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Bruder MR, Aucoin MG. A sensitive assay for scrutiny of Autographa californica multiple nucleopolyhedrovirus genes using CRISPR-Cas9. Appl Microbiol Biotechnol 2023:10.1007/s00253-023-12462-y. [PMID: 37233755 DOI: 10.1007/s00253-023-12462-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 02/09/2023] [Accepted: 02/27/2023] [Indexed: 05/27/2023]
Abstract
Baculoviruses have very large genomes and previous studies have demonstrated improvements in recombinant protein production and genome stability through the removal of some nonessential sequences. However, recombinant baculovirus expression vectors (rBEVs) in widespread use remain virtually unmodified. Traditional approaches for generating knockout viruses (KOVs) require several experimental steps to remove the target gene prior to the generation of the virus. In order to optimize rBEV genomes by removing nonessential sequences, more efficient techniques for establishing and evaluating KOVs are required. Here, we have developed a sensitive assay utilizing CRISPR-Cas9-mediated gene targeting to examine the phenotypic impact of disruption of endogenous Autographa californica multiple nucleopolyhedrovirus (AcMNPV) genes. For validation, 13 AcMNPV genes were targeted for disruption and evaluated for the production of GFP and progeny virus - traits that are essential for their use as vectors for recombinant protein production. The assay involves transfection of sgRNA into a Cas9-expressing Sf9 cell line followed by infection with a baculovirus vector carrying the gfp gene under the p10 or p6.9 promoters. This assay represents an efficient strategy for scrutinizing AcMNPV gene function through targeted disruption, and represents a valuable tool for developing an optimized rBEV genome. KEY POINTS: [Formula: see text] A method to scrutinize the essentiality of baculovirus genes was developed. [Formula: see text] The method uses Sf9-Cas9 cells, a targeting plasmid carrying a sgRNA, and a rBEV-GFP. [Formula: see text] The method allows scrutiny by only needing to modify the targeting sgRNA plasmid.
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Affiliation(s)
- Mark R Bruder
- Department of Chemical Engineering, University of Waterloo, 200 University Ave. W., Waterloo, N2L 3G1, Ontario, Canada
| | - Marc G Aucoin
- Department of Chemical Engineering, University of Waterloo, 200 University Ave. W., Waterloo, N2L 3G1, Ontario, Canada.
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2
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Qi Y, Wang SS, Li LL. IE1 of Autographa californica Multiple Nucleopolyhedrovirus Activates Low Levels of Late Gene Expression in the Absence of Virus RNA Polymerase. Microbiol Spectr 2023; 11:e0343222. [PMID: 36511657 PMCID: PMC9927509 DOI: 10.1128/spectrum.03432-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 11/14/2022] [Indexed: 12/15/2022] Open
Abstract
Early and late gene expressions of baculoviruses have been known to rely on host RNA polymerase II and a virus-encoded RNA polymerase, separately. In this study, we found that Autographa californica multiple nucleopolyhedrovirus (AcMNPV) recombinant bacmids with the individual RNA polymerase subunit genes deleted could support low levels of expression of a reporter gene under the control of the promoter of a typical late gene, vp39, in transfected Sf9 cells. Through multistep subcloning of a genomic library of the virus and transient expression assay analysis, ie1 was identified to be the only viral gene that was responsible for activation of late gene expression in the absence of the viral RNA polymerase. Furthermore, IE1 was found to be capable of activating reporter gene expression from the promoters of additional late genes polh, p6.9, odv-e18, odv-e25, and gp41, independent of any additional viral factors. Deletion of ie1 from the virus genome eliminated late gene expression. The IE1-activated late gene expression was enhanced by the viral hr4b. It was shown to be insensitive to inhibition of α-amanitin and did not appear to have stable transcription start sites. It is proposed that IE1 may serve to recruit newly synthesized viral RNA polymerase to viral DNA by activating low levels of pretranscription of the late genes to create an appropriate DNA conformation. IMPORTANCE The late gene expression of baculovirus has been known to depend on the virus-encoded RNA polymerase, which consists of four subunits. The immediate-early gene ie1 was found to be required for viral early gene expression, late gene expression, and DNA replication. How it functions in late gene expression remains unclear. In this study, we found that AcMNPV IE1 could activate low levels of gene expression from late gene promoters independently of any additional viral factors, with nonspecific transcription start sites. This new finding will shed light on the role of IE1 in the regulation of late gene expression and the understanding of the mechanism of late gene transcription initiation.
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Affiliation(s)
- Yong Qi
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan, China
| | - Shan-Shan Wang
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan, China
| | - Lu-Lin Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan, China
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A selection marker-free method for gene deletion and editing in baculovirus genomes. J Virol Methods 2022; 310:114624. [PMID: 36165821 DOI: 10.1016/j.jviromet.2022.114624] [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: 07/03/2022] [Revised: 09/07/2022] [Accepted: 09/17/2022] [Indexed: 12/24/2022]
Abstract
Here, we develop a simple, efficient, bacmid-based, selection marker-free method for gene deletion and editing in baculovirus genomes. Specifically, based on pFastbac1, a donor plasmid with long left and right homology arms but without a reporter was constructed for disrupting ie1, an essential baculovirus gene. Instead of ligating with a plasmid, the homology arms were introduced to the polyhedrin locus of BmNPV bacmid using the BmNPV bac-to-bac expression system. Two viruses generated from the modified bacmid and unmodified BmNPV bacmid were then used to co-infect BmN cells in order that recombination takes place at the ie1 locus between them. Finally, without multiple rounds of purification, total cellular DNA was isolated, transformed into Cacl2-treated competent DH10B cells, and then blue colonies were selected for PCR screening. Remarkably, the proportion of blue colonies containing ie1-disrupted bacmid was found to be around 7 %. Moreover, using primers flanking the homology arms further confirmed that all these positive recombinants were double crossovers. These findings indicate that our method is also capable of gene modification if inverse PCR or seamless cloning is used to construct the donor plasmid and sequencing is employed to select positive colonies.
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Chen T, Duan X, Hu H, Shang Y, Hu Y, Deng F, Wang H, Wang M, Hu Z. Systematic Analysis of 42 Autographa Californica Multiple Nucleopolyhedrovirus Genes Identifies An Additional Six Genes Involved in the Production of Infectious Budded Virus. Virol Sin 2021; 36:762-773. [PMID: 33683665 PMCID: PMC8379328 DOI: 10.1007/s12250-021-00355-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 12/29/2020] [Indexed: 01/15/2023] Open
Abstract
Baculoviruses have been widely used as a vector for expressing foreign genes. Among numerous baculoviruses, Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is the most frequently used and it encodes 155 open reading frames (ORFs). Here, we systematically investigated the impact of 42 genes of AcMNPV on the production of infectious budded viruses (BVs) by constructing gene-knockout bacmids and subsequently conducting transfection and infection assays. The results showed that among the 39 functionally unverified genes and 3 recently reported genes, 36 are dispensable for infectious BV production, as the one-step growth curves of the gene-knockout viruses were not significantly different from those of the parental virus. Three genes (ac62, ac82 and ac106/107) are essential for infectious BV production, as deletions thereof resulted in complete loss of infectivity while the repaired viruses showed no significant difference in comparison to the parental virus. In addition, three genes (ac13, ac51 and ac120) are important but not essential for infectious BV production, as gene-knockout viruses produced significantly lower BV levels than that of the parental virus or repaired viruses. We then grouped the 155 AcMNPV genes into three categories (Dispensable, Essential, or Important for infectious BV production). Based on our results and previous publications, we constructed a schematic diagram of a potential mini-genome of AcMNPV, which contains only essential and important genes. The results shed light on our understanding of functional genomics of baculoviruses and provide fundamental information for future engineering of baculovirus expression system.
