1
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Zhang QY, Liu SQ, Li XD, Li JQ, Zhang YN, Deng CL, Zhang HL, Li XF, Fang CX, Yang FX, Zhang B, Xu Y, Ye HQ. Sequence duplication in 3' UTR modulates virus replication and virulence of Japanese encephalitis virus. Emerg Microbes Infect 2021; 11:123-135. [PMID: 34877923 PMCID: PMC8725919 DOI: 10.1080/22221751.2021.2016354] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Japanese encephalitis virus (JEV), an important neurotropic pathogen, belongs to the genus Flavivirus of the family Flaviviridae and has caused huge threat to public health. It is still obscure regarding the functions of stem-loop (SL) and dumbbell (DB) domains of JEV 3' UTR in viral replication and virulence. In the current study, using the infectious clone of JEV SA14 strain as a backbone, we constructed a series of deletion mutants of 3' UTR to investigate their effects on virus replication. The results showed that partial deletions within SL or DB domain had no apparent effects on virus replication in both mammalian (BHK-21) and mosquito (C6/36) cells, suggesting that they were not involved in viral host-specific replication. However, the entire SL domain deletion (ΔVR) significantly reduced virus replication in both cell lines, indicating the important role of the complete SL domain in virus replication. The revertant of ΔVR mutant virus was obtained by serial passage in BHK-21 cells that acquired a duplication of DB domain (DB-dup) in the 3' UTR, which greatly restored virus replication as well as the capability to produce the subgenomic flavivirus RNAs (sfRNAs). Interestingly, the DB-dup mutant virus was highly attenuated in C57BL/6 mice despite replicating similar to WT JEV. These findings demonstrate the significant roles of the duplicated structures in 3' UTR in JEV replication and provide a novel strategy for the design of live-attenuated vaccines.
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Affiliation(s)
- Qiu-Yan Zhang
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China.,The Joint Center of Translational Precision Medicine, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Si-Qing Liu
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Xiao-Dan Li
- School of Medicine, Hunan Normal University, Changsha, People's Republic of China
| | - Jia-Qi Li
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China.,University of Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Ya-Nan Zhang
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Cheng-Lin Deng
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Hong-Lei Zhang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, People's Republic of China
| | - Xu-Fang Li
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China
| | - Chun-Xiao Fang
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China
| | - Feng-Xia Yang
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China
| | - Bo Zhang
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China.,The Joint Center of Translational Precision Medicine, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China.,Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Yi Xu
- The Joint Center of Translational Precision Medicine, Department of Infectious Diseases, Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, People's Republic of China.,The Joint Center of Translational Precision Medicine, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Han-Qing Ye
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, People's Republic of China
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2
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The Pseudo-Circular Genomes of Flaviviruses: Structures, Mechanisms, and Functions of Circularization. Cells 2021; 10:cells10030642. [PMID: 33805761 PMCID: PMC7999817 DOI: 10.3390/cells10030642] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/19/2021] [Accepted: 03/02/2021] [Indexed: 11/23/2022] Open
Abstract
The circularization of viral genomes fulfills various functions, from evading host defense mechanisms to promoting specific replication and translation patterns supporting viral proliferation. Here, we describe the genomic structures and associated host factors important for flaviviruses genome circularization and summarize their functional roles. Flaviviruses are relatively small, single-stranded, positive-sense RNA viruses with genomes of approximately 11 kb in length. These genomes contain motifs at their 5′ and 3′ ends, as well as in other regions, that are involved in circularization. These motifs are highly conserved throughout the Flavivirus genus and occur both in mature virions and within infected cells. We provide an overview of these sequence motifs and RNA structures involved in circularization, describe their linear and circularized structures, and discuss the proteins that interact with these circular structures and that promote and regulate their formation, aiming to clarify the key features of genome circularization and understand how these affect the flaviviruses life cycle.
