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Mustafa Z, Manzoor Khan H, Ghazanfar Ali S, Sami H, Almatroudi A, Alam Khan M, Khan A, Al-Megrin WAI, Allemailem KS, Ahmad I, El-Kady A, Suliman Al-Muzaini M, Azam Khan M, Azam M. Distinct inflammatory markers in primary and secondary dengue infection: can cytokines CXCL5, CXCL9, and CCL17 act as surrogate markers? Pathog Glob Health 2024:1-10. [PMID: 38884301 DOI: 10.1080/20477724.2024.2365581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024] Open
Abstract
Dengue fever poses a significant global health threat, with symptoms including dengue hemorrhagic fever and dengue shock syndrome. Each year, India experiences fatal dengue outbreaks with severe manifestations. The primary cause of severe inflammatory responses in dengue is a cytokine storm. Individuals with a secondary dengue infection of a different serotype face an increased risk of complications due to antibody-dependent enhancement. Therefore, it is crucial to identify potential risk factors and biomarkers for effective disease management. In the current study, we assessed the prevalence of dengue infection in and around Aligarh, India, and explored the role of cytokines, including CXCL5, CXCL9, and CCL17, in primary and secondary dengue infections, correlating them with various clinical indices. Among 1,500 suspected cases, 367 tested positive for dengue using Real-Time PCR and ELISA. In secondary dengue infections, the serum levels of CXCL5, CXCL9, and CCL17 were significantly higher than in primary infections (P < 0.05). Dengue virus (DENV)-2 showed the highest concentrations of CXCL5 and CCL17, whereas DENV-1 showed the highest concentrations of CXCL9. Early detection of these cytokines could serve as potential biomarkers for diagnosing severe dengue, and downregulation of these cytokines may prove beneficial for the treatment of severe dengue infections.
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Affiliation(s)
- Zeeshan Mustafa
- Department of Microbiology, Jawaharlal Nehru Medical College (JNMC), AMU, Aligarh, India
| | - Haris Manzoor Khan
- Department of Microbiology, Jawaharlal Nehru Medical College (JNMC), AMU, Aligarh, India
| | - Syed Ghazanfar Ali
- Viral Research & Diagnostic Laboratory, Department of Microbiology, JNMC, AMU, Aligarh, India
| | - Hiba Sami
- Department of Microbiology, Jawaharlal Nehru Medical College (JNMC), AMU, Aligarh, India
| | - Ahmad Almatroudi
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Masood Alam Khan
- Department of Basic Health Sciences, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Arif Khan
- Department of Basic Health Sciences, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Wafa Abdullah I Al-Megrin
- Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Khaled S Allemailem
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
| | - Islam Ahmad
- Viral Research & Diagnostic Laboratory, Department of Microbiology, JNMC, AMU, Aligarh, India
| | - Asmaa El-Kady
- Department of Medical Parasitology, Faculty of Medicine, South Valley University, Qena, Egypt
| | | | | | - Mohd Azam
- Department of Medical Laboratories, College of Applied Medical Sciences, Qassim University, Buraydah, Saudi Arabia
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Yu J, Huang C, Wang Z, Kaushik RS, Sheng Z, Li F, Wang D. Development and characterization of an inducible assay system to measure Zika virus capsid interactions. J Med Virol 2022; 94:5392-5400. [PMID: 35822280 PMCID: PMC9474601 DOI: 10.1002/jmv.27991] [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: 07/04/2022] [Accepted: 07/08/2022] [Indexed: 12/15/2022]
Abstract
The global spread of the mosquito-borne Zika virus (ZIKV) infection and its complications including Guillain-Barré syndrome and fetus microcephaly in 2015 have made ZIKV as a significant public health threat. The capsid protein plays crucial roles in ZIKV replication and thus represents an attractive therapeutic target. However, inhibitors of ZIKV capsid assembly have not been rigorously identified due to the lack of a target-based screening system. In this study, we developed a novel ZIKV capsid interaction method based on a split-luciferase complementation assay, which can be used to measure and quantify ZIKV capsid-capsid (C-C) interaction by the restored luciferase signal when capsid proteins interact with each other. Furthermore, a Tet-on inducible stable cell line was generated to screen inhibitors of capsid dimerization. By using of this system, peptides (Pep.15-24 in the N-terminal region of ZIKV capsid protein and Pep.44-58 in the α2 helix of ZIKV capsid protein) were identified to inhibit ZIKV C-C interaction. Overall, this study developed a novel inducible assay system to measure ZIKV capsid interaction and identify ZIKV capsid multimerization inhibitors, which will be applied for future discovery of ZIKV assembly inhibitors.
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Affiliation(s)
- Jieshi Yu
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA
| | - Chen Huang
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA
| | - Zhao Wang
- Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007
| | - Radhey S. Kaushik
- Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007
| | - Zizhang Sheng
- Aaron Diamond AIDS Research Center, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Feng Li
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA
| | - Dan Wang
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA
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Dengue NS2A Protein Orchestrates Virus Assembly. Cell Host Microbe 2019; 26:606-622.e8. [PMID: 31631053 DOI: 10.1016/j.chom.2019.09.015] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/04/2019] [Accepted: 09/25/2019] [Indexed: 01/12/2023]
Abstract
Dengue virus assembly requires cleavage of viral C-prM-E polyprotein into three structural proteins (capsid, premembrane, and envelope), packaging of viral RNA with C protein into nucleocapsid, and budding of prM and E proteins into virions. The molecular mechanisms underlying these assembly events are unclear. Here, we show that dengue nonstructural protein 2A (NS2A protein) recruits viral RNA, structural proteins, and protease to the site of virion assembly and coordinates nucleocapsid and virus formation. The last 285 nucleotides of viral 3' UTR serve as a "recruiting signal for packaging" that binds to a cytosolic loop of NS2A. This interaction allows NS2A to recruit nascent RNA from the replication complex to the virion assembly site. NS2A also recruits the C-prM-E polyprotein and NS2B-NS3 protease to the virion assembly site by interacting with prM, E, and NS3, leading to coordinated C-prM-E cleavage. Mature C protein assembles onto genomic RNA to form nucleocapsid, followed by prM and E envelopment and virion formation.
