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Bardossy ES, Volpe S, Alvarez DE, Filomatori CV. A conserved Y-shaped RNA structure in the 3'UTR of chikungunya virus genome as a host-specialized element that modulates viral replication and evolution. PLoS Pathog 2023; 19:e1011352. [PMID: 37126493 PMCID: PMC10174580 DOI: 10.1371/journal.ppat.1011352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 05/11/2023] [Accepted: 04/11/2023] [Indexed: 05/02/2023] Open
Abstract
RNA viral genomes compact information into functional RNA structures. Here, using chikungunya virus as a model, we investigated the structural requirements of conserved RNA elements in the 3' untranslated region (3'UTR) for viral replication in mosquito and mammalian cells. Using structural predictions and co-variation analysis, we identified a highly stable and conserved Y-shaped structure (SLY) at the end of the 3'UTR that is duplicated in the Asian lineage. Functional studies with mutant viruses showed that the SLY has host-specific functions during viral replication and evolution. The SLY positively modulates viral replication in mosquito cells but has the opposite effect in mammalian cells. Additional structural/functional analyses showed that maintaining the Y-shaped fold and specific nucleotides in the loop are critical for full SLY functionality and optimal viral replication in mosquito cells. Experimental adaptation of viruses with duplicated SLYs to mammalian cells resulted in the generation of heterogeneous viral populations comprising variants with diverse 3'UTRs, contrasting with the homogeneous populations from viruses without SLY copies. Altogether, our findings constitute the first evidence of an RNA secondary structure in the 3'UTR of chikungunya virus genome that plays host-dependent functions.
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Affiliation(s)
- Eugenia Soledad Bardossy
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín-CONICET, Buenos Aires, Argentina
- Escuela de Bio y Nanotecnología, Universidad de San Martín, Buenos Aires, Argentina
| | - Sebastiano Volpe
- Escuela de Bio y Nanotecnología, Universidad de San Martín, Buenos Aires, Argentina
| | - Diego Ezequiel Alvarez
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín-CONICET, Buenos Aires, Argentina
- Escuela de Bio y Nanotecnología, Universidad de San Martín, Buenos Aires, Argentina
| | - Claudia Verónica Filomatori
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín-CONICET, Buenos Aires, Argentina
- Escuela de Bio y Nanotecnología, Universidad de San Martín, Buenos Aires, Argentina
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2
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Pareek A, Kumar R, Mudgal R, Neetu N, Sharma M, Kumar P, Tomar S. Alphavirus antivirals targeting RNA‐dependent RNA polymerase domain of nsP4 divulged using surface plasmon resonance. FEBS J 2022; 289:4901-4924. [DOI: 10.1111/febs.16397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 01/13/2022] [Accepted: 02/11/2022] [Indexed: 01/01/2023]
Affiliation(s)
- Akshay Pareek
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Ravi Kumar
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Rajat Mudgal
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Neetu Neetu
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Monica Sharma
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Pravindra Kumar
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
| | - Shailly Tomar
- Department of Biosciences and Bioengineering Indian Institute of Technology Roorkee Roorkee India
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Abstract
Alphaviruses are positive-strand RNA viruses, typically transmitted by mosquitoes between vertebrate hosts. They encode four essential replication proteins, the non-structural proteins nsP1-4, which possess the enzymatic activities of RNA capping, RNA helicase, site-specific protease, ADP-ribosyl removal and RNA polymerase. Alphaviruses have been key models in the study of membrane-associated RNA replication, which is a conserved feature among the positive-strand RNA viruses of animals and plants. We review new structural and functional information on the nsPs and their interaction with host proteins and membranes, as well as with viral RNA sequences. The dodecameric ring structure of nsP1 is likely to be one of the evolutionary innovations that facilitated the success of the progenitors of current positive-strand RNA viruses.
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Affiliation(s)
- Tero Ahola
- Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Gerald McInerney
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, Estonia.
