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Chew MF, Poh KS, Poh CL. Peptides as Therapeutic Agents for Dengue Virus. Int J Med Sci 2017; 14:1342-1359. [PMID: 29200948 PMCID: PMC5707751 DOI: 10.7150/ijms.21875] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/01/2017] [Indexed: 12/19/2022] Open
Abstract
Dengue is an important global threat caused by dengue virus (DENV) that records an estimated 390 million infections annually. Despite the availability of CYD-TDV as a commercial vaccine, its long-term efficacy against all four dengue virus serotypes remains unsatisfactory. There is therefore an urgent need for the development of antiviral drugs for the treatment of dengue. Peptide was once a neglected choice of medical treatment but it has lately regained interest from the pharmaceutical industry following pioneering advancements in technology. In this review, the design of peptide drugs, antiviral activities and mechanisms of peptides and peptidomimetics (modified peptides) action against dengue virus are discussed. The development of peptides as inhibitors for viral entry, replication and translation is also described, with a focus on the three main targets, namely, the host cell receptors, viral structural proteins and viral non-structural proteins. The antiviral peptides designed based on these approaches may lead to the discovery of novel anti-DENV therapeutics that can treat dengue patients.
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Affiliation(s)
- Miaw-Fang Chew
- Research Centre for Biomedical Sciences, Sunway University, Bandar Sunway, Selangor 47500, Malaysia
| | - Keat-Seong Poh
- Department of Surgery, Faculty of Medicine, University of Malaya, Jalan Universiti, Kuala Lumpur, 50603, Malaysia
| | - Chit-Laa Poh
- Research Centre for Biomedical Sciences, Sunway University, Bandar Sunway, Selangor 47500, Malaysia
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52
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Xu HT, Hassounah SA, Colby-Germinario SP, Oliveira M, Fogarty C, Quan Y, Han Y, Golubkov O, Ibanescu I, Brenner B, Stranix BR, Wainberg MA. Purification of Zika virus RNA-dependent RNA polymerase and its use to identify small-molecule Zika inhibitors. J Antimicrob Chemother 2017; 72:727-734. [PMID: 28069884 DOI: 10.1093/jac/dkw514] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 11/01/2016] [Indexed: 12/21/2022] Open
Abstract
Background The viral RNA-dependent RNA polymerase (RdRp) enzymes of the Flaviviridae family are essential for viral replication and are logically important targets for development of antiviral therapeutic agents. Zika virus (ZIKV) is a rapidly re-emerging human pathogen for which no vaccine or antiviral agent is currently available. Methods To facilitate development of ZIKV RdRp inhibitors, we have established an RdRp assay using purified recombinant ZIKV NS5 polymerase. Results We have shown that both the hepatitis C virus (HCV) nucleoside inhibitor sofosbuvir triphosphate and a pyridoxine-derived non-nucleoside small-molecule inhibitor, DMB213, can act against ZIKV RdRp activity at IC 50 s of 7.3 and 5.2 μM, respectively, in RNA synthesis reactions catalysed by recombinant ZIKV NS5 polymerase. Cell-based assays confirmed the anti-ZIKV activity of sofosbuvir and DMB213 with 50% effective concentrations (EC 50 s) of 8.3 and 4.6 μM, respectively. Control studies showed that DMB213 did not inhibit recombinant HIV-1 reverse transcriptase and showed only very weak inhibition of HIV-1 integrase strand-transfer activity. The S604T substitution in motif B of the ZIKV RdRp, which corresponds to the S282T substitution in motif B of HCV RdRp, which confers resistance to nucleotide inhibitors, also conferred resistance to sofosbuvir triphosphate, but not to DMB213. Enzyme assays showed that DMB213 appears to be competitive with natural nucleoside triphosphate (NTP) substrates. Conclusions Recombinant ZIKV RdRp assays can be useful tools for the screening of both nucleos(t)ide compounds and non-nucleotide metal ion-chelating agents that interfere with ZIKV replication.
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Affiliation(s)
- Hong-Tao Xu
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Said A Hassounah
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Susan P Colby-Germinario
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Maureen Oliveira
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Clare Fogarty
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Yudong Quan
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Yingshan Han
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Olga Golubkov
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Ilinca Ibanescu
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Bluma Brenner
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | | | - Mark A Wainberg
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada.,Department of Medicine, McGill University, Montreal, Quebec, Canada.,Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
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53
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Tarasuk M, Songprakhon P, Chimma P, Sratongno P, Na-Bangchang K, Yenchitsomanus PT. Alpha-mangostin inhibits both dengue virus production and cytokine/chemokine expression. Virus Res 2017; 240:180-189. [PMID: 28864423 DOI: 10.1016/j.virusres.2017.08.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 08/10/2017] [Accepted: 08/23/2017] [Indexed: 12/21/2022]
Abstract
Since severe dengue virus (DENV) infection in humans associates with both high viral load and massive cytokine production - referred to as "cytokine storm", an ideal drug for treatment of DENV infection should efficiently inhibit both virus production and cytokine expression. In searching for such an ideal drug, we discovered that α-mangostin (α-MG), a major bioactive compound purified from the pericarp of the mangosteen fruit (Garcinia mangostana Linn), which has been used in traditional medicine for several conditions including trauma, diarrhea, wound infection, pain, fever, and convulsion, inhibits both DENV production in cultured hepatocellular carcinoma HepG2 and Huh-7 cells, and cytokine/chemokine expression in HepG2 cells. α-MG could also efficiently inhibit all four serotypes of DENV. Treatment of DENV-infected cells with α-MG (20μM) significantly reduced the infection rates of four DENV serotypes by 47-55%. α-MG completely inhibited production of DENV-1 and DENV-3, and markedly reduced production of DENV-2 and DENV-4 by 100 folds. Furthermore, it could markedly reduce cytokine (IL-6 and TNF-α) and chemokine (RANTES, MIP-1β, and IP-10) transcription. These actions of α-MG are more potent than those of antiviral agent (ribavirin) and anti-inflammatory drug (dexamethasone). Thus, α-MG is potential to be further developed as therapeutic agent for DENV infection.
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Affiliation(s)
- Mayuri Tarasuk
- Graduate Program in Bioclinical Sciences, Chulabhorn International College of Medicine, Thammasat University, Pathumthani, 12121, Thailand
| | - Pucharee Songprakhon
- Division of Molecular Medicine, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Pattamawan Chimma
- Research Division, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand; Center for Emerging and Neglected Infectious Disease, Mahidol University, Bangkok 73170, Thailand
| | - Panudda Sratongno
- Research Division, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand; Center for Emerging and Neglected Infectious Disease, Mahidol University, Bangkok 73170, Thailand
| | - Kesara Na-Bangchang
- Graduate Program in Bioclinical Sciences, Chulabhorn International College of Medicine, Thammasat University, Pathumthani, 12121, Thailand
| | - Pa-Thai Yenchitsomanus
- Division of Molecular Medicine, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
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54
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Brand C, Bisaillon M, Geiss BJ. Organization of the Flavivirus RNA replicase complex. WILEY INTERDISCIPLINARY REVIEWS-RNA 2017; 8. [PMID: 28815931 DOI: 10.1002/wrna.1437] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/09/2017] [Accepted: 07/13/2017] [Indexed: 12/20/2022]
Abstract
Flaviviruses, such as dengue, Japanese encephalitis, West Nile, yellow fever, and Zika viruses, are serious human pathogens that cause significant morbidity and mortality globally each year. Flaviviruses are single-stranded, positive-sense RNA viruses, and encode two multidomain proteins, NS3 and NS5, that possess all enzymatic activities required for genome replication and capping. NS3 and NS5 interact within virus-induced replication compartments to form the RNA genome replicase complex. Although the individual enzymatic activities of both proteins have been extensively studied and are well characterized, there are still gaps in our understanding of how they interact to efficiently coordinate their respective activities during positive-strand RNA synthesis and capping. Here, we discuss what is known about the structures and functions of the NS3 and NS5 proteins and propose a preliminary NS3:NS5:RNA interaction model based on a large body of literature about how the viral enzymes function, physical restraints between NS3 and NS5, as well as critical steps in the replication process. WIREs RNA 2017, 8:e1437. doi: 10.1002/wrna.1437 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Carolin Brand
- Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Martin Bisaillon
- Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Brian J Geiss
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA.,School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA
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55
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Kumar S, Subbarao BL, Kumari R, Hallan V. Molecular characterization of a novel cryptic virus infecting pigeonpea plants. PLoS One 2017; 12:e0181829. [PMID: 28771507 PMCID: PMC5542627 DOI: 10.1371/journal.pone.0181829] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 07/08/2017] [Indexed: 12/24/2022] Open
Abstract
A new member of the genus Deltapartitivirus was identified containing three dsRNAs with an estimated size of 1.71, 1.49 and 1.43 kb. The dsRNAs were extracted from symptomless pigeonpea [Cajanus cajan (L.) Millspaugh] plants cv. Erra Kandulu. This new virus with 4.64 kb genome was tentatively named Arhar cryptic virus-1 (ArCV-1). The genomic RNAs were amplified and characterized by sequence independent single primer amplification. The dsRNAs shared a highly conserved 16 nt 5' non-coding region (5'-GATAATGATCCAAGGA-3'). The largest dsRNA (dsRNA-1) was identified as the viral RNA dependent RNA polymerase (replicase), predicted to encode a putative 55.34 kDa protein (P1). The two other smaller dsRNAs (dsRNA-2 and dsRNA-3) predicted to encode for putative capsid proteins of 38.50kDa (P2) and 38.51kDa (P3), respectively. Phylogenetic analysis indicated that ArCV-1 formed a clade together with Fragaria chiloensis cryptic virus, Rosa multiflora cryptic virus and Rose cryptic virus-1, indicating that ArCV-1 could be a new member of the genus Deltapartitivirus. ArCV-1 3Dpol structure revealed several interesting features. The 3Dpol in its full-length shares structural similarities with members of the family Caliciviridaeand family Picornaviridae. In addition, fourth dsRNA molecule (dsRNA-2A), not related to ArCV-1 genome, was found in the same plant tissue. The dsRNA-2A (1.6 kb) encodes a protein (P4), with a predicted size of 44.5 kDa. P4 shares similarity with coat protein genes of several cryptic viruses, in particular the bipartite cryptic viruses including Raphanus sativus cryptic virus-3. This is the first report of occurrence of a cryptic virus in pigeonpea plants.
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Affiliation(s)
- Surender Kumar
- Academy of Scientific and Innovative Research (AcSIR), CSIR-Institute of Himalayan Bioresource Technology (CSIR-IHBT) Campus, Palampur, India
- Department of Biotechnology, Plant Virus Lab, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India
| | | | - Reenu Kumari
- Department of Biotechnology, Plant Virus Lab, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India
| | - Vipin Hallan
- Department of Biotechnology, Plant Virus Lab, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India
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56
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Xu HT, Colby-Germinario SP, Hassounah SA, Fogarty C, Osman N, Palanisamy N, Han Y, Oliveira M, Quan Y, Wainberg MA. Evaluation of Sofosbuvir (β-D-2'-deoxy-2'-α-fluoro-2'-β-C-methyluridine) as an inhibitor of Dengue virus replication<sup/>. Sci Rep 2017; 7:6345. [PMID: 28740124 PMCID: PMC5524696 DOI: 10.1038/s41598-017-06612-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/31/2017] [Indexed: 12/26/2022] Open
Abstract
We evaluated Sofosbuvir (SOF), the anti-hepatitis C virus prodrug of β-d-2'-deoxy-2'-α-fluoro-2'-β-C-methyluridine-5'-monophosphate, for potential inhibitory activity against DENV replication. Both cell-based and biochemical assays, based on use of purified DENV full-length NS5 enzyme, were studied. Cytopathic effect protection and virus yield reduction assays confirmed that SOF possessed anti-DENV activity in cell culture with a 50% effective concentration (EC50) of 4.9 µM and 1.4 µM respectively. Real-time RT-PCR verified that SOF inhibits generation of viral RNA with an EC50 of 9.9 µM. Purified DENV NS5 incorporated the active triphosphate form (SOF-TP) into nascent RNA, causing chain-termination. Relative to the natural UTP, the incorporation efficiency of SOF-TP was low (discrimination value = 327.5). In a primer extension assay, SOF-TP was active against DENV NS5 wild-type polymerase activity with an IC50 of 14.7 ± 2.5 µM. The S600T substitution in the B Motif of DENV polymerase conferred 4.3-fold resistance to SOF-TP; this was due to decreased incorporation efficiency rather than enhanced excision of the incorporated SOF nucleotide. SOF has antiviral activity against DENV replication. The high discrimination value in favor of UTP in enzyme assays may not necessarily preclude antiviral activity in cells. SOF may be worthy of evaluation against severe DENV infections in humans.