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Affiliation(s)
- Tong Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
- University of Chinese Academy of Sciences, Beijing, 10049, China
| | - Xiaoyan Duan
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
- University of Chinese Academy of Sciences, Beijing, 10049, China
| | - Hengrui Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
- University of Chinese Academy of Sciences, Beijing, 10049, China
| | - Yu Shang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Yangbo Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Fei Deng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Hualin Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Manli Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China.
| | - Zhihong Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China.
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Miele SAB, Cerrudo CS, Parsza CN, Nugnes MV, Mengual Gómez DL, Belaich MN, Ghiringhelli PD. Identification of Multiple Replication Stages and Origins in the Nucleopolyhedrovirus of Anticarsia gemmatalis. Viruses 2019; 11:E648. [PMID: 31311127 PMCID: PMC6669502 DOI: 10.3390/v11070648] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/10/2019] [Accepted: 07/12/2019] [Indexed: 12/13/2022] Open
Abstract
To understand the mechanism of replication used by baculoviruses, it is essential to describe all the factors involved, including virus and host proteins and the sequences where DNA synthesis starts. A lot of work on this topic has been done, but there is still confusion in defining what sequence/s act in such functions, and the mechanism of replication is not very well understood. In this work, we performed an AgMNPV replication kinetics into the susceptible UFL-Ag-286 cells to estimate viral genome synthesis rates. We found that the viral DNA exponentially increases in two different phases that are temporally separated by an interval of 5 h, probably suggesting the occurrence of two different mechanisms of replication. Then, we prepared a plasmid library containing virus fragments (0.5-2 kbp), which were transfected and infected with AgMNPV in UFL-Ag-286 cells. We identified 12 virus fragments which acted as origins of replication (ORI). Those fragments are in close proximity to core genes. This association to the core genome would ensure vertical transmission of ORIs. We also predict the presence of common structures on those fragments that probably recruit the replication machinery, a structure also present in previously reported ORIs in baculoviruses.
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Affiliation(s)
- Solange A B Miele
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
- Institute for Integrative Biology of the Cell (I2BC), Evolution and Maintenance of Circular Chromosomes, CEA, CNRS, Univ. Paris Sud, Université Paris-Saclay, 91190 Saint-Aubin, France
| | - Carolina S Cerrudo
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
| | - Cintia N Parsza
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
| | - María Victoria Nugnes
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
| | - Diego L Mengual Gómez
- Laboratorio de Oncología Molecular, Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
| | - Mariano N Belaich
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina.
| | - P Daniel Ghiringhelli
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular-Área Virosis de Insectos, Instituto de Microbiología Básica y Aplicada (IMBA), Universidad Nacional de Quilmes, CONICET, Bernal B1876BXD, Argentina
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Bossert M, Carstens EB. Sequential deletion of AcMNPV homologous regions leads to reductions in budded virus production and late protein expression. Virus Res 2018; 256:125-133. [PMID: 30121325 DOI: 10.1016/j.virusres.2018.08.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 08/10/2018] [Accepted: 08/14/2018] [Indexed: 10/28/2022]
Abstract
Homologous regions (hrs) have been predicted to act as origins of baculovirus DNA replication. Hrs have also been shown to function as enhancers of virus transcription. Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) carries eight hrs. In order to assess the role of hrs in virus replication in vivo, we applied a two-step RED recombination system for site-specific mutagenesis to sequentially delete each hr from a bacmid copy of AcMNPV. We then characterized the ability of the bacmids carrying different numbers of hrs or no hr to produce polyhedra and budded virus in transfected cells. We also investigated the ability of virus supernatants from transfected cells to produce budded virus and polyhedra when used to infect cells. We also characterized the expression of specific early and late virus proteins in transfected cells. The results demonstrated that removal of five hrs had little or no effect on virus infection but deleting all eight hrs compromised budded virus production and delayed early and late gene expression but did not completely eliminate assembly of infectious virus. We conclude that multiple hrs ensure an effective virus infection cycle with production of high titers of budded virus and polyhedra.
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Affiliation(s)
- Maike Bossert
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3Y6, Canada
| | - Eric B Carstens
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3Y6, Canada.
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8
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Baculovirus LEF-11 Hijack Host ATPase ATAD3A to Promote Virus Multiplication in Bombyx mori cells. Sci Rep 2017; 7:46187. [PMID: 28393927 PMCID: PMC5385504 DOI: 10.1038/srep46187] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/10/2017] [Indexed: 11/22/2022] Open
Abstract
Research on molecular mechanisms that viruses use to regulate the host apparatus is important in virus infection control and antiviral therapy exploration. Our previous research showed that the Bombyx mori nucleopolyhedrovirus (BmNPV) LEF-11 localized to dense regions of the cell nucleus and is required for viral DNA replication. Herein, we examined the mechanism of LEF-11 on BmNPV multiplication and demonstrated that baculovirus LEF-11 interacts with Bombyx mori ATAD3A and HSPD1 (HSP60) protein. Furthermore, we showed that LEF-11 has the ability to induce and up-regulate the expression of ATAD3A and HSPD1, phenomena that were both reversed upon knockdown of lef-11. Our findings showed that ATAD3A and HSPD1 were necessary and contributed to BmNPV multiplication in Bombyx mori cells. Moreover, ATAD3A was found to directly interact with HSPD1. Interestingly, ATAD3A was required for the expression of HSPD1, while the knockdown of HSPD1 had no obvious effect on the expression level of ATAD3A. Taken together, the data presented in the current study demonstrated that baculovirus LEF-11 hijacks the host ATPase family members, ATAD3A and HSPD1, efficiently promote the multiplication of the virus. This study furthers our understanding of how baculovirus modulates energy metabolism of the host and provides a new insight into the molecular mechanisms of antiviral research.
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9
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Yang R, Zhang J, Feng M, Wu X. Identification of Bombyx mori nucleopolyhedrovirus bm58a as an auxiliary gene and its requirement for cell lysis and larval liquefaction. J Gen Virol 2016; 97:3039-3050. [DOI: 10.1099/jgv.0.000614] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Rui Yang
- College of Animal Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Jianjia Zhang
- College of Animal Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Min Feng
- College of Animal Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Xiaofeng Wu
- College of Animal Sciences, Zhejiang University, Hangzhou 310058, PR China
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Xu X, Zhou X, Nan H, Zhao Y, Bai Y, Ou Y, Chen H. Aggregation of AcMNPV LEF-10 and Its Impact on Viral Late Gene Expression. PLoS One 2016; 11:e0154835. [PMID: 27152613 PMCID: PMC4859499 DOI: 10.1371/journal.pone.0154835] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 04/20/2016] [Indexed: 12/24/2022] Open
Abstract
The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) late expression factor gene lef-10 has been identified to be required for viral late gene expression by transient expression assay. Our previous work has shown that the gene product LEF-10 can form very stable high-molecular-weight complexes, but the structure and function of the protein remain unknown. In this study, we demonstrated that LEF-10 was essential for the replication of AcMNPV, and its truncated fragment containing amino acid residues 1 to 48 were sufficient to support the virus survival. Our data also suggested that the LEF-10 could spontaneously aggregate to form punctate spots in virus infected Sf9 cells at low frequency, and the aggregation of the protein could be induced by LEF-10 over-expression. When the protein aggregated to form punctate spots, soluble LEF-10 proteins were depleted and this could result in the down-regulation of viral late gene expression.