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Structure and Sequence Requirements for RNA Capping at the Venezuelan Equine Encephalitis Virus RNA 5' End. J Virol 2021; 95:e0077721. [PMID: 34011549 DOI: 10.1128/jvi.00777-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Venezuelan equine encephalitis virus (VEEV) is a reemerging arthropod-borne virus causing encephalitis in humans and domesticated animals. VEEV possesses a positive single-stranded RNA genome capped at its 5' end. The capping process is performed by the nonstructural protein nsP1, which bears methyl and guanylyltransferase activities. The capping reaction starts with the methylation of GTP. The generated m7GTP is complexed to the enzyme to form an m7GMP-nsP1 covalent intermediate. The m7GMP is then transferred onto the 5'-diphosphate end of the viral RNA. Here, we explore the specificities of the acceptor substrate in terms of length, RNA secondary structure, and/or sequence. Any diphosphate nucleosides but GDP can serve as acceptors of the m7GMP to yield m7GpppA, m7GpppC, or m7GpppU. We show that capping is more efficient on small RNA molecules, whereas RNAs longer than 130 nucleotides are barely capped by the enzyme. The structure and sequence of the short, conserved stem-loop, downstream to the cap, is an essential regulatory element for the capping process. IMPORTANCE The emergence, reemergence, and expansion of alphaviruses (genus of the family Togaviridae) are a serious public health and epizootic threat. Venezuelan equine encephalitis virus (VEEV) causes encephalitis in human and domesticated animals, with a mortality rate reaching 80% in horses. To date, no efficient vaccine or safe antivirals are available for human use. VEEV nonstructural protein 1 (nsP1) is the viral capping enzyme characteristic of the Alphavirus genus. nsP1 catalyzes methyltransferase and guanylyltransferase reactions, representing a good therapeutic target. In the present report, we provide insights into the molecular features and specificities of the cap acceptor substrate for the guanylylation reaction.
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LaPointe AT, Sokoloski KJ. De-Coding the Contributions of the Viral RNAs to Alphaviral Pathogenesis. Pathogens 2021; 10:pathogens10060771. [PMID: 34205345 PMCID: PMC8233893 DOI: 10.3390/pathogens10060771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/14/2021] [Accepted: 06/17/2021] [Indexed: 11/16/2022] Open
Abstract
Alphaviruses are positive-sense RNA arboviruses that are capable of causing severe disease in otherwise healthy individuals. There are many aspects of viral infection that determine pathogenesis and major efforts regarding the identification and characterization of virulence determinants have largely focused on the roles of the nonstructural and structural proteins. Nonetheless, the viral RNAs of the alphaviruses themselves play important roles in regard to virulence and pathogenesis. In particular, many sequences and secondary structures within the viral RNAs play an important part in the development of disease and may be considered important determinants of virulence. In this review article, we summarize the known RNA-based virulence traits and host:RNA interactions that influence alphaviral pathogenesis for each of the viral RNA species produced during infection. Overall, the viral RNAs produced during infection are important contributors to alphaviral pathogenesis and more research is needed to fully understand how each RNA species impacts the host response to infection as well as the development of disease.
