised patients. Ribavirin treatment is currently used to treat such chronic infections. Recently, seven virus-host recombinant viruses were characterized in immunocompromised patients. These viruses have incorporated a portion of a human gene fragment into their genome. We studied the consequences of these insertions on the replication capacity. We found that these inserted fragments could enhance virus replication for five of the seven recombinant variants. We also showed that the recombinant variants with replicative advantages were less sensitive to ribavirin in vitro. Finally, we found that the mechanisms leading to such a replicative advantage do not seem to rely on the post-translational modifications introduced by the human gene fragment that could have modified the function of the viral protein. The mechanisms involved in improving the replication of such recombinant viruses remain to be explored.
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Affiliation(s)
- Olivia Paronetto
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
| | - Claire Allioux
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
| | - Chloé Diméglio
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Lhorane Lobjois
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
| | - Nicolas Jeanne
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Noémie Ranger
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Jérôme Boineau
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Mélanie Pucelle
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Sofia Demmou
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Florence Abravanel
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Sabine Chapuy-Regaud
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Jacques Izopet
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
| | - Sébastien Lhomme
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), UMR 5051 (CNRS), UMR 1291 (INSERM), Université Toulouse III-Paul Sabatier, Toulouse, France
- Laboratoire de Virologie, Hôpital Purpan, CHU Toulouse, Toulouse, France
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4
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Versini R, Sritharan S, Aykac Fas B, Tubiana T, Aimeur SZ, Henri J, Erard M, Nüsse O, Andreani J, Baaden M, Fuchs P, Galochkina T, Chatzigoulas A, Cournia Z, Santuz H, Sacquin-Mora S, Taly A. A Perspective on the Prospective Use of AI in Protein Structure Prediction. J Chem Inf Model 2024; 64:26-41. [PMID: 38124369 DOI: 10.1021/acs.jcim.3c01361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
AlphaFold2 (AF2) and RoseTTaFold (RF) have revolutionized structural biology, serving as highly reliable and effective methods for predicting protein structures. This article explores their impact and limitations, focusing on their integration into experimental pipelines and their application in diverse protein classes, including membrane proteins, intrinsically disordered proteins (IDPs), and oligomers. In experimental pipelines, AF2 models help X-ray crystallography in resolving the phase problem, while complementarity with mass spectrometry and NMR data enhances structure determination and protein flexibility prediction. Predicting the structure of membrane proteins remains challenging for both AF2 and RF due to difficulties in capturing conformational ensembles and interactions with the membrane. Improvements in incorporating membrane-specific features and predicting the structural effect of mutations are crucial. For intrinsically disordered proteins, AF2's confidence score (pLDDT) serves as a competitive disorder predictor, but integrative approaches including molecular dynamics (MD) simulations or hydrophobic cluster analyses are advocated for accurate dynamics representation. AF2 and RF show promising results for oligomeric models, outperforming traditional docking methods, with AlphaFold-Multimer showing improved performance. However, some caveats remain in particular for membrane proteins. Real-life examples demonstrate AF2's predictive capabilities in unknown protein structures, but models should be evaluated for their agreement with experimental data. Furthermore, AF2 models can be used complementarily with MD simulations. In this Perspective, we propose a "wish list" for improving deep-learning-based protein folding prediction models, including using experimental data as constraints and modifying models with binding partners or post-translational modifications. Additionally, a meta-tool for ranking and suggesting composite models is suggested, driving future advancements in this rapidly evolving field.
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Affiliation(s)
- Raphaelle Versini
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Sujith Sritharan
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Burcu Aykac Fas
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Thibault Tubiana
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Sana Zineb Aimeur
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, 91405 Orsay, France
| | - Julien Henri
- Sorbonne Université, CNRS, Laboratoire de Biologie, Computationnelle et Quantitative UMR 7238, Institut de Biologie Paris-Seine, 4 Place Jussieu, F-75005 Paris, France
| | - Marie Erard
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, 91405 Orsay, France
| | - Oliver Nüsse
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, 91405 Orsay, France
| | - Jessica Andreani
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Marc Baaden
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Patrick Fuchs
- Sorbonne Université, École Normale Supérieure, PSL University, CNRS, Laboratoire des Biomolécules, LBM, 75005 Paris, France
- Université de Paris, UFR Sciences du Vivant, 75013 Paris, France
| | - Tatiana Galochkina
- Université Paris Cité and Université des Antilles and Université de la Réunion, INSERM, BIGR, F-75014 Paris, France
| | - Alexios Chatzigoulas
- Biomedical Research Foundation, Academy of Athens, 11527 Athens, Greece
- Department of Informatics and Telecommunications, National and Kapodistrian University of Athens, 15784 Athens, Greece
| | - Zoe Cournia
- Biomedical Research Foundation, Academy of Athens, 11527 Athens, Greece
- Department of Informatics and Telecommunications, National and Kapodistrian University of Athens, 15784 Athens, Greece
| | - Hubert Santuz
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Sophie Sacquin-Mora
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
| | - Antoine Taly
- Laboratoire de Biochimie Théorique, CNRS (UPR9080), Université Paris Cité, F-75005 Paris, France
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5
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Karlin DG. WIV, a protein domain found in a wide number of arthropod viruses, which probably facilitates infection. J Gen Virol 2024; 105. [PMID: 38193819 DOI: 10.1099/jgv.0.001948] [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] [Indexed: 01/10/2024] Open
Abstract
The most powerful approach to detect distant homologues of a protein is based on structure prediction and comparison. Yet this approach is still inapplicable to many viral proteins. Therefore, we applied a powerful sequence-based procedure to identify distant homologues of viral proteins. It relies on three principles: (1) traces of sequence similarity can persist beyond the significance cutoff of homology detection programmes; (2) candidate homologues can be identified among proteins with weak sequence similarity to the query by using 'contextual' information, e.g. taxonomy or type of host infected; (3) these candidate homologues can be validated using highly sensitive profile-profile comparison. As a test case, this approach was applied to a protein without known homologues, encoded by ORF4 of Lake Sinai viruses (which infect bees). We discovered that the ORF4 protein contains a domain that has homologues in proteins from >20 taxa of viruses infecting arthropods. We called this domain 'widespread, intriguing, versatile' (WIV), because it is found in proteins with a wide variety of functions and within varied domain contexts. For example, WIV is found in the NSs protein of tospoviruses, a global threat to food security, which infect plants as well as their arthropod vectors; in the RNA2 ORF1-encoded protein of chronic bee paralysis virus, a widespread virus of bees; and in various proteins of cypoviruses, which infect the silkworm Bombyx mori. Structural modelling with AlphaFold indicated that the WIV domain has a previously unknown fold, and bibliographical evidence suggests that it facilitates infection of arthropods.
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Affiliation(s)
- David G Karlin
- Division Phytomedicine, Thaer-Institute of Agricultural and Horticultural Sciences, Humboldt-Universität zu Berlin, Lentzeallee 55/57, D-14195 Berlin, Germany
- Independent Researcher, Marseille, France
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6
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Pierce DM, Buchanan FJT, Macrae FL, Mills JT, Cox A, Abualsaoud KM, Ward JC, Ariëns RAS, Harris M, Stonehouse NJ, Herod MR. Thrombin cleavage of the hepatitis E virus polyprotein at multiple conserved locations is required for genome replication. PLoS Pathog 2023; 19:e1011529. [PMID: 37478143 PMCID: PMC10395923 DOI: 10.1371/journal.ppat.1011529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 07/03/2023] [Indexed: 07/23/2023] Open
Abstract
The genomes of positive-sense RNA viruses encode polyproteins that are essential for mediating viral replication. These viral polyproteins must undergo proteolysis (also termed polyprotein processing) to generate functional protein units. This proteolysis can be performed by virally-encoded proteases as well as host cellular proteases, and is generally believed to be a key step in regulating viral replication. Hepatitis E virus (HEV) is a leading cause of acute viral hepatitis. The positive-sense RNA genome is translated to generate a polyprotein, termed pORF1, which is necessary and sufficient for viral genome replication. However, the mechanism of polyprotein processing in HEV remains to be determined. In this study, we aimed to understand processing of this polyprotein and its role in viral replication using a combination of in vitro translation experiments and HEV sub-genomic replicons. Our data suggest no evidence for a virally-encoded protease or auto-proteolytic activity, as in vitro translation predominantly generates unprocessed viral polyprotein precursors. However, seven cleavage sites within the polyprotein (suggested by bioinformatic analysis) are susceptible to the host cellular protease, thrombin. Using two sub-genomic replicon systems, we demonstrate that mutagenesis of these sites prevents replication, as does pharmacological inhibition of serine proteases including thrombin. Overall, our data supports a model where HEV uses host proteases to support replication and could have evolved to be independent of a virally-encoded protease for polyprotein processing.
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Affiliation(s)
- Danielle M Pierce
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Frazer J T Buchanan
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Fraser L Macrae
- Discovery and Translational Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Jake T Mills
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Abigail Cox
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Khadijah M Abualsaoud
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- Department of Laboratory and Blood Bank, Al Mikhwah General Hospital, Al Mikhwah, Saudi Arabia
| | - Joseph C Ward
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Robert A S Ariëns
- Discovery and Translational Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Mark Harris
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Nicola J Stonehouse
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Morgan R Herod
- School of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
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7
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Zahmanova G, Takova K, Tonova V, Koynarski T, Lukov LL, Minkov I, Pishmisheva M, Kotsev S, Tsachev I, Baymakova M, Andonov AP. The Re-Emergence of Hepatitis E Virus in Europe and Vaccine Development. Viruses 2023; 15:1558. [PMID: 37515244 PMCID: PMC10383931 DOI: 10.3390/v15071558] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/11/2023] [Accepted: 07/13/2023] [Indexed: 07/30/2023] Open
Abstract
Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. Transmission of HEV mainly occurs via the fecal-oral route (ingesting contaminated water or food) or by contact with infected animals and their raw meat products. Some animals, such as pigs, wild boars, sheep, goats, rabbits, camels, rats, etc., are natural reservoirs of HEV, which places people in close contact with them at increased risk of HEV disease. Although hepatitis E is a self-limiting infection, it could also lead to severe illness, particularly among pregnant women, or chronic infection in immunocompromised people. A growing number of studies point out that HEV can be classified as a re-emerging virus in developed countries. Preventative efforts are needed to reduce the incidence of acute and chronic hepatitis E in non-endemic and endemic countries. There is a recombinant HEV vaccine, but it is approved for use and commercially available only in China and Pakistan. However, further studies are needed to demonstrate the necessity of applying a preventive vaccine and to create conditions for reducing the spread of HEV. This review emphasizes the hepatitis E virus and its importance for public health in Europe, the methods of virus transmission and treatment, and summarizes the latest studies on HEV vaccine development.
