1
|
Chaumont L, Collet B, Boudinot P. Protein kinase double-stranded RNA-dependent (PKR) in antiviral defence in fish and mammals. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2023; 145:104732. [PMID: 37172664 DOI: 10.1016/j.dci.2023.104732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 05/07/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
The interferon-inducible double-stranded RNA-dependent protein kinase (PKR) is one of the key antiviral arms of the innate immune system. Upon binding of viral double stranded RNA, a viral Pattern Associated Molecular Pattern (PAMP), PKR gets activated and phosphorylates the eukaryotic initiation factor 2α (eIF2α) resulting in a protein shut-down that limits viral replication. Since its discovery in the mid-seventies, PKR has been shown to be involved in multiple important cellular processes including apoptosis, proinflammatory and innate immune responses. Viral subversion mechanisms of PKR underline its importance in the antiviral response of the host. PKR activation pathways and its mechanisms of action were previously identified and characterised mostly in mammalian models. However, fish Pkr and fish-specific paralogue Z-DNA-dependent protein kinase (Pkz) also play key role in antiviral defence. This review gives an update on the current knowledge on fish Pkr/Pkz, their conditions of activation and their implication in the immune responses to viruses, in comparison to their mammalian counterparts.
Collapse
Affiliation(s)
- Lise Chaumont
- Université Paris-Saclay, INRAE, UVSQ, VIM, Jouy-en-Josas, 78350, France
| | - Bertrand Collet
- Université Paris-Saclay, INRAE, UVSQ, VIM, Jouy-en-Josas, 78350, France
| | - Pierre Boudinot
- Université Paris-Saclay, INRAE, UVSQ, VIM, Jouy-en-Josas, 78350, France.
| |
Collapse
|
2
|
Falco A, Bello-Perez M, Díaz-Puertas R, Mold M, Adamek M. Update on the Inactivation Procedures for the Vaccine Development Prospects of a New Highly Virulent RGNNV Isolate. Vaccines (Basel) 2021; 9:vaccines9121441. [PMID: 34960187 PMCID: PMC8705346 DOI: 10.3390/vaccines9121441] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 11/30/2021] [Accepted: 12/03/2021] [Indexed: 01/01/2023] Open
Abstract
Viral nervous necrosis (VNN) caused by the nervous necrosis virus (NNV) affects a broad range of primarily marine fish species, with mass mortality rates often seen among larvae and juveniles. Its genetic diversification may hinder the effective implementation of preventive measures such as vaccines. The present study describes different inactivation procedures for developing an inactivated vaccine against a new NNV isolate confirmed to possess deadly effects upon the European seabass (Dicentrarchus labrax), an important Mediterranean farmed fish species that is highly susceptible to this disease. First, an NNV isolate from seabass adults diagnosed with VNN was rescued and the sequences of its two genome segments (RNA1 and RNA2) were classified into the red-spotted grouper NNV (RGNNV) genotype, closely clustering to the highly pathogenic 283.2009 isolate. The testing of different inactivation procedures revealed that the virus particles of this isolate showed a marked resistance to heat (for at least 60 °C for 120 min with and without 1% BSA) but that they were fully inactivated by 3 mJ/cm2 UV-C irradiation and 24 h 0.2% formalin treatment, which stood out as promising NNV-inactivation procedures for potential vaccine candidates. Therefore, these procedures are feasible, effective, and rapid response strategies for VNN control in aquaculture.
Collapse
Affiliation(s)
- Alberto Falco
- Institute of Research, Development and Innovation in Healthcare Biotechnology in Elche (IDiBE), Miguel Hernández University, 03202 Elche, Spain; (M.B.-P.); (R.D.-P.)
- Correspondence:
| | - Melissa Bello-Perez
- Institute of Research, Development and Innovation in Healthcare Biotechnology in Elche (IDiBE), Miguel Hernández University, 03202 Elche, Spain; (M.B.-P.); (R.D.-P.)
| | - Rocío Díaz-Puertas
- Institute of Research, Development and Innovation in Healthcare Biotechnology in Elche (IDiBE), Miguel Hernández University, 03202 Elche, Spain; (M.B.-P.); (R.D.-P.)
| | - Matthew Mold
- The Birchall Centre, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK;
| | - Mikolaj Adamek
- Fish Disease Research Unit, Institute for Parasitology, University of Veterinary Medicine, 30559 Hannover, Germany;
| |
Collapse
|
3
|
Investigation of betanodavirus in sea bass (Dicentrarchus labrax) at all production stages in all hatcheries and on selected farms in Turkey. Arch Virol 2021; 166:3343-3356. [PMID: 34604927 DOI: 10.1007/s00705-021-05254-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 08/12/2021] [Indexed: 10/20/2022]
Abstract
Viral nervous necrosis (VNN) is one of the most important problems in sea bass culture. Although there have been many studies on detection and molecular characterization of betanodavirus, the causative agent of VNN, there has been little focus on understanding its prevalence to create epidemiological maps. The purpose of this study was to investigate the prevalence of betanodavirus in active sea bass hatcheries and on selected farms in Turkey by RT-qPCR. A total of 2460 samples, including fertilized eggs, prelarvae, postlarvae, fry, and fingerlings, were collected from 16 hatcheries to cover all production stages. A total of 600 sea bass were also collected from 20 farms. Betanodavirus was detected in one hatchery (1/16) in fingerling-sized sea bass, and the prevalence of betanodavirus at the hatchery level was calculated to be 6.25%. Betanodavirus was also detected on one farm (1/20) in fingerling-sized sea bass, and the prevalence of betanodavirus at the farm level was calculated to be 5%. Virus isolation initially could not be achieved in E-11 cells, but later, SSN-1 cells were used successfully. Partial genome sequence analysis of the RNA1 and RNA2 segments of the viruses revealed that they were of the red-spotted grouper nervous necrosis virus genotype, which is endemic in the Mediterranean basin. The absence of mortality related to VNN in the hatcheries and on the farms, the healthy appearance of the sea bass, the low viral load detected, and the results of retrospective epidemiological studies indicated that the infection was subclinical. Not detecting betanodavirus in other age groups where biosecurity was implemented indicates that there was no active infection. In light of these findings, it can be concluded that there was no betanodavirus circulating in hatcheries, and the virus might have been of seawater origin.
Collapse
|
4
|
Nervous Necrosis Virus Coat Protein Mediates Host Translation Shutoff through Nuclear Translocalization and Degradation of Polyadenylate Binding Protein. J Virol 2021; 95:e0236420. [PMID: 34133901 DOI: 10.1128/jvi.02364-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Nervous necrosis virus (NNV) belongs to the Betanodavirus genus of the Nodaviridae family and is the main cause of viral nervous necrosis disease in marine fish larvae and juveniles worldwide. The NNV virion contains two positive-sense, single-stranded RNA genomes, which encode RNA-dependent RNA polymerase, coat protein, and B2 protein. Interestingly, NNV infection can shut off host translation in orange-spotted grouper (Epinephelus coioides) brain cells; however, the detailed mechanisms of this action remain unknown. In this study, we discovered that the host translation factor, polyadenylate binding protein (PABP), is a key target during NNV takeover of host translation machinery. Additionally, ectopic expression of NNV coat protein is sufficient to trigger nuclear translocalization and degradation of PABP, followed by translation shutoff. A direct interaction between NNV coat protein and PABP was demonstrated, and this binding requires the NNV coat protein N-terminal shell domain and PABP proline-rich linker region. Notably, we also showed that degradation of PABP during later stages of infection is mediated by the ubiquitin-proteasome pathway. Thus, our study reveals that the NNV coat protein hijacks host PABP, causing its relocalization to the nucleus and promoting its degradation to stimulate host translation shutoff. IMPORTANCE Globally, more than 200 species of aquacultured and wild marine fish are susceptible to NNV infection. Devastating outbreaks of this virus have been responsible for massive economic damage in the aquaculture industry, but the molecular mechanisms by which NNV affects its host remain largely unclear. In this study, we show that NNV hijacks translation in host brain cells, with the viral coat protein binding to host PABP to promote its nuclear translocalization and degradation. This previously unknown mechanism of NNV-induced host translation shutoff greatly enhances the understanding of NNV pathogenesis and provides useful insights and novel tools for development of NNV treatments, such as the use of orange-spotted grouper brain cells as an in vitro model system.
Collapse
|
5
|
Kaplan M, Pekmez K, Özkan B, Çağırgan AA, Kalaycı G. Detection of RGNNV genotype betanodavirus in the Black Sea and monitoring studies. DISEASES OF AQUATIC ORGANISMS 2021; 144:117-121. [PMID: 33884960 DOI: 10.3354/dao03583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Viral nervous necrosis (VNN), caused by betanodavirus, is a significant viral infection that threatens marine aquaculture. Freshwater and marine fish farms in Turkey are subjected to annual pathogen screenings. In 2016, during the Nervous Necrosis Virus screening program conducted in the Black Sea, betanodavirus was unexpectedly detected using real-time reverse transcription-polymerase chain reaction in apparently healthy sea bass. Phylogenetic analysis of both the RNA1 and RNA2 segments of the virus determined that the betanodavirus detected was red-spotted grouper nervous necrosis virus genotype (RGNNV). Following the initial discovery of betanodavirus in the Black Sea, monitoring studies performed over a 3 yr period have not indicated any additional presence of the virus. The absence of clinical symptoms related to VNN disease in the area's marine fish farms and the surrounding detection zone, and the fact that the virus has not been detected anew in monitoring programmes conducted following the initial detection, indicate that there is no virus circulation in the detection zone.