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Affiliation(s)
- Autumn T. LaPointe
- Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KT 40202, USA;
| | - Kevin J. Sokoloski
- Center for Predictive Medicine and Emerging Infectious Diseases, University of Louisville, Louisville, KT 40202, USA
- Correspondence:
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The Host DHX9 DExH-Box Helicase Is Recruited to Chikungunya Virus Replication Complexes for Optimal Genomic RNA Translation. J Virol 2019; 93:JVI.01764-18. [PMID: 30463980 DOI: 10.1128/jvi.01764-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 11/19/2018] [Indexed: 12/19/2022] Open
Abstract
Beyond their role in cellular RNA metabolism, DExD/H-box RNA helicases are hijacked by various RNA viruses in order to assist replication of the viral genome. Here, we identify the DExH-box RNA helicase 9 (DHX9) as a binding partner of chikungunya virus (CHIKV) nsP3 mainly interacting with the C-terminal hypervariable domain. We show that during early CHIKV infection, DHX9 is recruited to the plasma membrane, where it associates with replication complexes. At a later stage of infection, DHX9 is, however, degraded through a proteasome-dependent mechanism. Using silencing experiments, we demonstrate that while DHX9 negatively controls viral RNA synthesis, it is also required for optimal mature nonstructural protein translation. Altogether, this study identifies DHX9 as a novel cofactor for CHIKV replication in human cells that differently regulates the various steps of CHIKV life cycle and may therefore mediate a switch in RNA usage from translation to replication during the earliest steps of CHIKV replication.IMPORTANCE The reemergence of chikungunya virus (CHIKV), an alphavirus that is transmitted to humans by Aedes mosquitoes, is a serious global health threat. In the absence of effective antiviral drugs, CHIKV infection has a significant impact on human health, with chronic arthritis being one of the most serious complications. The molecular understanding of host-virus interactions is a prerequisite to the development of targeted therapeutics capable to interrupt viral replication and transmission. Here, we identify the host cell DHX9 DExH-Box helicase as an essential cofactor for early CHIKV genome translation. We demonstrate that CHIKV nsP3 protein acts as a key factor for DHX9 recruitment to replication complexes. Finally, we establish that DHX9 behaves as a switch that regulates the progression of the viral cycle from translation to genome replication. This study might therefore have a significant impact on the development of antiviral strategies.
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Blakney AK, McKay PF, Shattock RJ. Structural Components for Amplification of Positive and Negative Strand VEEV Splitzicons. Front Mol Biosci 2018; 5:71. [PMID: 30094239 PMCID: PMC6070733 DOI: 10.3389/fmolb.2018.00071] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/09/2018] [Indexed: 01/25/2023] Open
Abstract
RNA is a promising nucleic acid technology for both vaccines and therapeutics, and replicon RNA has gained traction as a next-generation RNA modality. Replicon RNA self-amplifies using a replicase complex derived from alphaviral non-structural proteins and yields higher protein expression than a similar dose of messenger RNA. Here, we debut RNA splitzicons; a split replicon system wherein the non-structural proteins (NSPs) and the gene of interest are encoded on separate RNA molecules, but still exhibit the self-amplification properties of replicon RNA. We designed both positive and negative strand splitzicons encoding firefly luciferase as a reporter protein to determine which structural components, including the 5' untranslated region (UTR), a 51-nucleotide conserved sequence element (CSE) from the first nonstructural protein, the subgenomic promoter (SGP) and corresponding untranslated region, and an internal ribosomal entry site (IRES) affect amplification. When paired with a NSP construct derived from the whole, wild type replicon, both the positive and negative strand splitzicons were amplified. The combination of the 51nt CSE, subgenomic promoter and untranslated region were imperative for the positive strand splitzicon, while the negative strand was amplified simply with inclusion of the subgenomic promoter. The splitzicons were amplified by NSPs in multiple cell types and show increasing protein expression with increasing doses of NSP. Furthermore, both the positive and negative strand splitzicons continued to amplify over the course of 72 h, up to >100,000-fold. This work demonstrates a system for screening the components required for amplification from the positive and negative strand intermediates of RNA replicons and presents a new approach to RNA replicon technology.