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Javed F, Manzoor KN, Ali M, Haq IU, Khan AA, Zaib A, Manzoor S. Zika virus: what we need to know? J Basic Microbiol 2017; 58:3-16. [DOI: 10.1002/jobm.201700398] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 09/19/2017] [Accepted: 09/03/2017] [Indexed: 01/22/2023]
Affiliation(s)
- Farakh Javed
- Department of Microbiology; University of Haripur; Haripur Pakistan
| | | | - Mubashar Ali
- Department of Microbiology; University of Haripur; Haripur Pakistan
| | - Irshad U. Haq
- Department of Microbiology; University of Haripur; Haripur Pakistan
| | - Abid A. Khan
- Department of Biosciences; COMSATS Institute of Information Technology; Islamabad Pakistan
| | - Assad Zaib
- Department of Medical Lab Technology; University of Haripur; Haripur Pakistan
| | - Sobia Manzoor
- Atta-ur-Rehman School of Applied Bio-Sciences; National University of Science and Technology; Islamabad Pakistan
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5
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The flavivirus capsid protein: Structure, function and perspectives towards drug design. Virus Res 2017; 227:115-123. [DOI: 10.1016/j.virusres.2016.10.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/29/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022]
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Abstract
Dengue virus affects hundreds of millions of people each year around the world, causing a tremendous social and economic impact on affected countries. The aim of this review is to summarize our current knowledge of the functions, structure, and interactions of the viral capsid protein. The primary role of capsid is to package the viral genome. There are two processes linked to this function: the recruitment of the viral RNA during assembly and the release of the genome during infection. Although particle assembly takes place on endoplasmic reticulum membranes, capsid localizes in nucleoli and lipid droplets. Why capsid accumulates in these locations during infection remains unknown. In this review, we describe available data and discuss new ideas on dengue virus capsid functions and interactions. We believe that a deeper understanding of how the capsid protein works during infection will create opportunities for novel antiviral strategies, which are urgently needed to control dengue virus infections.
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Affiliation(s)
- Laura A Byk
- Fundación Instituto Leloir-National Research Council for Science and Technology (CONICET), Buenos Aires 1405, Argentina;
| | - Andrea V Gamarnik
- Fundación Instituto Leloir-National Research Council for Science and Technology (CONICET), Buenos Aires 1405, Argentina;
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7
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Zhu Z, Chan JFW, Tee KM, Choi GKY, Lau SKP, Woo PCY, Tse H, Yuen KY. Comparative genomic analysis of pre-epidemic and epidemic Zika virus strains for virological factors potentially associated with the rapidly expanding epidemic. Emerg Microbes Infect 2016; 5:e22. [PMID: 26980239 PMCID: PMC4820678 DOI: 10.1038/emi.2016.48] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 03/03/2016] [Indexed: 12/21/2022]
Abstract
Less than 20 sporadic cases of human Zika virus (ZIKV) infection were reported in Africa and Asia before 2007, but large outbreaks involving up to 73% of the populations on the Pacific islands have started since 2007, and spread to the Americas in 2014. Moreover, the clinical manifestation of ZIKV infection has apparently changed, as evident by increasing reports of neurological complications, such as Guillain-Barré syndrome in adults and congenital anomalies in neonates. We comprehensively compared the genome sequences of pre-epidemic and epidemic ZIKV strains with complete genome or complete polyprotein sequences available in GenBank. Besides the reported phylogenetic clustering of the epidemic strains with the Asian lineage, we found that the topology of phylogenetic tree of all coding regions is the same except that of the non-structural 2B (NS2B) coding region. This finding was confirmed by bootscan analysis and multiple sequence alignment, which suggested the presence of a fragment of genetic recombination at NS2B with that of Spondweni virus. Moreover, the representative epidemic strain possesses one large bulge of nine bases instead of an external loop on the first stem-loop structure at the 3'-untranslated region just distal to the stop codon of the NS5 in the 1947 pre-epidemic prototype strain. Fifteen amino acid substitutions are found in the epidemic strains when compared with the pre-epidemic strains. As mutations in other flaviviruses can be associated with changes in virulence, replication efficiency, antigenic epitopes and host tropism, further studies would be important to ascertain the biological significance of these genomic changes.
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Affiliation(s)
- Zheng Zhu
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Jasper Fuk-Woo Chan
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
| | - Kah-Meng Tee
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Garnet Kwan-Yue Choi
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
| | - Susanna Kar-Pui Lau
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
| | - Patrick Chiu-Yat Woo
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
| | - Herman Tse
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
| | - Kwok-Yung Yuen
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
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Jia F, Zhu X, Xu F. A single adaptive point mutation in Japanese encephalitis virus capsid is sufficient to render the virus as a stable vector for gene delivery. Virology 2016; 490:109-18. [DOI: 10.1016/j.virol.2016.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 01/06/2016] [Accepted: 01/07/2016] [Indexed: 01/01/2023]
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Iglesias NG, Mondotte JA, Byk LA, De Maio FA, Samsa MM, Alvarez C, Gamarnik AV. Dengue Virus Uses a Non-Canonical Function of the Host GBF1-Arf-COPI System for Capsid Protein Accumulation on Lipid Droplets. Traffic 2015; 16:962-77. [PMID: 26031340 DOI: 10.1111/tra.12305] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 05/22/2015] [Accepted: 05/24/2015] [Indexed: 12/14/2022]
Abstract
Dengue viruses cause the most important human viral disease transmitted by mosquitoes. In recent years, a great deal has been learned about molecular details of dengue virus genome replication; however, little is known about genome encapsidation and the functions of the viral capsid protein. During infection, dengue virus capsid progressively accumulates around lipid droplets (LDs) by an unknown mechanism. Here, we examined the process by which the viral capsid is transported from the endoplasmic reticulum (ER) membrane, where the protein is synthesized, to LDs. Using different methods of intervention, we found that the GBF1-Arf1/Arf4-COPI pathway is necessary for capsid transport to LDs, while the process is independent of both COPII components and Golgi integrity. The transport was sensitive to Brefeldin A, while a drug resistant form of GBF1 was sufficient to restore capsid subcellular distribution in infected cells. The mechanism by which LDs gain or lose proteins is still an open question. Our results support a model in which the virus uses a non-canonical function of the COPI system for capsid accumulation on LDs, providing new ideas for antiviral strategies.