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Affiliation(s)
- Hong-Tao Xu
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.
| | - Susan P Colby-Germinario
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Said A Hassounah
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Clare Fogarty
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Nathan Osman
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Navaneethan Palanisamy
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.,Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada.,HBIGS, University of Heidelberg, Heidelberg, Germany
| | - Yingshan Han
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Maureen Oliveira
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Yudong Quan
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Mark A Wainberg
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.,Department of Medicine, McGill University, Montreal, Quebec, Canada.,Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
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57
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Targeting heat shock factor 1 as an antiviral strategy against dengue virus replication in vitro and in vivo. Antiviral Res 2017; 145:44-53. [PMID: 28733114 DOI: 10.1016/j.antiviral.2017.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 07/12/2017] [Accepted: 07/13/2017] [Indexed: 11/22/2022]
Abstract
Fever onset is correlated with viremia in dengue virus (DENV) patients. Heat shock factor 1 (HSF1), a heat stress response host transcription factor, plays a crucial role in regulating multiple cellular functions, as well as the onset of infectious diseases. This study evaluated the role of HSF1 in DENV replication as a means of regulating DENV infection in vitro and in vivo. DENV infection activated HSF1 in both Ca2+ and protein kinase A-dependent manners. Inhibiting HSF1 effectively reduced DENV replication, not only in THP-1 cells but also in primary human monocytes. Activated HSF1 contributed to DENV replication by upregulating autophagy-related protein (Atg) 7, as autophagy is crucial for virus replication. Heat stress also activated HSF1, which in turn facilitated DENV replication. Activated HSF1, the increased Atg7, and autophagic induction were founded in the DENV-infected brains and pharmacologically inhibiting HSF1 reduced autophagy, viral protein expression, neuropathy, and mortality. These results provide new insight into HSF1 as a novel host factor for DENV infection through its role in facilitating autophagy-regulated viral replication in the brains.
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58
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Teramoto T, Balasubramanian A, Choi KH, Padmanabhan R. Serotype-specific interactions among functional domains of dengue virus 2 nonstructural proteins (NS) 5 and NS3 are crucial for viral RNA replication. J Biol Chem 2017; 292:9465-9479. [PMID: 28396347 DOI: 10.1074/jbc.m117.775643] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 03/21/2017] [Indexed: 11/06/2022] Open
Abstract
Four serotypes of mosquito-borne dengue virus (DENV), evolved from a common ancestor, are human pathogens of global significance for which there is no vaccine or antiviral drug available. The N-terminal domain of DENV NS5 has guanylyltransferase and methyltransferase (MTase), and the C-terminal region has the polymerase (POL), all of which are important for 5'-capping and RNA replication. The crystal structure of NS5 shows it as a dimer, but the functional evidence for NS5 dimer is lacking. Our studies showed that the substitution of DENV2 NS5 MTase or POL for DENV4 NS5 within DENV2 RNA resulted in a severe attenuation of replication in the transfected BHK-21 cells. A replication-competent species was evolved with the acquired mutations in the DENV2 and DENV4 NS5 MTase or POL domain or in the DENV2 NS3 helicase domain in the DENV2 chimera RNAs by repeated passaging of infected BHK-21 or mosquito cells. The linker region of seven residues in NS5, rich in serotype-specific residues, is important for the recovery of replication fitness in the chimera RNA. Our results, taken together, provide genetic evidence for a serotype-specific interaction between NS3 and NS5 as well as specific interdomain interaction within NS5 required for RNA replication. Genome-wide RNAseq analysis revealed the distribution of adaptive mutations in RNA quasispecies. Those within NS3 and NS5 are located at the surface and/or within the NS5 dimer interface, providing a functional significance to the crystal structure NS5 dimer.
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Affiliation(s)
- Tadahisa Teramoto
- From the Department of Microbiology and Immunology, School of Medicine, Georgetown University, Washington, D. C. 20057 and
| | - Anuradha Balasubramanian
- From the Department of Microbiology and Immunology, School of Medicine, Georgetown University, Washington, D. C. 20057 and
| | - Kyung H Choi
- the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555-0156
| | - Radhakrishnan Padmanabhan
- From the Department of Microbiology and Immunology, School of Medicine, Georgetown University, Washington, D. C. 20057 and
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59
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Zhao B, Yi G, Du F, Chuang YC, Vaughan RC, Sankaran B, Kao CC, Li P. Structure and function of the Zika virus full-length NS5 protein. Nat Commun 2017; 8:14762. [PMID: 28345656 PMCID: PMC5378950 DOI: 10.1038/ncomms14762] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 01/30/2017] [Indexed: 12/11/2022] Open
Abstract
The recent outbreak of Zika virus (ZIKV) has infected over 1 million people in over 30 countries. ZIKV replicates its RNA genome using virally encoded replication proteins. Nonstructural protein 5 (NS5) contains a methyltransferase for RNA capping and a polymerase for viral RNA synthesis. Here we report the crystal structures of full-length NS5 and its polymerase domain at 3.0 Å resolution. The NS5 structure has striking similarities to the NS5 protein of the related Japanese encephalitis virus. The methyltransferase contains in-line pockets for substrate binding and the active site. Key residues in the polymerase are located in similar positions to those of the initiation complex for the hepatitis C virus polymerase. The polymerase conformation is affected by the methyltransferase, which enables a more efficiently elongation of RNA synthesis in vitro. Overall, our results will contribute to future studies on ZIKV infection and the development of inhibitors of ZIKV replication. Zika virus infection can cause human birth defects and Guillain-Barré syndrome. Here the authors present the structures of the full-length nonstructural protein 5 and its RNA-dependent RNA polymerase domain of Zika virus, which are targets for inhibitors of virus replication.
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Affiliation(s)
- Baoyu Zhao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Guanghui Yi
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Fenglei Du
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Yin-Chih Chuang
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Robert C Vaughan
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Banumathi Sankaran
- Molecular Biophysics and Integrated Bioimaging, Berkeley Center for Structural Biology, 1 Cyclotron Road, Lawrence Berkeley National Lab, Berkeley 94720, USA
| | - C Cheng Kao
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Pingwei Li
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
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60
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Non-Canonical Roles of Dengue Virus Non-Structural Proteins. Viruses 2017; 9:v9030042. [PMID: 28335410 PMCID: PMC5371797 DOI: 10.3390/v9030042] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/06/2017] [Accepted: 03/08/2017] [Indexed: 12/15/2022] Open
Abstract
The Flaviviridae family comprises a number of human pathogens, which, although sharing structural and functional features, cause diseases with very different outcomes. This can be explained by the plurality of functions exerted by the few proteins coded by viral genomes, with some of these functions shared among members of a same family, but others being unique for each virus species. These non-canonical functions probably have evolved independently and may serve as the base to the development of specific therapies for each of those diseases. Here it is discussed what is currently known about the non-canonical roles of dengue virus (DENV) non-structural proteins (NSPs), which may account for some of the effects specifically observed in DENV infection, but not in other members of the Flaviviridae family. This review explores how DENV NSPs contributes to the physiopathology of dengue, evasion from host immunity, metabolic changes, and redistribution of cellular components during infection.
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61
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Wang CC, Hsu YC, Wu HC, Wu HN. Insights into the coordinated interplay of the sHP hairpin and its co-existing and mutually-exclusive dengue virus terminal RNA elements for viral replication. Virology 2017; 505:56-70. [PMID: 28235683 DOI: 10.1016/j.virol.2017.02.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 02/08/2017] [Accepted: 02/10/2017] [Indexed: 12/15/2022]
Abstract
Terminal RNA elements of the dengue virus (DENV) genome are necessary for balanced stability of linear and circular conformations during replication. We examined the small hairpin (sHP) and co-existing and mutually-exclusive terminal RNA elements by mutagenesis analysis, compensatory mutation screening, and by probing with RNA fragments to explore localized RNA folding and long-range RNA interactions. We found that the first base pair of the sHP and the stability of SLB and the 3'SL bottom stem affected circularization; sHPgc/C10631G+G10644C prohibited circularization, sHPuG accelerated and stabilized 5'-to-3' RNA hybridization, while C94A and A97G and C10649 mutations loosened SLB and 3'SL, respectively, for circularization. sHPuG+C10649G induced circularization and impeded replication, whereas point mutations that loosened the UAR or DAR ds region, strengthened the sHP, or reinforced the 3'SL bottom stem, rescued the replication deficiency. Overall, we reveal structural and sequence features and interplay of DENV genome terminal RNA elements essential to viral replication.
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Affiliation(s)
- Chun-Chung Wang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Yu-Chen Hsu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Hsin-Chieh Wu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China; Faculty of Life Sciences and Institute of Genomic Sciences, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Huey-Nan Wu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
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62
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Potisopon S, Ferron F, Fattorini V, Selisko B, Canard B. Substrate selectivity of Dengue and Zika virus NS5 polymerase towards 2'-modified nucleotide analogues. Antiviral Res 2016; 140:25-36. [PMID: 28041959 DOI: 10.1016/j.antiviral.2016.12.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 12/28/2016] [Accepted: 12/29/2016] [Indexed: 12/11/2022]
Abstract
In targeting the essential viral RNA-dependent RNA-polymerase (RdRp), nucleotide analogues play a major role in antiviral therapies. In the Flaviviridae family, the hepatitis C virus (HCV) can be eradicated from chronically infected patients using a combination of drugs which generally include the 2'-modified uridine analogue Sofosbuvir, delivered as nucleotide prodrug. Dengue and Zika viruses are emerging flaviviruses whose RdRp is closely related to that of HCV, yet no nucleoside drug has been clinically approved for these acute infections. We have purified dengue and Zika virus full-length NS5, the viral RdRps, and used them to assemble a stable binary complex made of NS5 and virus-specific RNA primer/templates. The complex was used to assess the selectivity of NS5 towards nucleotide analogues bearing modifications at the 2'-position. We show that dengue and Zika virus RdRps exhibit the same discrimination pattern: 2'-O-Me > 2'-C-Me-2'-F > 2'-C-Me nucleoside analogues, unlike HCV RdRp for which the presence of the 2'-F is beneficial rendering the discrimination pattern 2'-O-Me > 2'-C-Me ≥ 2'-C-Me-2'-F. Both 2'-C-Me and 2'-C-Me-2'-F analogues act as non-obligate RNA chain terminators. The dengue and Zika NS5 nucleotide selectivity towards 2'-modified NTPs mirrors potency of the corresponding analogues in infected cell cultures.