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3
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Zeng M, Duan Y, Zhang W, Wang M, Jia R, Zhu D, Liu M, Zhao X, Yang Q, Wu Y, Zhang S, Liu Y, Zhang L, Yu Y, Chen S, Cheng A. Universal RNA Secondary Structure Insight Into Mosquito-Borne Flavivirus (MBFV) cis-Acting RNA Biology. Front Microbiol 2020; 11:473. [PMID: 32292394 PMCID: PMC7118588 DOI: 10.3389/fmicb.2020.00473] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 03/04/2020] [Indexed: 12/22/2022] Open
Abstract
Mosquito-borne flaviviruses (MBFVs) spread between vertebrate (mammals and birds) and invertebrate (mosquitoes) hosts. The cis-acting RNAs of MBFV share common evolutionary origins and contain frequent alterations, which control the balance of linear and circular genome conformations and allow effective replication. Importantly, multiple cis-acting RNAs interact with trans-acting regulatory RNA-binding proteins (RBPs) and affect the MBFV lifecycle process, including viral replicase binding, viral RNA translation-cyclisation-synthesis and nucleocapsid assembly. Considering that extensive structural probing analyses have been performed on MBFV cis-acting RNAs, herein the homologous RNA structures are online folded and consensus structures are constructed by sort. The specific traits and underlying biology of MBFV cis-acting RNA are illuminated accordingly in a review of RNA structure. These findings deepen our understanding of MBFV cis-acting RNA biology and serve as a resource for designing therapeutics in targeting protein-viral RNA interaction or viral RNA secondary structures.
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Affiliation(s)
- Miao Zeng
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yanping Duan
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Wei Zhang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Mingshu Wang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Renyong Jia
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Dekang Zhu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Mafeng Liu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Xinxin Zhao
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Qiao Yang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Ying Wu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Shaqiu Zhang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Yunya Liu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Ling Zhang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yangling Yu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Shun Chen
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Anchun Cheng
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
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Different Degrees of 5'-to-3' DAR Interactions Modulate Zika Virus Genome Cyclization and Host-Specific Replication. J Virol 2020; 94:JVI.01602-19. [PMID: 31826997 PMCID: PMC7022364 DOI: 10.1128/jvi.01602-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 12/06/2019] [Indexed: 01/06/2023] Open
Abstract
Mosquito-borne flaviviruses, which include many important human pathogens, such as West Nile virus (WNV), dengue virus (DENV), and Zika virus (ZIKV), have caused numerous emerging epidemics in recent years. Details of the viral genome functions necessary for effective viral replication in mosquito and vertebrate hosts remain obscure. Here, using ZIKV as a model, we found that the conserved "downstream of AUG region" (DAR), which is known to be an essential element for genome cyclization, is involved in viral replication in a host-specific manner. Mutational analysis of the DAR element showed that a single-nucleotide mismatch between the 5' DAR and the 3' DAR had little effect on ZIKV replication in mammalian cells but dramatically impaired viral propagation in mosquito cells. The revertant viruses passaged in mosquito cells generated compensatory mutations restoring the base pairing of the DAR, further confirming the importance of the complementarity of the DAR in mosquito cells. We demonstrate that a single-nucleotide mutation in the DAR is sufficient to destroy long-range RNA interaction of the ZIKV genome and affects de novo RNA synthesis at 28°C instead of 37°C, resulting in the different replication efficiencies of the mutant viruses in mosquito and mammalian cells. Our results reveal a novel function of the circular form of the flavivirus genome in host-specific viral replication, providing new ideas to further explore the functions of the viral genome during host adaptation.IMPORTANCE Flaviviruses naturally cycle between the mosquito vector and vertebrate hosts. The disparate hosts provide selective pressures that drive virus genome evolution to maintain efficient replication during host alteration. Host adaptation may occur at different stages of the viral life cycle, since host-specific viral protein processing and virion conformations have been reported in the individual hosts. However, the viral determinants and the underlying mechanisms associated with host-specific functions remain obscure. In this study, using Zika virus, we found that the DAR-mediated genome cyclization regulates viral replication differently and is under different selection pressures in mammalian and mosquito cells. A more constrained complementarity of the DAR is required in mosquito cells than in mammalian cells. Since the DAR element is stably maintained among mosquito-borne flaviviruses, our findings could provide new information for understanding the role of flavivirus genome cyclization in viral adaptation and RNA evolution in the two hosts.