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Affiliation(s)
- Gergana Zahmanova
- Department of Plant Physiology and Molecular Biology, University of Plovdiv, 4000 Plovdiv, Bulgaria
- Department of Technology Transfer and IP Management, Center of Plant Systems Biology and Biotechnology, 4000 Plovdiv, Bulgaria
| | - Katerina Takova
- Department of Plant Physiology and Molecular Biology, University of Plovdiv, 4000 Plovdiv, Bulgaria
| | - Valeria Tonova
- Department of Plant Physiology and Molecular Biology, University of Plovdiv, 4000 Plovdiv, Bulgaria
| | - Tsvetoslav Koynarski
- Department of Animal Genetics, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria
| | - Laura L Lukov
- Faculty of Sciences, Brigham Young University-Hawaii, Laie, HI 96762, USA
| | - Ivan Minkov
- Department of Technology Transfer and IP Management, Center of Plant Systems Biology and Biotechnology, 4000 Plovdiv, Bulgaria
- Institute of Molecular Biology and Biotechnologies, 4108 Markovo, Bulgaria
| | - Maria Pishmisheva
- Department of Infectious Diseases, Pazardzhik Multiprofile Hospital for Active Treatment, 4400 Pazardzhik, Bulgaria
| | - Stanislav Kotsev
- Department of Infectious Diseases, Pazardzhik Multiprofile Hospital for Active Treatment, 4400 Pazardzhik, Bulgaria
| | - Ilia Tsachev
- Department of Microbiology, Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria
| | - Magdalena Baymakova
- Department of Infectious Diseases, Military Medical Academy, 1606 Sofia, Bulgaria
| | - Anton P Andonov
- Department of Medical Microbiology and Infectious Diseases, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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8
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Nodavirus RNA replication crown architecture reveals proto-crown precursor and viral protein A conformational switching. Proc Natl Acad Sci U S A 2023; 120:e2217412120. [PMID: 36693094 PMCID: PMC9945985 DOI: 10.1073/pnas.2217412120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Positive-strand RNA viruses replicate their genomes in virus-induced membrane vesicles, and the resulting RNA replication complexes are a major target for virus control. Nodavirus studies first revealed viral RNA replication proteins forming a 12-fold symmetric "crown" at the vesicle opening to the cytosol, an arrangement recently confirmed to extend to distantly related alphaviruses. Using cryoelectron microscopy (cryo-EM), we show that mature nodavirus crowns comprise two stacked 12-mer rings of multidomain viral RNA replication protein A. Each ring contains an ~19 nm circle of C-proximal polymerase domains, differentiated by strikingly diverged positions of N-proximal RNA capping/membrane binding domains. The lower ring is a "proto-crown" precursor that assembles prior to RNA template recruitment, RNA synthesis, and replication vesicle formation. In this proto-crown, the N-proximal segments interact to form a toroidal central floor, whose 3.1 Å resolution structure reveals many mechanistic details of the RNA capping/membrane binding domains. In the upper ring, cryo-EM fitting indicates that the N-proximal domains extend radially outside the polymerases, forming separated, membrane-binding "legs." The polymerase and N-proximal domains are connected by a long linker accommodating the conformational switch between the two rings and possibly also polymerase movements associated with RNA synthesis and nonsymmetric electron density in the lower center of mature crowns. The results reveal remarkable viral protein multifunctionality, conformational flexibility, and evolutionary plasticity and insights into (+)RNA virus replication and control.
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9
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Fieulaine S, Tubiana T, Bressanelli S. De novo modelling of HEV replication polyprotein: Five-domain breakdown and involvement of flexibility in functional regulation. Virology 2023; 578:128-140. [PMID: 36527931 DOI: 10.1016/j.virol.2022.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 12/01/2022] [Accepted: 12/02/2022] [Indexed: 12/14/2022]
Abstract
Hepatitis E virus (HEV), a major cause of acute viral hepatitis, is a single-stranded, positive-sense RNA virus. As such, it encodes a 1700-residue replication polyprotein pORF1 that directs synthesis of new viral RNA in infected cells. Here we report extensive modeling with AlphaFold2 of the full-length pORF1, and its production by in vitro translation. From this, we give a detailed update on the breakdown into domains of HEV pORF1. We also provide evidence that pORF1's N-terminal domain is likely to oligomerize to form a dodecameric pore, homologously to what has been described for Chikungunya virus. Beyond providing accurate folds for its five domains, our work highlights that there is no canonical protease encoded in pORF1 and that flexibility in several functionally important regions rather than proteolytic processing may serve to regulate HEV RNA synthesis.
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Affiliation(s)
- Sonia Fieulaine
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
| | - Thibault Tubiana
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
| | - Stéphane Bressanelli
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
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10
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Wang Y, Zhao C, Qi Y, Geng Y. Hepatitis E Virus. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1417:1-13. [PMID: 37223855 DOI: 10.1007/978-981-99-1304-6_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Since the sequence of hepatitis E virus (HEV) was determined from a patient with enterically transmitted non-A, non-B hepatitis in 1989, similar sequences have been isolated from many different animals, including pigs, wild boars, deer, rabbits, bats, rats, chicken, and trout. All of these sequences have the same genomic organization, which contains open reading frames (ORFs) 1, 2, and 3, although their genomic sequences are variable. Some have proposed that they be classified as new family, Hepeviridae, which would be further divided into different genera and species according to their sequence variability. The size of these virus particles generally ranged from 27 to 34 nm. However, HEV virions produced in cell culture differ in structure from the viruses found in feces. Those from cell culture have a lipid envelope and either lack or have a little ORF3, whereas the viruses isolated from feces lack a lipid envelope but have ORF3 on their surfaces. Surprisingly, most of the secreted ORF2 proteins from both these sources are not associated with HEV RNA.
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Affiliation(s)
- Youchun Wang
- Institute of Medical Biology, Chinese Academy of Medical Science & Peking Union Medical College, Kunming, China.
| | - Chenyan Zhao
- Division of HIV/AIDS and Sex-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Ying Qi
- Division of HIV/AIDS and Sex-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Yansheng Geng
- Key Laboratory of Public Health Safety of Hebei Province, School of Public Health, Hebei University, Baoding, China
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11
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Carvalho PPD, Alves NA. Featuring ACE2 binding SARS-CoV and SARS-CoV-2 through a conserved evolutionary pattern of amino acid residues. J Biomol Struct Dyn 2022; 40:11719-11728. [PMID: 34486937 PMCID: PMC8425439 DOI: 10.1080/07391102.2021.1965028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Spike (S) glycoproteins mediate the coronavirus entry into the host cell. The S1 subunit of S-proteins contains the receptor-binding domain (RBD) that is able to recognize different host receptors, highlighting its remarkable capacity to adapt to their hosts along the viral evolution. While RBD in spike proteins is determinant for the virus-receptor interaction, the active residues lie at the receptor-binding motif (RBM), a region located in RBD that plays a fundamental role binding the outer surface of their receptors. Here, we address the hypothesis that SARS-CoV and SARS-CoV-2 strains able to use angiotensin-converting enzyme 2 (ACE2) proteins have adapted their RBM along the viral evolution to explore specific conformational topology driven by the residues YGF to infect host cells. We also speculate that this YGF-based mechanism can act as a protein signature located at the RBM to distinguish coronaviruses able to use ACE2 as a cell entry receptor.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Patrícia P. D. Carvalho
- Departamento de Física, FFCLRP, Universidade de São Paulo, Ribeirão Preto, SP, Brazil,CONTACT Patrícia P. D. Carvalho ;
| | - Nelson A. Alves
- Departamento de Física, FFCLRP, Universidade de São Paulo, Ribeirão Preto, SP, Brazil,Nelson Alves
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12
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den Boon JA, Zhan H, Unchwaniwala N, Horswill M, Slavik K, Pennington J, Navine A, Ahlquist P. Multifunctional Protein A Is the Only Viral Protein Required for Nodavirus RNA Replication Crown Formation. Viruses 2022; 14:v14122711. [PMID: 36560715 PMCID: PMC9788154 DOI: 10.3390/v14122711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/23/2022] [Accepted: 11/24/2022] [Indexed: 12/12/2022] Open
Abstract
Positive-strand RNA virus RNA genome replication occurs in membrane-associated RNA replication complexes (RCs). Nodavirus RCs are outer mitochondrial membrane invaginations whose necked openings to the cytosol are "crowned" by a 12-fold symmetrical proteinaceous ring that functions as the main engine of RNA replication. Similar protein crowns recently visualized at the openings of alphavirus and coronavirus RCs highlight their broad conservation and functional importance. Using cryo-EM tomography, we earlier showed that the major nodavirus crown constituent is viral protein A, whose polymerase, RNA capping, membrane interaction and multimerization domains drive RC formation and function. Other viral proteins are strong candidates for unassigned EM density in the crown. RNA-binding RNAi inhibitor protein B2 co-immunoprecipitates with protein A and could form crown subdomains that protect nascent viral RNA and dsRNA templates. Capsid protein may interact with the crown since nodavirus virion assembly has spatial and other links to RNA replication. Using cryoelectron tomography and complementary approaches, we show that, even when formed in mammalian cells, nodavirus RC crowns generated without B2 and capsid proteins are functional and structurally indistinguishable from mature crowns in infected Drosophila cells expressing all viral proteins. Thus, the only nodaviral factors essential to form functional RCs and crowns are RNA replication protein A and an RNA template. We also resolve apparent conflicts in prior results on B2 localization in infected cells, revealing at least two distinguishable pools of B2. The results have significant implications for crown structure, assembly, function and control as an antiviral target.
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Affiliation(s)
- Johan A. den Boon
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
- McArdle Laboratory for Cancer Research, University of Wisconsin–Madison, Madison, WI 53705, USA
| | - Hong Zhan
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Nuruddin Unchwaniwala
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Mark Horswill
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
- McArdle Laboratory for Cancer Research, University of Wisconsin–Madison, Madison, WI 53705, USA
| | - Kailey Slavik
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Janice Pennington
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Amanda Navine
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Paul Ahlquist
- John W. and Jeanne M. Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA
- Institute for Molecular Virology, University of Wisconsin–Madison, Madison, WI 53706, USA
- McArdle Laboratory for Cancer Research, University of Wisconsin–Madison, Madison, WI 53705, USA
- Correspondence:
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13
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Genetic Reassortment between Endemic and Introduced Macrobrachium rosenbergii Nodaviruses in the Murray-Darling Basin, Australia. Viruses 2022; 14:v14102186. [PMID: 36298741 PMCID: PMC9612130 DOI: 10.3390/v14102186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 09/30/2022] [Accepted: 10/01/2022] [Indexed: 11/05/2022] Open
Abstract
Macrobrachium rosenbergii nodavirus (MrNV)—the aetiological agent of white tail disease—is a major limiting factor of crustacean aquaculture as it causes up to 100% mortality in M. rosenbergii larvae and juveniles. Despite the importance of MrNV, there have been few studies on the phylogenetic diversity and geographic range of this virus in Australian waterways. Here, we detected MrNV genomes in common carp (Cyprinus carpio) metatranscriptomes sampled at five freshwater sites across the Murray-Darling Basin (MDB), Australia. We identified genetic divergence of the RNA-dependent RNA polymerase gene between MrNV sequences identified in the northern and southern rivers of the MDB. Northern viruses exhibited strong phylogenetic clustering with MrNV from China, whereas the southern viruses were more closely related to MrNV from Australia. However, all five viruses were closely related in the capsid protein, indicative of genetic reassortment of the RNA1 and RNA2 segments between Australian and introduced MrNV. In addition, we identified Macrobrachium australiense in two of the five MrNV-positive libraries, suggesting that these species may be important reservoir hosts in the MDB. Overall, this study reports the first occurrence of MrNV outside of the Queensland region in Australia and provides evidence for genetic reassortment between endemic and introduced MrNV.