Collapse
Affiliation(s)
- Murat Kaplan
- Izmir/Bornova Veterinary Control Institute, Virology Department, 35010, Izmir, Turkey
| | | | | | | | | |
Collapse
|
6
|
Overexpression of an insect virus encoded silencing suppressor does not enhance plants' susceptibility to its natural virus. Virusdisease 2021; 32:338-342. [PMID: 34350319 DOI: 10.1007/s13337-020-00644-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 11/27/2020] [Indexed: 10/21/2022] Open
Abstract
RNA silencing plays a key role in shielding plant and animal hosts against viral invasion and infection. Viruses encode RNA silencing suppressors (RSS) to block small RNA guided silencing of viral transcripts. The B2 protein encoded by Flock House virus (FHV) is a well-characterized RSS that facilitates infection in insects. It has been shown to act as a functional RSS in plants. FHVB2 over-expressing tobacco plants were used to study the effect of RSS on plant susceptibility to Tobacco mosaic virus (TMV), its natural pathogen. The major symptoms observed in TMV-infected transgenic plants were greenish mosaic, puckering and distortion of leaves, but the infected transgenic leaves were able to resist chlorophyll loss. The infected leaves of transgenic plants showed no significant difference in accumulation of virus when compared with that of the wild type plants. FHVB2 plants showed higher levels of H2O2 and the ROS scavenging enzymes, APX and SOD. This suggests that interference of FHVB2 with RNA silencing machinery may activate alternative defense pathways in the plants so that they are not overly sensitive to TMV infection. Supplementary Information The online version contains supplementary material available at 10.1007/s13337-020-00644-5.
Collapse
|
7
|
Structure and dsRNA-binding activity of the Birnavirus Drosophila X Virus VP3 protein. J Virol 2021; 95:JVI.02166-20. [PMID: 33239452 PMCID: PMC7851550 DOI: 10.1128/jvi.02166-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Birnavirus multifunctional protein VP3 plays an essential role coordinating the virus life cycle, interacting with the capsid protein VP2, with the RNA-dependent RNA polymerase VP1 and with the dsRNA genome. Furthermore, the role of this protein in controlling host cell responses triggered by dsRNA and preventing gene silencing has been recently demonstrated. Here we report the X-ray structure and dsRNA-binding activity of the N-terminal domain of Drosophila X virus (DXV) VP3. The domain folds in a bundle of three α-helices and arranges as a dimer, exposing to the surface a well-defined cluster of basic residues. Site directed mutagenesis combined with Electrophoretic Mobility Shift Assays (EMSA) and Surface Plasmon Resonance (SPR) revealed that this cluster, as well as a flexible and positively charged region linking the first and second globular domains of DXV VP3, are essential for dsRNA-binding. Also, RNA silencing studies performed in insect cell cultures confirmed the crucial role of this VP3 domain for the silencing suppression activity of the protein.IMPORTANCE The Birnavirus moonlighting protein VP3 plays crucial roles interacting with the dsRNA genome segments to form stable ribonucleoprotein complexes and controlling host cell immune responses, presumably by binding to and shielding the dsRNA from recognition by the host silencing machinery. The structural, biophysical and functional data presented in this work has identified the N-terminal domain of VP3 as responsible for the dsRNA-binding and silencing suppression activities of the protein in Drosophila X virus.
Collapse
|
8
|
Ren Y, Li X, Tian Z, Xu Y, Zhang R, Li Y. Zebrafish as an animal model for the antiviral RNA interference pathway. J Gen Virol 2021; 102. [PMID: 33507144 DOI: 10.1099/jgv.0.001552] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The zebrafish (Danio rerio) possesses evolutionarily conserved innate and adaptive immunity as a mammal and has recently become a popular vertebrate model to exploit infection and immunity. Antiviral RNA interference (RNAi) has been illuminated in various model organisms, including Arabidopsis thaliana, Drosophila melanogaster, Caenorhabditis elegans and mice. However, to date, there is no report on the antiviral RNAi pathway of zebrafish. Here, we have evaluated the possible use of zebrafish to study antiviral RNAi with Sindbis virus (SINV), vesicular stomatitis virus (VSV) and Nodamura virus (NoV). We find that SINVs and NoVs induce the production of virus-derived small interfering RNAs (vsiRNAs), the hallmark of antiviral RNAi, with a preference for a length of 22 nucleotides, after infection of larval zebrafish. Meanwhile, the suppressor of RNAi (VSR) protein, NoV B2, may affect the accumulation of the NoV in zebrafish. Furthermore, taking advantage of the fact that zebrafish argonaute-2 (Ago2) protein is naturally deficient in cleavage compared with that of mammals, we provide evidence that the slicing activity of human Ago2 can virtually inhibit the accumulation of RNA virus after being ectopically expressed in larval zebrafish. Thus, zebrafish may be a unique model organism to study the antiviral RNAi pathway.
Collapse
Affiliation(s)
- Yanxin Ren
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200438, PR China
| | - Xueyu Li
- School of Basic Medical Sciences, Wuhan University, Wuhan, PR China
| | - Zhonghui Tian
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200438, PR China
| | - Yan Xu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200438, PR China
| | - Ruilin Zhang
- School of Basic Medical Sciences, Wuhan University, Wuhan, PR China
| | - Yang Li
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200438, PR China
| |
Collapse
|
9
|
Betanodavirus and VER Disease: A 30-year Research Review. Pathogens 2020; 9:pathogens9020106. [PMID: 32050492 PMCID: PMC7168202 DOI: 10.3390/pathogens9020106] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/22/2020] [Accepted: 02/04/2020] [Indexed: 12/18/2022] Open
Abstract
The outbreaks of viral encephalopathy and retinopathy (VER), caused by nervous necrosis virus (NNV), represent one of the main infectious threats for marine aquaculture worldwide. Since the first description of the disease at the end of the 1980s, a considerable amount of research has gone into understanding the mechanisms involved in fish infection, developing reliable diagnostic methods, and control measures, and several comprehensive reviews have been published to date. This review focuses on host–virus interaction and epidemiological aspects, comprising viral distribution and transmission as well as the continuously increasing host range (177 susceptible marine species and epizootic outbreaks reported in 62 of them), with special emphasis on genotypes and the effect of global warming on NNV infection, but also including the latest findings in the NNV life cycle and virulence as well as diagnostic methods and VER disease control.
Collapse
|
10
|
Rajendren S, Manning AC, Al-Awadi H, Yamada K, Takagi Y, Hundley HA. A protein-protein interaction underlies the molecular basis for substrate recognition by an adenosine-to-inosine RNA-editing enzyme. Nucleic Acids Res 2019; 46:9647-9659. [PMID: 30202880 PMCID: PMC6182170 DOI: 10.1093/nar/gky800] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/27/2018] [Indexed: 01/06/2023] Open
Abstract
Adenosine deaminases that act on RNA (ADARs) convert adenosine to inosine within double-stranded regions of RNA, resulting in increased transcriptomic diversity, as well as protection of cellular double-stranded RNA (dsRNA) from silencing and improper immune activation. The presence of dsRNA-binding domains (dsRBDs) in all ADARs suggests these domains are important for substrate recognition; however, the role of dsRBDs in vivo remains largely unknown. Herein, our studies indicate the Caenorhabditis elegans ADAR enzyme, ADR-2, has low affinity for dsRNA, but interacts with ADR-1, an editing-deficient member of the ADAR family, which has a 100-fold higher affinity for dsRNA. ADR-1 uses one dsRBD to physically interact with ADR-2 and a second dsRBD to bind to dsRNAs, thereby tethering ADR-2 to substrates. ADR-2 interacts with >1200 transcripts in vivo, and ADR-1 is required for 80% of these interactions. Our results identify a novel mode of substrate recognition for ADAR enzymes and indicate that protein-protein interactions can guide substrate recognition for RNA editors.
Collapse
Affiliation(s)
- Suba Rajendren
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Aidan C Manning
- Medical Sciences Program, Indiana University, Bloomington, IN 47405, USA
| | - Haider Al-Awadi
- Medical Sciences Program, Indiana University, Bloomington, IN 47405, USA
| | - Kentaro Yamada
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yuichiro Takagi
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Heather A Hundley
- Medical Sciences Program, Indiana University, Bloomington, IN 47405, USA
| |
Collapse
|
11
|
Langut Y, Edinger N, Flashner-Abramson E, Melamed-Book N, Lebendiker M, Levi-Kalisman Y, Klein S, Levitzki A. PSMA-homing dsRNA chimeric protein vector kills prostate cancer cells and activates anti-tumor bystander responses. Oncotarget 2018; 8:24046-24062. [PMID: 28445962 PMCID: PMC5421826 DOI: 10.18632/oncotarget.15733] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 02/11/2017] [Indexed: 01/12/2023] Open
Abstract
The treatment of metastatic androgen-resistant prostate cancer remains a challenge. We describe a protein vector that selectively delivers synthetic dsRNA, polyinosinic/polycytidylic acid (polyIC), to prostate tumors by targeting prostate specific membrane antigen (PSMA), which is overexpressed on the surface of prostate cancer cells. The chimeric protein is built from the double stranded RNA (dsRNA) binding domain of PKR tethered to a single chain anti-PSMA antibody. When complexed with polyIC, the chimera demonstrates selective and efficient killing of prostate cancer cells. The treatment causes the targeted cancer cells to undergo apoptosis and to secrete toxic cytokines. In a bystander effect, these cytokines kill neighboring cancer cells that do not necessarily overexpress PSMA, and activate immune cells that enhance the killing effect. The strong effects of the targeted polyIC are demonstrated on both 2D cell cultures and 3D tumor spheroids.
Collapse
Affiliation(s)
- Yael Langut
- Department of Biological Chemistry, Unit of Cellular Signaling, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nufar Edinger
- Department of Biological Chemistry, Unit of Cellular Signaling, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Efrat Flashner-Abramson
- Department of Biological Chemistry, Unit of Cellular Signaling, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Naomi Melamed-Book
- Department of Biological Chemistry, Unit of Bio-Imaging, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Mario Lebendiker
- The Protein Purification Facility, Wolfson Center for Applied Structural Biology, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yael Levi-Kalisman
- The Center for Nanoscience and Nanotechnology, Silberman Institute for Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Shoshana Klein
- Department of Biological Chemistry, Unit of Cellular Signaling, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alexander Levitzki
- Department of Biological Chemistry, Unit of Cellular Signaling, Silberman Institute of Life Sciences, Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel
| |
Collapse
|
12
|
Su YC, Reshi L, Chen LJ, Li WH, Chiu HW, Hong JR. Nuclear targeting of the betanodavirus B1 protein via two arginine-rich domains induces G1/S cell cycle arrest mediated by upregulation of p53/p21. Sci Rep 2018; 8:3079. [PMID: 29449573 PMCID: PMC5814437 DOI: 10.1038/s41598-018-21340-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 02/02/2018] [Indexed: 12/20/2022] Open
Abstract
The molecular functions of betanodavirus non-structural protein B and its role in host cell survival remain unclear. In the present study, we examined the roles of specific nuclear targeting domains in B1 localization as well as the effect of B1 nuclear localization on the cell cycle and host cell survival. The B1 protein of the Red spotted grouper nervous necrosis virus (RGNNV) was detected in GF-1 grouper cells as early as 24 hours post-infection (hpi). Using an EYFP-B1 fusion construct, we observed nuclear localization of the B1 protein (up to 99%) in GF-1 cells at 48 hpi. The nuclear localization of B1 was mediated by two arginine-rich nuclear targeting domains (B domain: 46RRSRR51; C domain: 63RDKRPRR70) and domain C was more important than domain B in this process. B1 nuclear localization correlated with upregulation of p53 and p21(wef1/cip1); downregulation of Cyclin D1, CDK4 and Mdm2; and G1/S cell cycle arrest in GF-1 cells. In conclusion, nuclear targeting of the RGNNV B1 protein via two targeting domains causes cell cycle arrest by up-regulating p53/p21 and down-regulating Mdm2, thereby regulating host cell survival.