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Affiliation(s)
- Supanee Potisopon
- Aix-Marseille Université, AFMB (Laboratoire d'Architecture et Fonction de Macromolécules Biologiques) UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France; CNRS, AFMB UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France
| | - François Ferron
- Aix-Marseille Université, AFMB (Laboratoire d'Architecture et Fonction de Macromolécules Biologiques) UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France; CNRS, AFMB UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France
| | - Véronique Fattorini
- Aix-Marseille Université, AFMB (Laboratoire d'Architecture et Fonction de Macromolécules Biologiques) UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France; CNRS, AFMB UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France
| | - Barbara Selisko
- Aix-Marseille Université, AFMB (Laboratoire d'Architecture et Fonction de Macromolécules Biologiques) UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France; CNRS, AFMB UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France.
| | - Bruno Canard
- Aix-Marseille Université, AFMB (Laboratoire d'Architecture et Fonction de Macromolécules Biologiques) UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France; CNRS, AFMB UMR 7257, 163 Avenue de Luminy, 13288 Marseille, France.
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63
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Tang Y, Yeh YT, Chen H, Yu C, Gao X, Diao Y. Comparison of four molecular assays for the detection of Tembusu virus. Avian Pathol 2016; 44:379-85. [PMID: 26443062 DOI: 10.1080/03079457.2015.1061650] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Tembusu virus (TMUV) belongs to the genus Flavivirus that may cause severe egg drop in ducks. In order to evaluate the most efficient TMUV detection method, the performances of a conventional RT-PCR (C-RT-PCR), a semi-nested PCR (SN-RT-PCR), a reverse-transcriptase real-time quantitative PCR (Q-RT-PCR), and a reverse-transcription loop-mediated isothermal amplification (RT-LAMP) targeting the TMUV virus-specific NS5 gene were examined. In order to compare the sensitivity of these four techniques, two templates were used: (1) plasmid DNA that contained a partial region of the NS5 gene and (2) genomic RNA from TMUV-positive cell culture supernatants. The sensitivities using plasmid DNA detection by C-RT-PCR, SN-RT-PCR, Q-RT-PCR, and RT-LAMP were 2 × 10(4) copies/μL, 20 copies/μL, 2 copies/μL, and 20 copies/μL, respectively. The sensitivities using genomic RNA for the C-RT-PCR, SN-RT-PCR, Q-RT-PCR, and RT-LAMP were 100 pg/tube, 100, 10, and 100 fg/tube, respectively. All evaluated assays were specific for TMUV detection. The TMUV-specific RNA was detected in cloacal swabs from experimentally infected ducks using these four methods with different rates (52-92%), but not in the control (non-inoculated) samples. The sensitivities of RT-PCR, SN-RT-PCR, Q-RT-PCR, and RT-LAMP performed with cloacal swabs collected from suspected TMUV infected ducks within 2 weeks of severe egg-drop were 38/69 (55.1%), 52/69 (75.4%), 57/69 (82.6%), and 55/69 (79.7%), respectively. In conclusion, both RT-LAMP and Q-RT-PCR can provide a rapid diagnosis of TMUV infection, but RT-LAMP is more useful in TMUV field situations or poorly equipped laboratories.
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Affiliation(s)
- Yi Tang
- a College of Veterinary Medicine , Shandong Agricultural University , Tai'an , Shandong 271018 , People's Republic of China.,b Department of Veterinary and Biomedical Sciences , The Pennsylvania State University , University Park , PA 16802 , USA
| | - Yin-Ting Yeh
- c Department of Biomedical Engineering , The Pennsylvania State University , University Park , PA 16802 , USA
| | - Hao Chen
- a College of Veterinary Medicine , Shandong Agricultural University , Tai'an , Shandong 271018 , People's Republic of China
| | - Chunmei Yu
- a College of Veterinary Medicine , Shandong Agricultural University , Tai'an , Shandong 271018 , People's Republic of China
| | - Xuhui Gao
- a College of Veterinary Medicine , Shandong Agricultural University , Tai'an , Shandong 271018 , People's Republic of China
| | - Youxiang Diao
- a College of Veterinary Medicine , Shandong Agricultural University , Tai'an , Shandong 271018 , People's Republic of China
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64
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Chang DC, Hoang LT, Mohamed Naim AN, Dong H, Schreiber MJ, Hibberd ML, Tan MJA, Shi PY. Evasion of early innate immune response by 2'-O-methylation of dengue genomic RNA. Virology 2016; 499:259-266. [PMID: 27716465 PMCID: PMC7172056 DOI: 10.1016/j.virol.2016.09.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 11/28/2022]
Abstract
Dengue virus (DENV) is the most prevalent mosquito-borne virus pathogen in humans. There is currently no antiviral therapeutic or widely available vaccine against dengue infection. The DENV RNA genome is methylated on its 5′ cap by its NS5 protein. DENV bearing a single E216A point mutation in NS5 loses 2′-O-methylation of its genome. While this mutant DENV is highly attenuated and immunogenic, the mechanism of this attenuation has not been elucidated. In this study, we find that replication of this mutant DENV is attenuated very early during infection. This early attenuation is not dependent on a functional type I interferon response and coincides with early activation of the innate immune response. Taken together, our data suggest that 2′-O-methylation of DENV genomic RNA is important for evasion of the host immune response during the very early stages of infection as the virus seeks to establish infection. Dengue virus lacking 2′-O-methylation of its genome is attenuated and immunogenic. This mutant virus is attenuated during the early stages of infection. 2′-O-methylation of virus RNA is important for evading the innate immune response.
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Affiliation(s)
| | - Long T Hoang
- Infectious Diseases, Genome Institute of Singapore, Singapore
| | | | | | | | - Martin L Hibberd
- Infectious Diseases, Genome Institute of Singapore, Singapore; Pathogen Molecular Biology, London School of Hygiene & Tropical Medicine, London, UK
| | | | - Pei-Yong Shi
- Novartis Institute of Tropical Diseases, Singapore; Department of Biochemistry and Molecular Biology, Department of Pharmacology and Toxicology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA.
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65
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Liu ZY, Li XF, Jiang T, Deng YQ, Ye Q, Zhao H, Yu JY, Qin CF. Viral RNA switch mediates the dynamic control of flavivirus replicase recruitment by genome cyclization. eLife 2016; 5. [PMID: 27692070 PMCID: PMC5101012 DOI: 10.7554/elife.17636] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 09/30/2016] [Indexed: 12/23/2022] Open
Abstract
Viral replicase recruitment and long-range RNA interactions are essential for RNA virus replication, yet the mechanism of their interplay remains elusive. Flaviviruses include numerous important human pathogens, e.g., dengue virus (DENV) and Zika virus (ZIKV). Here, we revealed a highly conserved, conformation-tunable cis-acting element named 5′-UAR-flanking stem (UFS) in the flavivirus genomic 5′ terminus. We demonstrated that the UFS was critical for efficient NS5 recruitment and viral RNA synthesis in different flaviviruses. Interestingly, stabilization of the DENV UFS impaired both genome cyclization and vRNA replication. Moreover, the UFS unwound in response to genome cyclization, leading to the decreased affinity of NS5 for the viral 5′ end. Thus, we propose that the UFS is switched by genome cyclization to regulate dynamic RdRp binding for vRNA replication. This study demonstrates that the UFS enables communication between flavivirus genome cyclization and RdRp recruitment, highlighting the presence of switch-like mechanisms among RNA viruses. DOI:http://dx.doi.org/10.7554/eLife.17636.001 Flaviviruses include a large family of viruses that are harmful to human health, such as dengue virus, West Nile virus and Zika virus. Understanding the details of the life cycle of these viruses is important for better controlling and treating the diseases that they cause. The genetic information of flaviviruses is stored in single-stranded molecules of RNA. To form new copies of a virus, the RNA must be replicated in a process that involves two critical steps. First, an enzyme called viral RNA polymerase NS5 must be recruited to a specific end of the RNA strand (known as the 5′ end). Then, the ends of the RNA strand bind together to form a circular loop. However, little is known about whether these two processes are linked, or how they are regulated. Using bioinformatics, biochemical and reverse genetics approaches, Liu et al. have now identified a new section of RNA in the 5′ end of the flavivirus RNA, named the 5′-UAR-flanking stem (or UFS for short), which is critical for viral replication. The UFS plays an important role in efficiently recruiting the NS5 viral RNA polymerase to the 5′ end of the flavivirus RNA. After the RNA forms a circle, the UFS unwinds. This makes the NS5 polymerase less likely to bind to the 5′ end of the RNA. Stabilizing the structure of the UFS impairs the ability of the RNA strand to form a circle, and hence reduces the ability of the RNA to replicate. Thus, the UFS links and enables communication between the processes that form the flavivirus RNA into a circle and that recruit the viral RNA polymerase to the RNA. The structural basis of the interaction between the flavivirus RNA 5′ end, including the UFS element, and the viral RNA polymerase now deserves further investigation. It will be also important to explore whether other types of viruses regulate their replication via a similar mechanism. DOI:http://dx.doi.org/10.7554/eLife.17636.002
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Affiliation(s)
- Zhong-Yu Liu
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Xiao-Feng Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Tao Jiang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Yong-Qiang Deng
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Qing Ye
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Hui Zhao
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Jiu-Yang Yu
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Cheng-Feng Qin
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
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66
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Li Y, Wong YL, Lee MY, Li Q, Wang QY, Lescar J, Shi PY, Kang C. Secondary Structure and Membrane Topology of the Full-Length Dengue Virus NS4B in Micelles. Angew Chem Int Ed Engl 2016; 55:12068-72. [DOI: 10.1002/anie.201606609] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Indexed: 01/15/2023]
Affiliation(s)
- Yan Li
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); 31 Biopolis Way, Nanos, #03-01 Singapore 138669 Singapore
| | - Ying Lei Wong
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); 31 Biopolis Way, Nanos, #03-01 Singapore 138669 Singapore
| | - Michelle Yueqi Lee
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); 31 Biopolis Way, Nanos, #03-01 Singapore 138669 Singapore
| | - Qingxin Li
- Institute of Chemical & Engineering Sciences; Agency for Science, Technology, and Research; 1 Pesek Road, Jurong Island Singapore 627833 Singapore
| | - Qing-Yin Wang
- Novartis Institute for Tropical Diseases; Singapore Singapore
| | - Julien Lescar
- School of Biological Sciences; Nanyang Technological University; Singapore Singapore
| | - Pei-Yong Shi
- Department of Biochemistry & Molecular Biology, Department of Pharmacology & Toxicology; Sealy Center for Structural Biology & Molecular Biophysics; University of Texas Medical Branch; Galveston TX USA
| | - CongBao Kang
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); 31 Biopolis Way, Nanos, #03-01 Singapore 138669 Singapore
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67
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Secondary Structure and Membrane Topology of the Full-Length Dengue Virus NS4B in Micelles. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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68
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Lim SP, Noble CG, Seh CC, Soh TS, El Sahili A, Chan GKY, Lescar J, Arora R, Benson T, Nilar S, Manjunatha U, Wan KF, Dong H, Xie X, Shi PY, Yokokawa F. Potent Allosteric Dengue Virus NS5 Polymerase Inhibitors: Mechanism of Action and Resistance Profiling. PLoS Pathog 2016; 12:e1005737. [PMID: 27500641 PMCID: PMC4976923 DOI: 10.1371/journal.ppat.1005737] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 06/09/2016] [Indexed: 11/24/2022] Open
Abstract
Flaviviruses comprise major emerging pathogens such as dengue virus (DENV) or Zika virus (ZIKV). The flavivirus RNA genome is replicated by the RNA-dependent-RNA polymerase (RdRp) domain of non-structural protein 5 (NS5). This essential enzymatic activity renders the RdRp attractive for antiviral therapy. NS5 synthesizes viral RNA via a “de novo” initiation mechanism. Crystal structures of the flavivirus RdRp revealed a “closed” conformation reminiscent of a pre-initiation state, with a well ordered priming loop that extrudes from the thumb subdomain into the dsRNA exit tunnel, close to the “GDD” active site. To-date, no allosteric pockets have been identified for the RdRp, and compound screening campaigns did not yield suitable drug candidates. Using fragment-based screening via X-ray crystallography, we found a fragment that bound to a pocket of the apo-DENV RdRp close to its active site (termed “N pocket”). Structure-guided improvements yielded DENV pan-serotype inhibitors of the RdRp de novo initiation activity with nano-molar potency that also impeded elongation activity at micro-molar concentrations. Inhibitors exhibited mixed inhibition kinetics with respect to competition with the RNA or GTP substrate. The best compounds have EC50 values of 1–2 μM against all four DENV serotypes in cell culture assays. Genome-sequencing of compound-resistant DENV replicons, identified amino acid changes that mapped to the N pocket. Since inhibitors bind at the thumb/palm interface of the RdRp, this class of compounds is proposed to hinder RdRp conformational changes during its transition from initiation to elongation. This is the first report of a class of pan-serotype and cell-active DENV RdRp inhibitors. Given the evolutionary conservation of residues lining the N pocket, these molecules offer insights to treat other serious conditions caused by flaviviruses. Dengue virus (DENV) is the world’s most prevalent mosquito-borne viral disease and nearly 40% of the world’s population is at risk of infection. Currently, no specific drugs are available to treat dengue or other flaviviral diseases. DENV NS5 is a large protein of 900 amino acids composed of two domains with key enzymatic activities for viral RNA replication in the host cell and constitutes a prime target for the design of anti-viral inhibitors. We performed a fragment-based screening by X-ray crystallography targeting the DENV NS5 polymerase and identified an allosteric binding pocket at the base of the thumb subdomain close to the enzyme active site. Potent inhibitors active in both DENV polymerase biochemical and cell-based assays were developed through structure-guided design. Resistant virus replicons grown in the presence of the inhibitor, harbored amino acid changes that mapped to the compound binding site. The proposed mode of action for this class of inhibitors is by impeding RdRp protein conformational changes during the transition from initiation to elongation phase of enzyme activity.
