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Xue Q, Swevers L, Taning CNT. Plant and insect virus-like particles: emerging nanoparticles for agricultural pest management. PEST MANAGEMENT SCIENCE 2023; 79:2975-2991. [PMID: 37103223 DOI: 10.1002/ps.7514] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 04/20/2023] [Accepted: 04/27/2023] [Indexed: 06/05/2023]
Abstract
Virus-like particles (VLPs) represent a biodegradable, biocompatible nanomaterial made from viral coat proteins that can improve the delivery of antigens, drugs, nucleic acids, and other substances, with most applications in human and veterinary medicine. Regarding agricultural viruses, many insect and plant virus coat proteins have been shown to assemble into VLPs accurately. In addition, some plant virus-based VLPs have been used in medical studies. However, to our knowledge, the potential application of plant/insect virus-based VLPs in agriculture remains largely underexplored. This review focuses on why and how to engineer coat proteins of plant/insect viruses as functionalized VLPs, and how to exploit VLPs in agricultural pest control. The first part of the review describes four different engineering strategies for loading cargo at the inner or the outer surface of VLPs depending on the type of cargo and purpose. Second, the literature on plant and insect viruses the coat proteins of which have been confirmed to self-assemble into VLPs is reviewed. These VLPs are good candidates for developing VLP-based agricultural pest control strategies. Lastly, the concepts of plant/insect virus-based VLPs for delivering insecticidal and antiviral components (e.g., double-stranded RNA, peptides, and chemicals) are discussed, which provides future prospects of VLP application in agricultural pest control. In addition, some concerns are raised about VLP production on a large scale and the short-term resistance of hosts to VLP uptake. Overall, this review is expected to stimulate interest and research exploring plant/insect virus-based VLP applications in agricultural pest management. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Qi Xue
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Luc Swevers
- Insect Molecular Genetics and Biotechnology, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
| | - Clauvis Nji Tizi Taning
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Konevtsova OV, Golushko IY, Podgornik R, Rochal SB. Integration of Cypoviruses into polyhedrin matrix. NANOSCALE ADVANCES 2023; 5:4140-4148. [PMID: 37560430 PMCID: PMC10408579 DOI: 10.1039/d3na00393k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/14/2023] [Indexed: 08/11/2023]
Abstract
Unlike in other viruses, in Cypoviruses the genome is doubly protected since their icosahedral capsids are embedded into a perfect polyhedrin crystal. Current experimental methods cannot resolve the resulting interface structure and we propose a symmetry-based approach to predict it. We reveal a remarkable match between the surfaces of Cypovirus and the outer polyhedrin matrix. The match arises due to the preservation of the common tetragonal symmetry, allowing perfect contacts of polyhedrin trimers with VP1 and VP5 capsid proteins. We highlight a crucial role of the VP5 proteins in embedding the Cypovirus into the polyhedrin matrix and discuss the relationship between the nucleoside triphosphatase activity of the proteins and their role in the superstructure formation. Additionally, we propose an electrostatic mechanism that drives the viral superstructure disassembly occurring in the alkaline environment of the insect intestines. Our study may underpin novel strategies for engineering proteinaceous nanocontainers in diverse biotechnological and chemical applications.