Collapse
Affiliation(s)
- Yu-Chin Su
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan
| | - Latif Reshi
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan.,Department of Life Science, College of Bioscience & Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan
| | - Lei-Jia Chen
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan
| | - Wei-Han Li
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan
| | - Hsuan-Wen Chiu
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan
| | - Jiann-Ruey Hong
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan, 701, Taiwan. .,Department of Biotechnology and Bioindustry, National Cheng Kung University, Tainan, 701, Taiwan.
| |
Collapse
|
13
|
Sudhagar A, Kumar G, El-Matbouli M. Transcriptome Analysis Based on RNA-Seq in Understanding Pathogenic Mechanisms of Diseases and the Immune System of Fish: A Comprehensive Review. Int J Mol Sci 2018; 19:ijms19010245. [PMID: 29342931 PMCID: PMC5796193 DOI: 10.3390/ijms19010245] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Revised: 01/08/2018] [Accepted: 01/10/2018] [Indexed: 12/12/2022] Open
Abstract
In recent years, with the advent of next-generation sequencing along with the development of various bioinformatics tools, RNA sequencing (RNA-Seq)-based transcriptome analysis has become much more affordable in the field of biological research. This technique has even opened up avenues to explore the transcriptome of non-model organisms for which a reference genome is not available. This has made fish health researchers march towards this technology to understand pathogenic processes and immune reactions in fish during the event of infection. Recent studies using this technology have altered and updated the previous understanding of many diseases in fish. RNA-Seq has been employed in the understanding of fish pathogens like bacteria, virus, parasites, and oomycetes. Also, it has been helpful in unraveling the immune mechanisms in fish. Additionally, RNA-Seq technology has made its way for future works, such as genetic linkage mapping, quantitative trait analysis, disease-resistant strain or broodstock selection, and the development of effective vaccines and therapies. Until now, there are no reviews that comprehensively summarize the studies which made use of RNA-Seq to explore the mechanisms of infection of pathogens and the defense strategies of fish hosts. This review aims to summarize the contemporary understanding and findings with regard to infectious pathogens and the immune system of fish that have been achieved through RNA-Seq technology.
Collapse
Affiliation(s)
- Arun Sudhagar
- Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna 1210, Austria.
- Central Institute of Fisheries Education, Rohtak Centre, Haryana 124411, India.
| | - Gokhlesh Kumar
- Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna 1210, Austria.
| | - Mansour El-Matbouli
- Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna 1210, Austria.
| |
Collapse
|
14
|
Thukral V, Varshney B, Ramly RB, Ponia SS, Mishra SK, Olsen CM, Banerjea AC, Mukherjee SK, Zaidi R, Rimstad E, Lal SK. s8ORF2 protein of infectious salmon anaemia virus is a RNA-silencing suppressor and interacts with Salmon salar Mov10 (SsMov10) of the host RNAi machinery. Virus Genes 2017; 54:199-214. [PMID: 29218433 PMCID: PMC7089075 DOI: 10.1007/s11262-017-1526-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 11/22/2017] [Indexed: 12/24/2022]
Abstract
The infectious salmon anaemia virus (ISAV) is a piscine virus, a member of Orthomyxoviridae family. It encodes at least 10 proteins from eight negative-strand RNA segments. Since ISAV belongs to the same virus family as Influenza A virus, with similarities in protein functions, they may hence be characterised by analogy. Like NS1 protein of Influenza A virus, s8ORF2 of ISAV is implicated in interferon antagonism and RNA-binding functions. In this study, we investigated the role of s8ORF2 in RNAi suppression in a well-established Agrobacterium transient suppression assay in stably silenced transgenic Nicotiana xanthi. In addition, s8ORF2 was identified as a novel interactor with SsMov10, a key molecule responsible for RISC assembly and maturation in the RNAi pathway. This study thus sheds light on a novel route undertaken by viral proteins in promoting viral growth, using the host RNAi machinery.
Collapse
Affiliation(s)
- Vandana Thukral
- Virology & Plant Molecular Biology Groups, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi, 110067, India
| | - Bhavna Varshney
- Virology & Plant Molecular Biology Groups, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi, 110067, India
| | - Rimatulhana B Ramly
- Norwegian University of Life Science, P.O. Box 8146 Dep., 0033, Oslo, Norway
| | - Sanket S Ponia
- Department of Virology, National Institute of Immunology, New Delhi, 110067, India
| | - Sumona Karjee Mishra
- Virology & Plant Molecular Biology Groups, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi, 110067, India.,Prantae Solutions Pvt. Ltd., KIIT-Campus 11, Bhubaneswar, Odisha, India
| | - Christel M Olsen
- Norwegian University of Life Science, P.O. Box 8146 Dep., 0033, Oslo, Norway
| | - Akhil C Banerjea
- Department of Virology, National Institute of Immunology, New Delhi, 110067, India
| | - Sunil K Mukherjee
- Virology & Plant Molecular Biology Groups, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi, 110067, India
| | - Rana Zaidi
- Department of Biochemistry, Faculty of Science, Jamia Hamdard, New Delhi, 110062, India
| | - Espen Rimstad
- Norwegian University of Life Science, P.O. Box 8146 Dep., 0033, Oslo, Norway
| | - Sunil K Lal
- Virology & Plant Molecular Biology Groups, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Road, New Delhi, 110067, India. .,School of Science, Monash University, Sunway Campus, Selangor, 47500, Malaysia.
| |
Collapse
|
15
|
Gillet FX, Garcia RA, Macedo LLP, Albuquerque EVS, Silva MCM, Grossi-de-Sa MF. Investigating Engineered Ribonucleoprotein Particles to Improve Oral RNAi Delivery in Crop Insect Pests. Front Physiol 2017; 8:256. [PMID: 28503153 PMCID: PMC5408074 DOI: 10.3389/fphys.2017.00256] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/10/2017] [Indexed: 01/15/2023] Open
Abstract
Genetically modified (GM) crops producing double-stranded RNAs (dsRNAs) are being investigated largely as an RNA interference (RNAi)-based resistance strategy against crop insect pests. However, limitations of this strategy include the sensitivity of dsRNA to insect gut nucleases and its poor insect cell membrane penetration. Working with the insect pest cotton boll weevil (Anthonomus grandis), we showed that the chimeric protein PTD-DRBD (peptide transduction domain—dsRNA binding domain) combined with dsRNA forms a ribonucleoprotein particle (RNP) that improves the effectiveness of the RNAi mechanism in the insect. The RNP slows down nuclease activity, probably by masking the dsRNA. Furthermore, PTD-mediated internalization in insect gut cells is achieved within minutes after plasma membrane contact, limiting the exposure time of the RNPs to gut nucleases. Therefore, the RNP provides an approximately 2-fold increase in the efficiency of insect gene silencing upon oral delivery when compared to naked dsRNA. Taken together, these data demonstrate the role of engineered RNPs in improving dsRNA stability and cellular entry, representing a path toward the design of enhanced RNAi strategies in GM plants against crop insect pests.
Collapse
Affiliation(s)
| | - Rayssa A Garcia
- Embrapa Genetic Resources and BiotechnologyBrasília, Brazil.,Department of Cellular Biology, Brasilia Federal University (UnB)Brasília, Brazil
| | | | | | | | - Maria F Grossi-de-Sa
- Embrapa Genetic Resources and BiotechnologyBrasília, Brazil.,Graduate Program in Genomics and Biotechnology, Catholic University of BrasiliaBrasilia, Brazil
| |
Collapse
|
16
|
Cheng YK, Wu YC, Chi SC. Humoral and cytokine responses in giant groupers after vaccination and challenge with betanodavirus. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2017; 67:385-394. [PMID: 27581743 DOI: 10.1016/j.dci.2016.08.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/26/2016] [Accepted: 08/26/2016] [Indexed: 06/06/2023]
Abstract
Giant groupers were immunized with two dosages (Vhigh and Vlow) of inactivated nervous necrosis virus (NNV) and subsequently challenged with NNV at 4 weeks post vaccination (wpv). Several indicators were used to analyze the protective effects of the NNV vaccine. The neutralizing antibody titer of fish serum mostly corresponded to the survival rate of immunized fish in the NNV challenge test. Extravascular IgM+ cells were detected in the brains of both NNV-infected and noninfected groupers. After NNV infection, CD8α and IgM gene expression increased in the brains, indicating CD8α+ and IgM+ lymphocyte infiltration. Moreover, the NNV load was not the highest in dead grouper brains, suggesting that this load in the brain was not the key factor for the death of groupers. However, the brains of dead fish showed the highest expression of the interleukin (IL)-1β gene, a neurotoxic factor in the brain. Therefore, IL-1β overexpression is likely to be associated with the death of NNV-infected groupers.