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Affiliation(s)
- Anna K Blakney
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Paul F McKay
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Robin J Shattock
- Department of Medicine, Imperial College London, London, United Kingdom
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8
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Pietilä MK, Hellström K, Ahola T. Alphavirus polymerase and RNA replication. Virus Res 2017; 234:44-57. [DOI: 10.1016/j.virusres.2017.01.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 01/05/2017] [Accepted: 01/09/2017] [Indexed: 10/20/2022]
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9
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Hellström K, Kallio K, Meriläinen HM, Jokitalo E, Ahola T. Ability of minus strands and modified plus strands to act as templates in Semliki Forest virus RNA replication. J Gen Virol 2016; 97:1395-1407. [DOI: 10.1099/jgv.0.000448] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Kirsi Hellström
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Katri Kallio
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Hanna-Mari Meriläinen
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Tero Ahola
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
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10
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Garcia-Moreno M, Sanz MA, Carrasco L. A Viral mRNA Motif at the 3'-Untranslated Region that Confers Translatability in a Cell-Specific Manner. Implications for Virus Evolution. Sci Rep 2016; 6:19217. [PMID: 26755446 PMCID: PMC4709744 DOI: 10.1038/srep19217] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/08/2015] [Indexed: 11/25/2022] Open
Abstract
Sindbis virus (SINV) mRNAs contain several motifs that participate in the regulation of their translation. We have discovered a motif at the 3′ untranslated region (UTR) of viral mRNAs, constituted by three repeated sequences, which is involved in the translation of both SINV genomic and subgenomic mRNAs in insect, but not in mammalian cells. These data illustrate for the first time that an element present at the 3′-UTR confers translatability to mRNAs from an animal virus in a cell-specific manner. Sequences located at the beginning of the 5′-UTR may also regulate SINV subgenomic mRNA translation in both cell lines in a context of infection. Moreover, a replicon derived from Sleeping disease virus, an alphavirus that have no known arthropod vector for transmission, is much more efficient in insect cells when the repeated sequences from SINV are inserted at its 3′-UTR, due to the enhanced translatability of its mRNAs. Thus, these findings provide a clue to understand, at the molecular level, the evolution of alphaviruses and their host range.
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Affiliation(s)
| | - Miguel Angel Sanz
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Madrid, Spain
| | - Luis Carrasco
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Madrid, Spain
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11
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Rupp JC, Sokoloski KJ, Gebhart NN, Hardy RW. Alphavirus RNA synthesis and non-structural protein functions. J Gen Virol 2015. [PMID: 26219641 DOI: 10.1099/jgv.0.000249] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans can be severely debilitating, and depending on the particular viral species, infection may result in encephalitis and possibly death. In recent years, alphaviruses have received significant attention from public health authorities as a consequence of the dramatic emergence of chikungunya virus in the Indian Ocean islands and the Caribbean. Currently, no safe, approved or effective vaccine or antiviral intervention exists for human alphavirus infection. The molecular biology of alphavirus RNA synthesis has been well studied in a few species of the genus and represents a general target for antiviral drug development. This review describes what is currently understood about the regulation of alphavirus RNA synthesis, the roles of the viral non-structural proteins in this process and the functions of cis-acting RNA elements in replication, and points to open questions within the field.
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Affiliation(s)
- Jonathan C Rupp
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Kevin J Sokoloski
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Natasha N Gebhart
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Richard W Hardy
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
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12
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Hyde JL, Chen R, Trobaugh DW, Diamond MS, Weaver SC, Klimstra WB, Wilusz J. The 5' and 3' ends of alphavirus RNAs--Non-coding is not non-functional. Virus Res 2015; 206:99-107. [PMID: 25630058 PMCID: PMC4654126 DOI: 10.1016/j.virusres.2015.01.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 01/15/2015] [Accepted: 01/17/2015] [Indexed: 11/08/2022]
Abstract
Evolution of the CHIKV 3′ UTR is shaped by fitness concerns in different hosts. The 5′ UTR can antagonize host innate immune defenses. 3′ UTR interactions with miRNAs determine cellular tropism and disease pathogenesis. Viral RNA stability is mediated by cellular HuR protein interaction with the 3′ UTR.
The non-coding regions found at the 5′ and 3′ ends of alphavirus genomes regulate viral gene expression, replication, translation and virus–host interactions, which have significant implications for viral evolution, host range, and pathogenesis. The functions of these non-coding regions are mediated by a combination of linear sequence and structural elements. The capped 5′ untranslated region (UTR) contains promoter elements, translational regulatory sequences that modulate dependence on cellular translation factors, and structures that help to avoid innate immune defenses. The polyadenylated 3′ UTR contains highly conserved sequence elements for viral replication, binding sites for cellular miRNAs that determine cell tropism, host range, and pathogenesis, and conserved binding regions for a cellular protein that influences viral RNA stability. Nonetheless, there are additional conserved elements in non-coding regions of the virus (e.g., the repeated sequence elements in the 3′ UTR) whose function remains obscure. Thus, key questions remain as to the function of these short yet influential untranslated segments of alphavirus RNAs.