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Affiliation(s)
| | - Ivan Yu Golushko
- Physics Faculty, Southern Federal University Rostov-on-Don Russia
| | - Rudolf Podgornik
- School of Physical Sciences and Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences Beijing 100049 China
- CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100190 China
- Wenzhou Institute of the University of Chinese Academy of Sciences Wenzhou Zhejiang 325000 China
| | - Sergei B Rochal
- Physics Faculty, Southern Federal University Rostov-on-Don Russia
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Ren F, Swevers L, Lu Q, Zhao Y, Yan J, Li H, Sun J. Effect of mutations in capsid shell protein on the assembly of BmCPV virus-like particles. J Gen Virol 2020; 102. [PMID: 33331809 DOI: 10.1099/jgv.0.001542] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a typical single-layer capsid dsRNA virus belonging to the genus Cypovirus in the family Reoviridae. The results of cryo-electron microscopy showed that the BmCPV capsid consists of 60 asymmetric units, and each asymmetric unit contains one turret protein (TP), two large protrusion proteins (LPP) and two capsid shell proteins (CSP). CSP has the ability to self-assemble into virus-like particles (VLPs), and the small protrusion domain (SPD) in CSP may play an essential role in the assembly of viral capsids. In this study, three critical amino acid sites, D828, S829 and V945, in the SPD were efficiently mutated (point mutation) based on the principle of PCR circular mutagenesis. Moreover, a multi-gene expression system, Ac-MultiBac baculovirus, was used to produce eight different recombinant VLPs in vitro. Transmission electron microscopy showed that the single site and double site mutations had little effect on the efficiency and morphology of the assembly of VLPs. Still, the simultaneous mutation of the three sites had a significant impact. The experimental results demonstrate that the SPD of CSP plays an essential role in assembly of the viral capsid, which lays the foundation for further analysis of the molecular and structural mechanism of BmCPV capsid assembly.
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Affiliation(s)
- Feifei Ren
- Insect Molecular Genetics and Biotechnology, Institute of Biosciences and Applications, National Centre for Scientific Research Demokritos, Aghia Paraskevi, Athens, Greece.,Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
| | - Luc Swevers
- Insect Molecular Genetics and Biotechnology, Institute of Biosciences and Applications, National Centre for Scientific Research Demokritos, Aghia Paraskevi, Athens, Greece
| | - Qiuyuan Lu
- Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
| | - Yongchao Zhao
- Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
| | - Jiming Yan
- Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
| | - Haiyun Li
- Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
| | - Jingchen Sun
- Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou 510642, PR China
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Xu C, Wang J, Yang J, Lei C, Hu J, Sun X. NSP2 forms viroplasms during Dendrolimus punctatus cypovirus infection. Virology 2019; 533:68-76. [PMID: 31125854 DOI: 10.1016/j.virol.2019.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/14/2019] [Accepted: 05/15/2019] [Indexed: 10/26/2022]
Abstract
Reoviruses are thought to replicate and assemble in special cytoplasmic structures called 'viroplasms'. However, little is known about the viroplasms of the insect reoviruses, the cypoviruses. To investigate the viroplasm of Dendrolimus punctatus cypovirus (DpCPV), all proteins encoded by the 10 genomic segments of DpCPV were expressed in Sf9 cells using the Bac-to-Bac system. The viral nonstructural protein NSP2 formed viroplasm-like dots which showed close apposition with the endoplasmic reticulum and were surrounded by intracellular membranes during transfection. Colocalization and coimmunoprecipitation assays showed that NSP2 interacts with 4 of 6 structural proteins and another 2 nonstructural proteins, while NSP1 only colocalized with VP4, and NSP3 did not colocalize with any structural protein. Immunoelectron microscopy revealed that NSP2 were nearby the endoplasmic reticulum and mitochondria, and viral particles were present in the electron-dense inclusions formed by NSP2. We proposed that NSP2 is responsible for forming the viroplasms structures of DpCPV.
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Affiliation(s)
- Congrui Xu
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jia Wang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jian Yang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chengfeng Lei
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China
| | - Jia Hu
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China
| | - Xiulian Sun
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, Hubei, China.
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Abstract
Virus-like particles (VLPs) are self-assembling platforms composed of viral structural proteins. They are used for a variety of purposes, ranging from the study of virus assembly to vaccine development. VLPs can be produced in plants, bacteria, yeast, and insect and mammalian cells. The baculovirus expression system is one of the most commonly used systems for production of VLPs in eukaryotic cells. This chapter provides a brief overview of the main strategies used to generate recombinant baculoviruses and the applications of insect virus-derived VLPs in basic and applied research. It then describes detailed protocols for generation of recombinant baculoviruses, screening for their expression of VLPs in insect cells, and VLP purification.