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Affiliation(s)
- Xiaodong Xu
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
- * E-mail: (XX); (HC)
| | - Xinyu Zhou
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
| | - Hao Nan
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
| | - Yu Zhao
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
| | - Yu Bai
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
| | - Yanmei Ou
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
| | - Hongying Chen
- College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, P. R. China
- * E-mail: (XX); (HC)
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Abstract
The development of baculovirus expression vector systems has accompanied a rapid expansion of our knowledge about the genes, their function and regulation in insect cells. Classification of these viruses has also been refined as we learn more about differences in gene content between isolates, how this affects virus structure and their replication in insect larvae. Baculovirus gene expression occurs in an ordered cascade, regulated by early, late and very late gene promoters. There is now a detailed knowledge of these promoter elements and how they interact first with host cell-encoded RNA polymerases and later with virus-encoded enzymes. The composition of this virus RNA polymerase is known. The virus replication process culminates in the very high level expression of both polyhedrin and p10 gene products in the latter stages of infection. It has also been realized that the insect host cell has innate defenses against baculoviruses in the form of an apoptotic response to virus invasion. Baculoviruses counter this by encoding apoptotic-suppressors, which also appear to have a role in determining the host range of the virus. Also of importance to our understanding of baculovirus expression systems is how the virus can accumulate mutations within genes that affect recombinant protein yield in cell culture. The summary in this chapter is not exhaustive, but should provide a good preparation to those wishing to use this highly successful gene expression system.
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Affiliation(s)
- Barbara J Kelly
- The Moyne Institute of Preventive Medicine, Trinity College, Dublin, Ireland
| | - Linda A King
- School of Biological and Molecular Sciences, Oxford Brookes University, Oxford, UK
| | - Robert D Possee
- NERC CEH (Oxford), Mansfield Road, Oxford, OX1, UK.
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK.
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Dong ZQ, Hu N, Zhang J, Chen TT, Cao MY, Li HQ, Lei XJ, Chen P, Lu C, Pan MH. Oligomerization of Baculovirus LEF-11 Is Involved in Viral DNA Replication. PLoS One 2015; 10:e0144930. [PMID: 26660313 PMCID: PMC4678028 DOI: 10.1371/journal.pone.0144930] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 11/25/2015] [Indexed: 11/18/2022] Open
Abstract
We have previously reported that baculovirus Bombyx mori nucleopolyhedrovirus (BmNPV) late expression factor 11 (lef-11) is associated with viral DNA replication and have demonstrated that it potentially interacts with itself; however, whether LEF-11 forms oligomers and the impact of LEF-11 oligomerization on viral function have not been substantiated. In this study, we first demonstrated that LEF-11 is capable of forming oligomers. Additionally, a series of analyses using BmNPV LEF-11 truncation mutants indicated that two distinct domains control LEF-11 oligomerization (aa 42–61 and aa 72–101). LEF-11 truncation constructs were inserted into a lef-11-knockout BmNPV bacmid, which was used to demonstrate that truncated LEF-11 lacking either oligomerization domain abrogates viral DNA replication. Finally, site-directed mutagenesis was used to determine that the conserved hydrophobic residues Y58&I59 (representing Y58 and I59), I85 and L88&L89 (representing L88 and L89) are required for LEF-11 oligomerization and viral DNA replication. Collectively, these data indicate that BmNPV LEF-11 oligomerization influences viral DNA replication.
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Affiliation(s)
- Zhan-Qi Dong
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Nan Hu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Jun Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
- Institutes of Life Sciences, Chongqing Medical University, Chongqing, 400716, China
| | - Ting-Ting Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Ming-Ya Cao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Hai-Qing Li
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Xue-Jiao Lei
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Peng Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Cheng Lu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
- Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
- * E-mail: (CL); (MP)
| | - Min-Hui Pan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
- Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
- * E-mail: (CL); (MP)
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Defining the roles of the baculovirus regulatory proteins IE0 and IE1 in genome replication and early gene transactivation. Virology 2014; 468-470:160-171. [DOI: 10.1016/j.virol.2014.07.044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 11/21/2022]
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14
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Autographa californica multiple nucleopolyhedrovirus DNA polymerase C terminus is required for nuclear localization and viral DNA replication. J Virol 2014; 88:10918-33. [PMID: 25008932 DOI: 10.1128/jvi.01167-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
UNLABELLED The DNA polymerase (DNApol) of the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is essential for viral DNA replication. The DNApol exonuclease and polymerase domains are highly conserved and are considered functional in DNA replication. However, the role of the DNApol C terminus has not yet been characterized. To identify whether only the exonuclease and polymerase domains are sufficient for viral DNA replication, several DNApol C-terminal truncations were cloned into a dnapol-null AcMNPV bacmid with a green fluorescent protein (GFP) reporter. Surprisingly, most of the truncation constructs, despite containing both exonuclease and polymerase domains, could not rescue viral DNA replication and viral production in bacmid-transfected Sf21 cells. Moreover, GFP fusions of these same truncations failed to localize to the nucleus. Truncation of the C-terminal amino acids 950 to 984 showed nuclear localization but allowed for only limited and delayed viral spread. The C terminus contains a typical bipartite nuclear localization signal (NLS) motif at residues 804 to 827 and a monopartite NLS motif at residues 939 to 948. Each NLS, as a GFP fusion peptide, localized to the nucleus, but both NLSs were required for nuclear localization of DNApol. Alanine substitutions in a highly conserved baculovirus DNApol sequence at AcMNPV DNApol amino acids 972 to 981 demonstrated its importance for virus production and DNA replication. Collectively, the data indicated that the C terminus of AcMNPV DNApol contains two NLSs and a conserved motif, all of which are required for nuclear localization of DNApol, viral DNA synthesis, and virus production. IMPORTANCE The baculovirus DNA polymerase (DNApol) is a highly specific polymerase that allows viral DNA synthesis and hence virus replication in infected insect cells. We demonstrated that the exonuclease and polymerase domains of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) alone are insufficient for viral DNA synthesis and virus replication. Rather, we identified three features, including two nuclear localization signals and a highly conserved 10-amino-acid sequence in the AcMNPV DNApol C terminus, all three of which are important for both nuclear localization of DNApol and for DNApol activity, as measured by viral DNA synthesis and virus replication.
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Zhang J, Dong ZQ, Zhang CD, He Q, Chen XM, Cao MY, Li HQ, Xiao WF, Lu C, Pan MH. Identification of a novel nuclear localization signal of baculovirus late expression factor 11. Virus Res 2014; 184:111-9. [DOI: 10.1016/j.virusres.2014.02.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/20/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
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16
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Kikhno I. Identification of a conserved non-protein-coding genomic element that plays an essential role in Alphabaculovirus pathogenesis. PLoS One 2014; 9:e95322. [PMID: 24740153 PMCID: PMC3989284 DOI: 10.1371/journal.pone.0095322] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 03/26/2014] [Indexed: 12/13/2022] Open
Abstract
Highly homologous sequences 154-157 bp in length grouped under the name of "conserved non-protein-coding element" (CNE) were revealed in all of the sequenced genomes of baculoviruses belonging to the genus Alphabaculovirus. A CNE alignment led to the detection of a set of highly conserved nucleotide clusters that occupy strictly conserved positions in the CNE sequence. The significant length of the CNE and conservation of both its length and cluster architecture were identified as a combination of characteristics that make this CNE different from known viral non-coding functional sequences. The essential role of the CNE in the Alphabaculovirus life cycle was demonstrated through the use of a CNE-knockout Autographa californica multiple nucleopolyhedrovirus (AcMNPV) bacmid. It was shown that the essential function of the CNE was not mediated by the presumed expression activities of the protein- and non-protein-coding genes that overlap the AcMNPV CNE. On the basis of the presented data, the AcMNPV CNE was categorized as a complex-structured, polyfunctional genomic element involved in an essential DNA transaction that is associated with an undefined function of the baculovirus genome.