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14
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Sathanantham P, Zhao W, He G, Murray A, Fenech E, Diaz A, Schuldiner M, Wang X. A conserved viral amphipathic helix governs the replication site-specific membrane association. PLoS Pathog 2022; 18:e1010752. [PMID: 36048900 PMCID: PMC9473614 DOI: 10.1371/journal.ppat.1010752] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 09/14/2022] [Accepted: 07/19/2022] [Indexed: 11/18/2022] Open
Abstract
Positive-strand RNA viruses assemble their viral replication complexes (VRCs) on specific host organelle membranes, yet it is unclear how viral replication proteins recognize and what motifs or domains in viral replication proteins determine their destinations. We show here that an amphipathic helix, helix B in replication protein 1a of brome mosaic virus (BMV), is necessary for 1a’s localization to the nuclear endoplasmic reticulum (ER) membrane where BMV assembles its VRCs. Helix B is also sufficient to target soluble proteins to the nuclear ER membrane in yeast and plant cells. We further show that an equivalent helix in several plant- and human-infecting viruses of the Alsuviricetes class targets fluorescent proteins to the organelle membranes where they form their VRCs, including ER, vacuole, and Golgi membranes. Our work reveals a conserved helix that governs the localization of VRCs among a group of viruses and points to a possible target for developing broad-spectrum antiviral strategies. Positive-strand RNA viruses [(+)RNA viruses] are the largest viral class that include numerous pathogens causing important diseases in humans, animals, and plants. During their infections, (+)RNA viruses assemble their viral replication complexes (VRCs), where they multiply themselves, at specific organelle membranes. An initial step to form VRCs is to target viral replication proteins to the designated organelle membranes. For brome mosaic virus (BMV), its replication protein 1a is responsible for the VRC formation at the nuclear endoplasmic reticulum (ER) membrane. We show that an amphipathic alpha-helix, helix B, in BMV 1a is necessary for the association of BMV 1a with the nuclear ER membrane and for BMV genome amplification. In addition, Helix B is sufficient to target several soluble proteins to the nuclear ER membrane in yeast and plant cells. BMV belongs to the Alsuviricetes class that includes viruses infecting humans, animals, and plants. We further show that the helix B across members of the Alsuviricetes class is sufficient to target fluorescence proteins to the designated organelle membranes. Our results reveal a conserved feature among a group of viruses in governing the associations with replication site-specific organelle membranes and point to a target to develop broad-spectrum antivirals.
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Affiliation(s)
- Preethi Sathanantham
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Wenhao Zhao
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Nanjing, China
| | - Guijuan He
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Austin Murray
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Emma Fenech
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Arturo Diaz
- Department of Biology, La Sierra University, Riverside, California, United States of America
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Xiaofeng Wang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail:
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15
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Zhang K, Law MCY, Nguyen TM, Tan YB, Wirawan M, Law YS, Jeong LS, Luo D. Molecular basis of specific viral RNA recognition and 5'-end capping by the Chikungunya virus nsP1. Cell Rep 2022; 40:111133. [PMID: 35905713 DOI: 10.1016/j.celrep.2022.111133] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 06/15/2022] [Accepted: 07/01/2022] [Indexed: 11/17/2022] Open
Abstract
Many viruses encode RNA-modifying enzymes to edit the 5' end of viral RNA to mimic the cellular mRNA for effective protein translation, genome replication, and evasion of the host defense mechanisms. Alphavirus nsP1 synthesizes the 5' end Cap-0 structure of viral RNAs. However, the molecular basis of the capping process remains unclear. We determine high-resolution cryoelectron microscopy (cryo-EM) structures of Chikungunya virus nsP1 in complex with m7GTP/SAH, covalently attached m7GMP, and Cap-0 viral RNA. These structures reveal details of viral-RNA-capping reactions and uncover a sequence-specific virus RNA-recognition pattern that, in turn, regulates viral-RNA-capping efficiency to ensure optimal genome replication and subgenomic RNA transcription. This sequence-specific enzyme-RNA pairing is conserved across all alphaviruses.
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Affiliation(s)
- Kuo Zhang
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore; School of Medicine, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Michelle Cheok Yien Law
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Trinh Mai Nguyen
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Yaw Bia Tan
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Melissa Wirawan
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Yee-Song Law
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Lak Shin Jeong
- College of Pharmacy, Seoul National University, Seoul, South Korea
| | - Dahai Luo
- Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive, Singapore 636921, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, EMB 06-01, 59 Nanyang Drive, Singapore 636921, Singapore; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 636921, Singapore.
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16
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Nishikiori M, den Boon JA, Unchwaniwala N, Ahlquist P. Crowning Touches in Positive-Strand RNA Virus Genome Replication Complex Structure and Function. Annu Rev Virol 2022; 9:193-212. [PMID: 35610038 DOI: 10.1146/annurev-virology-092920-021307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Positive-strand RNA viruses, the largest genetic class of eukaryotic viruses, include coronaviruses and many other established and emerging pathogens. A major target for understanding and controlling these viruses is their genome replication, which occurs in virus-induced membrane vesicles that organize replication steps and protect double-stranded RNA intermediates from innate immune recognition. The structure of these complexes has been greatly illuminated by recent cryo-electron microscope tomography studies with several viruses. One key finding in diverse systems is the organization of crucial viral RNA replication factors in multimeric rings or crowns that among other functions serve as exit channels gating release of progeny genomes to the cytosol for translation and encapsidation. Emerging results suggest that these crowns serve additional important purposes in replication complex assembly, function, and interaction with downstream processes such as encapsidation. The findings provide insights into viral function and evolution and new bases for understanding, controlling, and engineering positive-strand RNA viruses. Expected final online publication date for the Annual Review of Virology, Volume 9 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Masaki Nishikiori
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, Wisconsin, USA; .,Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Johan A den Boon
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, Wisconsin, USA; .,Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Nuruddin Unchwaniwala
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, Wisconsin, USA; .,Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Current affiliation: Assembly Biosciences, Inc., South San Francisco, California, USA
| | - Paul Ahlquist
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, Wisconsin, USA; .,Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
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17
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Cancela F, Noceti O, Arbiza J, Mirazo S. Structural aspects of hepatitis E virus. Arch Virol 2022; 167:2457-2481. [PMID: 36098802 PMCID: PMC9469829 DOI: 10.1007/s00705-022-05575-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/04/2022] [Indexed: 12/14/2022]
Abstract
Hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide. Hepatitis E is an enterically transmitted zoonotic disease that causes large waterborne epidemic outbreaks in developing countries and has become an increasing public-health concern in industrialized countries. In this setting, the infection is usually acute and self-limiting in immunocompetent individuals, although chronic cases in immunocompromised patients have been reported, frequently associated with several extrahepatic manifestations. Moreover, extrahepatic manifestations have also been reported in immunocompetent individuals with acute HEV infection. HEV belongs to the alphavirus-like supergroup III of single-stranded positive-sense RNA viruses, and its genome contains three partially overlapping open reading frames (ORFs). ORF1 encodes a nonstructural protein with eight domains, most of which have not been extensively characterized: methyltransferase, Y domain, papain-like cysteine protease, hypervariable region, proline-rich region, X domain, Hel domain, and RNA-dependent RNA polymerase. ORF2 and ORF3 encode the capsid protein and a multifunctional protein believed to be involved in virion release, respectively. The novel ORF4 is only expressed in HEV genotype 1 under endoplasmic reticulum stress conditions, and its exact function has not yet been elucidated. Despite important advances in recent years, the biological and molecular processes underlying HEV replication remain poorly understood, primarily due to a lack of detailed information about the functions of the viral proteins and the mechanisms involved in host-pathogen interactions. This review summarizes the current knowledge concerning HEV proteins and their biological properties, providing updated detailed data describing their function and focusing in detail on their structural characteristics. Furthermore, we review some unclear aspects of the four proteins encoded by the ORFs, highlighting the current key information gaps and discussing potential novel experimental strategies for shedding light on those issues.
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Affiliation(s)
- Florencia Cancela
- grid.11630.350000000121657640Sección Virología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Ofelia Noceti
- grid.414402.70000 0004 0469 0889Programa Nacional de Trasplante Hepático y Unidad Docente Asistencial Centro Nacional de Tratamiento Hepatobiliopancreatico. Hospital Central de las Fuerzas Armadas, Montevideo, Uruguay
| | - Juan Arbiza
- grid.11630.350000000121657640Sección Virología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Santiago Mirazo
- grid.11630.350000000121657640Sección Virología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay ,grid.11630.350000000121657640Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay ,Av. Alfredo Navarro 3051, PC 11600 Montevideo, Uruguay
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18
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Shafat Z, Hamza A, Deeba F, Parvez MK, Parveen S. Molecular insights into the Y-domain of hepatitis E virus using computational analyses. BENI-SUEF UNIVERSITY JOURNAL OF BASIC AND APPLIED SCIENCES 2021. [DOI: 10.1186/s43088-021-00154-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Abstract
Background
Hepatitis E virus (HEV) of the family Hepeviridae is a major causative agent of acute hepatitis in developing countries. The Y-domain is derived from multi-domain non-structural polyprotein encoded by open reading frame 1 (ORF1). Previous studies have demonstrated the essentiality of Y-domain sequences in HEV life cycle; however, its function remains completely unexplored. The following study was thus conceptualized to examine the detailed computational investigation for the putative Y-domain to estimate its phylogenetic assessment, physiochemical properties, structural and functional characteristics using in silico analyses.
Results
The phylogenetic assessment of Y-domain with a vast range of hosts indicated that the protein was very well conserved throughout the course of evolution. The Y-domain was found to be unstable, hydrophilic and basic in nature with high thermostability value. Structural analysis of Y-domain revealed mixed α/β structural fold of the protein having higher percentage of alpha-helices. The three-dimensional (3D) protein model generated through homology modelling revealed the presence of clefts, tunnels and pore. Gene ontology analysis predicted Y-domain protein’s involvement in several binding and catalytic activities as well as significant biological processes. Mutations in the conserved amino acids of the Y-domain suggested that it may stabilize or de-stabilize the protein structure that might affect its structure–function relationship.