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Affiliation(s)
- Nestor G Iglesias
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
| | - Juan A Mondotte
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
| | - Laura A Byk
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
| | - Federico A De Maio
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
| | - Marcelo M Samsa
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
| | - Cecilia Alvarez
- Centro de Investigaciones en Bioquímica Clínica e Inmunología-CONICET, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, UNC, 5000, Córdoba, Argentina
| | - Andrea V Gamarnik
- Fundación Instituto Leloir-CONICET, Avenida Patricias Argentinas 435, Buenos Aires, 1405, Argentina
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10
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Characterization of the mode of action of a potent dengue virus capsid inhibitor. J Virol 2014; 88:11540-55. [PMID: 25056895 DOI: 10.1128/jvi.01745-14] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Dengue viruses (DV) represent a significant global health burden, with up to 400 million infections every year and around 500,000 infected individuals developing life-threatening disease. In spite of attempts to develop vaccine candidates and antiviral drugs, there is a lack of approved therapeutics for the treatment of DV infection. We have previously reported the identification of ST-148, a small-molecule inhibitor exhibiting broad and potent antiviral activity against DV in vitro and in vivo (C. M. Byrd et al., Antimicrob. Agents Chemother. 57:15-25, 2013, doi:10 .1128/AAC.01429-12). In the present study, we investigated the mode of action of this promising compound by using a combination of biochemical, virological, and imaging-based techniques. We confirmed that ST-148 targets the capsid protein and obtained evidence of bimodal antiviral activity affecting both assembly/release and entry of infectious DV particles. Importantly, by using a robust bioluminescence resonance energy transfer-based assay, we observed an ST-148-dependent increase of capsid self-interaction. These results were corroborated by molecular modeling studies that also revealed a plausible model for compound binding to capsid protein and inhibition by a distinct resistance mutation. These results suggest that ST-148-enhanced capsid protein self-interaction perturbs assembly and disassembly of DV nucleocapsids, probably by inducing structural rigidity. Thus, as previously reported for other enveloped viruses, stabilization of capsid protein structure is an attractive therapeutic concept that also is applicable to flaviviruses. IMPORTANCE Dengue viruses are arthropod-borne viruses representing a significant global health burden. They infect up to 400 million people and are endemic to subtropical and tropical areas of the world. Currently, there are neither vaccines nor approved therapeutics for the prophylaxis or treatment of DV infections, respectively. This study reports the characterization of the mode of action of ST-148, a small-molecule capsid inhibitor with potent antiviral activity against all DV serotypes. Our results demonstrate that ST-148 stabilizes capsid protein self-interaction, thereby likely perturbing assembly and disassembly of viral nucleocapsids by inducing structural rigidity. This, in turn, might interfere with the release of viral RNA from incoming nucleocapsids (uncoating) as well as assembly of progeny virus particles. As previously reported for other enveloped viruses, we propose the capsid as a novel tractable target for flavivirus inhibitors.
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11
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Sangiambut S, Suphatrakul A, Sriburi R, Keelapang P, Puttikhunt C, Kasinrerk W, Malasit P, Sittisombut N. Sustained replication of dengue pseudoinfectious virus lacking the capsid gene by trans-complementation in capsid-producing mosquito cells. Virus Res 2013; 174:37-46. [DOI: 10.1016/j.virusres.2013.02.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 02/11/2013] [Accepted: 02/12/2013] [Indexed: 11/16/2022]
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12
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Ivanyi-Nagy R, Darlix JL. Reprint of: Core protein-mediated 5'-3' annealing of the West Nile virus genomic RNA in vitro. Virus Res 2012; 169:448-57. [PMID: 23022255 PMCID: PMC7172194 DOI: 10.1016/j.virusres.2012.09.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 05/08/2012] [Accepted: 05/08/2012] [Indexed: 12/21/2022]
Abstract
Genome cyclization through conserved RNA sequences located in the 5' and 3' terminal regions of flavivirus genomic RNA is essential for virus replication. Although the role of various cis-acting RNA elements in panhandle formation is well characterized, almost nothing is known about the potential contribution of protein cofactors to viral RNA cyclization. Proteins with nucleic acid chaperone activities are encoded by many viruses (e.g., retroviruses, coronaviruses) to facilitate RNA structural rearrangements and RNA-RNA interactions during the viral replicative cycle. Since the core protein of flaviviruses is also endowed with potent RNA chaperone activities, we decided to examine the effect of West Nile virus (WNV) core on 5'-3' genomic RNA annealing in vitro. Core protein binding resulted in a dramatic, dose-dependent increase in 5'-3' complex formation. Mutations introduced in either the UAR (upstream AUG region) or CS (conserved sequence) elements of the viral RNA diminished core protein-dependent annealing, while compensatory mutations restored the 5'-3' RNA interaction. The activity responsible for stimulating RNA annealing was mapped to the C-terminal RNA-binding region of WNV core protein. These results indicate that core protein - besides its function in viral particle formation - might be involved in the regulation of flavivirus genomic RNA cyclization, and thus virus replication.