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Affiliation(s)
- Irina Kikhno
- Institute of Molecular Biology & Genetics of Ukrainian Academy of Science, Kiev, Ukraine
- * E-mail:
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17
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Zhang J, He Q, Zhang CD, Chen XY, Chen XM, Dong ZQ, Li N, Kuang XX, Cao MY, Lu C, Pan MH. Inhibition of BmNPV replication in silkworm cells using inducible and regulated artificial microRNA precursors targeting the essential viral gene lef-11. Antiviral Res 2014; 104:143-52. [PMID: 24486953 DOI: 10.1016/j.antiviral.2014.01.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 01/17/2014] [Accepted: 01/22/2014] [Indexed: 01/05/2023]
Abstract
Bombyx mori nucleopolyhedrovirus (BmNPV) is a major silkworm pathogen, causing substantial economic losses to the sericulture industry annually. We demonstrate a novel anti-BmNPV system expressing mature artificial microRNAs (amiRNAs) targeting the viral lef-11 gene. The mature amiRNAs inhibited the lef-11 gene in silkworm BmN-SWU1 cells. Antiviral assays demonstrated that mature amiRNAs silenced the gene and inhibited BmNPV proliferation efficiently. As constitutive overexpression of mature amiRNAs may induce acute cellular toxicity, we further developed a novel virus-induced amiRNA expression system. The amiRNA cassette is regulated by a baculovirus-induced fusion promoter. This baculovirus-induced RNA interference system is strictly regulated by virus infection, which functions in a negative feedback loop to activate the expression of mature amiRNAs against lef-11 and subsequently control inhibition of BmNPV replication. Our study advances the use of a regulatable amiRNA cassette as a safe and effective tool for research of basic insect biology and antiviral application.
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Affiliation(s)
- Jun Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Qian He
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Chun-Dong Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Department of Biochemistry and Molecular Biology, Chongqing Medical University, Chongqing 400016, China
| | - Xiang-Yun Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Xue-Mei Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Zhan-Qi Dong
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Na Li
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Xiu-Xiu Kuang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Ming-Ya Cao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Cheng Lu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing 400716, China.
| | - Min-Hui Pan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing 400716, China.
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18
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Yu W, Du CY, Quan YP, Nie ZM, Chen J, Lv ZB, Zhang YZ. Characterization of late gene expression factor LEF-10 from Bombyx mori nucleopolyhedrovirus. Virus Res 2013; 175:45-51. [DOI: 10.1016/j.virusres.2013.03.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/26/2013] [Accepted: 03/26/2013] [Indexed: 12/14/2022]
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19
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Roy P, Noad R. Use of bacterial artificial chromosomes in baculovirus research and recombinant protein expression: current trends and future perspectives. ISRN MICROBIOLOGY 2012; 2012:628797. [PMID: 23762754 PMCID: PMC3671692 DOI: 10.5402/2012/628797] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 08/16/2012] [Indexed: 11/23/2022]
Abstract
The baculovirus expression system is one of the most successful and widely used eukaryotic protein expression methods. This short review will summarise the role of bacterial artificial chromosomes (BACS) as an enabling technology for the modification of the virus genome. For many years baculovirus genomes have been maintained in E. coli as bacterial artificial chromosomes, and foreign genes have been inserted using a transposition-based system. However, with recent advances in molecular biology techniques, particularly targeting reverse engineering of the baculovirus genome by recombineering, new frontiers in protein expression are being addressed. In particular, BACs have facilitated the propagation of disabled virus genomes that allow high throughput protein expression. Furthermore, improvement in the selection of recombinant viral genomes inserted into BACS has enabled the expression of multiprotein complexes by iterative recombineering of the baculovirus genome.
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Affiliation(s)
- Polly Roy
- Department of Pathogen Molecular Biology, Faculty of Infectious Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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20
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An ac34 deletion mutant of Autographa californica nucleopolyhedrovirus exhibits delayed late gene expression and a lack of virulence in vivo. J Virol 2012; 86:10432-43. [PMID: 22787232 DOI: 10.1128/jvi.00779-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Ac34 and its homologs are highly conserved in all sequenced alphabaculoviruses. In this paper, we show that ac34 transcripts were detected from 6 to 48 h postinfection (p.i.) in Autographa californica nucleopolyhedrovirus (AcMNPV)-infected Sf9 cells. Ac34 localized to both the cytoplasm and the nuclei of infected cells but was not a viral structural protein. To determine the function of ac34 in the viral life cycle, an ac34 knockout AcMNPV (vAc34KO) was constructed. Compared with wild-type and repair viruses, vAc34KO exhibited an approximately 100-fold reduction in infectious virus production. Further investigations showed that the ac34 deletion did not affect the replication of viral DNA, polyhedron formation, or nucleocapsid assembly but delayed the expression of late genes, such as vp39, 38k, and p6.9. Bioassays revealed that vAc34KO was unable to establish a fatal infection in Trichoplusia ni larvae via per os inoculation. Few infectious progeny viruses were detected in the hemolymph of the infected larvae, indicating that the replication of vAc34KO was attenuated. These results suggest that Ac34 is an activator protein that promotes late gene expression and is essential for the pathogenicity of AcMNPV.
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21
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Shen H, Zhou Y, Zhang W, Nin B, Wang H, Wang X, Shao S, Chen H, Guo Z, Liu X, Yao Q, Chen K. Characterization of Bombyx mori nucleopolyhedrovirus with a knockout of Bm17. Cytotechnology 2012; 64:711-8. [PMID: 22476564 DOI: 10.1007/s10616-012-9451-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 01/03/2012] [Indexed: 11/28/2022] Open
Abstract
Open reading frame 17 (Bm17) gene of Bombyx mori nucleopolyhedrovirus is a highly conserved gene in lepidopteran nucleopolyhedroviruses, but its function remains unknown. In this report, transient-expression and superinfection assays indicated that BM17 localized in the nucleus and cytoplasm of infected BmN cells. To determine the role of Bm17 in baculovirus life cycle, we constructed a Bm17 knockout virus and characterized its properties in cells. Analysis of the production and infection of budded virions, the level of viral DNA replication revealed showed that there was no significant difference among the mutant, the control, and the Bm17 repaired virus strains. These results suggest that BM17 is not essential for virus replication in cultured cells.
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Affiliation(s)
- Hongxing Shen
- School of Medical Science and Laborarory Medicine, Jiangsu University, Zhenjiang, 212013, People's Republic of China
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22
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Bombyx mori nucleopolyhedrovirus ORF54, a viral desmoplakin gene, is associated with the infectivity of budded virions. Arch Virol 2012; 157:1241-51. [PMID: 22446883 DOI: 10.1007/s00705-012-1276-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 02/07/2012] [Indexed: 12/25/2022]
Abstract
Bombyx mori nucleopolyhedrovirus (BmNPV) ORF54 (Bm54), a member of the viral desmoplakin N-terminus superfamily, is homologous to Autographa californica nucleopolyhedrovirus (AcMNPV) ORF66, which is required for the efficient egress of nucleocapsids from the nucleus and occlusion body formation. In this paper, we generated a bacmid with the Bm54 gene deleted via homologous recombination in Escherichia coli and characterized the mutant virus using a transfection-infection assay and transmission electron microscopy analysis. Our results demonstrated that the cells transfected with viral DNA lacking Bm54 produced non-infectious budded viruses (BVs). Electron microscopy showed that although the deletion of Bm54 did not affect assembly and release of nucleocapsids, it severely affected polyhedron formation. In conclusion, deletion of Bm54 resulted in non-infectious BV and defective polyhedra. Although the sequences of Bm54 and Ac66 are very similar, the two genes function quite differently in the regulation of viral life cycle.