Conclusions
This theoretical study will facilitate towards deciphering the role of unexplored Y-domain, thereby providing better understanding towards the pathogenesis of HEV infection.
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19
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Abstract
Alphaviruses are positive-strand RNA viruses, typically transmitted by mosquitoes between vertebrate hosts. They encode four essential replication proteins, the non-structural proteins nsP1-4, which possess the enzymatic activities of RNA capping, RNA helicase, site-specific protease, ADP-ribosyl removal and RNA polymerase. Alphaviruses have been key models in the study of membrane-associated RNA replication, which is a conserved feature among the positive-strand RNA viruses of animals and plants. We review new structural and functional information on the nsPs and their interaction with host proteins and membranes, as well as with viral RNA sequences. The dodecameric ring structure of nsP1 is likely to be one of the evolutionary innovations that facilitated the success of the progenitors of current positive-strand RNA viruses.
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Affiliation(s)
- Tero Ahola
- Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Gerald McInerney
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, Estonia.
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20
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Zhou Z, Xie Y, Wu C, Nan Y. The Hepatitis E Virus Open Reading Frame 2 Protein: Beyond Viral Capsid. Front Microbiol 2021; 12:739124. [PMID: 34690982 PMCID: PMC8529240 DOI: 10.3389/fmicb.2021.739124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 09/20/2021] [Indexed: 12/20/2022] Open
Abstract
Hepatitis E virus (HEV) is a zoonotic pathogen causing hepatitis in both human and animal hosts, which is responsible for acute hepatitis E outbreaks worldwide. The 7.2 kb genome of the HEV encodes three well-defined open reading frames (ORFs), where the ORF2 translation product acts as the major virion component to form the viral capsid. In recent years, besides forming the capsid, more functions have been revealed for the HEV-ORF2 protein, and it appears that HEV-ORF2 plays multiple functions in both viral replication and pathogenesis. In this review, we systematically summarize the recent research advances regarding the function of the HEV-ORF2 protein such as application in the development of a vaccine, regulation of the innate immune response and cellular signaling, involvement in host tropism and participation in HEV pathogenesis as a novel secretory factor. Progress in understanding more of the function of HEV-ORF2 protein beyond the capsid protein would contribute to improved control and treatment of HEV infection.
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Affiliation(s)
- Zhaobin Zhou
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, China
- Scientific Observing and Experimental Station of Veterinary Pharmacology and Diagnostic Technology, Ministry of Agriculture, Yangling, China
| | - Yinqian Xie
- Shaanxi Animal Disease Prevention and Control Center, Xi’an, China
| | - Chunyan Wu
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, China
- Scientific Observing and Experimental Station of Veterinary Pharmacology and Diagnostic Technology, Ministry of Agriculture, Yangling, China
| | - Yuchen Nan
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, China
- Scientific Observing and Experimental Station of Veterinary Pharmacology and Diagnostic Technology, Ministry of Agriculture, Yangling, China
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21
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Unchwaniwala N, Zhan H, den Boon JA, Ahlquist P. Cryo-electron microscopy of nodavirus RNA replication organelles illuminates positive-strand RNA virus genome replication. Curr Opin Virol 2021; 51:74-79. [PMID: 34601307 PMCID: PMC8504867 DOI: 10.1016/j.coviro.2021.09.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/10/2021] [Accepted: 09/13/2021] [Indexed: 11/18/2022]
Abstract
The nodavirus flock house virus recently provided a well-characterized model for the first cryo-electron microscope tomography of membrane-bound, positive-strand RNA ((+)RNA) virus genome replication complexes (RCs). The resulting first views of RC organization and complementary biochemical results showed that the viral RNA replication vesicle is tightly packed with the dsRNA genomic RNA replication intermediate, and that (+)ssRNA replication products are released through the vesicle neck to the cytosol through a 12-fold symmetric ring or crown of multi-functional viral RNA replication proteins, which likely also contribute to viral RNA synthesis. Subsequent studies identified similar crown-like RNA replication protein complexes in alphavirus and coronavirus RCs, indicating related mechanisms across highly divergent (+)RNA viruses. As outlined in this review, these results have significant implications for viral function, evolution and control.
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Affiliation(s)
- Nuruddin Unchwaniwala
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, 53715, United States; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI, 53706, United States; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI, 53705, United States
| | - Hong Zhan
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, 53715, United States; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI, 53706, United States; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI, 53705, United States
| | - Johan A den Boon
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, 53715, United States; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI, 53706, United States; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI, 53705, United States
| | - Paul Ahlquist
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, 53715, United States; Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI, 53706, United States; McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI, 53705, United States
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22
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Komatsu K, Sasaki N, Yoshida T, Suzuki K, Masujima Y, Hashimoto M, Watanabe S, Tochio N, Kigawa T, Yamaji Y, Oshima K, Namba S, Nelson RS, Arie T. Identification of a Proline-Kinked Amphipathic α-Helix Downstream from the Methyltransferase Domain of a Potexvirus Replicase and Its Role in Virus Replication and Perinuclear Complex Formation. J Virol 2021; 95:e0190620. [PMID: 34346768 PMCID: PMC8475525 DOI: 10.1128/jvi.01906-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 07/25/2021] [Indexed: 11/20/2022] Open
Abstract
Characterized positive-strand RNA viruses replicate in association with intracellular membranes. Regarding viruses in the genus Potexvirus, the mechanism by which their RNA-dependent RNA polymerase (replicase) associates with membranes is understudied. Here, by membrane flotation analyses of the replicase of Plantago asiatica mosaic potexvirus (PlAMV), we identified a region in the methyltransferase (MET) domain as a membrane association determinant. An amphipathic α-helix was predicted downstream from the core region of the MET domain, and hydrophobic amino acid residues were conserved in the helical sequences in replicases of other potexviruses. Nuclear magnetic resonance (NMR) analysis confirmed the amphipathic α-helical configuration and unveiled a kink caused by a highly conserved proline residue in the α-helix. Substitution of this proline residue and other hydrophobic and charged residues in the amphipathic α-helix abolished PlAMV replication. Ectopic expression of a green fluorescent protein (GFP) fusion with the entire MET domain resulted in the formation of a large perinuclear complex, where virus replicase and RNA colocated during virus infection. Except for the proline substitution, the amino acid substitutions in the α-helix that abolished virus replication also prevented the formation of the large perinuclear complex by the respective GFP-MET fusion. Small intracellular punctate structures were observed for all GFP-MET fusions, and in vitro high-molecular-weight complexes were formed by both replication-competent and -incompetent viral replicons and thus were not sufficient for replication competence. We discuss the roles of the potexvirus-specific, proline-kinked amphipathic helical structure in virus replication and intracellular large complex and punctate structure formation. IMPORTANCE RNA viruses characteristically associate with intracellular membranes during replication. Although virus replicases are assumed to possess membrane-targeting properties, their membrane association domains generally remain unidentified or poorly characterized. Here, we identified a proline-kinked amphipathic α-helix structure downstream from the methyltransferase core domain of PlAMV replicase as a membrane association determinant. This helical sequence, which includes the proline residue, was conserved among potexviruses and related viruses in the order Tymovirales. Substitution of the proline residue, but not the other residues necessary for replication, allowed formation of a large perinuclear complex within cells resembling those formed by PlAMV replicase and RNA during virus replication. Our results demonstrate the role of the amphipathic α-helix in PlAMV replicase in a perinuclear complex formation and virus replication and that perinuclear complex formation by the replicase alone will not necessarily indicate successful virus replication.
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Affiliation(s)
- Ken Komatsu
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
- Institute of Global Innovation Research (GIR), Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Nobumitsu Sasaki
- Institute of Global Innovation Research (GIR), Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
- Gene Research Center, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Tetsuya Yoshida
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Katsuhiro Suzuki
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Yuki Masujima
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Masayoshi Hashimoto
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Satoru Watanabe
- Laboratory for Cellular Structural Biology, RIKEN Center for Biosystems Dynamics Research, Yokohama, Japan
| | - Naoya Tochio
- Laboratory for Cellular Structural Biology, RIKEN Center for Biosystems Dynamics Research, Yokohama, Japan
| | - Takanori Kigawa
- Laboratory for Cellular Structural Biology, RIKEN Center for Biosystems Dynamics Research, Yokohama, Japan
| | - Yasuyuki Yamaji
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Kenro Oshima
- Faculty of Bioscience, Department of Clinical Plant Science, Hosei University, Koganei, Japan
| | - Shigetou Namba
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Richard S. Nelson
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Tsutomu Arie
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
- Institute of Global Innovation Research (GIR), Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
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23
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Shafat Z, Hamza A, Islam A, Al-Dosari MS, Parvez MK, Parveen S. Structural exploration of Y-domain reveals its essentiality in HEV pathogenesis. Protein Expr Purif 2021; 187:105947. [PMID: 34314826 DOI: 10.1016/j.pep.2021.105947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/08/2021] [Accepted: 07/21/2021] [Indexed: 12/19/2022]
Abstract
Hepatitis E virus (HEV) is a major causative agent of hepatitis E infections across the globe. Although the essentiality of HEV nonstructural polyprotein (pORF1) putative Y-domain (Yd) has been established in viral pathogenesis, its structural-functional role remains elusive. The current research discusses the novel exploration on Yd protein expression, purification, biophysical characterization and structure-based docking analysis. The codon optimized synthetic gene and optimized expression parameters i.e., 5 h induction with 0.25 mM IPTG at 37 °C, resulted in efficient production of Yd protein (∼40 kDa) in E. coli BL21(DE3) cells. Majority of the recombinant Yd (rYd) protein expressed as inclusion bodies was solubilized in 0.5% N-lauroylsarcosine and purified using Ni-NTA chromatography. Circular dichroism (CD) and UV visible absorption spectroscopic studies on Yd revealed both secondary and tertiary structure stability in alkaline range (pH 8.0-10.0), suggesting correlation with its physiological activity. Thus, loss in structure at low pH perhaps play crucial role in cytoplasmic-membrane interaction. The biophysical data were in good agreement with in-silico structural analyses, which suggested mixed α/β fold, non-random and basic nature of Yd protein. Furthermore, due to Yd protein essentiality in HEV replication and pathogenesis, it was considered as a template for docking and drug-likeness analyses. The 3D modeling of Yd protein and structure-based screening and drug-likeness of inhibitory compounds, including established antiviral drugs led to the identification of top nine promising candidates. Nonetheless, in vitro studies on the predicted interaction of Yd with intracellular-membrane towards establishing replication-complexes as well as validations of the proposed therapeutic agents are warranted.
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Affiliation(s)
- Zoya Shafat
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Abu Hamza
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Mohammed S Al-Dosari
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad K Parvez
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.
| | - Shama Parveen
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India.