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Affiliation(s)
- Roland Ivanyi-Nagy
- LaboRetro, INSERM U758, Ecole Normale Supérieure de Lyon, IFR128 Biosciences Lyon-Gerland, 46 allée d'Italie, 69364 Lyon, France
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Ivanyi-Nagy R, Darlix JL. Core protein-mediated 5'-3' annealing of the West Nile virus genomic RNA in vitro. Virus Res 2012; 167:226-35. [PMID: 22652509 PMCID: PMC7172325 DOI: 10.1016/j.virusres.2012.05.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 05/08/2012] [Accepted: 05/08/2012] [Indexed: 01/17/2023]
Abstract
Genome cyclization through conserved RNA sequences located in the 5' and 3' terminal regions of flavivirus genomic RNA is essential for virus replication. Although the role of various cis-acting RNA elements in panhandle formation is well characterized, almost nothing is known about the potential contribution of protein cofactors to viral RNA cyclization. Proteins with nucleic acid chaperone activities are encoded by many viruses (e.g., retroviruses, coronaviruses) to facilitate RNA structural rearrangements and RNA-RNA interactions during the viral replicative cycle. Since the core protein of flaviviruses is also endowed with potent RNA chaperone activities, we decided to examine the effect of West Nile virus (WNV) core on 5'-3' genomic RNA annealing in vitro. Core protein binding resulted in a dramatic, dose-dependent increase in 5'-3' complex formation. Mutations introduced in either the UAR (upstream AUG region) or CS (conserved sequence) elements of the viral RNA diminished core protein-dependent annealing, while compensatory mutations restored the 5'-3' RNA interaction. The activity responsible for stimulating RNA annealing was mapped to the C-terminal RNA-binding region of WNV core protein. These results indicate that core protein - besides its function in viral particle formation - might be involved in the regulation of flavivirus genomic RNA cyclization, and thus virus replication.
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Key Words
- cs, conserved sequence
- dar, downstream aug region
- db, dumbbell-like structure
- denv, dengue virus
- jev, japanese encephalitis virus
- orf, open reading frame
- rdrp, rna-dependent rna polymerase
- sfrna, subgenomic flavivirus rna
- tbev, tick-borne encephalitis virus
- uar, upstream aug region
- utr, untranslated region
- wnv, west nile virus
- yfv, yellow fever virus
- west nile virus
- core protein
- flaviviruses
- viral replication
- genome cyclization
- rna chaperoning
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Affiliation(s)
| | - Jean-Luc Darlix
- LaboRetro, INSERM U758, Ecole Normale Supérieure de Lyon, IFR128 Biosciences Lyon-Gerland, 46 allée d’Italie, 69364 Lyon, France
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Samsa MM, Mondotte JA, Caramelo JJ, Gamarnik AV. Uncoupling cis-Acting RNA elements from coding sequences revealed a requirement of the N-terminal region of dengue virus capsid protein in virus particle formation. J Virol 2012; 86:1046-58. [PMID: 22072762 PMCID: PMC3255831 DOI: 10.1128/jvi.05431-11] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/21/2011] [Indexed: 11/20/2022] Open
Abstract
Little is known about the mechanism of flavivirus genome encapsidation. Here, functional elements of the dengue virus (DENV) capsid (C) protein were investigated. Study of the N-terminal region of DENV C has been limited by the presence of overlapping cis-acting RNA elements within the protein-coding region. To dissociate these two functions, we used a recombinant DENV RNA with a duplication of essential RNA structures outside the C coding sequence. By the use of this system, the highly conserved amino acids FNML, which are encoded in the RNA cyclization sequence 5'CS, were found to be dispensable for C function. In contrast, deletion of the N-terminal 18 amino acids of C impaired DENV particle formation. Two clusters of basic residues (R5-K6-K7-R9 and K17-R18-R20-R22) were identified as important. A systematic mutational analysis indicated that a high density of positive charges, rather than particular residues at specific positions, was necessary. Furthermore, a differential requirement of N-terminal sequences of C for viral particle assembly was observed in mosquito and human cells. While no viral particles were observed in human cells with a virus lacking the first 18 residues of C, DENV propagation was detected in mosquito cells, although to a level about 50-fold less than that observed for a wild-type (WT) virus. We conclude that basic residues at the N terminus of C are necessary for efficient particle formation in mosquito cells but that they are crucial for propagation in human cells. This is the first report demonstrating that the N terminus of C plays a role in DENV particle formation. In addition, our results suggest that this function of C is differentially modulated in different host cells.
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Heterogeneous nuclear ribonucleoprotein A2 participates in the replication of Japanese encephalitis virus through an interaction with viral proteins and RNA. J Virol 2011; 85:10976-88. [PMID: 21865391 DOI: 10.1128/jvi.00846-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that is kept in a zoonotic transmission cycle between pigs and mosquitoes. JEV causes infection of the central nervous system with a high mortality rate in dead-end hosts, including humans. Many studies have suggested that the flavivirus core protein is not only a component of nucleocapsids but also an important pathogenic determinant. In this study, we identified heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2) as a binding partner of the JEV core protein by pulldown purification and mass spectrometry. Reciprocal coimmunoprecipitation analyses in transfected and infected cells confirmed a specific interaction between the JEV core protein and hnRNP A2. Expression of the JEV core protein induced cytoplasmic retention of hnRNP A2 in JEV subgenomic replicon cells. Small interfering RNA (siRNA)-mediated knockdown of hnRNP A2 resulted in a 90% reduction of viral RNA replication in cells infected with JEV, and the reduction was cancelled by the expression of an siRNA-resistant hnRNP A2 mutant. In addition to the core protein, hnRNP A2 also associated with JEV nonstructural protein 5, which has both methyltransferase and RNA-dependent RNA polymerase activities, and with the 5'-untranslated region of the negative-sense JEV RNA. During one-step growth, synthesis of both positive- and negative-strand JEV RNAs was delayed by the knockdown of hnRNP A2. These results suggest that hnRNP A2 plays an important role in the replication of JEV RNA through the interaction with viral proteins and RNA.