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Affiliation(s)
- Jennifer L Hyde
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Rubing Chen
- Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Derek W Trobaugh
- Center for Vaccine Research and Department of Microbiology and Molecular Genetics, University of Pittsburgh, 8031 BST3, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Michael S Diamond
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Scott C Weaver
- Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA.
| | - William B Klimstra
- Center for Vaccine Research and Department of Microbiology and Molecular Genetics, University of Pittsburgh, 8031 BST3, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA.
| | - Jeffrey Wilusz
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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13
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Cheng F, Tsvetkova IB, Khuong YL, Moore AW, Arnold RJ, Goicochea NL, Dragnea B, Mukhopadhyay S. The packaging of different cargo into enveloped viral nanoparticles. Mol Pharm 2012; 10:51-8. [PMID: 22876758 DOI: 10.1021/mp3002667] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Viral nanoparticles used for biomedical applications must be able to discriminate between tumor or virus-infected host cells and healthy host cells. In addition, viral nanoparticles must have the flexibility to incorporate a wide range of cargo, from inorganic metals to mRNAs to small molecules. Alphaviruses are a family of enveloped viruses for which some species are intrinsically capable of systemic tumor targeting. Alphavirus virus-like particles, or viral nanoparticles, can be generated from in vitro self-assembled core-like particles using nonviral nucleic acid. In this work, we expand on the types of cargo that can be incorporated into alphavirus core-like particles and the molecular requirements for packaging this cargo. We demonstrate that different core-like particle templates can be further enveloped to form viral nanoparticles that are capable of cell entry. We propose that alphaviruses can be selectively modified to create viral nanoparticles for biomedical applications and basic research.
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Affiliation(s)
- Fan Cheng
- Department of Biology, Indiana University, Bloomington, Indiana 47405, United States
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14
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Wang HG, Wang XF, Jing XY, Li Z, Zhang Y, Lv ZJ. Effect of mutations in a simian virus 40 PolyA signal enhancer on green fluorescent protein reporter gene expression. GENETICS AND MOLECULAR RESEARCH 2011; 10:1866-83. [PMID: 21948750 DOI: 10.4238/vol10-3gmr1169] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Our previous studies have shown that tandem Alu repeats inhibit green fluorescent protein (GFP) gene expression when inserted downstream of the GFP gene in the pEGFP-C1 vector. We found that the 22R sequence (5'-GTGAAAAAAATGCTTTATTTGT-3') from the antisense PolyA (240 bp polyadenylation signal) of simian virus 40, eliminated repression of GFP gene expression when inserted between the GFP gene and the Alu repeats. The 22R sequence contains an imperfect palindrome; based on RNA structure software prediction, it forms an unstable stem-loop structure, including a loop, a first stem, a bulge, and a second stem. Analysis of mutations of the loop length of the 22R sequence showed that the three-nucleotide loop (wild-type, 22R) induced much stronger GFP expression than did other loop lengths. Two mutations, 4TMI (A7→T, A17→T) and 5AMI (A6→T, T18→A), which caused the base type changes in the bulge and in the second stem in the 22R sequence, induced stronger GFP gene expression than 22R itself. Mutation of the bulge base (A17→T), leading to complete complementation of the stem, caused weaker GFP gene expression. Sequences without a palindrome (7pieA, 5'-GTGAAAAAAATG CAAAAAAAGT-3', 7pieT, 5'-GTGTTTTTTTTGCTTTTTTTGT-3') did not activate GFP gene expression. We conclude that an imperfect palindrome affects and can increase GFP gene expression.