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24
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Structural Insights into the Mechanisms of Action of Functionally Distinct Classes of Chikungunya Virus Nonstructural Protein 1 Inhibitors. Antimicrob Agents Chemother 2021; 65:e0256620. [PMID: 33875421 PMCID: PMC8218635 DOI: 10.1128/aac.02566-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chikungunya virus (CHIKV) nonstructural protein 1 (nsP1) harbors the methyltransferase (MTase) and guanylyltransferase (GTase) activities needed for viral RNA capping and represents a promising antiviral drug target. We compared the antiviral efficacies of nsP1 inhibitors belonging to the MADTP, CHVB, and FHNA series (6′-fluoro-homoneplanocin A [FHNA], its 3′-keto form, and 6′-β-fluoro-homoaristeromycin). Cell-based phenotypic cross-resistance assays revealed that the CHVB and MADTP series had similar modes of action that differed from that of the FHNA series. In biochemical assays with purified Semliki Forest virus and CHIKV nsP1, CHVB compounds strongly inhibited MTase and GTase activities, while MADTP-372 had a moderate inhibitory effect. FHNA did not directly inhibit the enzymatic activity of CHIKV nsP1. The first-of-their-kind molecular-docking studies with the cryo-electron microscopy (cryo-EM) structure of CHIKV nsP1, which is assembled into a dodecameric ring, revealed that the MADTP and CHVB series bind at the S-adenosylmethionine (SAM)-binding site in the capping domain, where they would function as competitive or noncompetitive inhibitors. The FHNA series was predicted to bind at the secondary binding pocket in the ring-aperture membrane-binding and oligomerization (RAMBO) domain, potentially interfering with the membrane binding and oligomerization of nsP1. Our cell-based and enzymatic assays, in combination with molecular docking and mapping of compound resistance mutations to the nsP1 structure, allowed us to group nsP1 inhibitors into functionally distinct classes. This study identified druggable pockets in the nsP1 dodecameric structure and provides a basis for the rational design, optimization, and combination of inhibitors of this unique and promising antiviral drug target.
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25
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Yang YL, Nan YC. Open reading frame 3 protein of hepatitis E virus: Multi-function protein with endless potential. World J Gastroenterol 2021; 27:2458-2473. [PMID: 34092969 PMCID: PMC8160619 DOI: 10.3748/wjg.v27.i20.2458] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/10/2021] [Accepted: 04/12/2021] [Indexed: 02/06/2023] Open
Abstract
Hepatitis E virus (HEV), a fecal-orally transmitted foodborne viral pathogen, causes acute hepatitis in humans and is responsible for hepatitis E outbreaks worldwide. Since the identification of HEV as a zoonotic agent, this virus has been isolated from a variety of hosts with an ever-expanding host range. HEV-open reading frame (ORF) 3, the smallest ORF in HEV genomes, initially had been perceived as an unremarkable HEV accessory protein. However, as novel HEV-ORF3 function has been discovered that is related to the existence of a putative third virion structural form, referred to as “quasi-enveloped” HEV particles, HEV is challenging the conventional virion structure-based classification scheme, which assigns all viruses to two groups, “enveloped” or “non-enveloped”. In this review, we systematically describe recent progress that has identified multiple pathogenic roles of HEV-ORF3, including roles in HEV virion release, biogenesis of quasi-enveloped virus, regulation of the host innate immune response, and interference with host signaling pathways. In addition, implications of HEV-ORF3-associated quasi-enveloped virions are discussed to guide future development of improved vaccines against zoonotic HEV infection.
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Affiliation(s)
- Yong-Lin Yang
- Department of Infectious Diseases, Taizhou People's Hospital, The Fifth Affiliated Hospital of Nantong University, Taizhou 225300, Jiangsu Province, China
- Department of General Practice, Nanjing First Hospital, Nanjing Medical University, Nanjing 210006, Jiangsu Province, China
| | - Yu-Chen Nan
- Department of Preventive Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, China
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26
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Zhang K, Law YS, Law MCY, Tan YB, Wirawan M, Luo D. Structural insights into viral RNA capping and plasma membrane targeting by Chikungunya virus nonstructural protein 1. Cell Host Microbe 2021; 29:757-764.e3. [DOI: 10.1016/j.chom.2021.02.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/10/2021] [Accepted: 02/22/2021] [Indexed: 01/30/2023]
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27
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Wang B, Meng XJ. Structural and molecular biology of hepatitis E virus. Comput Struct Biotechnol J 2021; 19:1907-1916. [PMID: 33995894 PMCID: PMC8079827 DOI: 10.1016/j.csbj.2021.03.038] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) is one of the most common causes of acute viral hepatitis, mainly transmitted by fecal-oral route but has also been linked to fulminant hepatic failure, chronic hepatitis, and extrahepatic neurological and renal diseases. HEV is an emerging zoonotic pathogen with a broad host range, and strains of HEV from numerous animal species are known to cross species barriers and infect humans. HEV is a single-stranded, positive-sense RNA virus in the family Hepeviridae. The genome typically contains three open reading frames (ORFs): ORF1 encodes a nonstructural polyprotein for virus replication and transcription, ORF2 encodes the capsid protein that elicits neutralizing antibodies, and ORF3, which partially overlaps ORF2, encodes a multifunctional protein involved in virion morphogenesis and pathogenesis. HEV virions are non-enveloped spherical particles in feces but exist as quasi-enveloped particles in circulating blood. Two types of HEV virus-like particles (VLPs), small T = 1 (270 Å) and native virion-sized T = 3 (320-340 Å) have been reported. There exist two distinct forms of capsid protein, the secreted form (ORF2S) inhibits antibody neutralization, whereas the capsid-associated form (ORF2C) self-assembles to VLPs. Four cis-reactive elements (CREs) containing stem-loops from secondary RNA structures have been identified in the non-coding regions and are critical for virus replication. This mini-review discusses the current knowledge and gaps regarding the structural and molecular biology of HEV with emphasis on the virion structure, genomic organization, secondary RNA structures, viral proteins and their functions, and life cycle of HEV.
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Affiliation(s)
- Bo Wang
- Center for Emerging, Zoonotic and Arthropod-borne Pathogens, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Xiang-Jin Meng
- Center for Emerging, Zoonotic and Arthropod-borne Pathogens, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
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28
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Advances in Hepatitis E Virus Biology and Pathogenesis. Viruses 2021; 13:v13020267. [PMID: 33572257 PMCID: PMC7915517 DOI: 10.3390/v13020267] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/21/2021] [Accepted: 02/02/2021] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) is one of the causative agents for liver inflammation across the world. HEV is a positive-sense single-stranded RNA virus. Human HEV strains mainly belong to four major genotypes in the genus Orthohepevirus A, family Hepeviridae. Among the four genotypes, genotype 1 and 2 are obligate human pathogens, and genotype 3 and 4 cause zoonotic infections. HEV infection with genotype 1 and 2 mainly presents as acute and self-limiting hepatitis in young adults. However, HEV infection of pregnant women with genotype 1 strains can be exacerbated to fulminant hepatitis, resulting in a high rate of case fatality. As pregnant women maintain the balance of maternal-fetal tolerance and effective immunity against invading pathogens, HEV infection with genotype 1 might dysregulate the balance and cause the adverse outcome. Furthermore, HEV infection with genotype 3 can be chronic in immunocompromised patients, with rapid progression, which has been a challenge since it was reported years ago. The virus has a complex interaction with the host cells in downregulating antiviral factors and recruiting elements to generate a conducive environment of replication. The virus-cell interactions at an early stage might determine the consequence of the infection. In this review, advances in HEV virology, viral life cycle, viral interference with the immune response, and the pathogenesis in pregnant women are discussed, and perspectives on these aspects are presented.
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29
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[Activation of positive-strand RNA virus genome replication complexes by host oxidation machinery and viroporins]. Uirusu 2021; 71:55-62. [PMID: 35526995 DOI: 10.2222/jsv.71.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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30
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Transmembrane redox regulation of genome replication functions in positive-strand RNA viruses. Curr Opin Virol 2020; 47:25-31. [PMID: 33383355 DOI: 10.1016/j.coviro.2020.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/02/2020] [Accepted: 12/08/2020] [Indexed: 02/07/2023]
Abstract
Positive-strand RNA virus genome replication takes place on intracellular membranes that separate the reduced cytosol from the oxidized extracellular/luminal milieu. Ongoing studies of these membrane-bounded genome replication complexes have revealed underlying common principles in their structure, assembly and functionalization, including transmembrane features and redox dependencies. Among these, members of the alphavirus, flavivirus, and picornavirus supergroups all encode membrane-permeabilizing viroporins required for efficient RNA replication. For flaviviruses and particularly alphavirus supergroup members, these viroporins are linked to activating viral RNA capping and potentially other later-stage RNA replication functions, and to local transmembrane release of oxidizing potential to trigger these changes in cytoplasmic RNA replication complexes. Further exploration of these emerging shared principles could spur development of broad-spectrum antivirals.
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31
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Affiliation(s)
- Nuruddin Unchwaniwala
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, USA. .,University of Wisconsin-Madison, Madison, WI, USA
| | - Paul Ahlquist
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI, USA. .,University of Wisconsin-Madison, Madison, WI, USA.,Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI, USA
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32
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Unchwaniwala N, Zhan H, Pennington J, Horswill M, den Boon JA, Ahlquist P. Subdomain cryo-EM structure of nodaviral replication protein A crown complex provides mechanistic insights into RNA genome replication. Proc Natl Acad Sci U S A 2020; 117:18680-18691. [PMID: 32690711 PMCID: PMC7414174 DOI: 10.1073/pnas.2006165117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
For positive-strand RNA [(+)RNA] viruses, the major target for antiviral therapies is genomic RNA replication, which occurs at poorly understood membrane-bound viral RNA replication complexes. Recent cryoelectron microscopy (cryo-EM) of nodavirus RNA replication complexes revealed that the viral double-stranded RNA replication template is coiled inside a 30- to 90-nm invagination of the outer mitochondrial membrane, whose necked aperture to the cytoplasm is gated by a 12-fold symmetric, 35-nm diameter "crown" complex that contains multifunctional viral RNA replication protein A. Here we report optimizing cryo-EM tomography and image processing to improve crown resolution from 33 to 8.5 Å. This resolves the crown into 12 distinct vertical segments, each with 3 major subdomains: A membrane-connected basal lobe and an apical lobe that together comprise the ∼19-nm-diameter central turret, and a leg emerging from the basal lobe that connects to the membrane at ∼35-nm diameter. Despite widely varying replication vesicle diameters, the resulting two rings of membrane interaction sites constrain the vesicle neck to a highly uniform shape. Labeling protein A with a His-tag that binds 5-nm Ni-nanogold allowed cryo-EM tomography mapping of the C terminus of protein A to the apical lobe, which correlates well with the predicted structure of the C-proximal polymerase domain of protein A. These and other results indicate that the crown contains 12 copies of protein A arranged basally to apically in an N-to-C orientation. Moreover, the apical polymerase localization has significant mechanistic implications for template RNA recruitment and (-) and (+)RNA synthesis.