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Chen Z, Lin X, Zhang Z, Huang J, Fu S, Huang R. EXO70 protein influences dengue virus secretion. Microbes Infect 2010; 13:143-50. [PMID: 21034848 DOI: 10.1016/j.micinf.2010.10.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 10/11/2010] [Accepted: 10/12/2010] [Indexed: 11/25/2022]
Abstract
The involvement of host proteins in assisting the exocytosis of flaviviruses is largely unknown. In this study, we aimed to investigate if dengue virus (DENV) utilizes the exocyst components to aid the exocytosis of virus particles. This study identified that EXO70 protein, a member of the exocyst complex influenced DENV infection. Dengue virus production was significantly attenuated in EXO70 knock-down cells. EXO70 did not influence viral transcription and translation. It influenced virus egression/secretion from DENV-infected cells. We also showed that EXO70 expression was up-regulated from 18 h post-infection following DENV infection. Although the envelope protein of DENV influenced EXO70 expression, the co-expression of pre-membrane and envelope proteins significantly increased the expression levels of EXO70 during DENV infection. When pre-membrane protein was expressed alone, there was no significant difference in the expression levels of EXO70. This indicated that the presence of pre-membrane protein might help in the proper folding of envelope protein. Increased expression levels of EXO70 might help in the exocytosis process of virus or subviral particles.
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Affiliation(s)
- Zhaoni Chen
- Department of Pharmacology, Guangxi Medical University, 22 Shuangyong Road, Nanning, Guangxi 530021, PR China
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18
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Li LL, Hu ST, Wang SH, Lee HH, Wang YT, Ping YH. Positive transcription elongation factor b (P-TEFb) contributes to dengue virus-stimulated induction of interleukin-8 (IL-8). Cell Microbiol 2010; 12:1589-603. [DOI: 10.1111/j.1462-5822.2010.01493.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Netsawang J, Noisakran S, Puttikhunt C, Kasinrerk W, Wongwiwat W, Malasit P, Yenchitsomanus PT, Limjindaporn T. Nuclear localization of dengue virus capsid protein is required for DAXX interaction and apoptosis. Virus Res 2009; 147:275-83. [PMID: 19944121 DOI: 10.1016/j.virusres.2009.11.012] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/17/2009] [Accepted: 11/19/2009] [Indexed: 11/19/2022]
Abstract
Dengue virus capsid protein (DENVC) localizes to both the cytoplasm and nucleus of dengue virus-infected cells. DENV C contains three nuclear localization signals (NLS), (6)KKAR(9), (73)KKSK(76), and the bipartite signal (85)RKeigrmlnilnRRRR(100). Stable HepG2 cells constitutively expressing DENV C, DENV C (Delta 85-100) and DENV C (Delta 73-100) were constructed to clarify whether nuclear translocation of DENV C affected apoptosis in liver cell line. While the wild-type DENV C could translocate into the nuclei of HepG2 cells, the mutant DENV Cs were restricted to the cytoplasm. The loss of nuclear localization of both mutant DENV Cs resulted in the disruption of their interactions with the apoptotic protein Daxx. Interestingly, upon treatment with anti-Fas antibody, the HepG2 cells expressing the wild-type DENV C showed significantly more apoptosis compared with the HepG2 cells expressing either mutant DENV C. To identify the amino acids required for DAXX interaction and apoptosis, substitution mutations either (K73A/K74A) or (R85A/K86A) were introduced into the C-terminal region of DENV C, and tested whether these mutations affected its interaction with Daxx and apoptosis. The results demonstrate that (73)KK and (85)RK of DENV C are important for its nuclear localization, interaction with DAXX and induction of apoptosis. This work is the first to demonstrate that nuclear localization of DENV C is required for DAXX interaction and apoptosis.
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Affiliation(s)
- Janjuree Netsawang
- Medical Molecular Biology Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
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20
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Dengue virus capsid protein usurps lipid droplets for viral particle formation. PLoS Pathog 2009; 5:e1000632. [PMID: 19851456 PMCID: PMC2760139 DOI: 10.1371/journal.ppat.1000632] [Citation(s) in RCA: 425] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 09/25/2009] [Indexed: 12/19/2022] Open
Abstract
Dengue virus is responsible for the highest rates of disease and mortality among the members of the Flavivirus genus. Dengue epidemics are still occurring around the world, indicating an urgent need of prophylactic vaccines and antivirals. In recent years, a great deal has been learned about the mechanisms of dengue virus genome amplification. However, little is known about the process by which the capsid protein recruits the viral genome during encapsidation. Here, we found that the mature capsid protein in the cytoplasm of dengue virus infected cells accumulates on the surface of ER-derived organelles named lipid droplets. Mutagenesis analysis using infectious dengue virus clones has identified specific hydrophobic amino acids, located in the center of the capsid protein, as key elements for lipid droplet association. Substitutions of amino acid L50 or L54 in the capsid protein disrupted lipid droplet targeting and impaired viral particle formation. We also report that dengue virus infection increases the number of lipid droplets per cell, suggesting a link between lipid droplet metabolism and viral replication. In this regard, we found that pharmacological manipulation of the amount of lipid droplets in the cell can be a means to control dengue virus replication. In addition, we developed a novel genetic system to dissociate cis-acting RNA replication elements from the capsid coding sequence. Using this system, we found that mislocalization of a mutated capsid protein decreased viral RNA amplification. We propose that lipid droplets play multiple roles during the viral life cycle; they could sequester the viral capsid protein early during infection and provide a scaffold for genome encapsidation. Dengue virus is the single most significant arthropod-borne virus pathogen in humans. In spite of the urgent medical need to control dengue infections, vaccines are still unavailable, and many aspects of dengue virus biology and pathogenesis remain elusive. We discovered a link between dengue virus replication and ER-derived organelles known as lipid droplets (LDs). Dengue infection increases the amount of LDs per cell and pharmacological inhibition of LD formation greatly reduces dengue virus replication. In addition, we have found that the viral capsid protein in infected cells accumulates on the surface of LDs. Manipulation of infectious clones and generation of new reporter dengue viruses allowed us to define the molecular basis of capsid protein association to LDs. Specific amino acids on the α2 helix, located in the center of the capsid protein, were found to be crucial for both accumulation of capsid protein on LDs and dengue virus infectious particle formation. We propose that LDs facilitate viral replication providing a platform for nucleocapsid formation during encapsidation. Our findings begin to unravel the complex mechanism by which dengue virus usurps cellular organelles to coordinate different steps of the viral life cycle.