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Affiliation(s)
| | | | | | - Tingjin Sherryl Soh
- Novartis Institute for Tropical Diseases, Singapore.,School of Biological Sciences, Nanyang Technological University, Singapore
| | - Abbas El Sahili
- School of Biological Sciences, Nanyang Technological University, Singapore
| | | | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, Singapore.,UPMC UMRS CR7-CNRS ERL 8255-INSERM U1135 Centre d'Immunologie et des Maladies Infectieuses, Centre Hospitalier Universitaire Pitié-Salpêtrière, Faculté de Médecine Pierre et Marie Curie, Paris, France
| | - Rishi Arora
- Novartis Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Timothy Benson
- Novartis Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Shahul Nilar
- Novartis Institute for Tropical Diseases, Singapore
| | | | - Kah Fei Wan
- Novartis Institute for Tropical Diseases, Singapore
| | | | - Xuping Xie
- Novartis Institute for Tropical Diseases, Singapore
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, Singapore
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69
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De Maio FA, Risso G, Iglesias NG, Shah P, Pozzi B, Gebhard LG, Mammi P, Mancini E, Yanovsky MJ, Andino R, Krogan N, Srebrow A, Gamarnik AV. The Dengue Virus NS5 Protein Intrudes in the Cellular Spliceosome and Modulates Splicing. PLoS Pathog 2016; 12:e1005841. [PMID: 27575636 PMCID: PMC5004807 DOI: 10.1371/journal.ppat.1005841] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 08/03/2016] [Indexed: 11/22/2022] Open
Abstract
Dengue virus NS5 protein plays multiple functions in the cytoplasm of infected cells, enabling viral RNA replication and counteracting host antiviral responses. Here, we demonstrate a novel function of NS5 in the nucleus where it interferes with cellular splicing. Using global proteomic analysis of infected cells together with functional studies, we found that NS5 binds spliceosome complexes and modulates endogenous splicing as well as minigene-derived alternative splicing patterns. In particular, we show that NS5 alone, or in the context of viral infection, interacts with core components of the U5 snRNP particle, CD2BP2 and DDX23, alters the inclusion/exclusion ratio of alternative splicing events, and changes mRNA isoform abundance of known antiviral factors. Interestingly, a genome wide transcriptome analysis, using recently developed bioinformatics tools, revealed an increase of intron retention upon dengue virus infection, and viral replication was improved by silencing specific U5 components. Different mechanistic studies indicate that binding of NS5 to the spliceosome reduces the efficiency of pre-mRNA processing, independently of NS5 enzymatic activities. We propose that NS5 binding to U5 snRNP proteins hijacks the splicing machinery resulting in a less restrictive environment for viral replication.
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Affiliation(s)
| | - Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Priya Shah
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Berta Pozzi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Pablo Mammi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | | | - Raul Andino
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Nevan Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Anabella Srebrow
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
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70
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Amraiz D, Zaidi NUSS, Fatima M. Development of robust in vitro RNA-dependent RNA polymerase assay as a possible platform for antiviral drug testing against dengue. Enzyme Microb Technol 2016; 92:26-30. [PMID: 27542741 PMCID: PMC7112394 DOI: 10.1016/j.enzmictec.2016.06.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 06/16/2016] [Accepted: 06/16/2016] [Indexed: 12/16/2022]
Abstract
Successful expression of recombinant RNA dependent RNA polymerase (RdRp) of DENV-2 in E. coli cells. Two step purification of enzymatically active RdRp protein using Ni-NTA and size exclusion columns. High level production of RdRp with final yield of 6.5 mg protein from 1 L of culture. Demonstration of in vitro polymerase activity of RdRp using homopolymeric RNA template. Optimization of RdRp assay conditions such as protein concentration, GTP concentration and incubation time of the reaction.
NS5 is the largest and most conserved protein among the four dengue virus (DENV) serotypes. It has been the target of interest for antiviral drug development due to its major role in replication. NS5 consists of two domains, the N-terminal methyltransferase domain and C-terminal catalytic RNA-dependent RNA polymerase (RdRp) domain. It is an unstable protein and is prone to inactivation upon prolonged incubation at room temperature, thus affecting the inhibitor screening assays. In the current study, we expressed and purified DENV RdRp alone in Esherichia coli (E. coli) cells. The N-terminally His-tagged construct of DENV RdRp was transformed into E. coli expression strain BL-21 (DE3) pLysS cells. Protein expression was induced with isopropyl-β-D-thiogalactopyranoside (IPTG) at a final concentration of 0.4 mM. The induced cultures were then grown for 20 h at 18 °C and cells were harvested by centrifugation at 6000 x g for 15 min at 4 °C. The recombinant protein was purified using HisTrap affinity column (Ni-NTA) and then the sample was subjected to size exclusion chromatography, which successfully removed the degradation product obtained during the previous purification step. The in vitro polymerase activity of RdRp was successfully demonstrated using homopolymeric polycytidylic acid (poly(rC)) RNA template. This study describes the high level production of enzymatically active DENV RdRp protein which can be used to develop assays for testing large number of compounds in a high-throughput manner. RdRp has the de novo initiation activity and the in vitro polymerase assays for the protein provide a platform for highly robust and efficient antiviral compound screening systems.
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Affiliation(s)
- Deeba Amraiz
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
| | - Najam-Us-Sahar Sadaf Zaidi
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
| | - Munazza Fatima
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
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71
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Production of a Recombinant Dengue Virus 2 NS5 Protein and Potential Use as a Vaccine Antigen. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2016; 23:460-469. [PMID: 27030586 DOI: 10.1128/cvi.00081-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 03/23/2016] [Indexed: 12/25/2022]
Abstract
Dengue fever is caused by any of the four known dengue virus serotypes (DENV1 to DENV4) that affect millions of people worldwide, causing a significant number of deaths. There are vaccines based on chimeric viruses, but they still are not in clinical use. Anti-DENV vaccine strategies based on nonstructural proteins are promising alternatives to those based on whole virus or structural proteins. The DENV nonstructural protein 5 (NS5) is the main target of anti-DENV T cell-based immune responses in humans. In this study, we purified a soluble recombinant form of DENV2 NS5 expressed in Escherichia coli at large amounts and high purity after optimization of expression conditions and purification steps. The purified DENV2 NS5 was recognized by serum from DENV1-, DENV2-, DENV3-, or DENV4-infected patients in an epitope-conformation-dependent manner. In addition, immunization of BALB/c mice with NS5 induced high levels of NS5-specific antibodies and expansion of gamma interferon- and tumor necrosis factor alpha-producing T cells. Moreover, mice immunized with purified NS5 were partially protected from lethal challenges with the DENV2 NGC strain and with a clinical isolate (JHA1). These results indicate that the recombinant NS5 protein preserves immunological determinants of the native protein and is a promising vaccine antigen capable of inducing protective immune responses.
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72
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A Proline-Rich N-Terminal Region of the Dengue Virus NS3 Is Crucial for Infectious Particle Production. J Virol 2016; 90:5451-61. [PMID: 27009958 DOI: 10.1128/jvi.00206-16] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 03/17/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Dengue virus is currently the most important insect-borne viral human pathogen. Viral nonstructural protein 3 (NS3) is a key component of the viral replication machinery that performs multiple functions during viral replication and participates in antiviral evasion. Using dengue virus infectious clones and reporter systems to dissect each step of the viral life cycle, we examined the requirements of different domains of NS3 on viral particle assembly. A thorough site-directed mutagenesis study based on solvent-accessible surface areas of NS3 revealed that, in addition to being essential for RNA replication, different domains of dengue virus NS3 are critically required for production of infectious viral particles. Unexpectedly, point mutations in the protease, interdomain linker, or helicase domain were sufficient to abolish infectious particle formation without affecting translation, polyprotein processing, or RNA replication. In particular, we identified a novel proline-rich N-terminal unstructured region of NS3 that contains several amino acid residues involved in infectious particle formation. We also showed a new role for the interdomain linker of NS3 in virion assembly. In conclusion, we present a comprehensive genetic map of novel NS3 determinants for viral particle assembly. Importantly, our results provide evidence of a central role of NS3 in the coordination of both dengue virus RNA replication and particle formation. IMPORTANCE Dengue virus is an important human pathogen, and its prominence is expanding globally; however, basic aspects of its biology are still unclear, hindering the development of effective therapeutic and prophylactic treatments. Little is known about the initial steps of dengue and other flavivirus particle assembly. This process involves a complex interplay between viral and cellular components, making it an attractive antiviral target. Unpredictably, we identified spatially separated regions of the large NS3 viral protein as determinants for dengue virus particle assembly. NS3 is a multifunctional enzyme that participates in different steps of the viral life cycle. Using reporter systems to dissect different viral processes, we identified a novel N-terminal unstructured region of the NS3 protein as crucial for production of viral particles. Based on our findings, we propose new ideas that include NS3 as a possible scaffold for the viral assembly process.