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Affiliation(s)
- Nuruddin Unchwaniwala
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Hong Zhan
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Janice Pennington
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Mark Horswill
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Johan A den Boon
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Paul Ahlquist
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715;
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI 53706
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Mutations on VEEV nsP1 relate RNA capping efficiency to ribavirin susceptibility. Antiviral Res 2020; 182:104883. [PMID: 32750467 DOI: 10.1016/j.antiviral.2020.104883] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 06/30/2020] [Accepted: 07/14/2020] [Indexed: 11/22/2022]
Abstract
Alphaviruses are arthropod-borne viruses of public health concern. To date no efficient vaccine nor antivirals are available for safe human use. During viral replication the nonstructural protein 1 (nsP1) catalyzes capping of genomic and subgenomic RNAs. The capping reaction is unique to the Alphavirus genus. The whole three-step process follows a particular order: (i) transfer of a methyl group from S-adenosyl methionine (SAM) onto a GTP forming m7GTP; (ii) guanylylation of the enzyme to form a m7GMP-nsP1adduct; (iii) transfer of m7GMP onto 5'-diphosphate RNA to yield capped RNA. Specificities of these reactions designate nsP1 as a promising target for antiviral drug development. In the current study we performed a mutational analysis on two nsP1 positions associated with Sindbis virus (SINV) ribavirin resistance in the Venezuelan equine encephalitis virus (VEEV) context through reverse genetics correlated to enzyme assays using purified recombinant VEEV nsP1 proteins. The results demonstrate that the targeted positions are strongly associated to the regulation of the capping reaction by increasing the affinity between GTP and nsP1. Data also show that in VEEV the S21A substitution, naturally occurring in Chikungunya virus (CHIKV), is a hallmark of ribavirin susceptibility. These findings uncover the specific mechanistic contributions of these residues to nsp1-mediated methyl-transfer and guanylylation reactions.
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Lhomme S, Migueres M, Abravanel F, Marion O, Kamar N, Izopet J. Hepatitis E Virus: How It Escapes Host Innate Immunity. Vaccines (Basel) 2020; 8:E422. [PMID: 32731452 PMCID: PMC7564545 DOI: 10.3390/vaccines8030422] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 07/23/2020] [Accepted: 07/24/2020] [Indexed: 12/12/2022] Open
Abstract
Hepatitis E virus (HEV) is a leading cause of viral hepatitis in the world. It is usually responsible for acute hepatitis, but can lead to a chronic infection in immunocompromised patients. The host's innate immune response is the first line of defense against a virus infection; there is growing evidence that HEV RNA is recognized by toll-like receptors (TLRs) and retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), leading to interferon (IFN) production. The IFNs activate interferon-stimulated genes (ISGs) to limit HEV replication and spread. HEV has developed strategies to counteract this antiviral response, by limiting IFN induction and signaling. This review summarizes the advances in our knowledge of intracellular pathogen recognition, interferon and inflammatory response, and the role of virus protein in immune evasion.
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Affiliation(s)
- Sébastien Lhomme
- National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (M.M.); (F.A.); (J.I.)
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Marion Migueres
- National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (M.M.); (F.A.); (J.I.)
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Florence Abravanel
- National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (M.M.); (F.A.); (J.I.)
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Olivier Marion
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
| | - Nassim Kamar
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
| | - Jacques Izopet
- National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (M.M.); (F.A.); (J.I.)
- INSERM UMR1043, CNRS UMR5282, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France; (O.M.); (N.K.)
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
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6'-β-Fluoro-Homoaristeromycin and 6'-Fluoro-Homoneplanocin A Are Potent Inhibitors of Chikungunya Virus Replication through Their Direct Effect on Viral Nonstructural Protein 1. Antimicrob Agents Chemother 2020; 64:AAC.02532-19. [PMID: 31964798 PMCID: PMC7179274 DOI: 10.1128/aac.02532-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 01/17/2020] [Indexed: 12/23/2022] Open
Abstract
Alphaviruses are arthropod-borne, positive-stranded RNA viruses capable of causing severe disease with high morbidity. Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness which can progress into chronic arthralgia. The current lack of vaccines and specific treatment for CHIKV infection underscores the need to develop new therapeutic interventions. To discover new antiviral agents, we performed a compound screen in cell culture-based infection models and identified two carbocyclic adenosine analogues, 6′-β-fluoro-homoaristeromycin (FHA) and 6′-fluoro-homoneplanocin A (FHNA), that displayed potent activity against CHIKV and Semliki Forest virus (SFV) with 50% effective concentrations in the nanomolar range at nontoxic concentrations. Alphaviruses are arthropod-borne, positive-stranded RNA viruses capable of causing severe disease with high morbidity. Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness which can progress into chronic arthralgia. The current lack of vaccines and specific treatment for CHIKV infection underscores the need to develop new therapeutic interventions. To discover new antiviral agents, we performed a compound screen in cell culture-based infection models and identified two carbocyclic adenosine analogues, 6′-β-fluoro-homoaristeromycin (FHA) and 6′-fluoro-homoneplanocin A (FHNA), that displayed potent activity against CHIKV and Semliki Forest virus (SFV) with 50% effective concentrations in the nanomolar range at nontoxic concentrations. The compounds, designed as inhibitors of the host enzyme S-adenosylhomocysteine (SAH) hydrolase, impeded postentry steps in CHIKV and SFV replication. Selection of FHNA-resistant mutants and reverse genetics studies demonstrated that the combination of mutations G230R and K299E in CHIKV nonstructural protein 1 (nsP1) conferred resistance to the compounds. Enzymatic assays with purified wild-type (wt) SFV nsP1 suggested that an oxidized (3′-keto) form, rather than FHNA itself, directly inhibited the MTase activity, while a mutant protein with the K231R and K299E substitutions was insensitive to the compound. Both wt nsP1 and the resistant mutant were equally sensitive to the inhibitory effect of SAH. Our combined data suggest that FHA and FHNA inhibit CHIKV and SFV replication by directly targeting the MTase activity of nsP1, rather than through an indirect effect on host SAH hydrolase. The high potency and selectivity of these novel alphavirus mRNA capping inhibitors warrant further preclinical investigation of these compounds.
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Lhomme S, Marion O, Abravanel F, Izopet J, Kamar N. Clinical Manifestations, Pathogenesis and Treatment of Hepatitis E Virus Infections. J Clin Med 2020; 9:E331. [PMID: 31991629 PMCID: PMC7073673 DOI: 10.3390/jcm9020331] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/14/2020] [Accepted: 01/22/2020] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis throughout the world. Most infections are acute but they can become chronic in immunocompromised patients, such as solid organ transplant patients, patients with hematologic malignancy undergoing chemotherapy and those with a human immunodeficiency virus (HIV) infection. Extra-hepatic manifestations, especially neurological and renal diseases, have also been described. To date, four main genotypes of HEV (HEV1-4) were described. HEV1 and HEV2 only infect humans, while HEV3 and HEV4 can infect both humans and animals, like pigs, wild boar, deer and rabbits. The real epidemiology of HEV has been underestimated because most infections are asymptomatic. This review focuses on the recent advances in our understanding of the pathophysiology of acute HEV infections, including severe hepatitis in patients with pre-existing liver disease and pregnant women. It also examines the mechanisms leading to chronic infection in immunocompromised patients and extra-hepatic manifestations. Acute infections are usually self-limiting and do not require antiviral treatment. Conversely, a chronic HEV infection can be cleared by decreasing the dose of immunosuppressive drugs or by treating with ribavirin for 3 months. Nevertheless, new drugs are needed for those cases in which ribavirin treatment fails.
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Affiliation(s)
- Sébastien Lhomme
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Olivier Marion
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
| | - Florence Abravanel
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Jacques Izopet
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Nassim Kamar
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
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Myoung J, Lee JY, Min KS. Methyltransferase of a cell culture-adapted hepatitis E inhibits the MDA5 receptor signaling pathway. J Microbiol 2019; 57:1126-1131. [PMID: 31758397 PMCID: PMC7090864 DOI: 10.1007/s12275-019-9478-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 12/14/2022]
Abstract
Hepatitis E virus (HEV) is a causative agent of acute hepatitis and jaundice. The number of human infections is approximated to be over 20 million cases per year. The transmission is mainly via the fecal-oral route and contaminated water and food are considered to be a major source of infection. As a mouse model is not available, a recent development of a cell culture-adapted HEV strain (47832c) is considered as a very important tools for molecular analysis of HEV pathogenesis in cells. Previously, we demonstrated that HEV-encoded methyltransferase (MeT) encoded by the 47832c strain inhibits MDA5- and RIG-I-mediated activation of interferon β (IFN-β) promoter. Here, we report that MeT impairs the phosphorylation and activation of interferon regulatory factor 3 and the p65 subunit of NF-κB in a dose-dependent manner. In addition, the MeT encoded by the 47832c, but not that of HEV clinical or field isolates (SAR-55, Mex-14, KC-1, and ZJ-1), displays the inhibitory effect. A deeper understanding of MeTmediated suppression of IFN-β expression would provide basis of the cell culture adaptation of HEV.
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Affiliation(s)
- Jinjong Myoung
- Korea Zoonosis Research Institute, Genetic Engineering Research Institute and Department of Bioactive Material Science, Jeonbuk National University, Jeonju, 54896, Republic of Korea.
| | - Jeong Yoon Lee
- Korea Zoonosis Research Institute, Genetic Engineering Research Institute and Department of Bioactive Material Science, Jeonbuk National University, Jeonju, 54896, Republic of Korea
| | - Kang Sang Min
- Korea Zoonosis Research Institute, Genetic Engineering Research Institute and Department of Bioactive Material Science, Jeonbuk National University, Jeonju, 54896, Republic of Korea
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Mudgal R, Mahajan S, Tomar S. Inhibition of Chikungunya virus by an adenosine analog targeting the SAM-dependent nsP1 methyltransferase. FEBS Lett 2019; 594:678-694. [PMID: 31623018 PMCID: PMC7164056 DOI: 10.1002/1873-3468.13642] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 09/23/2019] [Accepted: 10/02/2019] [Indexed: 01/02/2023]
Abstract
Alphaviruses, including Chikungunya (CHIKV) and Venezuelan equine encephalitis virus (VEEV), are among the leading causes of recurrent epidemics all over the world. Alphaviral nonstructural protein 1 (nsP1) orchestrates the capping of nascent viral RNA via its S-adenosyl methionine-dependent N-7-methyltransferase (MTase) and guanylyltransferase activities. Here, we developed and validated a novel capillary electrophoresis (CE)-based assay for measuring the MTase activity of purified VEEV and CHIKV nsP1. We employed the assay to assess the MTase inhibition efficiency of a few adenosine analogs and identified 5-iodotubercidin (5-IT) as an inhibitor of nsP1. The antiviral potency of 5-IT was evaluated in vitro using a combination of cell-based assays, which suggest that 5-IT is efficacious against CHIKV in cell culture (EC50 : 0.409 µm).