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23
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Baculovirus infection induces a DNA damage response that is required for efficient viral replication. J Virol 2011; 85:12547-56. [PMID: 21917957 DOI: 10.1128/jvi.05766-11] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several mammalian viruses have been shown to induce a cellular DNA damage response during replication, and in some cases, this response is required for optimal virus replication. However, nothing is known about whether a DNA damage response is stimulated by DNA viruses in invertebrates. Cell cycle arrest and apoptosis are two of the downstream effects of the DNA damage response, and both are stimulated by baculovirus infection, suggesting a possible relationship between baculoviruses and the DNA damage response. In the study described in this report, we found that replication of the baculovirus Autographa californica M nucleopolyhedrovirus (AcMNPV) in the cell line Sf9, derived from the lepidopteran insect Spodoptera frugiperda, stimulated a DNA damage response, as indicated by an increased abundance of the S. frugiperda P53 protein (SfP53) and phosphorylation of the histone variant protein H2AX. Stimulation of the DNA damage response was dependent on viral DNA replication. Inhibition of the DNA damage response prevented both the increase in SfP53 accumulation and H2AX phosphorylation and also caused a 10- to 100-fold reduction in virus production, along with decreased viral DNA replication and late gene expression. However, silencing of Sfp53 expression by RNA interference did not significantly affect AcMNPV replication or induction of apoptosis by a mutant of AcMNPV lacking the antiapoptotic gene p35, indicating that these processes are not dependent on SfP53 in Sf9 cells.
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24
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Identification of Autographa californica nucleopolyhedrovirus ac93 as a core gene and its requirement for intranuclear microvesicle formation and nuclear egress of nucleocapsids. J Virol 2011; 85:11664-74. [PMID: 21880748 DOI: 10.1128/jvi.05275-11] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Autographa californica nucleopolyhedrovirus (AcMNPV) orf93 (ac93) is a highly conserved uncharacterized gene that is found in all of the sequenced baculovirus genomes except for Culex nigripalpus NPV. In this report, using bioinformatics analyses, ac93 and odv-e25 (ac94) were identified as baculovirus core genes and thus p33-ac93-odv-e25 represent a cluster of core genes. To investigate the role of ac93 in the baculovirus life cycle, an ac93 knockout AcMNPV bacmid was constructed via homologous recombination in Escherichia coli. Fluorescence and light microscopy showed that the AcMNPV ac93 knockout did not spread by infection, and titration assays confirmed a defect in budded virus (BV) production. However, deletion of ac93 did not affect viral DNA replication. Electron microscopy indicated that ac93 was required for the egress of nucleocapsids from the nucleus and the formation of intranuclear microvesicles, which are precursor structures of occlusion-derived virus (ODV) envelopes. Immunofluorescence analyses showed that Ac93 was concentrated toward the cytoplasmic membrane in the cytoplasm and in the nuclear ring zone in the nucleus. Western blot analyses showed that Ac93 was associated with both nucleocapsid and envelope fractions of BV, but only the nucleocapsid fraction of ODV. Our results suggest that ac93, although not previously recognized as a core gene, is one that plays an essential role in the formation of the ODV envelope and the egress of nucleocapsids from the nucleus.
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25
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Su J, Lung O, Blissard GW. The Autographa californica multiple nucleopolyhedrovirus lef-5 gene is required for productive infection. Virology 2011; 416:54-64. [DOI: 10.1016/j.virol.2011.04.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/22/2011] [Accepted: 04/26/2011] [Indexed: 11/29/2022]
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26
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Yu M, Carstens EB. Characterization of an Autographa californica multiple nucleopolyhedrovirus mutant lacking the ac39(p43) gene. Virus Res 2010; 155:300-6. [PMID: 20974197 DOI: 10.1016/j.virusres.2010.10.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 10/15/2010] [Accepted: 10/15/2010] [Indexed: 01/12/2023]
Abstract
Open reading frame 39 [orf39(p43)] of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) is present in 10 isolates of the Alphabaculovirus genus. It is highly conserved in sequence and genomic location in the Group I but much less conserved in the Group II viruses. To investigate the potential role of p43 in AcMNPV infection, we constructed and characterized a p43 knockout mutant. The results showed that the p43 region was expressed as RNA from 3h post infection to at least 24h post infection, and its expression pattern was identical to the expression profile of its neighbouring gene, p47. P47 is an essential core gene component of the baculovirus RNA polymerase. The deletion of the p43 region was confirmed by PCR analysis of bacmid DNA and by RT-PCR analysis of RNA purified from p43 knockout infected cells. The results supported the hypothesis that a large transcript, initiating upstream of p47, includes the p43 ORF. Analyses of protein synthesis in p43 knockout infected cells clearly demonstrated that there were no obvious differences in the timing or amount of expression of P47, LEF-3, or VP39. Growth curves showed that infectious budded virus production and occlusion body formation were also not affected by the p43 knockout. We conclude that orf39(p43) is not essential for virus replication in cell culture.
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Affiliation(s)
- Mei Yu
- Department of Microbiology and Immunology, Queen's University, Kingston, Canada ON K7L 3N6
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27
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Functional analysis of Spodoptera litura nucleopolyhedrovirus p49 gene during Autographa californica nucleopolyhedrovirus infection of SpLi-221 cells. Virus Genes 2010; 41:441-9. [DOI: 10.1007/s11262-010-0520-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/31/2010] [Indexed: 10/19/2022]
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28
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Westenberg M, Soedling HM, Mann DA, Nicholson LJ, Dolphin CT. Counter-selection recombineering of the baculovirus genome: a strategy for seamless modification of repeat-containing BACs. Nucleic Acids Res 2010; 38:e166. [PMID: 20621982 PMCID: PMC2938205 DOI: 10.1093/nar/gkq596] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recombineering is employed to modify large DNA clones such as fosmids, BACs and PACs. Subtle and seamless modifications can be achieved using counter-selection strategies in which a donor cassette carrying both positive and negative markers inserted in the target clone is replaced by the desired sequence change. We are applying counter-selection recombineering to modify bacmid bMON14272, a recombinant baculoviral genome, as we wish to engineer the virus into a therapeutically useful gene delivery vector with cell targeting characteristics. Initial attempts to replace gp64 with Fusion (F) genes from other baculoviruses resulted in many rearranged clones in which the counter-selection cassette had been deleted. Bacmid bMON14272 contains nine highly homologous regions (hrs) and deletions were mapped to recombination between hr pairs. Recombineering modifications were attempted to decrease intramolecular recombination and/or increase recombineering efficiency. Of these only the use of longer homology arms on the donor molecule proved effective permitting seamless modification. bMON14272, because of the presence of the hr sequences, can be considered equivalent to a highly repetitive BAC and, as such, the optimized method detailed here should prove useful to others applying counter-selection recombineering to modify BACs or PACs containing similar regions of significant repeating homologies.
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Affiliation(s)
- Marcel Westenberg
- Pharmaceutical Science Division, King's College London, London SE1 9NH, UK
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29
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Open reading frame 60 of the Bombyx mori nucleopolyhedrovirus plays a role in budded virus production. Virus Res 2010; 151:185-91. [PMID: 20576538 DOI: 10.1016/j.virusres.2010.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 05/10/2010] [Accepted: 05/10/2010] [Indexed: 11/22/2022]
Abstract
Open reading frame 60 (bm60) of the Bombyx mori nucleopolyhedrovirus (BmNPV) is a conserved gene among group I and some group II NPVs. bm60 encodes a late expressed protein that localizes to both the cytoplasm and nucleus of infected cells. This paper describes the characterization of a BmNPV mutant (vbm60-Null) lacking functional bm60. It was observed that the production of budded virus (BV) was reduced by nearly an order of magnitude relative to wt virus in vbm60-Null-infected BmN cells and B. mori larvae. Quantitative real-time PCR assay showed that the viral DNA replication was affected in infected cells due to disruption of bm60. Larval bioassays showed that the speed of kill of vbm60-Null virus was greatly reduced, as it took approximately 28-36 h longer to kill the fifth instar B. mori larvae. These results suggest that BmNPV bm60 is not essential for viral replication, but required for efficient BV production.