Collapse
Affiliation(s)
- Yuan-Kai Cheng
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan
| | - Yu-Chi Wu
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan; Institute of Molecular Medicine, National Taiwan University, Taipei 10002, Taiwan.
| | - Shau-Chi Chi
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan.
| |
Collapse
|
17
|
Morick D, Saragovi A. Inhibition of nervous necrosis virus by ribavirin in a zebrafish larvae model. FISH & SHELLFISH IMMUNOLOGY 2017; 60:537-544. [PMID: 27833011 DOI: 10.1016/j.fsi.2016.11.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 11/03/2016] [Accepted: 11/04/2016] [Indexed: 06/06/2023]
Abstract
The guanosine analog ribavirin is a broad-spectrum antiviral drug, mostly used in human clinical practice. It has in vitro and in vivo activity against a broad range of RNA and DNA viruses. Here, we report that treatment of zebrafish larvae with ribavirin prior to infection with nervous necrosis virus (NNV) significantly reduces the mortality caused by the virus during the first 10 days post-infection. The RNA genome of NNV harvested from ribavirin-treated infected larvae contains three synonymous and one single non-synonymous mutation, resulting in the replacement of a serine codon with a glycine codon in the RNA-dependent RNA polymerase gene. Adding increasing amounts of guanosine to ribavirin prior to larvae infection did not impede the antiviral activity. Ribavirin treatment of uninfected larvae reduces the basal level of IFNγ, but increases the level of IL-1β mRNA expression. Furthermore, infecting larvae with NNV following ribavirin treatment reduces the expression levels of IFNγ, IFN-I, Mx, and TNF-α genes, while the expression of IL-1β is increased. These results suggest that cytokine modulation plays an important role in the activity of ribavirin against NNV. Mortality of more than 40 species of teleost fish, mostly larvae and juveniles, from NNV is a major obstacle in hatcheries, and impedes the supply of young fish to farms. Hence, cost-effective ribavirin treatment should be considered as an efficient means to reduce the peril of NNV.
Collapse
Affiliation(s)
- Danny Morick
- Department of Pathology and Immunology, Lautenberg Center for General and Tumor Immunology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Amijai Saragovi
- Department of Pathology and Immunology, Lautenberg Center for General and Tumor Immunology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| |
Collapse
|
18
|
Wen CM. Characterization and viral susceptibility of a brain cell line from brown-marbled grouper Epinephelus fuscoguttatus (Forsskål) with persistent betanodavirus infection. JOURNAL OF FISH DISEASES 2016; 39:1335-1346. [PMID: 27087415 DOI: 10.1111/jfd.12464] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 01/08/2016] [Accepted: 01/10/2016] [Indexed: 06/05/2023]
Abstract
A continuous cell line designated BMGB (brown-marbled grouper brain) was established from the brain tissues of the brown-marbled grouper Epinephelus fuscoguttatus and characterized. BMGB cells were identified as astroglial progenitor cells because they expressed glial fibrillary acidic protein and keratin and were persistently infected by betanodavirus, as confirmed through immunocytochemistry, polymerase chain reaction and immunoblot analyses. Because few intact virions were present in the BMGB cell culture fluid, the cytopathic effect (CPE) was not observed when the culture fluid was inoculated with GBC1 cells. However, BMGB cells displayed typical CPE after infection with additional betanodavirus, megalocytivirus and chum salmon reovirus. BMGB cells showed low myxovirus resistance (Mx) protein expression, which increased following betanodavirus and reovirus infection. Because the cells contained several unusual or degraded viral proteins, the persistent infection of betanodavirus in the BMGB cells may have resulted from a mechanism that destroys the viral proteins rather than the result of Mx protein expression. Despite the persistent betanodavirus infection, BMGB cells proliferated in a manner similar to other normal tropic fish cells and supported the propagation of several piscine viruses; however, the yield was lower than that of normal cells. The BMGB cells will be useful for investigating virus and host cell interaction.
Collapse
Affiliation(s)
- C M Wen
- Department of Life Sciences, National University of Kaohsiung, Kaohsiung, Taiwan.
| |
Collapse
|
19
|
Costa JZ, Thompson KD. Understanding the interaction between Betanodavirus and its host for the development of prophylactic measures for viral encephalopathy and retinopathy. FISH & SHELLFISH IMMUNOLOGY 2016; 53:35-49. [PMID: 26997200 DOI: 10.1016/j.fsi.2016.03.033] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/04/2016] [Accepted: 03/15/2016] [Indexed: 05/22/2023]
Abstract
Over the last three decades, the causative agent of viral encephalopathy and retinopathy (VER) disease has become a serious problem of marine finfish aquaculture, and more recently the disease has also been associated with farmed freshwater fish. The virus has been classified as a Betanodavirus within the family Nodaviridae, and the fact that Betanodaviruses are known to affect more than 120 different farmed and wild fish and invertebrate species, highlights the risk that Betanodaviruses pose to global aquaculture production. Betanodaviruses have been clustered into four genotypes, based on the RNA sequence of the T4 variable region of their capsid protein, and are named after the fish species from which they were first derived i.e. Striped Jack nervous necrosis virus (SJNNV), Tiger puffer nervous necrosis virus (TPNNV), Barfin flounder nervous necrosis virus (BFNNV) and Red-spotted grouper nervous necrosis virus (RGNNV), while an additional genotype turbot betanodavirus strain (TNV) has also been proposed. However, these genotypes tend to be associated with a particular water temperature range rather than being species-specific. Larvae and juvenile fish are especially susceptible to VER, with up to 100% mortality resulting in these age groups during disease episodes, with vertical transmission of the virus increasing the disease problem in smaller fish. A number of vaccine preparations have been tested in the laboratory and in the field e.g. inactivated virus, recombinant proteins, virus-like particles and DNA based vaccines, and their efficacy, based on relative percentage survival, has ranged from medium to high levels of protection to little or no protection. Ultimately a combination of effective prophylactic measures, including vaccination, is needed to control VER, and should also target larvae and broodstock stages of production to help the industry deal with the problem of vertical transmission. As yet there are no commercial vaccines for VER and the aquaculture industry eagerly awaits such a product. In this review we provide an overview on the current state of knowledge of the disease, the pathogen, and interactions between betanodavirus and its host, to provide a greater understanding of the multiple factors involved in the disease process. Such knowledge is needed to develop effective methods for controlling VER in the field, to protect the various aquaculture species farmed globally from the different Betanodavirus genotypes to which they are susceptible.
Collapse
Affiliation(s)
- Janina Z Costa
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Scotland, EH26 0PZ, United Kingdom.
| | - Kim D Thompson
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Scotland, EH26 0PZ, United Kingdom
| |
Collapse
|
20
|
Landeo-Ríos Y, Navas-Castillo J, Moriones E, Cañizares MC. The p22 RNA silencing suppressor of the crinivirus Tomato chlorosis virus preferentially binds long dsRNAs preventing them from cleavage. Virology 2016; 488:129-36. [PMID: 26629953 PMCID: PMC7111720 DOI: 10.1016/j.virol.2015.11.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 09/19/2015] [Accepted: 11/10/2015] [Indexed: 12/04/2022]
Abstract
Viruses encode silencing suppressor proteins to counteract RNA silencing. Because dsRNA plays a key role in silencing, a general silencing suppressor strategy is dsRNA binding. The p22 suppressor of the plant virus Tomato chlorosis virus (ToCV; genus Crinivirus, family Closteroviridae) has been described as having one of the longest lasting local suppressor activities. However, the mechanism of action of p22 has not been characterized. Here, we show that ToCV p22 binds long dsRNAs in vitro, thus interfering with their processing into small RNAs (sRNAs) by an RNase III-type Dicer homolog enzyme. Additionally, we have studied whether a putative zinc finger motif found in p22 has a role in dsRNA binding and suppressor function. The efficient ability of p22 to suppress RNA silencing, triggered by hairpin transcripts transiently expressed in planta, supports the relationship between its ability to bind dsRNA in vitro and its ability to inhibit RNA silencing in vivo.
Collapse
Affiliation(s)
- Yazmín Landeo-Ríos
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora"- Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Estación Experimental "La Mayora", 29750 Algarrobo-Costa, Málaga, Spain
| | - Jesús Navas-Castillo
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora"- Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Estación Experimental "La Mayora", 29750 Algarrobo-Costa, Málaga, Spain
| | - Enrique Moriones
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora"- Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Estación Experimental "La Mayora", 29750 Algarrobo-Costa, Málaga, Spain
| | - M Carmen Cañizares
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora"- Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Estación Experimental "La Mayora", 29750 Algarrobo-Costa, Málaga, Spain.
| |
Collapse
|
21
|
Reshi L, Wu JL, Wang HV, Hong JR. Aquatic viruses induce host cell death pathways and its application. Virus Res 2015; 211:133-44. [PMID: 26494167 DOI: 10.1016/j.virusres.2015.10.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/07/2015] [Accepted: 10/14/2015] [Indexed: 11/15/2022]
Abstract
Virus infections of mammalian and animal cells consist of a series of events. As intracellular parasites, viruses rely on the use of host cellular machinery. Through the use of cell culture and molecular approaches over the past decade, our knowledge of the biology of aquatic viruses has grown exponentially. The increase in aquaculture operations worldwide has provided new approaches for the transmission of aquatic viruses that include RNA and DNA viruses. Therefore, the struggle between the virus and the host for control of the cell's death machinery is crucial for survival. Viruses are obligatory intracellular parasites and, as such, must modulate apoptotic pathways to control the lifespan of their host to complete their replication cycle. This paper updates the discussion on the detailed mechanisms of action that various aquatic viruses use to induce cell death pathways in the host, such as Bad-mediated, mitochondria-mediated, ROS-mediated and Fas-mediated cell death circuits. Understanding how viruses exploit the apoptotic pathways of their hosts may provide great opportunities for the development of future potential therapeutic strategies and pathogenic insights into different aquatic viral diseases.