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73
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Ecdysones from Zoanthus spp. with inhibitory activity against dengue virus 2. Bioorg Med Chem Lett 2016; 26:2344-8. [DOI: 10.1016/j.bmcl.2016.03.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/05/2016] [Accepted: 03/09/2016] [Indexed: 11/20/2022]
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74
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Zhang Z, Lee Y, Sivertsen A, Skjeseth G, Haugslien S, Clarke JL, Wang QC, Blystad DR. Low Temperature Treatment Affects Concentration and Distribution of Chrysanthemum Stunt Viroid in Argyranthemum. Front Microbiol 2016; 7:224. [PMID: 26973607 PMCID: PMC4777735 DOI: 10.3389/fmicb.2016.00224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/12/2016] [Indexed: 12/23/2022] Open
Abstract
Chrysanthemum stunt viroid (CSVd) can infect Argyranthemum and cause serious economic loss. Low temperature treatment combined with meristem culture has been applied to eradicate viroids from their hosts, but without success in eliminating CSVd from diseased Argyranthemum. The objectives of this work were to investigate (1) the effect of low temperature treatment combined with meristem culture on elimination of CSVd, (2) the effect of low temperature treatment on CSVd distribution pattern in shoot apical meristem (SAM), and (3) CSVd distribution in flowers and stems of two infected Argyranthemum cultivars. After treatment with low temperature combined with meristem tip culture, two CSVd-free plants were found in 'Border Dark Red', but none in 'Yellow Empire'. With the help of in situ hybridization, we found that CSVd distribution patterns in the SAM showed no changes in diseased 'Yellow Empire' following 5°C treatment, compared with non-treated plants. However, the CSVd-free area in SAM was enlarged in diseased 'Border Dark Red' following prolonged 5°C treatment. Localization of CSVd in the flowers and stems of infected 'Border Dark Red' and 'Yellow Empire' indicated that seeds could not transmit CSVd in these two cultivars, and CSVd existed in phloem. Results obtained in the study contributed to better understanding of the distribution of CSVd in systemically infected plants and the combination of low temperature treatment and meristem tip culture for production of viroid-free plants.
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Affiliation(s)
- Zhibo Zhang
- The Plant Health and Biotechnology Division, Norwegian Institute of Bioeconomy ResearchÅs, Norway
- State Key Laboratory of Crop Stress Biology for Arid Areas, Key Laboratory of Genetic Improvement of Horticultural Crops of Northwest China, Department of Plant Sciences, College of Horticulture, Northwest A&F UniversityYangling, China
| | - YeonKyeong Lee
- Department of Plant Sciences, Norwegian University of Life ScienceÅs, Norway
| | - Astrid Sivertsen
- Department of Plant Sciences, Norwegian University of Life ScienceÅs, Norway
| | - Gry Skjeseth
- Department of Plant Sciences, Norwegian University of Life ScienceÅs, Norway
| | - Sissel Haugslien
- The Plant Health and Biotechnology Division, Norwegian Institute of Bioeconomy ResearchÅs, Norway
| | - Jihong Liu Clarke
- The Plant Health and Biotechnology Division, Norwegian Institute of Bioeconomy ResearchÅs, Norway
| | - Qiao-Chun Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Key Laboratory of Genetic Improvement of Horticultural Crops of Northwest China, Department of Plant Sciences, College of Horticulture, Northwest A&F UniversityYangling, China
| | - Dag-Ragnar Blystad
- The Plant Health and Biotechnology Division, Norwegian Institute of Bioeconomy ResearchÅs, Norway
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75
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Klema VJ, Ye M, Hindupur A, Teramoto T, Gottipati K, Padmanabhan R, Choi KH. Dengue Virus Nonstructural Protein 5 (NS5) Assembles into a Dimer with a Unique Methyltransferase and Polymerase Interface. PLoS Pathog 2016; 12:e1005451. [PMID: 26895240 PMCID: PMC4760774 DOI: 10.1371/journal.ppat.1005451] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 01/22/2016] [Indexed: 01/07/2023] Open
Abstract
Flavivirus nonstructural protein 5 (NS5) consists of methyltransferase (MTase) and RNA-dependent RNA polymerase (RdRp) domains, which catalyze 5'-RNA capping/methylation and RNA synthesis, respectively, during viral genome replication. Although the crystal structure of flavivirus NS5 is known, no data about the quaternary organization of the functional enzyme are available. We report the crystal structure of dengue virus full-length NS5, where eight molecules of NS5 are arranged as four independent dimers in the crystallographic asymmetric unit. The relative orientation of each monomer within the dimer, as well as the orientations of the MTase and RdRp domains within each monomer, is conserved, suggesting that these structural arrangements represent the biologically relevant conformation and assembly of this multi-functional enzyme. Essential interactions between MTase and RdRp domains are maintained in the NS5 dimer via inter-molecular interactions, providing evidence that flavivirus NS5 can adopt multiple conformations while preserving necessary interactions between the MTase and RdRp domains. Furthermore, many NS5 residues that reduce viral replication are located at either the inter-domain interface within a monomer or at the inter-molecular interface within the dimer. Hence the X-ray structure of NS5 presented here suggests that MTase and RdRp activities could be coordinated as a dimer during viral genome replication.
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Affiliation(s)
- Valerie J. Klema
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Mengyi Ye
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Aditya Hindupur
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Tadahisa Teramoto
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D.C., United States of America
| | - Keerthi Gottipati
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Radhakrishnan Padmanabhan
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D.C., United States of America
| | - Kyung H. Choi
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail:
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76
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Identification of a Pyridoxine-Derived Small-Molecule Inhibitor Targeting Dengue Virus RNA-Dependent RNA Polymerase. Antimicrob Agents Chemother 2015; 60:600-8. [PMID: 26574011 DOI: 10.1128/aac.02203-15] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 11/10/2015] [Indexed: 01/14/2023] Open
Abstract
The viral RNA-dependent RNA polymerase (RdRp) activity of the dengue virus (DENV) NS5 protein is an attractive target for drug design. Here, we report the identification of a novel class of inhibitor (i.e., an active-site metal ion chelator) that acts against DENV RdRp activity. DENV RdRp utilizes a two-metal-ion mechanism of catalysis; therefore, we constructed a small library of compounds, through mechanism-based drug design, aimed at chelating divalent metal ions in the catalytic site of DENV RdRp. We now describe a pyridoxine-derived small-molecule inhibitor that targets DENV RdRp and show that 5-benzenesulfonylmethyl-3-hydroxy-4-hydroxymethyl-pyridine-2-carboxylic acid hydroxyamide (termed DMB220) inhibited the RdRp activity of DENV serotypes 1 to 4 at low micromolar 50% inhibitory concentrations (IC50s of 5 to 6.7 μM) in an enzymatic assay. The antiviral activity of DMB220 against DENV infection was also verified in a cell-based assay and showed a 50% effective concentration (EC50) of <3 μM. Enzyme assays proved that DMB220 was competitive with nucleotide incorporation. DMB220 did not inhibit the enzymatic activity of recombinant HIV-1 reverse transcriptase and showed only weak inhibition of HIV-1 integrase strand transfer activity, indicating high specificity for DENV RdRp. S600T substitution in the DENV RdRp, which was previously shown to confer resistance to nucleoside analogue inhibitors (NI), conferred 3-fold hypersusceptibility to DMB220, and enzymatic analyses showed that this hypersusceptibility may arise from the decreased binding/incorporation efficiency of the natural NTP substrate without significantly impacting inhibitor binding. Thus, metal ion chelation at the active site of DENV RdRp represents a viable anti-DENV strategy, and DMB220 is the first of a new class of DENV inhibitor.
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77
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Klema VJ, Padmanabhan R, Choi KH. Flaviviral Replication Complex: Coordination between RNA Synthesis and 5'-RNA Capping. Viruses 2015; 7:4640-56. [PMID: 26287232 PMCID: PMC4576198 DOI: 10.3390/v7082837] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 07/30/2015] [Accepted: 08/04/2015] [Indexed: 12/28/2022] Open
Abstract
Genome replication in flavivirus requires (-) strand RNA synthesis, (+) strand RNA synthesis, and 51-RNA capping and methylation. To carry out viral genome replication, flavivirus assembles a replication complex, consisting of both viral and host proteins, on the cytoplasmic side of the endoplasmic reticulum (ER) membrane. Two major components of the replication complex are the viral non-structural (NS) proteins NS3 and NS5. Together they possess all the enzymatic activities required for genome replication, yet how these activities are coordinated during genome replication is not clear. We provide an overview of the flaviviral genome replication process, the membrane-bound replication complex, and recent crystal structures of full-length NS5. We propose a model of how NS3 and NS5 coordinate their activities in the individual steps of (-) RNA synthesis, (+) RNA synthesis, and 51-RNA capping and methylation.
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Affiliation(s)
- Valerie J Klema
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, TX 77555-0647, USA.
| | - Radhakrishnan Padmanabhan
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, DC 20057, USA.
| | - Kyung H Choi
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston, Galveston, TX 77555-0647, USA.
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78
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Flexibility of NS5 Methyltransferase-Polymerase Linker Region Is Essential for Dengue Virus Replication. J Virol 2015; 89:10717-21. [PMID: 26269182 DOI: 10.1128/jvi.01239-15] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 08/03/2015] [Indexed: 11/20/2022] Open
Abstract
We examined the function of the conserved Val/Ile residue within the dengue virus NS5 interdomain linker (residues 263 to 272) by site-directed mutagenesis. Gly substitution or Gly/Pro insertion after the conserved residue increased the linker flexibility and created slightly attenuated viruses. In contrast, Pro substitution abolished virus replication by imposing rigidity in the linker and restricting NS5's conformational plasticity. Our biochemical and reverse genetics experiments demonstrate that NS5 utilizes conformational regulation to achieve optimum viral replication.
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79
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Padmanabhan R, Takhampunya R, Teramoto T, Choi KH. Flavivirus RNA synthesis in vitro. Methods 2015; 91:20-34. [PMID: 26272247 DOI: 10.1016/j.ymeth.2015.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/03/2015] [Accepted: 08/04/2015] [Indexed: 12/21/2022] Open
Abstract
Establishment of in vitro systems to study mechanisms of RNA synthesis for positive strand RNA viruses have been very useful in the past and have shed light on the composition of protein and RNA components, optimum conditions, the nature of the products formed, cis-acting RNA elements and trans-acting protein factors required for efficient synthesis. In this review, we summarize our current understanding regarding the requirements for flavivirus RNA synthesis in vitro. We describe details of reaction conditions, the specificity of template used by either the multi-component membrane-bound viral replicase complex or by purified, recombinant RNA-dependent RNA polymerase. We also discuss future perspectives to extend the boundaries of our knowledge.
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Affiliation(s)
- Radhakrishnan Padmanabhan
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington DC 20057, United States.
| | - Ratree Takhampunya
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington DC 20057, United States
| | - Tadahisa Teramoto
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington DC 20057, United States
| | - Kyung H Choi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, United States
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80
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The search for nucleoside/nucleotide analog inhibitors of dengue virus. Antiviral Res 2015; 122:12-9. [PMID: 26241002 DOI: 10.1016/j.antiviral.2015.07.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 07/29/2015] [Accepted: 07/31/2015] [Indexed: 11/21/2022]
Abstract
Nucleoside analogs represent the largest class of antiviral agents and have been actively pursued for potential therapy of dengue virus (DENV) infection. Early success in the treatment of human immunodeficiency virus (HIV) infection and the recent approval of sofosbuvir for chronic hepatitis C have provided proof of concept for this class of compounds in clinics. Here we review (i) nucleoside analogs with known anti-DENV activity; (ii) challenges of the nucleoside antiviral approach for dengue; and (iii) potential strategies to overcome these challenges. This article forms part of a symposium in Antiviral Research on flavivirus drug discovery.