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21
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Puttikhunt C, Ong-Ajchaowlerd P, Prommool T, Sangiambut S, Netsawang J, Limjindaporn T, Malasit P, Kasinrerk W. Production and characterization of anti-dengue capsid antibodies suggesting the N terminus region covering the first 20 amino acids of dengue virus capsid protein is predominantly immunogenic in mice. Arch Virol 2009; 154:1211-21. [PMID: 19565324 DOI: 10.1007/s00705-009-0426-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 06/09/2009] [Indexed: 10/20/2022]
Abstract
We produced monoclonal and polyclonal antibodies to the capsid (C) protein of dengue serotype 2 virus (DV2 C). First, a maltose-binding protein fused to DV2 C protein (MBP-C) was overproduced in E. coli. The affinity-purified MBP-C protein was cleaved by factor Xa protease to obtain a recombinant DV2 C protein, which was then used for mouse immunizations. Two hybridoma cell lines producing anti-C Mabs as well as anti-C polyclonal antibody were successfully generated and characterized. Interestingly, all of the generated antibodies specifically recognized the first 20 amino acids of the DV2 C protein, as determined by peptide epitope mapping and via a recombinant DV2 C protein in which this region was deleted. The results suggested that this region is predominantly immunogenic in mice.
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Affiliation(s)
- Chunya Puttikhunt
- Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 12th Floor Adulyadej-Vikrom Building, Siriraj Hospital, Bangkok 10700, Thailand.
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22
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Discovery of insect and human dengue virus host factors. Nature 2009; 458:1047-50. [PMID: 19396146 PMCID: PMC3462662 DOI: 10.1038/nature07967] [Citation(s) in RCA: 291] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 02/26/2009] [Indexed: 12/31/2022]
Abstract
Dengue fever (DF) is the most frequent arthropod-borne viral disease of humans, with almost half of the world's population at risk of infection1. The high prevalence, lack of an effective vaccine, and absence of specific treatment conspire to make DF a global public health threat1, 2. Given their compact genomes, dengue viruses (DENV 1-4) and other flaviviruses likely require an extensive number of host factors; however, only a limited number of human, and an even smaller number of insect host factors have been identified3-10. To discover insect host factors required for DENV-2 propagation, we carried out a genome-wide RNA interference screen in Drosophila melanogaster cells using a well-established 22,632 dsRNA library. This screen identified 116 candidate dengue virus host factors (DVHFs) (Supplementary Fig. 1). While some were previously associated with flaviviruses (e.g., V-ATPases and alpha-glucosidases)3-5, 7, 9, 10, most DVHFs were newly implicated in DENV propagation. The dipteran DVHFs had eighty-two readily recognizable human homologues and, using a targeted siRNA screen, we showed that forty-two of these are human DVHFs. This indicates remarkable conservation of required factors between dipteran and human hosts. This work suggests novel approaches to control infection in the insect vector and the mammalian host.
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23
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Helices alpha2 and alpha3 of West Nile virus capsid protein are dispensable for assembly of infectious virions. J Virol 2009; 83:5581-91. [PMID: 19297470 DOI: 10.1128/jvi.02653-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The internal hydrophobic sequence within the flaviviral capsid protein (protein C) plays an important role in the assembly of infectious virions. Here, this sequence was analyzed in a West Nile virus lineage I isolate (crow V76/1). An infectious cDNA clone was constructed and used to introduce deletions into the internal hydrophobic domain which comprises helix alpha2 and part of the loop intervening helices alpha2 and alpha3. In total, nine capsid deletion mutants (4 to 14 amino acids long) were constructed and tested for virus viability. Some of the short deletions did not significantly affect growth in cell culture, whereas larger deletions removing almost the entire hydrophobic region significantly impaired viral growth. Efficient growth of the majority of mutants could, however, be restored by the acquisition of second-site mutations. In most cases, these resuscitating mutations were point mutations within protein C changing individual amino acids into more hydrophobic residues, reminiscent of what had been observed previously for another flavivirus, tick-borne encephalitis virus. However, we also identified viable spontaneous pseudorevertants with more than one-third of the capsid protein removed, i.e., 36 or 37 of a total of 105 residues, including all of helix alpha3 and a hydrophilic segment connecting alpha3 and alpha4. These large deletions are predicted to induce formation of large, predominantly hydrophobic fusion helices which may substitute for the loss of the internal hydrophobic domain, underlining the unrivaled structural and functional flexibility of protein C.
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24
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Xu Q, Canutescu AA, Wang G, Shapovalov M, Obradovic Z, Dunbrack RL. Statistical analysis of interface similarity in crystals of homologous proteins. J Mol Biol 2008; 381:487-507. [PMID: 18599072 DOI: 10.1016/j.jmb.2008.06.002] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Revised: 05/30/2008] [Accepted: 06/02/2008] [Indexed: 11/27/2022]
Abstract
Many proteins function as homo-oligomers and are regulated via their oligomeric state. For some proteins, the stoichiometry of homo-oligomeric states under various conditions has been studied using gel filtration or analytical ultracentrifugation experiments. The interfaces involved in these assemblies may be identified using cross-linking and mass spectrometry, solution-state NMR, and other experiments. However, for most proteins, the actual interfaces that are involved in oligomerization are inferred from X-ray crystallographic structures using assumptions about interface surface areas and physical properties. Examination of interfaces across different Protein Data Bank (PDB) entries in a protein family reveals several important features. First, similarities in space group, asymmetric unit size, and cell dimensions and angles (within 1%) do not guarantee that two crystals are actually the same crystal form, containing similar relative orientations and interactions within the crystal. Conversely, two crystals in different space groups may be quite similar in terms of all the interfaces within each crystal. Second, NMR structures and an existing benchmark of PDB crystallographic entries consisting of 126 dimers as well as larger structures and 132 monomers were used to determine whether the existence or lack of common interfaces across multiple crystal forms can be used to predict whether a protein is an oligomer or not. Monomeric proteins tend to have common interfaces across only a minority of crystal forms, whereas higher-order structures exhibit common interfaces across a majority of available crystal forms. The data can be used to estimate the probability that an interface is biological if two or more crystal forms are available. Finally, the Protein Interfaces, Surfaces, and Assemblies (PISA) database available from the European Bioinformatics Institute is more consistent in identifying interfaces observed in many crystal forms compared with the PDB and the European Bioinformatics Institute's Protein Quaternary Server (PQS). The PDB, in particular, is missing highly likely biological interfaces in its biological unit files for about 10% of PDB entries.