Collapse
Affiliation(s)
- Latif Reshi
- Laboratory of Molecular Virology and Biotechnology, College of Bioscience and Biotechnology, Institute of Biotechnology, National Cheng Kung University, No 1. University Road, Tainan City 701, Taiwan, ROC; Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1. University Road, Tainan City 701, Taiwan, ROC
| | - Jen-Leih Wu
- Laboratory of Marine Molecular Biology and Biotechnology, Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei 115, Taiwan, ROC
| | - Hao-Ven Wang
- Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1. University Road, Tainan City 701, Taiwan, ROC
| | - Jiann-Ruey Hong
- Laboratory of Molecular Virology and Biotechnology, College of Bioscience and Biotechnology, Institute of Biotechnology, National Cheng Kung University, No 1. University Road, Tainan City 701, Taiwan, ROC.
| |
Collapse
|
22
|
Reshi ML, Wu JL, Wang HV, Hong JR. RNA interference technology used for the study of aquatic virus infections. FISH & SHELLFISH IMMUNOLOGY 2014; 40:14-23. [PMID: 24945574 DOI: 10.1016/j.fsi.2014.06.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/05/2014] [Accepted: 06/09/2014] [Indexed: 06/03/2023]
Abstract
Aquaculture is one of the most important economic activities in Asia and is presently the fastest growing sector of food production in the world. Explosive increases in global fish farming have been accompanied by an increase in viral diseases. Viral infections are responsible for huge economic losses in fish farming, and control of these viral diseases in aquaculture remains a serious challenge. Recent advances in biotechnology have had a significant impact on disease reduction in aquaculture. RNAi is one of the most important technological breakthroughs in modern biology, allowing us to directly observe the effects of the loss of specific genes in living systems. RNA interference technology has emerged as a powerful tool for manipulating gene expression in the laboratory. This technology represents a new therapeutic approach for treating aquatic diseases, including viral infections. RNAi technology is based on a naturally occurring post-transcriptional gene silencing process mediated by the formation of dsRNA. RNAi has been proven widely effective for gene knockdown in mammalian cultured cells, but its utility in fish remains unexplored. This review aims to highlight the RNAi technology that has made significant contributions toward the improvement of aquatic animal health and will also summarize the current status and future strategies concerning the therapeutic applications of RNAi to combat viral disease in aquacultured organisms.
Collapse
Affiliation(s)
- Mohammad Latif Reshi
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, No 1, University Road, Tainan City 701, Taiwan, ROC; Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan, ROC
| | - Jen-Leih Wu
- Laboratory of Marine Molecular Biology and Biotechnology, Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei 115, Taiwan, ROC
| | - Hao-Ven Wang
- Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan, ROC
| | - Jiann-Ruey Hong
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, No 1, University Road, Tainan City 701, Taiwan, ROC.
| |
Collapse
|
23
|
Chen YM, Wang TY, Chen TY. Immunity to betanodavirus infections of marine fish. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 43:174-83. [PMID: 23916690 DOI: 10.1016/j.dci.2013.07.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 07/26/2013] [Accepted: 07/26/2013] [Indexed: 05/07/2023]
Abstract
Betanodaviruses cause viral nervous necrosis in numerous fish species, but some species are resistant to infection by these viruses. It is essential to fully characterize the immune responses that underlie this protective response. Complete characterization of the immune responses against nodaviruses may allow the development of methods that stimulate fish immunity and of an effective betanodavirus vaccine. Such strategies could include stimulation of specific immune system responses or blockage of factors that decrease the immune response. The innate immune system clearly provides a front-line defense, and this includes the production of interferons and other cytokines. Interferons that are released inside infected cells and that suppress viral replication may be the most ancient form of innate immunity. This review focuses on the immune responses of fish to betanodavirus infection.
Collapse
Affiliation(s)
- Young-Mao Chen
- Laboratory of Molecular Genetics, Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Translational Center for Marine Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Agriculture Biotechnology Research Center, National Cheng Kung University, Tainan 70101, Taiwan
| | - Ting-Yu Wang
- Laboratory of Molecular Genetics, Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Translational Center for Marine Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan
| | - Tzong-Yueh Chen
- Laboratory of Molecular Genetics, Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Translational Center for Marine Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Agriculture Biotechnology Research Center, National Cheng Kung University, Tainan 70101, Taiwan; University Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan; Research Center of Ocean Environment and Technology, National Cheng Kung University, Tainan 70101, Taiwan.
| |
Collapse
|
24
|
Wen CM, Ku CC, Wang CS. Viral susceptibility, transfection and growth of SPB--a fish neural progenitor cell line from the brain of snubnose pompano, Trachinotus blochii (Lacépède). JOURNAL OF FISH DISEASES 2013; 36:657-667. [PMID: 23305502 DOI: 10.1111/jfd.12067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 11/08/2012] [Accepted: 11/11/2012] [Indexed: 06/01/2023]
Abstract
This study investigates the susceptibilities of the SPB cell line to fish viruses including giant seaperch iridovirus (GSIV-K1), red sea bream iridovirus (RSIV-Ku), grouper nervous necrosis virus (GNNV-K1), chum salmon reovirus (CSV) and eel herpesvirus (HVA). GSIV-K1, RSIV-Ku and CSV replicated well in SPB cells, with a significant cytopathic effect and virus production. However, the cells were HVA and GNNV refractory. To examine the ability of SPB cells to stably express foreign protein, expression vectors encoding GNNV B1 and B2 fused to enhanced green fluorescent protein (EGFP) and GSIV ORF35L fused to DsRed were constructed and introduced by transfection into SPB cells. Stable transfectants displayed different morphologies compared with SPB and with each other. EGFP-B1 was predominantly localized in the nuclei, EFPF-B2 was distributed throughout the cytoplasm and nucleus, and granular 35L-DsRed was localized with secreted vesicles. The expression of EFPF-B2 in SPB cells produced blebs on the surface, but the cells showing stable expression of EGFP, EGFP-B1 or 35L-DsRed showed normal morphologies. Results show the SPB cells and the transfected cells grow well at temperatures between 20 and 35 °C and with serum-dependent growth. SPB cells are suitable for studies on foreign protein expression and virology.
Collapse
Affiliation(s)
- C-M Wen
- Department of Life Sciences, National University of Kaohsiung, Kaohsiung, Nan-Tzu District, Taiwan.
| | | | | |
Collapse
|
25
|
Lima PC, Harris JO, Cook M. Exploring RNAi as a therapeutic strategy for controlling disease in aquaculture. FISH & SHELLFISH IMMUNOLOGY 2013; 34:729-743. [PMID: 23276883 DOI: 10.1016/j.fsi.2012.11.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 11/21/2012] [Accepted: 11/30/2012] [Indexed: 06/01/2023]
Abstract
Aquatic animal diseases are one of the most significant constraints to the development and management of aquaculture worldwide. As a result, measures to combat diseases of fish and shellfish have assumed a high priority in many aquaculture-producing countries. RNA interference (RNAi), a natural mechanism for post-transcriptional silencing of homologous genes by double-stranded RNA (dsRNA), has emerged as a powerful tool not only to investigate the function of specific genes, but also to suppress infection or replication of many pathogens that cause severe economic losses in aquaculture. However, despite the enormous potential as a novel therapeutical approach, many obstacles must still be overcome before RNAi therapy finds practical application in aquaculture, largely due to the potential for off-target effects and the difficulties in providing safe and effective delivery of RNAi molecules in vivo. In the present review, we discuss the current knowledge of RNAi as an experimental tool, as well as the concerns and challenges ahead for the application of such technology to combat infectious disease of farmed aquatic animals.
Collapse
Affiliation(s)
- Paula C Lima
- CSIRO Marine and Atmospheric Research, C/-CSIRO Livestock Industries, QBP, 306 Carmody Rd, St Lucia, QLD 4067, Australia
| | | | | |
Collapse
|
26
|
Hong JR. Betanodavirus: Mitochondrial disruption and necrotic cell death. World J Virol 2013; 2:1-5. [PMID: 24175224 PMCID: PMC3785042 DOI: 10.5501/wjv.v2.i1.1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 03/01/2013] [Indexed: 02/05/2023] Open
Abstract
Betanodaviruses cause viral nervous necrosis, an infectious neuropathological condition in fish that is characterized by necrosis of the central nervous system, including the brain and retina. This disease can cause mass mortality in larval and juvenile populations of several teleost species and is of global economic importance. The mechanism of brain and retina damage during betanodavirus infection is poorly understood. In this review, we will focus recent results that highlight betanodavirus infection-induced molecular death mechanisms in vitro. Betanodavirus can induce host cellular death and post-apoptotic necrosis in fish cells. Betanodavirus-induced necrotic cell death is also correlated with loss of mitochondrial membrane potential in fish cells, as this necrotic cell death is blocked by the mitochondrial membrane permeability transition pore inhibitor bongkrekic acid and the expression of the anti-apoptotic Bcl-2 family member zfBcl-xL. Moreover, this mitochondria-mediated necrotic cell death may require a caspase-independent pathway. A possible cellular death pathway involving mitochondrial function and the modulator zfBcl-xs is discussed which may provide new insights into the necrotic pathogenesis of betanodavirus.
Collapse
|
27
|
Valli A, Busnadiego I, Maliogka V, Ferrero D, Castón JR, Rodríguez JF, García JA. The VP3 factor from viruses of Birnaviridae family suppresses RNA silencing by binding both long and small RNA duplexes. PLoS One 2012; 7:e45957. [PMID: 23049903 PMCID: PMC3458112 DOI: 10.1371/journal.pone.0045957] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 08/23/2012] [Indexed: 12/23/2022] Open
Abstract
RNA silencing is directly involved in antiviral defense in a wide variety of eukaryotic organisms, including plants, fungi, invertebrates, and presumably vertebrate animals. The study of RNA silencing-mediated antiviral defences in vertebrates is hampered by the overlap with other antiviral mechanisms; thus, heterologous systems are often used to study the interplay between RNA silencing and vertebrate-infecting viruses. In this report we show that the VP3 protein of the avian birnavirus Infectious bursal disease virus (IBDV) displays, in addition to its capacity to bind long double-stranded RNA, the ability to interact with double-stranded small RNA molecules. We also demonstrate that IBDV VP3 prevents the silencing mediated degradation of a reporter mRNA, and that this silencing suppression activity depends on its RNA binding ability. Furthermore, we find that the anti-silencing activity of IBDV VP3 is shared with the homologous proteins expressed by both insect- and fish-infecting birnaviruses. Finally, we show that IBDV VP3 can functionally replace the well-characterized HCPro silencing suppressor of Plum pox virus, a potyvirus that is unable to infect plants in the absence of an active silencing suppressor. Altogether, our results support the idea that VP3 protects the viral genome from host sentinels, including those of the RNA silencing machinery.