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81
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Lim SP, Noble CG, Shi PY. The dengue virus NS5 protein as a target for drug discovery. Antiviral Res 2015; 119:57-67. [DOI: 10.1016/j.antiviral.2015.04.010] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/19/2015] [Accepted: 04/11/2015] [Indexed: 12/25/2022]
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82
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Zmurko J, Neyts J, Dallmeier K. Flaviviral NS4b, chameleon and jack-in-the-box roles in viral replication and pathogenesis, and a molecular target for antiviral intervention. Rev Med Virol 2015; 25:205-23. [PMID: 25828437 PMCID: PMC4864441 DOI: 10.1002/rmv.1835] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 02/16/2015] [Accepted: 02/17/2015] [Indexed: 12/27/2022]
Abstract
Dengue virus and other flaviviruses such as the yellow fever, West Nile, and Japanese encephalitis viruses are emerging vector-borne human pathogens that affect annually more than 100 million individuals and that may cause debilitating and potentially fatal hemorrhagic and encephalitic diseases. Currently, there are no specific antiviral drugs for the treatment of flavivirus-associated disease. A better understanding of the flavivirus-host interactions during the different events of the flaviviral life cycle may be essential when developing novel antiviral strategies. The flaviviral non-structural protein 4b (NS4b) appears to play an important role in flaviviral replication by facilitating the formation of the viral replication complexes and in counteracting innate immune responses such as the following: (i) type I IFN signaling; (ii) RNA interference; (iii) formation of stress granules; and (iv) the unfolded protein response. Intriguingly, NS4b has recently been shown to constitute an excellent target for the selective inhibition of flavivirus replication. We here review the current knowledge on NS4b.
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Affiliation(s)
- Joanna Zmurko
- KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Virology and Chemotherapy
| | - Johan Neyts
- KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Virology and Chemotherapy
| | - Kai Dallmeier
- KU Leuven, Rega Institute for Medical Research, Department of Microbiology and Immunology, Laboratory of Virology and Chemotherapy
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83
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Xie X, Zou J, Wang QY, Shi PY. Targeting dengue virus NS4B protein for drug discovery. Antiviral Res 2015; 118:39-45. [DOI: 10.1016/j.antiviral.2015.03.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/06/2015] [Accepted: 03/13/2015] [Indexed: 10/23/2022]
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84
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Kim JK, Kim JM, Song BH, Yun SI, Yun GN, Byun SJ, Lee YM. Profiling of viral proteins expressed from the genomic RNA of Japanese encephalitis virus using a panel of 15 region-specific polyclonal rabbit antisera: implications for viral gene expression. PLoS One 2015; 10:e0124318. [PMID: 25915765 PMCID: PMC4410938 DOI: 10.1371/journal.pone.0124318] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 02/27/2015] [Indexed: 12/16/2022] Open
Abstract
Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is closely related to West Nile (WN), yellow fever (YF), and dengue (DEN) viruses. Its plus-strand genomic RNA carries a single open reading frame encoding a polyprotein that is cleaved into three structural (C, prM/M, and E) and at least seven nonstructural (NS1/NS1', NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins, based on previous work with WNV, YFV, and DENV. Here, we aimed to profile experimentally all the viral proteins found in JEV-infected cells. We generated a collection of 15 JEV-specific polyclonal antisera covering all parts of the viral protein-coding regions, by immunizing rabbits with 14 bacterially expressed glutathione-S-transferase fusion proteins (for all nine viral proteins except NS2B) or with a chemically synthesized oligopeptide (for NS2B). In total lysates of JEV-infected BHK-21 cells, immunoblotting with these antisera revealed: (i) three mature structural proteins (~12-kDa C, ~8-kDa M, and ~53-kDa E), a precursor of M (~24-kDa prM) and three other M-related proteins (~10-14 kDa); (ii) the predicted ~45-kDa NS1 and its frameshift product, ~58-kDa NS1', with no evidence of the predicted ~25-kDa NS2A; (iii) the predicted but hardly detectable ~14-kDa NS2B and an unexpected but predominant ~12-kDa NS2B-related protein; (iv) the predicted ~69-kDa NS3 plus two major cleavage products (~34-kDa NS3N-term and ~35-kDa NS3C-term), together with at least nine minor proteins of ~16-52 kDa; (v) the predicted ~14-kDa NS4A; (vi) two NS4B-related proteins (~27-kDa NS4B and ~25-kDa NS4B'); and (vii) the predicted ~103-kDa NS5 plus at least three other NS5-related proteins (~15 kDa, ~27 kDa, and ~90 kDa). Combining these data with confocal microscopic imaging of the proteins' intracellular localization, our study is the first to provide a solid foundation for the study of JEV gene expression, which is crucial for elucidating the regulatory mechanisms of JEV genome replication and pathobiology.
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Affiliation(s)
- Jin-Kyoung Kim
- Department of Animal, Dairy, and Veterinary Sciences; Utah Science Technology and Research, College of Agriculture and Applied Sciences, Utah State University, Logan, Utah, United States of America
| | - Jeong-Min Kim
- Department of Microbiology, College of Medicine, Chungbuk National University, Cheongju, South Korea
| | - Byung-Hak Song
- Department of Animal, Dairy, and Veterinary Sciences; Utah Science Technology and Research, College of Agriculture and Applied Sciences, Utah State University, Logan, Utah, United States of America
| | - Sang-Im Yun
- Department of Animal, Dairy, and Veterinary Sciences; Utah Science Technology and Research, College of Agriculture and Applied Sciences, Utah State University, Logan, Utah, United States of America
| | - Gil-Nam Yun
- Department of Microbiology, College of Medicine, Chungbuk National University, Cheongju, South Korea
| | - Sung-June Byun
- Animal Biotechnology Division, Korea National Institute of Animal Science, Suwon, South Korea
| | - Young-Min Lee
- Department of Animal, Dairy, and Veterinary Sciences; Utah Science Technology and Research, College of Agriculture and Applied Sciences, Utah State University, Logan, Utah, United States of America
- * E-mail:
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85
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Niyomrattanakit P, Wan KF, Chung KY, Abas SN, Seh CC, Dong H, Lim CC, Chao AT, Lee CB, Nilar S, Lescar J, Shi PY, Beer D, Lim SP. Stabilization of dengue virus polymerase in de novo initiation assay provides advantages for compound screening. Antiviral Res 2015; 119:36-46. [PMID: 25896272 DOI: 10.1016/j.antiviral.2015.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/08/2015] [Accepted: 04/12/2015] [Indexed: 02/06/2023]
Abstract
Dengue virus (DENV) NS5 protein comprises an N-terminal methyltransferase domain and a C-terminal RNA-dependent RNA polymerase domain (RdRp). DENV RdRp is responsible for viral RNA synthesis via a de novo initiation mechanism and represents an attractive target for anti-viral therapy. Herein we describe the characterization of its de novo initiation activities by PAGE analyses and the knowledge gained was used to develop a fluorescent-based assay. A highly processive and robust assay was achieved by addition of cysteine in the assay buffer. This stabilized the apo-enzyme, and rendered optimal de novo initiation activity while balancing its intrinsic terminal transferase activity. Steady-state kinetic parameters of the NTP and RNA substrates under these optimal conditions were determined for DENV1-4 FL NS5. Heavy metal ions such as Zn(++) and Co(++) as well as high levels of monovalent salts, suppressed DENV polymerase de novo initiation activities. This assay was validated with nucleotide chain terminators and used to screen two diverse small library sets. The screen data obtained was further compared with concurrent screens performed with a DENV polymerase elongation fluorescent assay utilizing pre-complexed enzyme-RNA. A higher hit-rate was obtained for the de novo initiation assay compared to the elongation assay (∼2% versus ∼0.1%). All the hits from the latter assay are also identified in the de novo initiation assay, indicating that the de novo initiation assay performed with the stabilized apo-enzyme has the advantage of providing additional chemical starting entities for inhibiting this enzyme.
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Affiliation(s)
- Pornwaratt Niyomrattanakit
- Novartis Institute for Tropical Diseases, Singapore; Maveta Company Limited, 26/522 Paholyothin 62/1 S, Saimai, Bangkok 10220, Thailand(1)
| | - Kah Fei Wan
- Novartis Institute for Tropical Diseases, Singapore.
| | - Ka Yan Chung
- Novartis Institute for Tropical Diseases, Singapore; Division of Structural Biology and Biochemistry, School of Biological Sciences, Nanyang Technological University, Singapore
| | | | | | | | | | | | | | - Shahul Nilar
- Novartis Institute for Tropical Diseases, Singapore
| | - Julien Lescar
- Division of Structural Biology and Biochemistry, School of Biological Sciences, Nanyang Technological University, Singapore; INSERM UMRS 945 "Immunité et Infection", Centre Hospitalier Universitaire Pitié-Salpêtrière, Faculté de Médecine et Université Pierre et Marie Curie, 91 Bd de l'Hôpital, 75013 Paris, France
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, Singapore
| | - David Beer
- Novartis Institute for Tropical Diseases, Singapore
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86
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Determinants of Dengue Virus NS4A Protein Oligomerization. J Virol 2015; 89:6171-83. [PMID: 25833044 DOI: 10.1128/jvi.00546-15] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 03/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Flavivirus NS4A protein induces host membrane rearrangement and functions as a replication complex component. The molecular details of how flavivirus NS4A exerts these functions remain elusive. Here, we used dengue virus (DENV) as a model to characterize and demonstrate the biological relevance of flavivirus NS4A oligomerization. DENV type 2 (DENV-2) NS4A protein forms oligomers in infected cells or when expressed alone. Deletion mutagenesis mapped amino acids 50 to 76 (spanning the first transmembrane domain [TMD1]) of NS4A as the major determinant for oligomerization, while the N-terminal 50 residues contribute only slightly to the oligomerization. Nuclear magnetic resonance (NMR) analysis of NS4A amino acids 17 to 80 suggests that residues L31, L52, E53, G66, and G67 could participate in oligomerization. Ala substitution for 15 flavivirus conserved NS4A residues revealed that these amino acids are important for viral replication. Among the 15 mutated NS4A residues, 2 amino acids (E50A and G67A) are located within TMD1. Both E50A and G67A attenuated viral replication, decreased NS4A oligomerization, and reduced NS4A protein stability. In contrast, NS4A oligomerization was not affected by the replication-defective mutations (R12A, P49A, and K80A) located outside TMD1. trans complementation experiments showed that expression of wild-type NS4A alone was not sufficient to rescue the replication-lethal NS4A mutants. However, the presence of DENV-2 replicons could partially restore the replication defect of some lethal NS4A mutants (L26A and K80A), but not others (L60A and E122A), suggesting an unidentified mechanism governing the outcome of complementation in a mutant-dependent manner. Collectively, the results have demonstrated the importance of TMD1-mediated NS4A oligomerization in flavivirus replication. IMPORTANCE We report that DENV NS4A forms oligomers. Such NS4A oligomerization is mediated mainly through amino acids 50 to 76 (spanning the first transmembrane domain [TMD1]). The biological importance of NS4A oligomerization is demonstrated by results showing that mutations of flavivirus conserved residues (E50A and G67A located within TMD1) reduced the oligomerization and stability of the NS4A protein, leading to attenuated viral replication. A systematic mutagenesis analysis demonstrated that flavivirus conserved NS4A residues are important for DENV replication. A successful trans complementation of replication-lethal NS4A mutant virus requires wild-type NS4A in the context of the viral replication complex. The wild-type NS4A protein alone is not sufficient to rescue the replication defect of NS4A mutants. Intriguingly, distinct NS4A mutants yielded different complementation outcomes in the replicon-containing cells. Overall, the study has enhanced our understanding of flavivirus NS4A at the molecular level. The results also suggest that inhibitor blocking of NS4A oligomerization could be explored for antiviral drug discovery.