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30
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Identification of a domain of the baculovirus Autographa californica multiple nucleopolyhedrovirus single-strand DNA-binding protein LEF-3 essential for viral DNA replication. J Virol 2010; 84:6153-62. [PMID: 20357098 DOI: 10.1128/jvi.00115-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) lef-3 is one of nine genes required for viral DNA replication in transient assays. LEF-3 is predicted to contain several domains related to its functions, including nuclear localization, single-strand DNA binding, oligomerization, interaction with P143 helicase, and interaction with a viral alkaline nuclease. To investigate the essential nature of LEF-3 and the roles it may play during baculovirus DNA replication, a lef-3 null bacmid (bKO-lef3) was constructed in Escherichia coli and characterized in Sf21 cells. The results showed that AcMNPV lef-3 is essential for DNA replication, budded virus production, and late gene expression in vivo. Cells transfected with the lef-3 knockout bacmid produced low levels of early proteins (P143, DNA polymerase, and early GP64) and no late proteins (P47, VP39, or late GP64). To investigate the functional role of domains within the LEF-3 open reading frame in the presence of the whole viral genome, plasmids expressing various LEF-3 truncations were transfected into Sf21 cells together with bKO-lef3 DNA. The results showed that expression of AcMNPV LEF-3 amino acids 1 to 125 was sufficient to stimulate viral DNA replication and to support late gene expression. Expression of Choristoneura fumiferana MNPV lef-3 did not rescue any LEF-3 functions. The construction of a LEF-3 amino acid 1 to 125 rescue bacmid revealed that this region of LEF-3, when expressed in the presence of the rest of the viral genome, stimulated viral DNA replication and late and very late protein expression, as well as budded virus production.
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31
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Autographa californica multiple nucleopolyhedrovirus LEF-2 is a capsid protein required for amplification but not initiation of viral DNA replication. J Virol 2010; 84:5015-24. [PMID: 20219928 DOI: 10.1128/jvi.02423-09] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The late expression factor 2 gene (lef-2) of baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has been identified as one of the factors essential for origin-dependent DNA replication in transient expression assays and has been shown to be involved in late/very late gene expression. To study the function of lef-2 in the life cycle of AcMNPV, lef-2 knockout and repair bacmids were generated by homologous recombination in Escherichia coli. Growth curve analysis showed that lef-2 was essential for virus production. Interestingly, a DNA replication assay indicated that lef-2 is not required for the initiation of viral DNA replication and that, rather, it is required for the amplification of DNA replication. lef-2 is also required for the expression of late and very late genes, as the expression of these genes was abolished by lef-2 deletion. Temporal and spatial distributions of LEF-2 protein in infected cells were also analyzed, and the data showed that LEF-2 protein was localized to the virogenic stroma in the nuclei of the infected cells. Analysis of purified virus particles revealed that LEF-2 is a viral protein component of both budded and occlusion-derived virions, predominantly in the nucleocapsids of the virus particles. This observation suggests that LEF-2 may be required immediately after virus entry into host cells for efficient viral DNA replication.
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32
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Peng K, Wu M, Deng F, Song J, Dong C, Wang H, Hu Z. Identification of protein-protein interactions of the occlusion-derived virus-associated proteins of Helicoverpa armigera nucleopolyhedrovirus. J Gen Virol 2009; 91:659-70. [PMID: 19906939 DOI: 10.1099/vir.0.017103-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The purpose of this study was to identify protein-protein interactions among the components of the occlusion-derived virus (ODV) of Helicoverpa armigera nucleopolyhedrovirus (HearNPV), a group II alphabaculovirus in the family Baculoviridae. To achieve this, 39 selected genes of potential ODV structural proteins were cloned and expressed in the Gal4 yeast two-hybrid (Y2H) system. The direct-cross Y2H assays identified 22 interactions comprising 13 binary interactions [HA9-ODV-EC43, ODV-E56-38K, ODV-E56-PIF3, LEF3-helicase, LEF3-alkaline nuclease (AN), GP41-38K, GP41-HA90, 38K-PIF3, 38K-PIF2, VP80-HA100, ODV-E66-PIF3, ODV-E66-PIF2 and PIF3-PIF2] and nine self-associations (IE1, HA44, LEF3, HA66, GP41, CG30, 38K, PIF3 and P24). Five of these interactions - LEF3-helicase and LEF3-AN, and the self-associations of IE1, LEF3 and 38K - have been reported previously in Autographa californica multiple nucleopolyhedrovirus. As HA44 and HA100 were two newly identified ODV proteins of group II viruses, their interactions were further confirmed. The self-association of HA44 was verified with a His pull-down assay and the interaction of VP80-HA100 was confirmed by a co-immunoprecipitation assay. A summary of the protein-protein interactions of baculoviruses reported so far, comprising 68 interactions with 45 viral proteins and five host proteins, is presented, which will facilitate our understanding of the molecular mechanisms of baculovirus infection.
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Affiliation(s)
- Ke Peng
- State Key Laboratory of Virology and Joint Laboratory of Invertebrate Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China
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33
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Cohen DPA, Marek M, Davies BG, Vlak JM, van Oers MM. Encyclopedia of Autographa californica nucleopolyhedrovirus genes. Virol Sin 2009. [DOI: 10.1007/s12250-009-3059-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
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34
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Noad RJ, Stewart M, Boyce M, Celma CC, Willison KR, Roy P. Multigene expression of protein complexes by iterative modification of genomic Bacmid DNA. BMC Mol Biol 2009; 10:87. [PMID: 19725957 PMCID: PMC2749033 DOI: 10.1186/1471-2199-10-87] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 09/02/2009] [Indexed: 02/26/2023] Open
Abstract
Background Many cellular multi-protein complexes are naturally present in cells at low abundance. Baculovirus expression offers one approach to produce milligram quantities of correctly folded and processed eukaryotic protein complexes. However, current strategies suffer from the need to produce large transfer vectors, and the use of repeated promoter sequences in baculovirus, which itself produces proteins that promote homologous recombination. One possible solution to these problems is to construct baculovirus genomes that express each protein in a complex from a separate locus within the viral DNA. However current methods for selecting such recombinant genomes are too inefficient to routinely modify the virus in this way. Results This paper reports a method which combines the lambda red and bacteriophage P1 Cre-recombinase systems to efficiently generate baculoviruses in which protein complexes are expressed from multiple, single-locus insertions of foreign genes. This method is based on an 88 fold improvement in the selection of recombinant viruses generated by red recombination techniques through use of a bipartite selection cassette. Using this system, seven new genetic loci were identified in the AcMNPV genome suitable for the high level expression of recombinant proteins. These loci were used to allow the recovery two recombinant virus-like particles with potential biotechnological applications (influenza A virus HA/M1 particles and bluetongue virus VP2/VP3/VP5/VP7 particles) and the mammalian chaperone and cancer drug target CCT (16 subunits formed from 8 proteins). Conclusion 1. Use of bipartite selections can significantly improve selection of modified bacterial artificial chromosomes carrying baculovirus DNA. Furthermore this approach is sufficiently robust to allow routine modification of the virus genome. 2. In addition to the commonly used p10 and polyhedrin loci, the ctx, egt, 39k, orf51, gp37, iap2 and odv-e56 loci in AcMNPV are all suitable for the high level expression of heterologous genes. 3. Two protein, four protein and eight protein complexes including virus-like particles and cellular chaperone complexes can be produced using the new approach.