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5
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Replication-Defective West Nile Virus with NS1 Deletion as a New Vaccine Platform for Flavivirus. J Virol 2019; 93:JVI.00720-19. [PMID: 31189715 DOI: 10.1128/jvi.00720-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/10/2019] [Indexed: 02/03/2023] Open
Abstract
We previously produced a replication-defective West Nile virus (WNV) lacking NS1 (WNV-ΔNS1) that could propagate at low levels (105 infectious units [IU]/ml) in a 293T cell line expressing wild-type (WT) NS1. This finding indicates the potential of developing WNV-ΔNS1 as a noninfectious vaccine. To explore this idea, we developed an NS1-expressing Vero cell line (VeroNS1) that significantly improved the yield of WNV-ΔNS1 (108 IU/ml). We evaluated the safety and efficacy of WNV-ΔNS1 in mice. WNV-ΔNS1 appeared to be safe, as no replicative virus was found in naive Vero cells after continuous culturing of WNV-ΔNS1 in VeroNS1 cells for 15 rounds. WNV-ΔNS1 was noninfectious in mice, even when IFNAR-/- mice were administered a high dose of WNV-ΔNS1. Vaccination with a single dose of WNV-ΔNS1 protected mice from a highly lethal challenge with WT WNV. The antibody response against WNV correlated well with the protection of vaccinated mice. Our study demonstrates the potential of the NS1 trans complementation system as a new platform for flavivirus vaccine development.IMPORTANCE Many flaviviruses are significant human pathogens that frequently cause outbreaks and epidemics around the world. Development of novel vaccine platforms against these pathogens is a public health priority. Using WNV as a model, we developed a new vaccine platform for flaviviruses. WNV containing a NS1 deletion (WNV-ΔNS1) could be efficiently trans complemented in Vero cells that constitutively expressed WT NS1 protein. A single-dose immunization with WNV-ΔNS1 elicited robust immune responses in mice. The immunized animals were fully protected against pathogenic WNV infection. No adverse effects related to the WNV-ΔNS1 vaccination were observed. The results have demonstrated the potential of the NS1 complementation system as an alternative platform for flavivirus vaccine development, especially for highly pathogenic flaviviruses.
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6
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Zhang HL, Ye HQ, Liu SQ, Deng CL, Li XD, Shi PY, Zhang B. West Nile Virus NS1 Antagonizes Interferon Beta Production by Targeting RIG-I and MDA5. J Virol 2017; 91:e02396-16. [PMID: 28659477 PMCID: PMC5571242 DOI: 10.1128/jvi.02396-16] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 06/20/2017] [Indexed: 11/20/2022] Open
Abstract
West Nile virus (WNV) is a mosquito-borne flavivirus that causes epidemics of encephalitis and viscerotropic disease worldwide. This virus has spread rapidly and has posed a significant public health threat since the outbreak in New York City in 1999. The interferon (IFN)-mediated antiviral response represents an important component of virus-host interactions and plays an essential role in regulating viral replication. Previous studies have suggested that multifunctional nonstructural proteins encoded by flaviviruses antagonize the host IFN response via various means in order to establish efficient viral replication. In this study, we demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes IFN-β production, most likely through suppression of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) activation. In a dual-luciferase reporter assay, WNV NS1 significantly inhibited the activation of the IFN-β promoter after Sendai virus infection or poly(I·C) treatment. NS1 also suppressed the activation of the IFN-β promoter when it was stimulated by interferon regulatory factor 3 (IRF3)/5D or its upstream molecules in the RLR signaling pathway. Furthermore, NS1 blocked the phosphorylation and nuclear translocation of IRF3 upon stimulation by various inducers. Mechanistically, WNV NS1 targets RIG-I and melanoma differentiation-associated gene 5 (MDA5) by interacting with them and subsequently causing their degradation by the proteasome. Furthermore, WNV NS1 inhibits the K63-linked polyubiquitination of RIG-I, thereby inhibiting the activation of downstream sensors in the RLR signaling pathway. Taken together, our results reveal a novel mechanism by which WNV NS1 interferes with the host antiviral response.IMPORTANCE WNV Nile virus (WNV) has received increased attention since its introduction to the United States. However, the pathogenesis of this virus is poorly understood. This study demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes the induction of interferon beta (IFN-β) by interacting with and degrading retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5), which are crucial viral sensors in the host innate immune system. Further experiments suggested that NS1-mediated inhibition of the RIG-I-like receptor (RLR) signaling pathway involves inhibition of RIG-I K63-linked polyubiquitination and that the proteasome plays a role in RIG-I degradation. This study provides new insights into the regulation of WNV NS1 in the RLR signaling pathway and reveals a novel mechanism by which WNV evades the host innate immune response. The novel findings may guide us to discover new therapeutic targets and develop effective vaccines for WNV infections.