Collapse
Affiliation(s)
- Adrian Valli
- Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | | | | | - Diego Ferrero
- Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | | | | | | |
Collapse
|
28
|
Seo JK, Kwon SJ, Rao ALN. Molecular dissection of Flock house virus protein B2 reveals that electrostatic interactions between N-terminal domains of B2 monomers are critical for dimerization. Virology 2012; 432:296-305. [PMID: 22721960 DOI: 10.1016/j.virol.2012.05.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 05/16/2012] [Accepted: 05/28/2012] [Indexed: 11/18/2022]
Abstract
Flock house virus (FHV) encodes a suppressor protein B2 to overcome antiviral RNA silencing during infection. Biochemical analyses have shown that a homodimer of B2 binds to double-stranded RNA to inhibit dicer-mediated cleavage of dsRNA and incorporation of small interfering RNAs into the RNA-induced silencing complex. In this study, using FHV-Nicotiana benthamiana system, we identified that the charged amino acids at the N-terminus of B2 are critical for dimerization. Interestingly, B2 mutants defective in dimerization exhibited enhanced silencing suppressor activity, Furthermore, we found that the C-terminal charged amino acids are dispensable for B2 dimerization and viral RNA silencing suppression but are critical for transgene silencing suppression. Additional yeast two hybrid assays revealed that dimerization of B2 is not essential for interacting with the RNA silencing machinery. Taken together, our data provide evidence that both monomeric and dimeric B2 proteins function in different modes to suppress RNA silencing.
Collapse
Affiliation(s)
- Jang-Kyun Seo
- Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521-0122, USA
| | | | | |
Collapse
|
29
|
RNA binding by a novel helical fold of b2 protein from wuhan nodavirus mediates the suppression of RNA interference and promotes b2 dimerization. J Virol 2011; 85:9543-54. [PMID: 21734038 DOI: 10.1128/jvi.00785-11] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Wuhan nodavirus (WhNV) is a newly identified member of the Nodaviridae family with a bipartite genome of positive-sense RNAs. A nonstructural protein encoded by subgenomic RNA3 of nodaviruses, B2, serves as a potent RNA silencing suppressor (RSS) by sequestering RNA duplexes. We have previously demonstrated that WhNV B2 blocks RNA silencing in cultured Drosophila cells. However, the molecular mechanism by which WhNV B2 functions remains unknown. Here, we successfully established an RNA silencing system in cells derived from Pieris rapae, a natural host of WhNV, by introducing into these cells double-stranded RNA (dsRNA)-expressing plasmids or chemically synthesized small interfering RNAs (siRNAs). Using this system, we revealed that the WhNV B2 protein inhibited Dicer-mediated dsRNA cleavage and the incorporation of siRNA into the RNA-induced silencing complex (RISC) by sequestering dsRNA and siRNA. Based on the modeled B2 3-dimensional structure, serial single alanine replacement mutations and N-terminal deletion analyses showed that the RNA-binding domain of B2 is formed by its helices α2 and α3, while helix α1 mediates B2 dimerization. Furthermore, positive feedback between RNA binding and B2 dimerization was uncovered by gel shift assay and far-Western blotting, revealing that B2 dimerization is required for its binding to RNA, whereas RNA binding to B2 in turn promotes its dimerization. All together, our findings uncovered a novel RNA-binding mode of WhNV B2 and provided evidence that the promotion effect of RNA binding on dimerization exists in a viral RSS protein.
Collapse
|
30
|
Kitagishi Y, Okumura N, Yoshida H, Tateishi C, Nishimura Y, Matsuda S. Dicer functions in aquatic species. JOURNAL OF AMINO ACIDS 2011; 2011:782187. [PMID: 22312469 PMCID: PMC3268030 DOI: 10.4061/2011/782187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 04/02/2011] [Indexed: 12/04/2022]
Abstract
Dicer is an RNase III enzyme with two catalytic subunits, which catalyzes the cleavage of double-stranded RNA to small interfering RNAs and micro-RNAs, which are mainly involved in invasive nucleic acid defense and endogenous genes regulation. Dicer is abundantly expressed in embryos, indicating the importance of the protein in early embryonic development. In addition, Dicer is thought to be involved in defense mechanism against foreign nucleic acids such as viruses. This paper will mainly focus on the recent progress of Dicer-related research and discuss potential RNA interference pathways in aquatic species.
Collapse
Affiliation(s)
- Yasuko Kitagishi
- Department of Environmental Health Science, Nara Women's University, Kita-Uoya Nishimachi, Nara 630-8506, Japan
| | | | | | | | | | | |
Collapse
|
31
|
Biacchesi S. The reverse genetics applied to fish RNA viruses. Vet Res 2011; 42:12. [PMID: 21314978 PMCID: PMC3037892 DOI: 10.1186/1297-9716-42-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 11/18/2010] [Indexed: 02/05/2023] Open
Abstract
Aquaculture has expanded rapidly to become a major economic and food-producing sector worldwide these last 30 years. In parallel, viral diseases have emerged and rapidly spread from farm to farm causing enormous economic losses. The most problematic viruses encountered in the field are mainly, but not exclusively, RNA viruses belonging to the Novirhabdovirus, Aquabirnavirus, Alphavirus and Betanodavirus genera. The recent establishment of reverse genetics systems to recover infectious fish RNA viruses entirely from cDNA has made possible to genetically manipulate the viral genome. These systems have provided powerful tools to study all aspects of the virus biology and virus-host interactions but also gave the opportunity to use these viruses as live vaccines or as gene vectors. This review provides an overview on the recent breakthroughs achieved by using these reverse genetics systems in terms of viral protein function, virulence and host-specificity factor, vaccine development and vector design.
Collapse
Affiliation(s)
- Stéphane Biacchesi
- Unité de Virologie et Immunologie Moléculaires, INRA, CRJ, 78352 Jouy-en-Josas, France.
| |
Collapse
|
32
|
Su YC, Hong JR. Betanodavirus B2 causes ATP depletion-induced cell death via mitochondrial targeting and complex II inhibition in vitro and in vivo. J Biol Chem 2010; 285:39801-10. [PMID: 20870718 DOI: 10.1074/jbc.m110.164988] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The betanodavirus non-structural protein B2 is a newly discovered necrotic death factor with a still unknown role in regulation of mitochondrial function. In the present study, we examined protein B2-mediated inhibition of mitochondrial complex II activity, which results in ATP depletion and thereby in a bioenergetic crisis in vitro and in vivo. Expression of protein B2 was detected early at 24 h postinfection with red-spotted grouper nervous necrosis virus in the cytoplasm. Later B2 was found in mitochondria using enhanced yellow fluorescent protein (EYFP) and immuno-EM analysis. Furthermore, the B2 mitochondrial targeting signal peptide was analyzed by serial deletion and specific point mutation. The sequence of the B2 targeting signal peptide ((41)RTFVISAHAA(50)) was identified and its presence correlated with loss of mitochondrial membrane potential in fish cells. Protein B2 also was found to dramatically inhibit complex II (succinate dehydrogenase) activity, which impairs ATP synthesis in fish GF-1 cells as well as human embryonic kidney 293T cells. Furthermore, when B2 was injected into zebrafish embryos at the one-cell stage to determine its cytotoxicity and ability to inhibit ATP synthesis, we found that B2 caused massive embryonic cell death and depleted ATP resulting in further embryonic death at 10 and 24 h post-fertilization. Taken together, our results indicate that betanodavirus protein B2-induced cell death is due to direct targeting of the mitochondrial matrix by a specific signal peptide that targets mitochondria and inhibits mitochondrial complex II activity thereby reducing ATP synthesis.
Collapse
Affiliation(s)
- Yu-Chin Su
- Laboratory of Molecular Virology and Biotechnology, Institute of Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
| | | |
Collapse
|
33
|
Adachi K, Sumiyoshi K, Ariyasu R, Yamashita K, Zenke K, Okinaka Y. Susceptibilities of medaka (Oryzias latipes) cell lines to a betanodavirus. Virol J 2010; 7:150. [PMID: 20624282 PMCID: PMC2908575 DOI: 10.1186/1743-422x-7-150] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 07/12/2010] [Indexed: 11/19/2022] Open
Abstract
Background Betanodaviruses, members of the family Nodaviridae, have bipartite, positive-sense RNA genomes and are the causal agents of viral nervous necrosis in many marine fish species. Recently, the viruses were shown to infect a few freshwater fish species including a model fish medaka (Oryzias latipes). Although virological study using cultured medaka cells would provide a lot of insight into virus-fish interactions in molecular aspects, no such cells have yet been tested for virus susceptibility. Results We tested ten medaka cell lines for susceptibilities to redspotted grouper nervous necrosis virus (RGNNV). Although the viral coat protein was detected in all the cell lines inoculated, the levels of cytopathic effect development and viral propagation were quite different among the cell lines. Those levels were especially high in OLHNI-1 and OLHNI-2 cells, but were extremely low in OLME-104 cells. Some cell lines entered into antiviral state after RGNNV infections probably because of inducing an antiviral system. This is the first report to examine the susceptibilities of cultured medaka cells against a virus. Conclusion OLHNI-1 and OLHNI-2 cells are candidates of new standard cells for betanodavirus study because of their high susceptibilities to the virus and their several advantages as model fish cells.
Collapse
Affiliation(s)
- Kei Adachi
- Graduate School of Biosphere Science, Hiroshima University, Higashi-hiroshima 739-8528, Japan
| | | | | | | | | | | |
Collapse
|
34
|
Singh G, Korde R, Malhotra P, Mukherjee S, Bhatnagar RK. Systematic deletion and site-directed mutagenesis of FHVB2 establish the role of C-terminal amino acid residues in RNAi suppression. Biochem Biophys Res Commun 2010; 398:290-5. [PMID: 20599719 DOI: 10.1016/j.bbrc.2010.06.083] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 06/20/2010] [Indexed: 01/02/2023]
Abstract
Viruses and siRNA/miRNA machinery of the host cell interact in diverse ways with the virus encoded RNAi suppressor proteins. These interactions have implications on the replication and pathogenicity of the virus and also on the immune response of the host. Suppressor protein B2 of insect Flock House Virus (FHVB2), has been shown to mediate RNAi suppression via N-terminal region by directly binding to dsRNA. We have previously shown that FHVB2 protein also interacts with host Dicer protein via its PAZ domain. In the present study, we performed systematic mutagenesis studies to map the FHVB2 regions involved in mediating suppression of RNAi. Progressive deletion of 17 amino acids from N- and C-terminii of FHVB2 resulted in cumulative decrease in RNAi suppression activity of FHVB2. The deletion of 17 amino acids from the C-terminus resulted in more reduction in RNAi suppression in comparison to the N-terminal deletions. Subsequently, we generated 17 successive point mutants of FHVB2 C-terminus and evaluated the RNAi suppression activity for each of the point mutants. Each point mutation resulted in a significant reduction in RNAi suppression activity of FHVB2. These results provide evidence for the role of C-terminal of FHVB2 in RNAi suppression.