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Affiliation(s)
- Rob J Noad
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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Baculovirus DNA replication-specific expression factors trigger apoptosis and shutoff of host protein synthesis during infection. J Virol 2009; 83:11123-32. [PMID: 19706708 DOI: 10.1128/jvi.01199-09] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Apoptosis is an important antivirus defense. To define the poorly understood pathways by which invertebrates respond to viruses by inducing apoptosis, we have identified replication events that trigger apoptosis in baculovirus-infected cells. We used RNA silencing to ablate factors required for multiplication of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Transfection with double-stranded RNA (dsRNA) complementary to the AcMNPV late expression factors (lefs) that are designated as replicative lefs (lef-1, lef-2, lef-3, lef-11, p143, dnapol, and ie-1/ie-0) blocked virus DNA synthesis and late gene expression in permissive Spodoptera frugiperda cells. dsRNAs specific to designated nonreplicative lefs (lef-8, lef-9, p47, and pp31) blocked late gene expression without affecting virus DNA replication. Thus, both classes of lefs functioned during infection as defined. Silencing the replicative lefs prevented AcMNPV-induced apoptosis of Spodoptera cells, whereas silencing the nonreplicative lefs did not. Thus, the activity of replicative lefs or virus DNA replication is sufficient to trigger apoptosis. Confirming this conclusion, AcMNPV-induced apoptosis was suppressed by silencing the replicative lefs in cells from a divergent species, Drosophila melanogaster. Silencing replicative but not nonreplicative lefs also abrogated AcMNPV-induced shutdown of host protein synthesis, suggesting that virus DNA replication triggers inhibition of host biosynthetic processes and that apoptosis and translational arrest are linked. Our findings suggest that baculovirus DNA replication triggers a host cell response similar to the DNA damage response in vertebrates, which causes translational arrest and apoptosis. Pathways for detecting virus invasion and triggering apoptosis may therefore be conserved between insects and mammals.
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Abstract
In the present study, we studied the feasibility of deleting essential genes in insect cells by using bacmid and purifying recombinant bacmid in Escherichia coli DH10B cells. To disrupt the orf4 (open reading frame 4) gene of BmNPV [Bm (Bombyx mori) nuclear polyhedrosis virus], a transfer vector was constructed and co-transfected with BmNPV bacmid into Bm cells. Three passages of viruses were carried out in Bm cells, followed by one round of purification. Subsequently, bacmid DNA was extracted and transformed into competent DH10B cells. A colony harbouring only orf4-disrupted bacmid DNA was identified by PCR. A mixture of recombinant (white colonies) and non-recombinant (blue colonies) bacmids were also transformed into DH10B cells. PCR with M13 primers showed that the recombinant and non-recombinant bacmids were separated after transformation. The result confirmed that purification of recombinant viruses could be carried out simply by transformation and indicated that this method could be used to delete essential genes. Orf4-disrupted bacmid DNA was extracted and transfected into Bm cells. Viable viruses were produced, showing that orf4 was not an essential gene.
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Wu YL, Chao YC. The establishment of a controllable expression system in baculovirus: stimulated overexpression of polyhedrin promoter by LEF-2. Biotechnol Prog 2009; 24:1232-40. [PMID: 19194936 DOI: 10.1002/btpr.47] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Previously, controllable gene expression in baculovirus was not possible using an insect system. We found that this was due to a high background activation of minimal promoter by the viral polyhedrin upstream (pu) sequence. Here, by truncation of the pu sequence, regulatory gene expression was established through the tetracycline regulatory expression system. This novel system was used to test the stimulatory function of the polyhedrin promoter by the controlled expression of the late expression factor-2 (lef-2). To efficiently trace lef-2 expression and analyze suppression of this gene, the coding sequences of lef-2 and enhanced green fluorescent protein (egfp) were ligated together to generate a fusion protein, and an approximately 100-fold suppression of egfp-lef-2 expression was achieved by doxycycline treatment. A very low level expression of lef-2 was found to be sufficient for proper expression of polyhedrin promoter; however, progressively higher levels of lef-2 expression could stimulate much higher-than-original polyhedrin promoter expression in the viral genome. This system was found to exhibit significantly better suppression than the double-stranded RNA (dsRNA) strategy, and would be useful for expression of foreign or viral genes whose functions require the interaction of multiple and/or unknown baculovirus gene products.
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Affiliation(s)
- Yueh-Lung Wu
- Institute of Biotechnology, National Chung-Kung University, Tainan, Taiwan
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Tian CH, Zhao JF, Xu YP, Xue J, Zhang BQ, Cui YJ, Zhang MJ, Bao YY, Zhang CX. Involvement of Bombyx mori nucleopolyhedrovirus ORF41 (Bm41) in BV production and ODV envelopment. Virology 2009; 387:184-92. [DOI: 10.1016/j.virol.2009.02.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 12/27/2008] [Accepted: 02/06/2009] [Indexed: 11/28/2022]
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Liu C, Li Z, Wu W, Li L, Yuan M, Pan L, Yang K, Pang Y. Autographa californica multiple nucleopolyhedrovirus ac53 plays a role in nucleocapsid assembly. Virology 2008; 382:59-68. [PMID: 18851866 DOI: 10.1016/j.virol.2008.09.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 07/10/2008] [Accepted: 09/03/2008] [Indexed: 01/09/2023]
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) orf53 (ac53) is a highly conserved gene existing in all sequenced Lepidoptera and Hymenoptera baculoviruses, but its function remains unknown. To investigate its role in the baculovirus life cycle, an ac53 deletion virus (vAc(ac53KO-PH-GFP)) was generated through homologous recombination in Escherichia coli. Fluorescence and light microscopy and titration analysis revealed that vAc(ac53KO-PH-GFP) could not produce infectious budded virus in infected Sf9 cells. Real-time PCR demonstrated that the ac53 deletion did not affect the levels of viral DNA replication. Electron microscopy showed that many lucent tubular shells devoid of the nucleoprotein core are present in the virogenic stroma and ring zone, indicating that the ac53 knockout affected nucleocapsid assembly. With a recombinant virus expressing an Ac53-GFP fusion protein, we observed that Ac53 was distributed within the cytoplasm and nucleus at 24 h post-infection, but afterwards accumulated predominantly near the nucleus-cytoplasm boundary. These data demonstrate that ac53 is involved in nucleocapsid assembly and is an essential gene for virus production.
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Affiliation(s)
- Chao Liu
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, China
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Yuan M, Wu W, Liu C, Wang Y, Hu Z, Yang K, Pang Y. A highly conserved baculovirus gene p48 (ac103) is essential for BV production and ODV envelopment. Virology 2008; 379:87-96. [PMID: 18656219 DOI: 10.1016/j.virol.2008.06.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 05/28/2008] [Accepted: 06/04/2008] [Indexed: 10/21/2022]
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) p48 (ac103) is a highly conserved baculovirus gene of unknown function. In the present study, we generated a knockout of the p48 gene in an AcMNPV bacmid and investigated the role of P48 in baculovirus life cycle. The p48-null Bacmid vAc(P48-KO-PH-GFP) was unable to propagate in cell culture, while a 'repair' Bacmid vAc(P48-REP-PH-GFP) was able to replicate in a manner similar to a wild-type Bacmid vAc(PH-GFP). Titration assays and Western blotting confirmed that vAc(P48-KO-PH-GFP) was unable to produce budded viruses (BVs). qPCR analysis showed that p48 deletion did not affect viral DNA replication. Electron microscopy indicated that P48 was required for nucleocapsid envelopment to form occlusion-derived viruses (ODVs) and their subsequent occlusion. Confocal analysis showed that P48 prominently condensed in the centre of the nucleus. Our results demonstrate that P48 plays an essential role in BV production and ODV envelopment in the AcMNPV life cycle.