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Affiliation(s)
- H G Wang
- Hebei Key Lab of Laboratory Animal, Department of Genetics, Hebei Medical University, Shijiazhuang, Hebei Province, China
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15
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Wang H, Sun W, Li Z, Wang X, Lv Z. Identification and characterization of two critical sequences in SV40PolyA that activate the green fluorescent protein reporter gene. Genet Mol Biol 2011; 34:396-405. [PMID: 21931509 PMCID: PMC3168177 DOI: 10.1590/s1415-47572011005000018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 03/23/2011] [Indexed: 11/30/2022] Open
Abstract
Alu repeats or Line-1-ORF2 (ORF2) inhibit expression of the green fluorescent protein (GFP) gene when inserted downstream of this gene in the vector pEGFP-C1. In this work, we studied cis-acting elements that eliminated the repression of GFP gene expression induced by Alu and ORF2 and sequence characteristics of these elements. We found that sense and antisense PolyA of simian virus 40 (SV40PolyA, 240 bp) eliminated the repression of GFP gene expression when inserted between the GFP gene and the Alu (283 bp) repeats or ORF2 (3825 bp) in pAlu14 (14 tandem Alu repeats were inserted downstream of the GFP gene in the vector pEGFP-C1) or pORF2. Antisense SV40PolyA (PolyAas) induced stronger gene expression than its sense orientation (PolyA). Of four 60-bp segments of PolyAas (1F1R, 2F2R, 3F3R and 4F4R) inserted independently into pAlu14, only two (2F2R and 3F3R) eliminated the inhibition of GFP gene expression induced by Alu repeats. Deletion analysis revealed that a 17 nucleotide AT repeat (17ntAT; 5′-AAAAAAATGCTTTATTT-3′) in 2F2R and the fragment 3F38d9 (5′-ATAAACAAGTTAACAACA ACAATTGCATT-3′) in 3F3R were critical sequences for activating the GFP gene. Sequence and structural analyses showed that 17ntAT and 3F38d9 included imperfect palindromes and may form a variety of unstable stem-loops. We suggest that the presence of imperfect palindromes and unstable stem-loops in DNA enhancer elements plays an important role in GFP gene activation.
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Affiliation(s)
- Honggang Wang
- Hebei Key Lab of Laboratory Animal, Department of Genetics, Hebei Medical University, Shijiazhuang, Hebei Province, China
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16
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Wang HG, Ma H, Li Z, Zhang B, Jing XY, Zhang Y, Lv ZJ. [Detection and sequence analysis of an imperfect stem-loop structure in cis activating gene element from SV40PolyA]. YI CHUAN = HEREDITAS 2011; 33:337-46. [PMID: 21482523 DOI: 10.3724/sp.j.1005.2011.00337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Our previous studies showed that tandem Alu repeats inhibited GFP gene expression when they were inserted into the downstream of GFP gene in pEGFP-C1 vector and HeLa cells were then transfected transiently. The sequence named 2F2R (second 60 bp from the 5' end of SV40PolyA antisense strand) eliminated the repression of GFP gene expression induced by Alu repeats when 2F2R was inserted between GFP and Alu repeats. In this study the deletion of 2F2R DNA showed that 45R (45 bp in 2F2R 5'end), 30R (30 bp in 2F2R 5' end) and 22R (22 bp in 2F2R 5' end) activated GFP gene expression, and the activating actions of the double tandem sequences were stronger than those of their corresponding single sequences. Secloop (22 bp near the center in 2F2R) and Poly4 (30 bp in 2F2R 3' end) sequences did not activate GFP gene expression. The activating action of 30R-Poly4 sequence formed by ligating 30R with Poly4 by 9 bp was lower than that of 2F2R. The linking base number between two 22R sequences did not influence the GFP gene expression obviously. Sequence 22R (5'-GTGAAAAAAATGCTTTATTTGT-3') contains an imperfect palindrome sequence and may form an imperfect stem-loop structure including a 3nt loop, 3 bp first stem, 2nt bulge, and 3bp second stem. The mutations changing stem-loop structure of 22R influenced the GFP gene activation significantly and neither the excessively stable nor excessively unstable stem-loop structures were in favour of GFP gene activation, which suggested that the suitably imperfect stem-loop structures had something with gene activation.