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Affiliation(s)
- Rajat Mudgal
- Department of Biotechnology, Indian Institute of Technology Roorkee, India
| | - Supreeti Mahajan
- Department of Biotechnology, Indian Institute of Technology Roorkee, India
| | - Shailly Tomar
- Department of Biotechnology, Indian Institute of Technology Roorkee, India
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Kim KS. Current Challenges in the Development of Vaccines and Drugs Against Emerging Vector-borne Diseases. Curr Med Chem 2019; 26:2974-2986. [PMID: 30394204 DOI: 10.2174/0929867325666181105121146] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 10/31/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023]
Abstract
Vectors are living organisms that transmit infectious diseases from an infected animal to humans or another animal. Biological vectors such as mosquitoes, ticks, and sand flies carry pathogens that multiply within their bodies prior to delivery to a new host. The increased prevalence of Vector-Borne Diseases (VBDs) such as Aedes-borne dengue, Chikungunya (CHIKV), Zika (ZIKV), malaria, Tick-Borne Disease (TBD), and scrub typhus has a huge impact on the health of both humans and livestock worldwide. In particular, zoonotic diseases transmitted by mosquitoes and ticks place a considerable burden on public health. Vaccines, drugs, and vector control methods have been developed to prevent and treat VBDs and have prevented millions of deaths. However, development of such strategies is falling behind the rapid emergence of VBDs. Therefore, a comprehensive approach to fighting VBDs must be considered immediately. In this review, I focus on the challenges posed by emerging outbreaks of VBDs and discuss available drugs and vaccines designed to overcome this burden. Research into promising drugs needs to be upgraded and fast-tracked, and novel drugs or vaccines being tested in in vitro and in vivo models need to be moved into human clinical trials. Active preventive tactics, as well as new and upgraded diagnostics, surveillance, treatments, and vaccination strategies, need to be monitored constantly if we are to manage VBDs of medical importance.
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Affiliation(s)
- Kwang-Sun Kim
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 46241, Korea
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Design and Use of Chikungunya Virus Replication Templates Utilizing Mammalian and Mosquito RNA Polymerase I-Mediated Transcription. J Virol 2019; 93:JVI.00794-19. [PMID: 31217251 DOI: 10.1128/jvi.00794-19] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 06/18/2019] [Indexed: 01/20/2023] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus. It has a positive-sense RNA genome that also serves as the mRNA for four nonstructural proteins (nsPs) representing subunits of the viral replicase. Coupling of nsP and RNA synthesis complicates analysis of viral RNA replication. We developed trans-replication systems, where production of replication-competent RNA and expression of viral replicase are uncoupled. Mammalian and mosquito RNA polymerase I promoters were used to produce noncapped RNA templates, which are poorly translated relative to CHIKV replicase-generated capped RNAs. It was found that, in human cells, constructs driven by RNA polymerase I promoters of human and Chinese hamster origin performed equally well. In contrast, RNA polymerase I promoters from Aedes mosquitoes exhibited strong species specificity. In both mammalian and mosquito cells, novel trans-replicase assays had exceptional sensitivity, with up to 105-fold higher reporter expression in the presence of replicase relative to background. Using this highly sensitive assay to analyze CHIKV nsP1 functionality, several mutations that severely reduced, but did not completely block, CHIKV replicase activity were identified: (i) nsP1 tagged at its N terminus with enhanced green fluorescent protein; (ii) mutations D63A and Y248A, blocking the RNA capping; and (iii) mutation R252E, affecting nsP1 membrane anchoring. In contrast, a mutation in the nsP1 palmitoylation site completely inactivated CHIKV replicase in both human and mosquito cells and was lethal for the virus. Our data confirm that this novel system provides a valuable tool to study CHIKV replicase, RNA replication, and virus-host interactions.IMPORTANCE Chikungunya virus (CHIKV) is a medically important pathogen responsible for recent large-scale epidemics. The development of efficient therapies against CHIKV has been hampered by gaps in our understanding of how nonstructural proteins (nsPs) function to form the viral replicase and replicate virus RNA. Here we describe an extremely sensitive assay to analyze the effects of mutations on the virus RNA synthesis machinery in cells of both mammalian (host) and mosquito (vector) origin. Using this system, several lethal mutations in CHIKV nsP1 were shown to reduce but not completely block the ability of its replicase to synthesize viral RNAs. However, in contrast to related alphaviruses, CHIKV replicase was completely inactivated by mutations preventing palmitoylation of nsP1. These data can be used to develop novel, virus-specific antiviral treatments.
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LeDesma R, Nimgaonkar I, Ploss A. Hepatitis E Virus Replication. Viruses 2019; 11:E719. [PMID: 31390784 PMCID: PMC6723718 DOI: 10.3390/v11080719] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 12/19/2022] Open
Abstract
Hepatitis E virus (HEV) is a small quasi-enveloped, (+)-sense, single-stranded RNA virus belonging to the Hepeviridae family. There are at least 20 million HEV infections annually and 60,000 HEV-related deaths worldwide. HEV can cause up to 30% mortality in pregnant women and progress to liver cirrhosis in immunocompromised individuals and is, therefore, a greatly underestimated public health concern. Although a prophylactic vaccine for HEV has been developed, it is only licensed in China, and there is currently no effective, non-teratogenic treatment. HEV encodes three open reading frames (ORFs). ORF1 is the largest viral gene product, encoding the replicative machinery of the virus including a methyltransferase, RNA helicase, and an RNA-dependent RNA polymerase. ORF1 additionally contains a number of poorly understood domains including a hypervariable region, a putative protease, and the so-called 'X' and 'Y' domains. ORF2 is the viral capsid essential for formation of infectious particles and ORF3 is a small protein essential for viral release. In this review, we focus on the domains encoded by ORF1, which collectively mediate the virus' asymmetric genome replication strategy. We summarize what is known, unknown, and hotly debated regarding the coding and non-coding regions of HEV ORF1, and present a model of how HEV replicates its genome.
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Affiliation(s)
- Robert LeDesma
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Ila Nimgaonkar
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Alexander Ploss
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA.
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New Phylogenetic Grouping of Positive-Sense RNA Viruses Is Concordant with Replication Complex Morphology. mBio 2019; 10:mBio.01402-19. [PMID: 31363030 PMCID: PMC6667620 DOI: 10.1128/mbio.01402-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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Abstract
Hepatitis E virus (HEV) possesses many of the features of other positive-stranded RNA viruses but also adds HEV-specific nuances, making its virus-host interactions unique. Slow virus replication kinetics and fastidious growth conditions, coupled with the historical lack of an efficient cell culture system to propagate the virus, have left many gaps in our understanding of its structure and replication cycle. Recent advances in culturing selected strains of HEV and resolving the 3D structure of the viral capsid are filling in knowledge gaps, but HEV remains an extremely understudied pathogen. Many steps in the HEV life cycle and many aspects of HEV pathogenesis remain unknown, such as the host and viral factors that determine cross-species infection, the HEV-specific receptor(s) on host cells, what determines HEV chronicity and the ability to replicate in extrahepatic sites, and what regulates processing of the open reading frame 1 (ORF1) nonstructural polyprotein.
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Affiliation(s)
- Scott P Kenney
- Food Animal Health Research Program, The Ohio State University, Wooster, Ohio 44691
| | - Xiang-Jin Meng
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
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Carissimo G, Ng LFP. Understanding Molecular Pathogenesis with Chikungunya Virus Research Tools. Curr Top Microbiol Immunol 2019; 435:33-53. [PMID: 30888547 DOI: 10.1007/82_2019_158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Since its re-emergence in 2006, Chikungunya has been a major health concern in endemic areas. Transmitted by Aedes mosquitoes to mammalian hosts, Chikungunya leads to persistent debilitating symptoms in a high proportion of symptomatic human cases. In this review, we present several tools on the mosquito vector side as well as on the mammalian side that have been used to advance research on Chikungunya transmission and immunopathogenesis. These tools lead to key understandings of viral replication in both hosts, and innate and adaptive responses mediating virus clearance and pathology in mammals. This comprehension of viral mechanisms has allowed the development of promising treatment avenues in animal models that will need to be further explored. However, research efforts need to continue in order to develop better and unbiased tools to assess antiviral and treatment strategies as well as further understand immune mechanisms at play in human pathologies.
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Affiliation(s)
- Guillaume Carissimo
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore, Singapore
| | - Lisa F P Ng
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore, Singapore. .,Institute of Infection and Global Health, University of Liverpool, Liverpool, UK. .,Laboratory of Microbial Immunity, Singapore Immunology Network, 8A Biomedical Grove, #04-06, Immunos, Biopolis, 138648, Singapore.
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Cowpea chlorotic mottle bromovirus replication proteins support template-selective RNA replication in Saccharomyces cerevisiae. PLoS One 2018; 13:e0208743. [PMID: 30586378 PMCID: PMC6306254 DOI: 10.1371/journal.pone.0208743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 11/22/2018] [Indexed: 11/19/2022] Open
Abstract
Positive-strand RNA viruses generally assemble RNA replication complexes on rearranged host membranes. Alphaviruses, other members of the alpha-like virus superfamily, and many other positive-strand RNA viruses invaginate host membrane into vesicular RNA replication compartments, known as spherules, whose interior is connected to the cytoplasm. Brome mosaic virus (BMV) and its close relative, cowpea chlorotic mottle virus (CCMV), form spherules along the endoplasmic reticulum. BMV spherule formation and RNA replication can be fully reconstituted in S. cerevisiae, enabling many studies identifying host factors and viral interactions essential for these processes. To better define and understand the conserved, core pathways of bromovirus RNA replication, we tested the ability of CCMV to similarly support spherule formation and RNA replication in yeast. Paralleling BMV, we found that CCMV RNA replication protein 1a was the only viral factor necessary to induce spherule membrane rearrangements and to recruit the viral 2a polymerase (2apol) to the endoplasmic reticulum. CCMV 1a and 2apol also replicated CCMV and BMV genomic RNA2, demonstrating core functionality of CCMV 1a and 2apol in yeast. However, while BMV and CCMV 1a/2apol strongly replicate each others’ genomic RNA3 in plants, neither supported detectable CCMV RNA3 replication in yeast. Moreover, in contrast to plant cells, in yeast CCMV 1a/2apol supported only limited replication of BMV RNA3 (<5% of that by BMV 1a/2apol). In keeping with this, we found that in yeast CCMV 1a was significantly impaired in recruiting BMV or CCMV RNA3 to the replication complex. Overall, we show that many 1a and 2apol functions essential for replication complex assembly, and their ability to be reconstituted in yeast, are conserved between BMV and CCMV. However, restrictions of CCMV RNA replication in yeast reveal previously unknown 1a-linked, RNA-selective host contributions to the essential early process of recruiting viral RNA templates to the replication complex.