Collapse
Affiliation(s)
- Gatikrushna Singh
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | | | | | | | | |
Collapse
|
35
|
Sepulcre MP, Muñoz I, Roca FJ, López-Muñoz A, Mulero V. Molecular strategies used by fish pathogens to interfere with host-programmed cell death. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2010; 34:603-610. [PMID: 20097221 DOI: 10.1016/j.dci.2010.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 01/13/2010] [Accepted: 01/13/2010] [Indexed: 05/28/2023]
Abstract
Cell death is of pivotal importance in the regulation of the immune response and has a direct impact in disease resistance. Fish are becoming an interesting model organism to study the immune response since they hold a key phylogenetic position and many species are of high economic interest. The role of cell death in the immune response has recently been investigated in fish and the molecules and pathways orchestrating cell death in this group of animals have begun to be elucidated. In this study, we will summarize the different molecular strategies displayed by major fish bacterial and viral pathogens to interfere with programmed cell death of the host as well as the relevance of cell death in the resolution of the infectious diseases caused by these pathogens.
Collapse
Affiliation(s)
- María P Sepulcre
- Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, Murcia, Spain
| | | | | | | | | |
Collapse
|
36
|
Abstract
Nuclear DNA helicase II (NDH II) was first isolated from calf thymus using a DNA-unwinding assay. Subsequently it has been shown to be a homologue of human RNA helicase A (RHA) and the maleless protein (MLE) from Drosophila. Accordingly, the protein possesses both DNA and RNA unwinding activities. Also, it can use all four NTPs or dNTPs to fuel the reaction. At its N-terminus it possesses two double-strand RNA binding domains (dsRBD I and II), while the C-terminus comprises an imperfect glycine (G)- and arginine (R)-rich repeat, a so-called RGG-box that preferably binds to ssDNA or ssRNA. Many proteins interact with NDH II both at its N- and C-terminus and thereby mediate transcriptional regulation, RNA processing, and transport, the DNA damage response and genome surveillance. The latter includes the histone variant gamma-H2AX and the Werner syndrome helicase (WRN). Here we describe experimental approaches to obtain mechanistic information about this important nuclear helicase.
Collapse
|
37
|
George CX, Li Z, Okonski KM, Toth AM, Wang Y, Samuel CE. Tipping the balance: antagonism of PKR kinase and ADAR1 deaminase functions by virus gene products. J Interferon Cytokine Res 2010; 29:477-87. [PMID: 19715457 DOI: 10.1089/jir.2009.0065] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The protein kinase regulated by RNA (PKR) and the adenosine deaminase acting on RNA (ADAR1) are interferon-inducible enzymes that play important roles in biologic processes including the antiviral actions of interferons, signal transduction, and apoptosis. PKR catalyzes the RNA-dependent phosphorylation of protein synthesis initiation factor eIF-2 alpha, thereby leading to altered translational patterns in interferon-treated and virus-infected cells. PKR also modulates signal transduction responses, including the induction of interferon. ADAR1 catalyzes the deamination of adenosine (A) to generate inosine (I) in RNAs with double-stranded character. Because I is recognized as G instead of A, A-to-I editing by ADAR1 can lead to genetic recoding and altered RNA structures. The importance of PKR and ADAR1 in innate antiviral immunity is illustrated by a number of viruses that encode either RNA or protein viral gene products that antagonize PKR and ADAR1 enzymatic activity, localization, or stability.
Collapse
Affiliation(s)
- Cyril X George
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California 93106, USA
| | | | | | | | | | | |
Collapse
|
38
|
Körber S, Shaik Syed Ali P, Chen JCH. Structure of the RNA-binding domain of Nodamura virus protein B2, a suppressor of RNA interference. Biochemistry 2010; 48:2307-9. [PMID: 19249868 DOI: 10.1021/bi900126s] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein B2 from Nodamura virus (NMV B2), a member of the Nodavirus family, acts as a suppressor of RNA interference (RNAi). The N-terminal domain of NMV B2, consisting of residues 1-79, recognizes double-stranded RNA (dsRNA). The 2.5 A crystal structure of the RNA-binding domain of NMV B2 shows a dimeric, helical bundle structure. The structure shows a conserved set of RNA-binding residues compared with flock house virus B2, despite limited sequence identity. The crystal packing places the RNA-binding residues along one face of symmetry-related molecules, suggesting a potential platform for recognition of dsRNA.
Collapse
Affiliation(s)
- Stephanie Körber
- Institute of Biophysical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | | | | |
Collapse
|
39
|
Myles KM, Morazzani EM, Adelman ZN. Origins of alphavirus-derived small RNAs in mosquitoes. RNA Biol 2009; 6:387-91. [PMID: 19535909 DOI: 10.4161/rna.6.4.8946] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The continual transmission in nature of many arthropod-borne viruses depends on the establishment of a persistent, nonpathogenic infection in a mosquito vector. The importance of antiviral immunity directed by small RNAs in the mechanism by which alphaviruses establish a persistent, nonpathogenic infection in the mosquito vector has recently been demonstrated. The origin of the small RNAs central to this RNA silencing response has recently been the subject of debate. Here we briefly summarize what is known about the mechanism of small RNA-directed immunity in invertebrates, and discuss current models for the viral triggers of this response. Finally, we summarize evidence indicating that alphavirus double-stranded replicative intermediates trigger an exogenous-siRNA pathway in mosquitoes resulting in the biogenesis of virus-derived siRNAs.
Collapse
Affiliation(s)
- Kevin M Myles
- Department of Entomology, Virginia Tech, Blacksburg, Virginia 24061, USA.
| | | | | |
Collapse
|
40
|
Olveira JG, Souto S, Dopazo CP, Thiéry R, Barja JL, Bandín I. Comparative analysis of both genomic segments of betanodaviruses isolated from epizootic outbreaks in farmed fish species provides evidence for genetic reassortment. J Gen Virol 2009; 90:2940-2951. [PMID: 19710256 DOI: 10.1099/vir.0.013912-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Sequencing of the full coding region of both genomic segments of seven betanodavirus strains isolated from different farmed species in Spain and Portugal revealed that six were reassortants, exhibiting a red-spotted grouper nervous necrosis virus (RGNNV)-type RNA1 and a striped jack nervous necrosis virus (SJNNV)-type RNA2. Analysis of sequences of reassortant strains at both the genomic and protein levels revealed the existence of differences compared with type strains of both genotypes. These differences were greater in the polymerase sequence, which is remarkable because viral structural proteins generally diverge more rapidly than non-structural proteins. Changes in two amino acids observed in the SJNNV capsid protein might be involved in the colonization of new host species by these reassortant strains. In addition, a more extensive phylogenetic analysis, including partial sequences of both RNA segments of 16 other Iberian nodaviruses, confirmed the existence of reassortment between RGNNV and SJNNV.
Collapse
Affiliation(s)
- J G Olveira
- Unidad de Ictiopatología-Patología Viral, Departamento de Microbiología y Parasitología, Instituto de Acuicultura, Universidad de Santiago de Compostela, Spain
| | - S Souto
- Unidad de Ictiopatología-Patología Viral, Departamento de Microbiología y Parasitología, Instituto de Acuicultura, Universidad de Santiago de Compostela, Spain
| | - C P Dopazo
- Unidad de Ictiopatología-Patología Viral, Departamento de Microbiología y Parasitología, Instituto de Acuicultura, Universidad de Santiago de Compostela, Spain
| | - R Thiéry
- French Food Safety Agency, BP111, F-06902 Sophia Antipolis, France
| | - J L Barja
- Unidad de Ictiopatología-Patología Viral, Departamento de Microbiología y Parasitología, Instituto de Acuicultura, Universidad de Santiago de Compostela, Spain
| | - I Bandín
- Unidad de Ictiopatología-Patología Viral, Departamento de Microbiología y Parasitología, Instituto de Acuicultura, Universidad de Santiago de Compostela, Spain
| |
Collapse
|
41
|
Singh G, Popli S, Hari Y, Malhotra P, Mukherjee S, Bhatnagar RK. Suppression of RNA silencing by Flock house virus B2 protein is mediated through its interaction with the PAZ domain of Dicer. FASEB J 2009; 23:1845-57. [PMID: 19193719 DOI: 10.1096/fj.08-125120] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
RNA silencing is a conserved pathway that functions as an antiviral mechanism. The majority of viruses encode silencing suppressors that interfere with siRNA- and miRNA-guided silencing pathways. The insect flock house virus B2 protein (FHVB2) functions as an RNAi silencing suppressor that inhibits siRNA biogenesis. Here, we describe the generation of a GFP silent sensor line (Sf21) and a GFP sensor line expressing FHVB2 to study RNAi suppression mechanisms. Overexpression of FHVB2 resulted in suppression of GFP-RNAi and resumption of GFP expression. Protein fractionation studies with FHVB2-transfected cells showed that FHVB2 associates with a high-molecular-weight complex of Dicer and dsRNA/siRNAs. Yeast two-hybrid and pulldown assays revealed an interaction between FHVB2 and Drosophila Dicer proteins that appeared to involve PAZ domains. To map the FHVB2 domains interacting with Dicer, we used a 17-residue C-terminal deletion mutant. RNAi suppression was reversed in cells transfected with the FHVB2 mutant as revealed by loss of GFP. Additional yeast two-hybrid and in vitro pulldown assays confirmed that the C-terminal region of FHVB2 was involved in the interaction with the PAZ domains of Dicers. These results thus reveal a novel interaction between FHVB2 and Dicer that leads to suppression of siRNA biogenesis.