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Affiliation(s)
- Hong-Gang Wang
- Department of Genetics, Hebei Key Lab of Laboratory Animal, Hebei Medical University, Shijiazhuang 050017, China.
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17
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Cheng F, Mukhopadhyay S. Generating enveloped virus-like particles with in vitro assembled cores. Virology 2011; 413:153-60. [PMID: 21334709 DOI: 10.1016/j.virol.2011.02.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 01/20/2011] [Accepted: 02/01/2011] [Indexed: 01/19/2023]
Abstract
Alphaviruses are comprised of a nucleocapsid core surrounded by a lipid membrane containing glycoprotein spikes. Previous work demonstrated that in vitro assembled core-like particles are similar in structure to the nucleocapsid core in the native virus. Here we demonstrate that in vitro assembled core-like particles can be inserted into viral glycoprotein-expressing cells to generate enveloped virus-like particles. These virus-like particles bud from cells like native virus, are similar in size to the native virus, and can enter cells to release the contents of the core-like particle into the cytoplasm of the cell. Virus-like particles can be used to infect cells with biological and non-biological cargoes. The generation of enveloped virus-like particles containing an in vitro core and in vivo synthesized glycoproteins has applications for gene and drug delivery, medical imaging, and also basic mechanistic studies of virus assembly.
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Affiliation(s)
- Fan Cheng
- Department of Biology, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN 47405, USA.
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18
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Antiviral RNA interference responses induced by Semliki Forest virus infection of mosquito cells: characterization, origin, and frequency-dependent functions of virus-derived small interfering RNAs. J Virol 2010; 85:2907-17. [PMID: 21191029 DOI: 10.1128/jvi.02052-10] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RNA interference (RNAi) is an important mosquito defense mechanism against arbovirus infection. In this paper we study the processes underlying antiviral RNAi in Aedes albopictus-derived U4.4 mosquito cells infected with Semliki Forest virus (SFV) (Togaviridae; Alphavirus). The production of virus-derived small interfering RNAs (viRNAs) from viral double-stranded RNA (dsRNA) is a key event in this host response. dsRNA could be formed by RNA replication intermediates, by secondary structures in RNA genomes or antigenomes, or by both. Which of these dsRNAs is the substrate for the generation of viRNAs is a fundamental question. Here we used deep sequencing of viRNAs and bioinformatic analysis of RNA secondary structures to gain insights into the characteristics and origins of viRNAs. An asymmetric distribution of SFV-derived viRNAs with notable areas of high-level viRNA production (hot spots) and no or a low frequency of viRNA production (cold spots) along the length of the viral genome with a slight bias toward the production of genome-derived viRNAs over antigenome-derived viRNAs was observed. Bioinformatic analysis suggests that hot spots of viRNA production are rarely but not generally associated with putative secondary structures in the SFV genome, suggesting that most viRNAs are derived from replicative dsRNA. A pattern of viRNAs almost identical to those of A. albopictus cells was observed for Aedes aegypti-derived Aag2 cells, suggesting common mechanisms that lead to viRNA production. Hot-spot viRNAs were found to be significantly less efficient at mediating antiviral RNAi than cold-spot viRNAs, pointing toward a nucleic acid-based viral decoy mechanism to evade the RNAi response.