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Affiliation(s)
- Hong-Lei Zhang
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Han-Qing Ye
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Si-Qing Liu
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Cheng-Lin Deng
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Xiao-Dan Li
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Pei-Yong Shi
- University of Texas Medical Branch, Galveston, Texas, USA
| | - Bo Zhang
- Chinese Academy of Sciences Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
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7
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Zhang PT, Shan C, Li XD, Liu SQ, Deng CL, Ye HQ, Shang BD, Shi PY, Lv M, Shen BF, Qin CF, Zhang B. Generation of a recombinant West Nile virus stably expressing the Gaussia luciferase for neutralization assay. Virus Res 2016; 211:17-24. [DOI: 10.1016/j.virusres.2015.09.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/22/2015] [Accepted: 09/23/2015] [Indexed: 10/23/2022]
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Nicholson BL, White KA. Functional long-range RNA-RNA interactions in positive-strand RNA viruses. Nat Rev Microbiol 2014; 12:493-504. [PMID: 24931042 PMCID: PMC7097572 DOI: 10.1038/nrmicro3288] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Long-range RNA–RNA interactions, many of which span several thousands of nucleotides, have been discovered within the genomes of positive-strand RNA viruses. These interactions mediate fundamental viral processes, including translation, replication and transcription. In certain plant viruses that have uncapped, non-polyadenylated RNA genomes, translation initiation is facilitated by 3′ cap-independent translational enhancers (3′ CITEs) that are located in or near to their 3′ UTRs. These RNA elements function by binding to either the ribosome-recruiting eukaryotic translation initiation factor 4F (eIF4F) complex or ribosomal subunits, and they enhance translation initiation by engaging the 5′ end of the genome via a 5′-to-3′ RNA-based bridge. The activities of the internal ribosome entry sites (IRESs) in the 5′ UTRs of various viruses are modulated by RNA-based interactions between the IRESs and elements near to the 3′ ends of their genomes. In several plant viruses, translational recoding events, including ribosomal frameshifting and stop codon readthrough, have been found to rely on long-range RNA–RNA interactions. Multiple 5′-to-3′ base-pairing interactions facilitate genome circularization in flaviviruses, which has been proposed to reposition the 5′-bound RNA-dependent RNA polymerase (RdRp) to the initiation site of negative-strand synthesis at the 3′ terminus. The long-distance interaction between two cis-acting replication elements in tombusviruses generates a bipartite RNA platform for the assembly of the replicase complex and repositions the internally bound RdRp to the 3′ terminus. Tombusviruses also rely on several long-range interactions that mediate the premature termination of the RdRp during negative-strand synthesis that leads to transcription of subgenomic mRNAs (sgmRNAs). In a coronavirus, an exceptionally long-range interaction, which spans ∼26,000 nucleotides, promotes polymerase repriming during the discontinuous template synthesis step of sgmRNA-N transcription. A challenge for the future will be to determine how these long-range interactions are integrated and regulated in the complex context of viral RNA genomes.
Long-range intragenomic RNA–RNA interactions in the genomes of positive-strand RNA viruses involve direct nucleotide base pairing and can span distances of thousands of nucleotides. In this Review, Nicholson and White discuss recent insights into the structure and function of these genomic features and highlight their diverse roles in the gene expression and genome replication of positive-strand RNA viruses. Positive-strand RNA viruses are important human, animal and plant pathogens that are defined by their single-stranded positive-sense RNA genomes. In recent years, it has become increasingly evident that interactions that occur between distantly positioned RNA sequences within these genomes can mediate important viral activities. These long-range intragenomic RNA–RNA interactions involve direct nucleotide base pairing and can span distances of thousands of nucleotides. In this Review, we discuss recent insights into the structure and function of these intriguing genomic features and highlight their diverse roles in the gene expression and genome replication of positive-strand RNA viruses.
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Affiliation(s)
- Beth L Nicholson
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
| | - K Andrew White
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
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9
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Replication cycle and molecular biology of the West Nile virus. Viruses 2013; 6:13-53. [PMID: 24378320 PMCID: PMC3917430 DOI: 10.3390/v6010013] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 12/27/2022] Open
Abstract
West Nile virus (WNV) is a member of the genus Flavivirus in the family Flaviviridae. Flaviviruses replicate in the cytoplasm of infected cells and modify the host cell environment. Although much has been learned about virion structure and virion-endosomal membrane fusion, the cell receptor(s) used have not been definitively identified and little is known about the early stages of the virus replication cycle. Members of the genus Flavivirus differ from members of the two other genera of the family by the lack of a genomic internal ribosomal entry sequence and the creation of invaginations in the ER membrane rather than double-membrane vesicles that are used as the sites of exponential genome synthesis. The WNV genome 3' and 5' sequences that form the long distance RNA-RNA interaction required for minus strand initiation have been identified and contact sites on the 5' RNA stem loop for NS5 have been mapped. Structures obtained for many of the viral proteins have provided information relevant to their functions. Viral nonstructural protein interactions are complex and some may occur only in infected cells. Although interactions between many cellular proteins and virus components have been identified, the functions of most of these interactions have not been delineated.