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Affiliation(s)
- Radhika Gopal
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Anette Schneemann
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA.
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Kundu A, Roychowdhury A, Bose M, Das AK, Ghosh AK. Reconstitution of the RNA-dependent RNA polymerase activity of Antheraea mylitta cypovirus in vitro using separately expressed different functional domains of the enzyme. J Gen Virol 2016; 97:1709-1719. [PMID: 27008451 DOI: 10.1099/jgv.0.000463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Antheraea mylitta cytoplasmic polyhedrosis virus is a segmented dsRNA virus of the family Reoviridae. Segment 2 (S2)-encoded RNA-dependent RNA polymerase (RdRp) helps the virus to propagate its genome in the host cell of the silkworm, Antheraea mylitta. Cloning, expression, purification and functional analysis of individual domains of RdRp have demonstrated that the purified domains interact in vitro. The central polymerase domain (PD) shows nucleotide binding properties, but neither the N-terminal domain (NTD) nor the C-terminal domain (CTD). Isolated PD does not exhibit RdRp activity but this activity can be reconstituted when all three domains are included in the reaction mixture. Molecular dynamics simulation suggests that the isolated PD has increased internal motions in comparison to when it is associated with the NTD and CTD. The motions of the separated PD may lead to the formation of a less accessible RNA template-binding channel and, thus, impair RdRp activity.
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Affiliation(s)
- Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
| | - Amlan Roychowdhury
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
| | - Madhuparna Bose
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
| | - Amit Kumar Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
| | - Ananta K Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
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Functional insights from molecular modeling, docking, and dynamics study of a cypoviral RNA dependent RNA polymerase. J Mol Graph Model 2015; 61:160-74. [PMID: 26264734 DOI: 10.1016/j.jmgm.2015.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/27/2015] [Accepted: 07/18/2015] [Indexed: 11/20/2022]
Abstract
Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) contains 11 double stranded RNA genome segments and infects tasar silkworm A. mylitta. RNA-dependent RNA polymerase (RdRp) is reported as a key enzyme responsible for propagation of the virus in the host cell but its structure function relationship still remains elusive. Here a computational approach has been taken to compare sequence and secondary structure of AmCPV RdRp with other viral RdRps to identify consensus motifs. Then a reliable pairwise sequence alignment of AmCPV RdRp with its closest sequence structure homologue λ3 RdRp is done to predict three dimensional structure of AmCPV RdRp. After comparing with other structurally known viral RdRps, important sequence and/or structural features involved in substrate entry or binding, polymerase reaction and the product release events have been identified. A conserved RNA pentanucleotide (5'-AGAGC-3') at the 3'-end of virus genome is predicted as cis-acting signal for RNA synthesis and its docking and simulation study along with the model of AmCPV RdRp has allowed to predict mode of template binding by the viral polymerase. It is found that template RNA enters into the catalytic center through nine sequence-independent and two sequence-dependent interactions with the specific amino acid residues. However, number of sequence dependent interactions remains almost same during 10 nano-second simulation time while total number of interactions decreases. Further, docking of N(7)-methyl-GpppG (mRNA cap) on the model as well as prediction of RNA secondary structure has shown the template entry process in the active site. These findings have led to postulate the mechanism of RNA-dependent RNA polymerization process by AmCPV RdRp. To our knowledge, this is the first report to evaluate structure function relationship of a cypoviral RdRp.