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Affiliation(s)
- Qifang Xu
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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25
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Sangiambut S, Keelapang P, Aaskov J, Puttikhunt C, Kasinrerk W, Malasit P, Sittisombut N. Multiple regions in dengue virus capsid protein contribute to nuclear localization during virus infection. J Gen Virol 2008; 89:1254-1264. [PMID: 18420804 DOI: 10.1099/vir.0.83264-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
During infection, the capsid (C) protein of many flaviviruses localizes to the nuclei and nucleoli of several infected cell lines; the underlying basis and significance of C protein nuclear localization remain poorly understood. In this study, double alanine-substitution mutations were introduced into three previously proposed nuclear-localization signals (at positions 6-9, 73-76 and 85-100) of dengue virus C protein, and four viable mutants, c(K6A,K7A), c(K73A,K74A), c(R85A,K86A) and c(R97A,R98A), were generated in a mosquito cell line in which C protein nuclear localization was rarely observed. Indirect immunofluorescence analysis revealed that, whilst C protein was present in the nuclei of PS and Vero cells throughout infection with a dengue serotype 2 parent virus, the substitution mutations in c(K73A,K74A) and c(R85A,K86A) resulted in an elimination of nuclear localization in PS cells and marked reduction in Vero cells. Mutants c(K6A,K7A) and c(R97A,R98A) exhibited reduced nuclear localization at the late period of infection in PS cells only. All four mutants displayed reduced replication in PS, Vero and C6/36 cells, but there was a lack of correlation between nuclear localization and viral growth properties. Distinct dibasic residues within dengue virus C protein, many of which were located on the solvent-exposed side of the C protein homodimer, contribute to its ability to localize to nuclei during virus infection.
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Affiliation(s)
- Sutha Sangiambut
- Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Poonsook Keelapang
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - John Aaskov
- School of Life Sciences, Queensland University of Technology, 2 George Street, Brisbane 4001, Australia
| | - Chunya Puttikhunt
- Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Watchara Kasinrerk
- Department of Clinical Immunology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Prida Malasit
- Medical Molecular Biology Unit, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Nopporn Sittisombut
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
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26
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Qi RF, Zhang L, Chi CW. Biological characteristics of dengue virus and potential targets for drug design. Acta Biochim Biophys Sin (Shanghai) 2008; 40:91-101. [PMID: 18235970 DOI: 10.1111/j.1745-7270.2008.00382.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Dengue infection is a major cause of morbidity in tropical and subtropical regions, bringing nearly 40% of the world population at risk and causing more than 20,000 deaths per year. But there is neither a vaccine for dengue disease nor antiviral drugs to treat the infection. In recent years, dengue infection has been particularly prevalent in India, Southeast Asia, Brazil, and Guangdong Province, China. In this article, we present a brief summary of the biological characteristics of dengue virus and associated flaviviruses, and outline the progress on studies of vaccines and drugs based on potential targets of the dengue virus.
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Affiliation(s)
- Rui-feng Qi
- Institute of Protein Research, Tongji University, Shanghai 200092, China
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27
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Patkar CG, Jones CT, Chang YH, Warrier R, Kuhn RJ. Functional requirements of the yellow fever virus capsid protein. J Virol 2007; 81:6471-81. [PMID: 17526891 PMCID: PMC1900127 DOI: 10.1128/jvi.02120-06] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 03/23/2007] [Indexed: 11/20/2022] Open
Abstract
Although it is known that the flavivirus capsid protein is essential for genome packaging and formation of infectious particles, the minimal requirements of the dimeric capsid protein for virus assembly/disassembly have not been characterized. By use of a trans-packaging system that involved packaging a yellow fever virus (YFV) replicon into pseudo-infectious particles by supplying the YFV structural proteins using a Sindbis virus helper construct, the functional elements within the YFV capsid protein (YFC) were characterized. Various N- and C-terminal truncations, internal deletions, and point mutations of YFC were analyzed for their ability to package the YFV replicon. Consistent with previous reports on the tick-borne encephalitis virus capsid protein, YFC demonstrates remarkable functional flexibility. Nearly 40 residues of YFC could be removed from the N terminus while the ability to package replicon RNA was retained. Additionally, YFC containing a deletion of approximately 27 residues of the C terminus, including a complete deletion of C-terminal helix 4, was functional. Internal deletions encompassing the internal hydrophobic sequence in YFC were, in general, tolerated to a lesser extent. Site-directed mutagenesis of helix 4 residues predicted to be involved in intermonomeric interactions were also analyzed, and although single mutations did not affect packaging, a YFC with the double mutation of leucine 81 and valine 88 was nonfunctional. The effects of mutations in YFC on the viability of YFV infection were also analyzed, and these results were similar to those obtained using the replicon packaging system, thus underscoring the flexibility of YFC with respect to the requirements for its functioning.