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10
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Development and characterization of West Nile virus replicon expressing secreted Gaussia luciferase. Virol Sin 2013; 28:161-6. [PMID: 23709059 DOI: 10.1007/s12250-013-3332-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 05/13/2013] [Indexed: 01/17/2023] Open
Abstract
We developed a Gaussia luciferase (Gluc) reporter replicon of West Nile virus (WNV) and used it to quantify viral translation and RNA replication. The advantage of the Gluc replicon is that Gaussia luciferase is secreted into the culture medium from cells transfected with Gluc replicon RNA, and the medium can be assayed directly for luciferase activity. Using a known Flavivirus inhibitor (NITD008), we demonstrated that the Gluc-WNV replicon could be used for antiviral screening. The Gluc-WNV-Rep will be useful for research in antiviral drug development programs, as well as for studying viral replication and pathogenesis of WNV.
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11
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Shang B, Deng C, Ye H, Xu W, Yuan Z, Shi PY, Zhang B. Development and characterization of a stable eGFP enterovirus 71 for antiviral screening. Antiviral Res 2012; 97:198-205. [PMID: 23267829 DOI: 10.1016/j.antiviral.2012.12.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 12/06/2012] [Accepted: 12/15/2012] [Indexed: 11/18/2022]
Abstract
Enterovirus 71 (EV71) is one of the major causative agents for hand, foot, and mouth disease. There is currently no clinically approved vaccine or antiviral treatment for EV71 infection. To facilitate antiviral drug discovery, we developed an infectious cDNA clone of an epidemic strain of EV71 and a stable eGFP reporter EV71. The reporter virus was generated by engineering the eGFP gene between the 5' untranslated region and VP4 gene of the EV71 genome. Vero cells transfected with the cDNA clone-derived RNA generated high titers (>10(6)PFU/ml) of the eGFP reporter virus. The reporter virus was infectious to Vero cells, producing robust eGFP fluorescence signals. Compared with the wild type virus, the reporter virus replicated slower in cell culture. To examine the stability of the reporter virus, we continuously passaged the virus on Vero cells for five rounds. The passaged viruses maintained the eGFP gene, demonstrating the stability of the reporter virus. Using a known EV71 inhibitor, we demonstrate that the reporter virus could be used for antiviral screening. The infectious cDNA clones of the wild type virus and the eGFP reporter viruses will be useful for antiviral research as well as for studying viral replication and pathogenesis of EV71.
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Affiliation(s)
- Baodi Shang
- Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Science, China
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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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Composition of the sequence downstream of the dengue virus 5' cyclization sequence (dCS) affects viral RNA replication. Virology 2011; 422:346-56. [PMID: 22137186 DOI: 10.1016/j.virol.2011.10.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 08/11/2011] [Accepted: 10/28/2011] [Indexed: 12/31/2022]
Abstract
RNA replication of dengue virus (DENV) requires an RNA-RNA mediated circularization of the viral genome, which includes at least three sets of complementary RNA sequences on both ends of the genome. The 5' and the 3' untranslated regions form several additional RNA elements that are involved in regulation of translation and required for RNA replication. Communication between the genomic termini results in a structural reorganization of the RNA elements, forming a functional RNA panhandle structure. Here we report that the sequence composition downstream of the 5' CS element in the capsid gene, designated as downstream CS (dCS) sequence - but not the capsid protein - also influences the ability of the viral genome to circularize and hence replicate by modulating the topology of the 5' end. These results provide insights for the design of reporter sub-genomic and genomic mosquito-borne flavivirus constructs and contribute to the understanding of viral RNA replication.
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Lei Y, Huang Y, Zhang H, Yu L, Zhang M, Dayton A. Functional interaction between cellular p100 and the dengue virus 3' UTR. J Gen Virol 2010; 92:796-806. [PMID: 21148275 DOI: 10.1099/vir.0.028597-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Host factors interacting with the dengue virus (DENV) 3' UTR are involved in virus replication, but their roles remain poorly understood. We used RNA affinity capture and mass spectrometry to identify p100 as a host cellular protein associated with the DENV 3' UTR. By using RNA immunoprecipitation and confocal immunofluorescence analysis we demonstrated an interaction between p100 and the 3' UTR in DENV-infected cells. We identified the A4 region (the extensive stem-loop structure at the 3' end) as the binding site of p100 by studying deletion mutants. p100 knockdown specifically reduced the levels of viral RNA and viral protein in DENV-infected cells. Furthermore, downregulation of p100 reduced the expression of a heterologously expressed luciferase-3' UTR(DENV) mRNA in an A4-dependent manner, confirming the binding data and the effects of p100 knockdown on viral replication. These results provide evidence that p100 interacts with the 3' UTR of DENV and is required for normal DENV replication.
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Affiliation(s)
- Yingfeng Lei
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852, USA
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