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87
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Kocabas F, Turan RD, Aslan GS. Fluorometric RdRp assay with self-priming RNA. Virus Genes 2015; 50:498-504. [PMID: 25749997 DOI: 10.1007/s11262-015-1187-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/27/2015] [Indexed: 10/23/2022]
Abstract
There is an outmost need for the identification of specific antiviral compounds. Current antivirals lack specificity, making them susceptible to off-target effects, and highlighting importance of development of assays to discover antivirals targeting viral specific proteins. Previous studies for identification of inhibitors of RNA-dependent RNA polymerase (RdRp) mostly relied on radioactive methods. This study describes a fluorometric approach to assess in vitro activity of viral RdRp for drug screening. Using readily available DNA- and RNA-specific fluorophores, we determined an optimum fluorometric approach that could be used in antiviral discovery specifically for RNA viruses by targeting RdRp. Here, we show that double-stranded RNA could be successfully distinguished from single-stranded RNA. In addition, we provide a strategy based on self-priming RNA to assess RdRp activity.
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Affiliation(s)
- Fatih Kocabas
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, 34755, Istanbul, Turkey,
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88
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Abstract
UNLABELLED Flavivirus replication is mediated by a membrane-associated replication complex where viral membrane proteins NS2A, NS2B, NS4A, and NS4B serve as the scaffold for the replication complex formation. Here, we used dengue virus serotype 2 (DENV-2) as a model to characterize viral NS4A-NS4B interaction. NS4A interacts with NS4B in virus-infected cells and in cells transiently expressing NS4A and NS4B in the absence of other viral proteins. Recombinant NS4A and NS4B proteins directly bind to each other with an estimated Kd (dissociation constant) of 50 nM. Amino acids 40 to 76 (spanning the first transmembrane domain, consisting of amino acids 50 to 73) of NS4A and amino acids 84 to 146 (also spanning the first transmembrane domain, consisting of amino acids 101 to 129) of NS4B are the determinants for NS4A-NS4B interaction. Nuclear magnetic resonance (NMR) analysis suggests that NS4A residues 17 to 80 form two amphipathic helices (helix α1, comprised of residues 17 to 32, and helix α2, comprised of residues 40 to 47) that associate with the cytosolic side of endoplasmic reticulum (ER) membrane and helix α3 (residues 52 to 75) that transverses the ER membrane. In addition, NMR analysis identified NS4A residues that may participate in the NS4A-NS4B interaction. Amino acid substitution of these NS4A residues exhibited distinct effects on viral replication. Three of the four NS4A mutations (L48A, T54A, and L60A) that affected the NS4A-NS4B interaction abolished or severely reduced viral replication; in contrast, two NS4A mutations (F71A and G75A) that did not affect NS4A-NS4B interaction had marginal effects on viral replication, demonstrating the biological relevance of the NS4A-NS4B interaction to DENV-2 replication. Taken together, the study has provided experimental evidence to argue that blocking the NS4A-NS4B interaction could be a potential antiviral approach. IMPORTANCE Flavivirus NS4A and NS4B proteins are essential components of the ER membrane-associated replication complex. The current study systematically characterizes the interaction between flavivirus NS4A and NS4B. Using DENV-2 as a model, we show that NS4A interacts with NS4B in virus-infected cells, in cells transiently expressing NS4A and NS4B proteins, or in vitro with recombinant NS4A and NS4B proteins. We mapped the minimal regions required for the NS4A-NS4B interaction to be amino acids 40 to 76 of NS4A and amino acids 84 to 146 of NS4B. NMR analysis revealed the secondary structure of amino acids 17 to 80 of NS4A and the NS4A amino acids that may participate in the NS4A-NS4B interaction. Functional analysis showed a correlation between viral replication and NS4A-NS4B interaction, demonstrating the biological importance of the NS4A-NS4B interaction. The study has advanced our knowledge of the molecular function of flavivirus NS4A and NS4B proteins. The results also suggest that inhibitors of the NS4A-NS4B interaction could be pursued for flavivirus antiviral development.
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89
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Sztuba-Solinska J, Le Grice SFJ. Insights into secondary and tertiary interactions of dengue virus RNA by SHAPE. Methods Mol Biol 2014; 1138:225-39. [PMID: 24696340 DOI: 10.1007/978-1-4939-0348-1_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Dengue virus (DENV) is a single-stranded positive-sense RNA virus belonging to the Flaviviridae family. The DENV RNA genome contains multiple cis-acting elements that continue to unravel their essential role in managing viral molecular processes. Attempts have been made to predict the secondary structure of DENV RNA using a variety of computational tools. Nevertheless, a greater degree of accuracy is achieved when these methods are complemented with structure probing experimentation. This chapter outlines detailed methodology for the structural study of DENV subgenomic minigenome RNA by applying high-throughput selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE). High-throughput SHAPE combines a novel chemical probing technology with reverse transcription, capillary electrophoresis, and secondary structure prediction software to rapidly and reproducibly determine the structure of RNAs from several hundred to several thousand nucleotides at single-nucleotide resolution. This methodology investigates local structure for all positions in a sequence-independent manner and as such it is particularly useful in predicting RNA secondary and tertiary interactions.
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Affiliation(s)
- Joanna Sztuba-Solinska
- RT Biochemistry Section, HIV Drug Resistance Program, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
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90
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Construction of plasmid, bacterial expression, purification, and assay of dengue virus type 2 NS5 methyltransferase. Methods Mol Biol 2014; 1138:361-73. [PMID: 24696348 DOI: 10.1007/978-1-4939-0348-1_22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Dengue virus (DENV), a member of mosquito-borne flavivirus, causes self-limiting dengue fever as well as life-threatening dengue hemorrhagic fever and dengue shock syndrome. Its positive sense RNA genome has a cap at the 5'-end and no poly(A) tail at the 3'-end. The viral RNA encodes a single polyprotein, C-prM-E-NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5. The polyprotein is processed into 3 structural proteins (C, prM, and E) and 7 nonstructural (NS) proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5). NS3 and NS5 are multifunctional enzymes performing various tasks in viral life cycle. The N-terminal domain of NS5 has distinct GTP and S-adenosylmethionine (SAM) binding sites. The role of GTP binding site is implicated in guanylyltransferase (GTase) activity of NS5. The SAM binding site is involved in both N-7 and 2'-O-methyltransferase (MTase) activities involved in formation of type I cap. The C-terminal domain of NS5 catalyzes RNA-dependent RNA polymerase (RdRp) activity involved in RNA synthesis. We describe the construction of the MTase domain of NS5 in an E. coli expression vector, purification of the enzyme, and conditions for enzymatic assays of N7- and 2'O-methyltransferase activities that yield the final type I 5'-capped RNA ((7Me)GpppA2'OMe-RNA).
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91
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Two distinct sets of NS2A molecules are responsible for dengue virus RNA synthesis and virion assembly. J Virol 2014; 89:1298-313. [PMID: 25392211 DOI: 10.1128/jvi.02882-14] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
UNLABELLED Flavivirus nonstructural protein 2A (NS2A) plays important roles in both viral RNA synthesis and virion assembly. The molecular details of how the NS2A protein modulates the two distinct events have not been defined. To address this question, we have performed a systematic mutagenesis of NS2A using dengue virus (DENV) serotype 2 (DENV-2) as a model. We identified two sets of NS2A mutations with distinct defects during a viral infection cycle. One set of NS2A mutations (D125A and G200A) selectively abolished viral RNA synthesis. Mechanistically, the D125A mutation abolished viral RNA synthesis through blocking the N-terminal cleavage of the NS2A protein, leading to an unprocessed NS1-NS2A protein; this result suggests that amino acid D125 (far downstream of the N terminus of NS2A) may contribute to the recognition of host protease at the NS1-NS2A junction. The other set of NS2A mutations (G11A, E20A, E100A, Q187A, and K188A) specifically impaired virion assembly without significantly affecting viral RNA synthesis. Remarkably, mutants defective in virion assembly could be rescued by supplying in trans wild-type NS2A molecules expressed from a replicative replicon, by wild-type NS2A protein expressed alone, by a mutant NS2A (G200A) that is lethal for viral RNA synthesis, or by a different mutant NS2A that is defective in virion assembly. In contrast, none of the mutants defective in viral RNA synthesis could be rescued by trans-complementation. Collectively, the results indicate that two distinct sets of NS2A molecules are responsible for DENV RNA synthesis and virion assembly. IMPORTANCE Dengue virus (DENV) represents the most prevalent mosquito-borne human pathogen. Understanding the replication of DENV is essential for development of vaccines and therapeutics. Here we characterized the function of DENV-2 NS2A using a systematic mutagenesis approach. The mutagenesis results revealed two distinct sets of NS2A mutations: one set of mutations that result in defects in viral RNA synthesis and another set of mutations that result in defects in virion assembly. trans-Complementation analysis showed that mutants defective in viral RNA synthesis could not be rescued by wild-type NS2A; in contrast, mutants defective in virion assembly could be successfully rescued by wild-type NS2A or even by a mutant NS2A that is incompetent to support viral RNA synthesis. These results support a model in which two distinct sets of NS2A molecules are responsible for DENV RNA synthesis (located in the viral replication complex) and virion assembly (located in the virion assembly/budding site). The study confirms and extends our understanding of the two critical roles of flavivirus NS2A in viral RNA synthesis and virion assembly.
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92
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Selisko B, Wang C, Harris E, Canard B. Regulation of Flavivirus RNA synthesis and replication. Curr Opin Virol 2014; 9:74-83. [PMID: 25462437 DOI: 10.1016/j.coviro.2014.09.011] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 09/18/2014] [Accepted: 09/26/2014] [Indexed: 01/21/2023]
Abstract
RNA synthesis and replication of the members of the Flavivirus genus (including dengue, West Nile and Japanese encephalitis viruses) is regulated by a wide variety of mechanisms and actors. These include the sequestration of the RNA-dependent RNA polymerase (RdRp) for functions other than RNA synthesis, regulatory interactions with other viral and host proteins within the replication complex (RC), and regulatory elements within the RNA genome itself. In this review, we discuss our current knowledge of the multiple levels at which Flavivirus RNA synthesis is controlled. We aim to bring together two active research fields: the structural and functional biology of individual proteins of the RC and the impressive wealth of knowledge acquired regarding the viral genomic RNA.
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Affiliation(s)
- Barbara Selisko
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Chunling Wang
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, 185 Li Ka Shing Center, Berkeley, CA 94720-3370, USA
| | - Eva Harris
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, 185 Li Ka Shing Center, Berkeley, CA 94720-3370, USA
| | - Bruno Canard
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France.
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93
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Smith TM, Lim SP, Yue K, Busby SA, Arora R, Seh CC, Wright SK, Nutiu R, Niyomrattanakit P, Wan KF, Beer D, Shi PY, Benson TE. Identifying initiation and elongation inhibitors of dengue virus RNA polymerase in a high-throughput lead-finding campaign. ACTA ACUST UNITED AC 2014; 20:153-63. [PMID: 25252731 DOI: 10.1177/1087057114551141] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Dengue virus (DENV) is the most significant mosquito-borne viral pathogen in the world and is the cause of dengue fever. The DENV RNA-dependent RNA polymerase (RdRp) is conserved among the four viral serotypes and is an attractive target for antiviral drug development. During initiation of viral RNA synthesis, the polymerase switches from a "closed" to "open" conformation to accommodate the viral RNA template. Inhibitors that lock the "closed" or block the "open" conformation would prevent viral RNA synthesis. Herein, we describe a screening campaign that employed two biochemical assays to identify inhibitors of RdRp initiation and elongation. Using a DENV subgenomic RNA template that promotes RdRp de novo initiation, the first assay measures cytosine nucleotide analogue (Atto-CTP) incorporation. Liberated Atto fluorophore allows for quantification of RdRp activity via fluorescence. The second assay uses the same RNA template but is label free and directly detects RdRp-mediated liberation of pyrophosphates of native ribonucleotides via liquid chromatography-mass spectrometry. The ability of inhibitors to bind and stabilize a "closed" conformation of the DENV RdRp was further assessed in a differential scanning fluorimetry assay. Last, active compounds were evaluated in a renilla luciferase-based DENV replicon cell-based assay to monitor cellular efficacy. All assays described herein are medium to high throughput, are robust and reproducible, and allow identification of inhibitors of the open and closed forms of DENV RNA polymerase.