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Zhou Y, Qin T, Xiao Y, Qin F, Lei C, Sun X. Genomic and biological characterization of a new cypovirus isolated from Dendrolimus punctatus. PLoS One 2014; 9:e113201. [PMID: 25419713 PMCID: PMC4242531 DOI: 10.1371/journal.pone.0113201] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 10/24/2014] [Indexed: 11/18/2022] Open
Abstract
A novel cypovirus (designated DpCPV-MC) was isolated from the pine moth Dendrolimus punctatus using serial in vivo cloning procedures. DpCPV-MC occurs in typical polyhedral occlusion bodies, containing a number of spherical virions. Laboratory bioassays indicated that the infectivity of DpCPV-MC against second-instar Spodoptera exigua larvae does not differ significantly from that of Dendrolimus punctatus cypovirus 1. Full-length amplification of the DpCPV-MC cDNAs identified 16 dsRNA genome segments. Each segment encodes one open reading frame with unique conserved terminal sequences at the 5′ and 3′ ends, which differ from those of all previously reported cypoviruses. On a phylogenetic tree based on the amino acid sequences of the polyhedrin of 19 cypovirus species, DpCPV-MC was closest to the type-4 cypoviruses. Homology searches showed that ten segments of DpCPV-MC (S1, S2, S3, S4, S5, S7, S8, S9, S12, and S13) encode putative CPV structural and nonstructural proteins, three segments (S6, S10 and S14) encode putative insect proteins or other viral proteins, and the other three segments (S11, S15, and S16) encode proteins that have no obvious sequence similarity to any known protein. Based on RNA secondary structures analysis, two segments of them (S11 and S16) were predicted to possibly transcript less efficiently than the other segments. We speculate that DpCPV-MC is composed of several genotypes. The ten CPV-related segments constantly exist in all genotypes, and one or two of the six CPV-unrelated segments co-exist with the ten CPV-related segments in one DpCPV-MC genotype, thus each virion contains no more than 12 segments. Based on our results and the literature, DpCPV-MC is a new cypovirus (Cypovirus 22, strain DpCPV-22).
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Affiliation(s)
- Yin Zhou
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Tongcheng Qin
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Yuzhou Xiao
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Fujun Qin
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Chengfeng Lei
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Xiulian Sun
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China
- * E-mail:
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Biswas P, Kundu A, Ghosh AK. Genome segment 4 of Antheraea mylitta cytoplasmic polyhedrosis virus encodes RNA triphosphatase and methyltransferases. J Gen Virol 2014; 96:95-105. [PMID: 25228490 DOI: 10.1099/vir.0.069716-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cloning and sequencing of Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) genome segment S4 showed that it consists of 3410 nt with a single ORF of 1110 aa which could encode a protein of ~127 kDa (p127). Bioinformatics analysis showed the presence of a 5' RNA triphosphatase (RTPase) domain (LRDR), a S-adenosyl-l-methionine (SAM)-binding (GxGxG) motif and the KDKE tetrad of 2'-O-methyltransferase (MTase), which suggested that S4 may encode RTPase and MTase. The ORF of S4 was expressed in Escherichia coli as a His-tagged fusion protein and purified by nickel-nitrilotriacetic acid affinity chromatography. Biochemical analysis of recombinant p127 showed its RTPase as well as SAM-dependent guanine N(7)-and ribose 2'-O-MTase activities. A MTase assay using in vitro transcribed AmCPV S2 RNA having a 5' G*pppG end showed that guanine N(7) methylation occurred prior to the ribose 2'-O methylation to yield a m(7)GpppG/m(7)GpppGm RNA cap. Mutagenesis of the SAM-binding (GxGxG) motif (G831A) completely abolished N(7)- and 2'-O-MTase activities, indicating the importance of these residues for capping. From the kinetic analysis, the Km values of N(7)-MTase for SAM and RNA were calculated as 4.41 and 0.39 µM, respectively. These results suggested that AmCPV S4-encoded p127 catalyses RTPase and two cap methylation reactions for capping the 5' end of viral RNA.