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Increasing the Capping Efficiency of the Sindbis Virus nsP1 Protein Negatively Affects Viral Infection. mBio 2018; 9:mBio.02342-18. [PMID: 30538185 PMCID: PMC6299483 DOI: 10.1128/mbio.02342-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alphaviruses have been the cause of both localized outbreaks and large epidemics of severe disease. Currently, there are no strategies or vaccines which are either safe or effective for preventing alphaviral infection or treating alphaviral disease. This deficit of viable therapeutics highlights the need to better understand the mechanisms behind alphaviral infection in order to develop novel antiviral strategies for treatment of alphaviral disease. In particular, this report details a previously uncharacterized aspect of the alphaviral life cycle: the importance of noncapped genomic viral RNAs for alphaviral infection. This offers new insights into the mechanisms of alphaviral replication and the impact of the noncapped genomic RNAs on viral packaging. Alphaviruses are arthropod-borne RNA viruses that are capable of causing severe disease and are a significant burden to public health. Alphaviral replication results in the production of both capped and noncapped viral genomic RNAs (ncgRNAs), which are packaged into virions during infections of vertebrate and invertebrate cells. However, the roles that the ncgRNAs play during alphaviral infection have yet to be exhaustively characterized. Here, the importance of the ncgRNAs to alphaviral infection was assessed by using mutations of the nsP1 protein of Sindbis virus (SINV), which altered the synthesis of the ncgRNAs during infection by modulating the protein’s capping efficiency. Specifically, point mutations at residues Y286A and N376A decreased capping efficiency whereas a point mutation at D355A increased the capping efficiency of the SINV genomic RNA during genuine viral infection. Viral growth kinetics levels were significantly reduced for the D355A mutant relative to wild-type infection, whereas the Y286A and N376A mutants showed modest decreases in growth kinetics. Overall genomic translation and nonstructural protein accumulation were found to correlate with increases and decreases in capping efficiency. However, genomic, minus-strand, and subgenomic viral RNA synthesis were largely unaffected by the modulation of alphaviral capping activity. In addition, translation of the subgenomic alphaviral RNA (vRNA) was found not to be impacted by changes in capping efficiency. The mechanism by which the decreased presence of ncgRNAs reduced viral growth kinetics levels operated through the impaired production of viral particles. Collectively, these data illustrate the importance of ncgRNAs to viral infection and suggest that they play an integral role in the production of viral progeny.
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Wolf YI, Kazlauskas D, Iranzo J, Lucía-Sanz A, Kuhn JH, Krupovic M, Dolja VV, Koonin EV. Origins and Evolution of the Global RNA Virome. mBio 2018; 9:e02329-18. [PMID: 30482837 PMCID: PMC6282212 DOI: 10.1128/mbio.02329-18] [Citation(s) in RCA: 310] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 10/31/2018] [Indexed: 01/12/2023] Open
Abstract
Viruses with RNA genomes dominate the eukaryotic virome, reaching enormous diversity in animals and plants. The recent advances of metaviromics prompted us to perform a detailed phylogenomic reconstruction of the evolution of the dramatically expanded global RNA virome. The only universal gene among RNA viruses is the gene encoding the RNA-dependent RNA polymerase (RdRp). We developed an iterative computational procedure that alternates the RdRp phylogenetic tree construction with refinement of the underlying multiple-sequence alignments. The resulting tree encompasses 4,617 RNA virus RdRps and consists of 5 major branches; 2 of the branches include positive-sense RNA viruses, 1 is a mix of positive-sense (+) RNA and double-stranded RNA (dsRNA) viruses, and 2 consist of dsRNA and negative-sense (-) RNA viruses, respectively. This tree topology implies that dsRNA viruses evolved from +RNA viruses on at least two independent occasions, whereas -RNA viruses evolved from dsRNA viruses. Reconstruction of RNA virus evolution using the RdRp tree as the scaffold suggests that the last common ancestors of the major branches of +RNA viruses encoded only the RdRp and a single jelly-roll capsid protein. Subsequent evolution involved independent capture of additional genes, in particular, those encoding distinct RNA helicases, enabling replication of larger RNA genomes and facilitating virus genome expression and virus-host interactions. Phylogenomic analysis reveals extensive gene module exchange among diverse viruses and horizontal virus transfer between distantly related hosts. Although the network of evolutionary relationships within the RNA virome is bound to further expand, the present results call for a thorough reevaluation of the RNA virus taxonomy.IMPORTANCE The majority of the diverse viruses infecting eukaryotes have RNA genomes, including numerous human, animal, and plant pathogens. Recent advances of metagenomics have led to the discovery of many new groups of RNA viruses in a wide range of hosts. These findings enable a far more complete reconstruction of the evolution of RNA viruses than was attainable previously. This reconstruction reveals the relationships between different Baltimore classes of viruses and indicates extensive transfer of viruses between distantly related hosts, such as plants and animals. These results call for a major revision of the existing taxonomy of RNA viruses.
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Affiliation(s)
- Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Darius Kazlauskas
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Vilnius, Lithuania
- Département de Microbiologie, Institut Pasteur, Paris, France
| | - Jaime Iranzo
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Adriana Lucía-Sanz
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
- Centro Nacional de Biotecnología, Madrid, Spain
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Frederick, Maryland, USA
| | - Mart Krupovic
- Département de Microbiologie, Institut Pasteur, Paris, France
| | - Valerian V Dolja
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
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The RNA Capping Enzyme Domain in Protein A is Essential for Flock House Virus Replication. Viruses 2018; 10:v10090483. [PMID: 30205593 PMCID: PMC6165433 DOI: 10.3390/v10090483] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 09/05/2018] [Accepted: 09/05/2018] [Indexed: 01/18/2023] Open
Abstract
The nodavirus flock house virus (FHV) and the alphavirus Semliki Forest virus (SFV) show evolutionarily intriguing similarities in their replication complexes and RNA capping enzymes. In this study, we first established an efficient FHV trans-replication system in mammalian cells, which disjoins protein expression from viral RNA synthesis. Following transfection, FHV replicase protein A was associated with mitochondria, whose outer surface displayed pouch-like invaginations with a ‘neck’ structure opening towards the cytoplasm. In mitochondrial pellets from transfected cells, high-level synthesis of both genomic and subgenomic RNA was detected in vitro and the newly synthesized RNA was of positive polarity. Secondly, we initiated the study of the putative RNA capping enzyme domain in protein A by mutating the conserved amino acids H93, R100, D141, and W215. RNA replication was abolished for all mutants inside cells and in vitro except for W215A, which showed reduced replication. Transfection of capped RNA template did not rescue the replication activity of the mutants. Comparing the efficiency of SFV and FHV trans-replication systems, the FHV system appeared to produce more RNA. Using fluorescent marker proteins, we demonstrated that both systems could replicate in the same cell. This work may facilitate the comparative analysis of FHV and SFV replication.
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Kaur R, Mudgal R, Narwal M, Tomar S. Development of an ELISA assay for screening inhibitors against divalent metal ion dependent alphavirus capping enzyme. Virus Res 2018; 256:209-218. [PMID: 29958924 DOI: 10.1016/j.virusres.2018.06.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 06/21/2018] [Accepted: 06/26/2018] [Indexed: 11/24/2022]
Abstract
Alphavirus non-structural protein, nsP1 has a distinct molecular mechanism of capping the viral RNAs than the conventional capping mechanism of host. Thus, alphavirus capping enzyme nsP1 is a potential drug target. nsP1 catalyzes the methylation of guanosine triphosphate (GTP) by transferring the methyl group from S-adenosylmethionine (SAM) to a GTP molecule at its N7 position with the help of nsP1 methyltransferase (MTase) followed by guanylylation (GT) reaction which involves the formation of m7GMP-nsP1 covalent complex by nsP1 guanylyltransferase (GTase). In subsequent reactions, m7GMP moiety is added to the 5' end of the viral ppRNA by nsP1 GTase resulting in the formation of cap0 structure. In the present study, chikungunya virus (CHIKV) nsP1 MTase and GT reactions were confirmed by an indirect non-radioactive colorimetric assay and western blot assay using an antibody specific for the m7G cap, respectively. The purified recombinant CHIKV nsP1 has been used for the development of a rapid and sensitive non-radioactive enzyme linked immunosorbent assay (ELISA) to identify the inhibitors of CHIKV nsP1. The MTase reaction is followed by GT reaction and resulted in m7GMP-nsP1 covalent complex formation. The developed ELISA nsP1 assay measures this m7GMP-nsP1 complex by utilizing anti-m7G cap monoclonal antibody. The mutation of a conserved residue Asp63 to Ala revealed its role in nsP1 enzyme reaction. Inductively coupled plasma mass spectroscopy (ICP-MS) was used to determine the presence of magnesium ions (Mg2+) in the purified nsP1 protein. The divalent metal ion selectivity and investigation show preference for Mg2+ ion by CHIKV nsP1. Additionally, using the developed ELISA nsP1 assay, the inhibitory effects of sinefungin, aurintricarboxylic acid (ATA) and ribavirin were determined and the IC50 values were estimated to be 2.69 μM, 5.72 μM and 1.18 mM, respectively.
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Affiliation(s)
- Ramanjit Kaur
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Rajat Mudgal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Manju Narwal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Shailly Tomar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
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Wong KZ, Chu JJH. The Interplay of Viral and Host Factors in Chikungunya Virus Infection: Targets for Antiviral Strategies. Viruses 2018; 10:E294. [PMID: 29849008 PMCID: PMC6024654 DOI: 10.3390/v10060294] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/13/2018] [Accepted: 05/28/2018] [Indexed: 12/14/2022] Open
Abstract
Chikungunya virus (CHIKV) has re-emerged as one of the many medically important arboviruses that have spread rampantly across the world in the past decade. Infected patients come down with acute fever and rashes, and a portion of them suffer from both acute and chronic arthralgia. Currently, there are no targeted therapeutics against this debilitating virus. One approach to develop potential therapeutics is by understanding the viral-host interactions. However, to date, there has been limited research undertaken in this area. In this review, we attempt to briefly describe and update the functions of the different CHIKV proteins and their respective interacting host partners. In addition, we also survey the literature for other reported host factors and pathways involved during CHIKV infection. There is a pressing need for an in-depth understanding of the interaction between the host environment and CHIKV in order to generate potential therapeutics.
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Affiliation(s)
- Kai Zhi Wong
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
| | - Justin Jang Hann Chu
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
- Institute of Molecular & Cell Biology, Agency for Science, Technology & Research (A*STAR), 61 Biopolis Drive, Proteos #06-05, Singapore 138673, Singapore.
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