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Affiliation(s)
- Chinmay G Patkar
- Department of Biological Sciences, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, USA
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28
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Zhu W, Qin C, Chen S, Jiang T, Yu M, Yu X, Qin E. Attenuated dengue 2 viruses with deletions in capsid protein derived from an infectious full-length cDNA clone. Virus Res 2007; 126:226-32. [PMID: 17412442 DOI: 10.1016/j.virusres.2007.03.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/05/2007] [Accepted: 03/08/2007] [Indexed: 11/22/2022]
Abstract
A full-length cDNA clone (pD212) of dengue virus type 2 isolated in China (DEN2-43) was constructed. Based on this, we constructed several mutants with deletions in capsid protein C using fusion PCR. These deletions removed part or almost all of the internal stretch of hydrophobic amino acid residues that is probably involved in virion assembly. We thus obtained viable mutant viruses. The propagation capacity of the mutant viruses in cell culture was impaired in parallel with the increasing size of the deletion, and the infectivity of mutant C(Delta42-59), from which all of helix III of capsid protein C was removed, was completely abolished. More importantly, the mutant viruses were highly attenuated in suckling mice but induced high levels of antibodies in adult mice. This study indicates that the structural and functional flexibility of capsid protein C make it a candidate target for the attenuation of dengue virus, which could open a promising new avenue for the development of live attenuated dengue vaccines.
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Affiliation(s)
- Wuyang Zhu
- State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing 100071, China
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29
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Abstract
Tick-borne encephalitis virus (TBEV) is an important human pathogen that causes severe neurological illness in large areas of Europe and Asia. The neuropathogenesis of this disease agent is determined by its capacity to enter the central nervous system (CNS) after peripheral inoculation ("neuroinvasiveness") and its ability to replicate and cause damage within the CNS ("neurovirulence"). TBEV is a small, enveloped flavivirus with an unsegmented, positive-stranded RNA genome. Mutations affecting various steps of its natural replication cycle were shown to influence its neuropathogenic properties. This review describes experimental approaches and summarizes results on molecular determinants of neurovirulence and neuroinvasiveness that have been identified for this virus. It focuses on molecular mechanisms of three particular steps of the viral life cycle that have been studied in some detail for TBEV and two closely related tick-borne flaviviruses (Louping ill virus (LIV) and Langat virus (LGTV)), namely (i) the envelope protein E and its role in viral attachment to the cell surface, (ii) the 3'-noncoding region of the genome and its importance for viral RNA replication, and (iii) the capsid protein C and its role in the assembly process of infectious virus particles. Mutations affecting each of these three molecular targets significantly influence neuropathogenesis of TBEV, particularly its neuroinvasiveness. The understanding of molecular determinants of TBEV neuropathogenesis is relevant for vaccine development, also against other flaviviruses.
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Affiliation(s)
- Christian W Mandl
- Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria.
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30
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Bhuvanakantham R, Ng ML. Analysis of self-association of West Nile virus capsid protein and the crucial role played by Trp 69 in homodimerization. Biochem Biophys Res Commun 2005; 329:246-55. [PMID: 15721300 DOI: 10.1016/j.bbrc.2005.01.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Indexed: 12/13/2022]
Abstract
The understanding of capsid (C) protein interactions with itself would provide important data on how the core is organized in flaviviruses during assembly. In this study, West Nile (WN) virus C protein was shown to form homodimers using yeast two-hybrid analysis in conjunction with mammalian two-hybrid and in vivo co-immunoprecipitation assays. To delineate the region on the C protein which mediates C-C dimerization, truncation studies were carried out. The results obtained clearly showed that the internal hydrophobic segment flanked by helix I and helix III of WN virus C protein is essential for the self-association of C protein. The crucial role played by Trp 69 in stabilizing the self-association of C protein was also demonstrated by mutating Trp to Gly/Arg/Phe. Substitution of the Trp residue with Gly/Arg abolished the dimerization, whereas substitution with Phe decreased the self-association significantly. The results of this study pinpoint a critical residue in the C protein that potentially plays a role in stabilizing the homotypic interaction.
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Affiliation(s)
- Raghavan Bhuvanakantham
- Flavivirology Laboratory, Department of Microbiology, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore
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31
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Mandl CW. Flavivirus Immunization with Capsid-Deletion Mutants: Basics, Benefits, and Barriers. Viral Immunol 2004; 17:461-72. [PMID: 15671744 DOI: 10.1089/vim.2004.17.461] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The flaviviruses comprise a number of arthropod-transmitted human disease agents that cause significant and increasing health threats in major parts of the world. The development of new vaccines is of vital importance, but the stringent need for safety, efficacy and cost-effectiveness together with the problems associated with the specific immune pathogenesis of some flavivirus infections impose significant challenges to innovative vaccine research. Using tick-borne encephalitis virus (TBEV) as a model, the viral capsid protein gene was recently identified as a novel target for generating flavivirus vaccines. This approach can be applied to produce either attenuated strains that can serve as live vaccines or to make a new type of a genetic vaccine consisting of non-infectious RNA replicons from which subviral particles are synthesized in vivo. Flaviviruses are small, enveloped viruses with an unsegmented positive-stranded RNA genome encoding a single polyprotein that is cleaved into the individual viral proteins. The specific introduction of various deletions and other mutations into the genomic segment coding for the capsid protein C and the biochemical and immunological characterization of the resulting mutants in cell culture and an animal model have revealed remarkable properties of this building block of the nucleocapsid and yielded information that opened the way for new vaccine approaches. In this review the in vitro and in vivo findings with various capsid deletion mutants of TBEV are summarized and discussed in the context of recent structural and biochemical data obtained for protein C of various flaviviruses. Potential benefits of this new strategy for generating flavivirus vaccines as well as hurdles that still have to be overcome are discussed in comparison to conventional or other experimental approaches. Capsid-deletion mutants can be used to rationally design safe and effective vaccine strains or to create new vaccines that combine advantages of genetic vaccination, conventional inactivated, and live vaccines.
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Affiliation(s)
- Christian W Mandl
- Institute of Virology, Medical University of Vienna, Vienna, Austria.
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