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19
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Liu Y, Wimmer E, Paul AV. Cis-acting RNA elements in human and animal plus-strand RNA viruses. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1789:495-517. [PMID: 19781674 PMCID: PMC2783963 DOI: 10.1016/j.bbagrm.2009.09.007] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 09/09/2009] [Accepted: 09/13/2009] [Indexed: 02/08/2023]
Abstract
The RNA genomes of plus-strand RNA viruses have the ability to form secondary and higher-order structures that contribute to their stability and to their participation in inter- and intramolecular interactions. Those structures that are functionally important are called cis-acting RNA elements because their functions cannot be complemented in trans. They can be involved not only in RNA/RNA interactions but also in binding of viral and cellular proteins during the complex processes of translation, RNA replication and encapsidation. Most viral cis-acting RNA elements are located in the highly structured 5'- and 3'-nontranslated regions of the genomes but sometimes they also extend into the adjacent coding sequences. In addition, some cis-acting RNA elements are embedded within the coding sequences far away from the genomic ends. Although the functional importance of many of these structures has been confirmed by genetic and biochemical analyses, their precise roles are not yet fully understood. In this review we have summarized what is known about cis-acting RNA elements in nine families of human and animal plus-strand RNA viruses with an emphasis on the most thoroughly characterized virus families, the Picornaviridae and Flaviviridae.
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Affiliation(s)
- Ying Liu
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11790, USA
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20
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Structural and functional elements of the promoter encoded by the 5' untranslated region of the Venezuelan equine encephalitis virus genome. J Virol 2009; 83:8327-39. [PMID: 19515761 DOI: 10.1128/jvi.00586-09] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Venezuelan equine encephalitis virus (VEEV) is one of the most pathogenic members of the Alphavirus genus in the Togaviridae family. The pathogenesis of this virus depends strongly on the sequences of the structural proteins and on the mutations in the RNA promoter encoded by the 5' untranslated region (5'UTR) of the viral genome. In this study, we performed a detailed investigation of the structural and functional elements of the 5'-terminal promoter and analyzed the effect of multiple mutations introduced into the VEEV 5'UTR on virus and RNA replication. The results of this study demonstrate that RNA replication is determined by two synergistically functioning RNA elements. One of them is a very 5'-terminal AU dinucleotide, which is not involved in the stable RNA secondary structure, and the second is a short, G-C-rich RNA stem. An increase or decrease in the stem's stability has deleterious effects on virus and RNA replication. In response to mutations in these RNA elements, VEEV replicative machinery was capable of developing new, compensatory sequences in the 5'UTR either containing 5'-terminal AUG or AU repeats or leading to the formation of new, heterologous stem-loops. Analysis of the numerous compensatory mutations suggested that at least two different mechanisms are involved in their generation. Some of the modifications introduced into the 5' terminus of the viral genome led to an accumulation of the mutations in the VEEV nsPs, which suggested to us that there is a direct involvement of these proteins in promoter recognition. Furthermore, our data provide new evidence that the 3' terminus of the negative-strand viral genome in the double-stranded RNA replicative intermediate is represented by a single-stranded RNA. Both the overall folding and the sequence determine its efficient function as a promoter for VEEV positive-strand RNA genome synthesis.
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Kulasegaran-Shylini R, Thiviyanathan V, Gorenstein DG, Frolov I. The 5'UTR-specific mutation in VEEV TC-83 genome has a strong effect on RNA replication and subgenomic RNA synthesis, but not on translation of the encoded proteins. Virology 2009; 387:211-21. [PMID: 19278709 DOI: 10.1016/j.virol.2009.02.027] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 01/20/2009] [Accepted: 02/18/2009] [Indexed: 02/06/2023]
Abstract
Venezuelan equine encephalitis virus (VEEV) is one of the most pathogenic members of the Alphavirus genus in the Togaviridae family. Viruses in the VEEV serocomplex continuously circulate in the Central and South America. The only currently available attenuated strain VEEV TC-83 is being used only for vaccination of at-risk laboratory workers and military personnel. Its attenuated phenotype was shown to rely only on two point mutations, one of which, G3A, was found in the 5' untranslated region (5'UTR) of the viral genome. Our data demonstrate that the G3A mutation strongly affects the secondary structure of VEEV 5'UTR, but has only a minor effect on translation. The indicated mutation increases replication of the viral genome, downregulates transcription of the subgenomic RNA, and, thus, affects the ratio of genomic and subgenomic RNA synthesis. These findings and the previously reported G3A-induced, higher sensitivity of VEEV TC-83 to IFN-alpha/beta suggest a plausible explanation for its attenuated phenotype.
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