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Affiliation(s)
- Thomas M Smith
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | | | - Kimberley Yue
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | - Scott A Busby
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | - Rishi Arora
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | | | - S Kirk Wright
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | - Razvan Nutiu
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
| | | | - Kah Fei Wan
- Novartis Institute for Tropical Diseases, Singapore
| | - David Beer
- Novartis Institute for Tropical Diseases, Singapore
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, Singapore
| | - Timothy E Benson
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
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94
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Potisopon S, Priet S, Collet A, Decroly E, Canard B, Selisko B. The methyltransferase domain of dengue virus protein NS5 ensures efficient RNA synthesis initiation and elongation by the polymerase domain. Nucleic Acids Res 2014; 42:11642-56. [PMID: 25209234 PMCID: PMC4191377 DOI: 10.1093/nar/gku666] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Viral RNA-dependent RNA polymerases (RdRps) responsible for the replication of single-strand RNA virus genomes exert their function in the context of complex replication machineries. Within these replication complexes the polymerase activity is often highly regulated by RNA elements, proteins or other domains of multi-domain polymerases. Here, we present data of the influence of the methyltransferase domain (NS5-MTase) of dengue virus (DENV) protein NS5 on the RdRp activity of the polymerase domain (NS5-Pol). The steady-state polymerase activities of DENV-2 recombinant NS5 and NS5-Pol are compared using different biochemical assays allowing the dissection of the de novo initiation, transition and elongation steps of RNA synthesis. We show that NS5-MTase ensures efficient RdRp activity by stimulating the de novo initiation and the elongation phase. This stimulation is related to a higher affinity of NS5 toward the single-strand RNA template indicating NS5-MTase either completes a high-affinity RNA binding site and/or promotes the correct formation of the template tunnel. Furthermore, the NS5-MTase increases the affinity of the priming nucleotide ATP upon de novo initiation and causes a higher catalytic efficiency of the polymerase upon elongation. The complex stimulation pattern is discussed under the perspective that NS5 adopts several conformations during RNA synthesis.
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Affiliation(s)
- Supanee Potisopon
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Stéphane Priet
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Axelle Collet
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Etienne Decroly
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Bruno Canard
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Barbara Selisko
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France CNRS, AFMB UMR 7257, 13288 Marseille, France
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95
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One severe acute respiratory syndrome coronavirus protein complex integrates processive RNA polymerase and exonuclease activities. Proc Natl Acad Sci U S A 2014; 111:E3900-9. [PMID: 25197083 DOI: 10.1073/pnas.1323705111] [Citation(s) in RCA: 389] [Impact Index Per Article: 38.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In addition to members causing milder human infections, the Coronaviridae family includes potentially lethal zoonotic agents causing severe acute respiratory syndrome (SARS) and the recently emerged Middle East respiratory syndrome. The ∼30-kb positive-stranded RNA genome of coronaviruses encodes a replication/transcription machinery that is unusually complex and composed of 16 nonstructural proteins (nsps). SARS-CoV nsp12, the canonical RNA-dependent RNA polymerase (RdRp), exhibits poorly processive RNA synthesis in vitro, at odds with the efficient replication of a very large RNA genome in vivo. Here, we report that SARS-CoV nsp7 and nsp8 activate and confer processivity to the RNA-synthesizing activity of nsp12. Using biochemical assays and reverse genetics, the importance of conserved nsp7 and nsp8 residues was probed. Whereas several nsp7 mutations affected virus replication to a limited extent, the replacement of two nsp8 residues (P183 and R190) essential for interaction with nsp12 and a third (K58) critical for the interaction of the polymerase complex with RNA were all lethal to the virus. Without a loss of processivity, the nsp7/nsp8/nsp12 complex can associate with nsp14, a bifunctional enzyme bearing 3'-5' exoribonuclease and RNA cap N7-guanine methyltransferase activities involved in replication fidelity and 5'-RNA capping, respectively. The identification of this tripartite polymerase complex that in turn associates with the nsp14 proofreading enzyme sheds light on how coronaviruses assemble an RNA-synthesizing machinery to replicate the largest known RNA genomes. This protein complex is a fascinating example of the functional integration of RNA polymerase, capping, and proofreading activities.
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96
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Abstract
Dengue virus (DENV) is an emerging mosquito-borne human pathogen that affects millions of individuals each year by causing severe and potentially fatal syndromes. Despite intense research efforts, no approved vaccine or antiviral therapy is yet available. Overcoming this limitation requires detailed understanding of the intimate relationship between the virus and its host cell, providing the basis to devise optimal prophylactic and therapeutic treatment options. With the advent of novel high-throughput technologies including functional genomics, transcriptomics, proteomics, and lipidomics, new important insights into the DENV replication cycle and the interaction of this virus with its host cell have been obtained. In this chapter, we provide a comprehensive overview on the current status of the DENV research field, covering every step of the viral replication cycle with a particular focus on virus-host cell interaction. We will also review specific chemical inhibitors targeting cellular factors and processes of relevance for the DENV replication cycle and their possible exploitation for the development of next generation antivirals.
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97
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Teramoto T, Boonyasuppayakorn S, Handley M, Choi KH, Padmanabhan R. Substitution of NS5 N-terminal domain of dengue virus type 2 RNA with type 4 domain caused impaired replication and emergence of adaptive mutants with enhanced fitness. J Biol Chem 2014; 289:22385-400. [PMID: 24904061 DOI: 10.1074/jbc.m114.584466] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Flavivirus NS3 and NS5 are required in viral replication and 5'-capping. NS3 has NS2B-dependent protease, RNA helicase, and 5'-RNA triphosphatase activities. NS5 has 5'-RNA methyltransferase (MT)/guanylyltransferase (GT) activities within the N-terminal 270 amino acids and the RNA-dependent RNA polymerase (POL) activity within amino acids 271-900. A chimeric NS5 containing the D4MT/D4GT and the D2POL domains in the context of wild-type (WT) D2 RNA was constructed. RNAs synthesized in vitro were transfected into baby hamster kidney cells. The viral replication was analyzed by an indirect immunofluorescence assay to monitor NS1 expression and by quantitative real-time PCR. WT D2 RNA-transfected cells were NS1- positive by day 5, whereas the chimeric RNA-transfected cells became NS1-positive ∼30 days post-transfection in three independent experiments. Sequence analysis covering the entire genome revealed the appearance of a single K74I mutation within the D4MT domain ∼16 days post-transfection in two experiments. In the third, D290N mutation in the conserved NS3 Walker B motif appeared ≥16 days post-transfection. A time course study of serial passages revealed that the 30-day supernatant had gradually evolved to gain replication fitness. Trans-complementation by co-expression of WT D2 NS5 accelerated viral replication of chimeric RNA without changing the K74I mutation. However, the MT and POL activities of NS5 WT D2 and the chimeric NS5 proteins with or without the K74I mutation are similar. Taken together, our results suggest that evolution of the functional interactions involving the chimeric NS5 protein encoded by the viral genome species is essential for gain of viral replication fitness.
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Affiliation(s)
- Tadahisa Teramoto
- From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and
| | - Siwaporn Boonyasuppayakorn
- From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and
| | - Misty Handley
- From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and
| | - Kyung H Choi
- the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555-0156
| | - Radhakrishnan Padmanabhan
- From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and
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98
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Li XD, Shan C, Deng CL, Ye HQ, Shi PY, Yuan ZM, Gong P, Zhang B. The interface between methyltransferase and polymerase of NS5 is essential for flavivirus replication. PLoS Negl Trop Dis 2014; 8:e2891. [PMID: 24852307 PMCID: PMC4031075 DOI: 10.1371/journal.pntd.0002891] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/10/2014] [Indexed: 12/15/2022] Open
Abstract
The flavivirus NS5 harbors both a methyltransferase (MTase) and an RNA-dependent RNA polymerase (RdRP). Both enzyme activities of NS5 are critical for viral replication. Recently, the full-length NS5 crystal structure of Japanese encephalitis virus reveals a conserved MTase-RdRP interface that features two conserved components: a six-residue hydrophobic network and a GTR sequence. Here we showed for the first time that these key interface components are essential for flavivirus replication by various reverse genetics approaches. Interestingly, some replication-impaired variants generated a common compensatory NS5 mutation outside the interface (L322F), providing novel routes to further explore the crosstalk between MTase and RdRP.
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Affiliation(s)
- Xiao-Dan Li
- CAS 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
| | - Chao Shan
- CAS 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
| | - Cheng-Lin Deng
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Han-Qing Ye
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Pei-Yong Shi
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Zhi-Ming Yuan
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Peng Gong
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- * E-mail: (PG); (BZ)
| | - Bo Zhang
- CAS Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- * E-mail: (PG); (BZ)
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99
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Caillet-Saguy C, Lim SP, Shi PY, Lescar J, Bressanelli S. Polymerases of hepatitis C viruses and flaviviruses: Structural and mechanistic insights and drug development. Antiviral Res 2014; 105:8-16. [DOI: 10.1016/j.antiviral.2014.02.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 01/31/2014] [Accepted: 02/10/2014] [Indexed: 11/29/2022]
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100
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Amodiaquine, an antimalarial drug, inhibits dengue virus type 2 replication and infectivity. Antiviral Res 2014; 106:125-34. [PMID: 24680954 PMCID: PMC4523242 DOI: 10.1016/j.antiviral.2014.03.014] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 03/14/2014] [Accepted: 03/18/2014] [Indexed: 12/14/2022]
Abstract
Dengue virus serotypes 1-4 (DENV1-4) are transmitted by mosquitoes which cause most frequent arboviral infections in the world resulting in ∼390 million cases with ∼25,000 deaths annually. There is no vaccine or antiviral drug currently available for human use. Compounds containing quinoline scaffold were shown to inhibit flavivirus NS2B-NS3 protease (NS2B-NS3pro) with good potencies. In this study, we screened quinoline derivatives, which are known antimalarial drugs for inhibition of DENV2 and West Nile virus (WNV) replication using the corresponding replicon expressing cell-based assays. Amodiaquine (AQ), one of the 4-aminoquinoline drugs, inhibited DENV2 infectivity measured by plaque assays, with EC50 and EC90 values of 1.08±0.09μM and 2.69±0.47 μM, respectively, and DENV2 RNA replication measured by Renilla luciferase reporter assay, with EC50 value of 7.41±1.09μM in the replicon expressing cells. Cytotoxic concentration (CC50) in BHK-21 cells was 52.09±4.25μM. The replication inhibition was confirmed by plaque assay of the extracellular virions as well as by qRT-PCR of the intracellular and extracellular viral RNA levels. AQ was stable for at least 96h and had minor inhibitory effect on entry, translation, and post-replication stages in the viral life cycle. DENV protease, 5'-methyltransferase, and RNA-dependent RNA polymerase do not seem to be targets of AQ. Both p-hydroxyanilino and diethylaminomethyl moieties are important for AQ to inhibit DENV2 replication and infectivity. Our results support AQ as a promising candidate for anti-flaviviral therapy.
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