Collapse
Affiliation(s)
- Gatikrushna Singh
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | | | | | | | | | | |
Collapse
|
42
|
Chen YM, Su YL, Shie PS, Huang SL, Yang HL, Chen TY. Grouper Mx confers resistance to nodavirus and interacts with coat protein. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2008; 32:825-836. [PMID: 18222539 DOI: 10.1016/j.dci.2007.12.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 12/03/2007] [Accepted: 12/06/2007] [Indexed: 05/25/2023]
Abstract
Over-expression of grouper Mx negatively regulated nodavirus activity through direct interaction, likely via the binding and perturbation of the intracellular localization of nodavirus coat protein. Deletion analysis of grouper Mx indicated that the coat protein binds to the effector domain of Mx. The presence of grouper Mx in a poly [I:C] interferon system inhibited nodavirus infection, demonstrating that grouper Mx over-expression has an inhibitory effect on both coat protein and RNA-dependent RNA polymerase of nodavirus antigens, which results in reduced viral yields. We conclude that grouper Mx has a key role in cellular resistance to nodavirus infection.
Collapse
Affiliation(s)
- Young-Mao Chen
- Laboratory of Molecular Genetics, Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
| | | | | | | | | | | |
Collapse
|
43
|
Adachi K, Ichinose T, Watanabe K, Kitazato K, Kobayashi N. Potential for the replication of the betanodavirus redspotted grouper nervous necrosis virus in human cell lines. Arch Virol 2007; 153:15-24. [PMID: 17906832 PMCID: PMC7086817 DOI: 10.1007/s00705-007-1051-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Accepted: 07/24/2007] [Indexed: 11/25/2022]
Abstract
The determination of the host ranges of viruses is important because of the possible emergence of infectious agents, which may result from the zoonotic transmission of animal viruses to humans. The family Nodaviridae, whose members are non-enveloped, positive-stranded bipartite RNA viruses, is comprised of the genera Alphanodavirus and Betanodavirus, whose members predominantly infect insects and fish, respectively. The alphanodaviruses can also infect suckling mice and suckling hamsters, resulting in paralysis and death. Pigs near the site of isolation of the Nodamura virus (NoV), an alphanodavirus, have been reported to have high levels of NoV neutralizing antibody, suggesting that they may be part of the natural host range of this virus. Betanodaviruses are the causative agents of viral nervous necrosis, which occurs in several species of fish. However, little is known regarding the mechanism of infection of these viruses. Whether betanodaviruses can infect hosts other than fish remains unclear. In this study, we examined the possibility that a betanodavirus, redspotted grouper nervous necrosis virus (RGNNV), can infect human cell lines and showed that this virus can attach to the cells but cannot penetrate them, although human cells can support the replication of the betanodavirus when viral RNAs are transfected. The betanodavirus in its present form cannot infect human cells.
Collapse
Affiliation(s)
- K. Adachi
- />Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - T. Ichinose
- />Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - K. Watanabe
- />Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - K. Kitazato
- />Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - N. Kobayashi
- />Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- />Central Research Center, AVSS Corporation, Nagasaki, Japan
| |
Collapse
|
44
|
Adachi K, Ichinose T, Takizawa N, Watanabe K, Kitazato K, Kobayashi N. Inhibition of betanodavirus infection by inhibitors of endosomal acidification. Arch Virol 2007; 152:2217-24. [PMID: 17891330 PMCID: PMC7086734 DOI: 10.1007/s00705-007-1061-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 08/27/2007] [Indexed: 12/03/2022]
Abstract
Betanodaviruses, members of the family Nodaviridae, have small positive-stranded bipartite RNA genomes and are the causal agent of viral nervous necrosis (VNN) in many species of marine farmed fish. In the aquaculture industry, outbreaks of betanodavirus infection and spread in larval and juvenile fish result in devastating damage and heavy economic loss. Although an urgent need exists to develop drugs that inhibit betanodavirus infection, there have been no reports about anti-betanodavirus drugs. Recently, it was reported that betanodaviruses were detected in the endosomes of infected cells, suggesting that betanodaviruses enter fish cells by endocytosis. This finding prompted us to examine whether blocking this endosomal pathway could provide a target for antiviral drug development. In this study, we examined the inhibitory effect of several lysosomotropic agents against betanodavirus infection in fish E-11 cells. The presence of 1 mM NH4Cl or 1 µM chloroquine in the medium inhibited the entry of betanodaviruses into cells and inhibited viral infection. The lysosomotropic agents bafilomycin A1 and monensin also inhibited virus-induced cytopathology and virus production. Our data demonstrate that inhibitors of endosomal acidification are candidates as antiviral agents against betanodavirus.
Collapse
Affiliation(s)
- K Adachi
- Laboratory of Molecular Biology of Infectious Agents, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | | | | | | | | | | |
Collapse
|
45
|
Ou MC, Chen YM, Jeng MF, Chu CJ, Yang HL, Chen TY. Identification of critical residues in nervous necrosis virus B2 for dsRNA-binding and RNAi-inhibiting activity through by bioinformatic analysis and mutagenesis. Biochem Biophys Res Commun 2007; 361:634-40. [PMID: 17669362 DOI: 10.1016/j.bbrc.2007.07.075] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2007] [Accepted: 07/16/2007] [Indexed: 11/26/2022]
Abstract
It is known that the non-structural B2 protein of nervous necrosis virus (NNV) plays an important role in viral replication and can inhibit the RNA interference system of the host cell. Moreover, the mechanism of NNV B2 protein to inhibit RNAi is by sequestration and protection of double strand (ds) RNA. In the flock house virus (FHV), a model alphanodavirus, the structural and mutational analysis of B2 identified that the positively charged Arg54 of the alpha2 helix mediated the dsRNA-binding activity. According to the betanodavirus B2 protein alignment and modeling results, the amino acid sequences and the predicted structure of betanodavirus B2 are different from alphanodaviruses. It was suggested that the four Arg residues of alpha3 helix between amino residues 52-60 of B2 may be involved in dsRNA-binding activity. Thus, this study replaced these four Arg residues with Gln at position 52 (R52Q), 53 (R53Q), 59 (R59Q), and 60 (R60Q) by site-directed mutagenesis method. The dsRNA-binding assays of these B2 mutants demonstrated that mB2(R53Q) and mB2(R60Q) mutants are dsRNA-binding defective. Moreover, we have found mB2(R53Q) and mB2(R60Q) could not antagonize RNAi by using HeLa cell as an RNAi inhibition model. These results suggested that Arg53 and Arg60 of betanodavirus B2 protein may be similar to Arg54 of alphanodavirus FHV B2 protein and are critical for dsRNA binding and RNAi-inhibiting. This study may serve as an example where bioinformatic analysis of related viral genomes may lead to meaningful structural and functional clues for certain viral proteins.
Collapse
Affiliation(s)
- Ming-Chang Ou
- Laboratory of Molecular Genetics, Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
| | | | | | | | | | | |
Collapse
|
46
|
Mézeth KB, Nylund S, Henriksen H, Patel S, Nerland AH, Szilvay AM. RNA-dependent RNA polymerase from Atlantic halibut nodavirus contains two signals for localization to the mitochondria. Virus Res 2007; 130:43-52. [PMID: 17602779 DOI: 10.1016/j.virusres.2007.05.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Revised: 05/08/2007] [Accepted: 05/14/2007] [Indexed: 11/21/2022]
Abstract
Nodaviruses encode an RNA-dependent RNA polymerase called Protein A that is responsible for replication of the viral RNA segments. The intracellular localization of Protein A from a betanodavirus isolated from Atlantic halibut (AHNV) was studied in infected fish cells and in transfected mammalian cells expressing Myc-tagged wild type Protein A and mutants. In infected cells Protein A localized to cytoplasmic structures resembling mitochondria and in transfected mammalian cells the AHNV Protein A was found to co-localize with mitochondrial proteins. Two independent mitochondrial targeting signals, one N-terminal comprising residues 1-40 and one internal consisting of residues 225-246 were sufficient to target both Protein A deletion mutants and enhanced green fluorescent protein (EGFP) to the mitochondria. The N-terminal signal corresponds to the mitochondrial targeting sequence of the Flock House Virus (FHV) Protein A while the internal signal is similar to the single targeting signal previously found in Greasy Grouper Nervous Necrosis Virus (GGNNV) Protein A.
Collapse
|
47
|
Fenner BJ, Goh W, Kwang J. Dissection of double-stranded RNA binding protein B2 from betanodavirus. J Virol 2007; 81:5449-59. [PMID: 17376906 PMCID: PMC1900263 DOI: 10.1128/jvi.00009-07] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Betanodaviruses are small RNA viruses that infect teleost fish and pose a considerable threat to marine aquaculture production. These viruses possess a small protein, termed B2, which binds to and protects double-stranded RNA. This prevents cleavage of virus-derived double-stranded RNAs (dsRNAs) by Dicer and subsequent production of small interfering RNA (siRNA), which would otherwise induce an RNA-silencing response against the virus. In this work, we have performed charged-to-alanine scanning mutagenesis of the B2 protein in order to identify residues required for dsRNA binding and protection. While the majority of the 19 mutated B2 residues were required for maximal dsRNA binding and protection in vitro, residues R53 and R60 were essential for both activities. Subsequent experiments in fish cells confirmed these findings by showing that mutations in these residues abolished accumulation of both the RNA1 and RNA2 components of the viral genome, in addition to preventing any significant induction of the host interferon gene, Mx. Moreover, an obvious positive correlation was found between dsRNA binding and protection in vitro and RNA1, RNA2, and Mx accumulation in fish cells, further validating the importance of the selected amino acid residues. The same trend was also demonstrated using an RNA silencing system in HeLa cells, with residues R53 and R60 being essential for suppression of RNA silencing. Importantly, we found that siRNA-mediated knockdown of Dicer dramatically enhanced the accumulation of a B2 mutant. In addition, we found that B2 is able to induce apoptosis in fish cells but that this was not the result of dsRNA binding.
Collapse
Affiliation(s)
- Beau J Fenner
- Animal Health Biotechnology, Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | | | | |
Collapse
|