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Affiliation(s)
- Poulomi Biswas
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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Cheng C, Shao Y, Su L, Zhou Y, Sun X. Interactions among Dendrolimus punctatus cypovirus proteins and identification of the genomic segment encoding its A-spike. J Gen Virol 2014; 95:1532-1538. [PMID: 24700101 DOI: 10.1099/vir.0.064022-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Revealing the interactions among cypovirus proteins would facilitate our understanding of the replication and assembly of this virus. In the present study, interactions among proteins encoded by the 10 segments of Dendrolimus punctatus cypovirus (DpCPV) were identified using yeast two-hybrid (Y2H) and far-Western blotting assays. In total, 24 pairs of interactions were detected. Twelve pairs of one-direction interactions, four pairs of binary interactions and four pairs of self-associations were identified in the Y2H assays. Another four pairs of interactions were identified by far-Western blotting. The interactions between the methyltransferase domain of the turret protein (VP3) and VP4 as well as between polyhedrin and VP4 were further confirmed by far-Western blotting and pull-down assays, respectively. In addition, immunogold labelling showed that the A-spike of DpCPV is formed by VP4. In conclusion, we obtained a protein-protein interaction network of DpCPV and showed that its A-spike is formed by VP4 encoded by genomic segment 6.
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Affiliation(s)
- Chuangang Cheng
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Yunpeng Shao
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Lan Su
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Yin Zhou
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Xiulian Sun
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
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Biswas P, Kundu A, Ghosh AK. Genome segment 5 of Antheraea mylitta cytoplasmic polyhedrosis virus encodes a bona fide guanylyltransferase. Virol J 2014; 11:53. [PMID: 24649879 PMCID: PMC4000049 DOI: 10.1186/1743-422x-11-53] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/10/2014] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV), a cypovirus of Reoviridae family, infects non mulberry Indian silk worm, Antheraea mylitta, and contains eleven segmented double stranded RNA in its genome (S1-S11). Some of its genome segments (S1-S3, and S6-S11) have been previously characterized but genome segment encoding the viral guanylyltransferase which helps in RNA capping has not been characterized. RESULTS In this study genome segment 5 (S5) of AmCPV was converted to cDNA, cloned and sequenced. S5 consisted of 2180 nucleotides, with one long ORF of 1818 nucleotides and could encode a protein of 606 amino acids with molecular mass of ~65 kDa (p65). Bioinformatics analysis showed presence of KLRS and HxnH motifs as observed in some other reoviral guanylyltransferase and suggests that S5 may encodes viral guanylyltransferase. The ORF of S5 was expressed in E. coli as 65 kDa his tagged fusion protein, purified through Ni-NTA chromatography and polyclonal antibody was raised. Immunoblot analysis of virion particles with the purified antibody showed specific immunoreactive band and suggests p65 as a viral structural protein. Functional analysis showed that recombinant p65 possesses guanylyltransferase activity, and transfers GMP moiety to the 5' diphosphate (A/G) ended viral RNA after the formation of p65-GMP complex for capping. Kinetic analysis showed K(m) of this enzyme for GTP and RNA was 34.24 uM and 98.35 nM, respectively. Site directed mutagenesis at K21A in KLRS motif, and H93A or H105A in HxnH motif completely abolished the autoguanylylation activity and indicates importance of these residues at these sites. Thermodynamic analysis showed p65-GTP interaction was primarily driven by enthalpy (ΔH = -399.1 ± 4.1 kJ/mol) whereas the p65-RNA interaction by favorable entropy (0.043 ± 0.0049 kJ/ mol). CONCLUSION Viral capping enzymes play a critical role in the post transcriptional or post replication modification in case of RNA virus. Our results of cloning, sequencing and functional analysis of AmCPV S5 indicates that S5 encoded p65 through its guanylyltransferase activity can transfer guanine residue to the 5' end of viral RNA for capping. Further studies will help to understand complete capping process of cypoviral RNA during viral replication within the viral capsid.
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Affiliation(s)
- Poulomi Biswas
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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