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Affiliation(s)
- Meijin Yuan
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, China
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Hilton S, Kemp E, Keane G, Winstanley D. A bacmid approach to the genetic manipulation of granuloviruses. J Virol Methods 2008; 152:56-62. [PMID: 18602169 DOI: 10.1016/j.jviromet.2008.05.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 05/08/2008] [Accepted: 05/14/2008] [Indexed: 11/18/2022]
Abstract
A Cydia pomonella granulovirus (CpGV) bacmid has been constructed, which allows rapid and efficient production of recombinant baculoviruses in Escherichia coli. An 8.6kbp bacterial DNA cassette derived from the AcMNPV Bac-to-Bac system was ligated into a unique PacI restriction site within an intergenic region flanking the DNA ligase gene of the CpGV genome. The CpGV bacmids produced in E. coli were transfected into a CpGV-permissive C. pomonella cell line and the transfected cells fed to larvae to amplify the virus. The enhanced green fluorescent protein (EGFP) gene under the constitutive Drosophila heat-shock promoter was transposed into the mini-attTn7 transposition site, using a modified pFASTBAC donor plasmid, to generate a recombinant CpGV bacmid which caused infected larvae to glow under UV light. Targeted homologous recombination was also achieved in a recombinant proficient E. coli strain (BJ5183). A chloramphenicol acetyl transferase (CAT) gene replaced the cathepsin (v-cath) gene in the bacmid to produce a v-cath-deletion mutant. This is the first published report of a granulovirus bacmid, which will allow easy manipulation of the CpGV genome, enabling future studies on granulovirus genes and biology.
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Affiliation(s)
- Sally Hilton
- Warwick HRI, The University of Warwick, Wellesbourne, Warwick CV35 9EF, UK.
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Ge JQ, Yang ZN, Tang XD, Xu HJ, Hong J, Chen JG, Zhang CX. Characterization of a nucleopolyhedrovirus with a deletion of the baculovirus core gene Bm67. J Gen Virol 2008; 89:766-774. [PMID: 18272769 DOI: 10.1099/vir.0.83398-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Open reading frame (ORF) 67 (Bm67) of the Bombyx mori nucleopolyhedrovirus (BmNPV) is a highly conserved gene that is found in all completely sequenced baculoviruses; its function is unknown. In the present study, a Bm67-knockout virus was generated for studying the role of Bm67 in the BmNPV infection cycle. Furthermore, a Bm67-repair bacmid was constructed by transposing the Bm67 native promoter-promoted Bm67 ORF into the polyhedrin locus of the Bm67-knockout bacmid. After these recombinant bacmids were transfected into BmN cells, the Bm67-knockout bacmid caused defects in the production of infectious budded viruses. However, the Bm67-repair bacmid could rescue the defect, and budded virus titres reached wild-type levels. Quantitative real-time PCR analysis indicated that Bm67 is required for normal levels of DNA synthesis or for the stability of nascent viral DNA at the early stage. Electron microscopic analysis revealed that the formation of normal-appearing nucleocapsids is reduced in Bm67-knockout bacmid-transfected cells, and nucleocapsids are rarely found in the cytoplasm. The presence of 'enveloped' nucleocapsids at the nucleoplasm bilayer indicated that they are enveloped abnormally. These results indicated that Bm67 is required for the production of infectious budded viruses and for assembly of envelope and nucleocapsids.
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Affiliation(s)
- Jun-Qing Ge
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
| | - Zhang-Nv Yang
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
| | - Xu-Dong Tang
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
| | - Hai-Jun Xu
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
| | - Jian Hong
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
| | - Jian-Guo Chen
- College of Life Sciences, Peking University, Beijing 100087, PR China
| | - Chuan-Xi Zhang
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
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Roles of LEF-4 and PTP/BVP RNA triphosphatases in processing of baculovirus late mRNAs. J Virol 2008; 82:5573-83. [PMID: 18385232 DOI: 10.1128/jvi.00058-08] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The baculovirus Autographa californica nucleopolyhedrovirus encodes two proteins with RNA triphosphatase activity. Late expression factor LEF-4, which is an essential gene, is a component of the RNA polymerase and also encodes the RNA capping enzyme guanylyltransferase. PTP/BVP is also an RNA triphosphatase, but is not essential for viral replication, possibly because its activity is redundant to that of LEF-4. To elucidate the role of these proteins in mRNA cap formation, a mutant virus that lacked both RNA triphosphatase activities was constructed. Infection studies revealed that the double-mutant virus was viable and normal with respect to the production of budded virus. Pulse-labeling studies and immunoblot analyses showed that late gene expression in the double mutant was equivalent to that in the wild type, while polyhedrin expression was slightly reduced. Direct analysis of the mRNA cap structure indicated no alteration of cap processing in the double mutant. Together, these results reveal that baculoviruses replicate and express their late genes at normal levels in the absence of its two different types of RNA triphosphatases.
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Functional analysis of the transmembrane (TM) domain of the Autographa californica multicapsid nucleopolyhedrovirus GP64 protein: substitution of heterologous TM domains. J Virol 2008; 82:3329-41. [PMID: 18216100 DOI: 10.1128/jvi.02104-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
GP64, the major envelope glycoprotein of the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) budded virion, is important for host cell receptor binding and mediates low-pH-triggered membrane fusion during entry by endocytosis. In the current study, we examined the functional role of the AcMNPV GP64 transmembrane (TM) domain by replacing the 23-amino-acid GP64 TM domain with corresponding TM domain sequences from a range of viral and cellular type I membrane proteins, including Orgyia pseudotsugata MNPV (OpMNPV) GP64 and F, thogotovirus GP75, Lymantria dispar MNPV (LdMNPV) F, human immunodeficiency virus type 1 (HIV-1) GP41, human CD4 and glycophorin A (GpA), and influenza virus hemagglutinin (HA), and with a glycosylphosphatidylinositol (GPI) anchor addition sequence. In transient expression experiments with Sf9 cells, chimeric GP64 proteins containing either a GPI anchor or TM domains from LdMNPV F or HIV-1 GP41 failed to localize to the cell surface and thus appear to be incompatible with either GP64 structure or cell transport. All of the mutant constructs detected at the cell surface mediated hemifusion (outer leaflet merger) upon low-pH treatment, but only those containing TM domains from CD4, GpA, OpMNPV GP64, and thogotovirus GP75 mediated pore formation and complete membrane fusion activity. This supports a model in which partial fusion (hemifusion) proceeds by a mechanism that is independent of the TM domain and the TM domain participates in the enlargement or expansion of fusion pores after hemifusion. GP64 proteins containing heterologous TM domains mediated virion budding with dramatically differing levels of efficiency. In addition, chimeric GP64 proteins containing TM domains from CD4, GpA, HA, and OpMNPV F were incorporated into budded virions but were unable to rescue the infectivity of a gp64 null virus, whereas those with TM domains from OpMNPV GP64 and thogotovirus GP75 rescued infectivity. These results show that in addition to its basic role in membrane anchoring, the GP64 TM domain is critically important for GP64 trafficking, membrane fusion, virion budding, and virus infectivity. These critical functions were replaced only by TM domains from related viral membrane proteins.
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Abstract
The development of baculovirus expression vector systems has accompanied a rapid expansion of our knowledge about the genes, their function, and regulation in insect cells. Classification of these viruses has also been refined as we learn more about differences in gene content between isolates, how this affects virus structure, and their replication in insect larvae. Baculovirus gene expression occurs in an ordered cascade, regulated by early, late, and very late gene promoters. There is now a detailed knowledge of these promoter elements and how they interact first with host cell-encoded RNA polymerases and later with virus-encoded enzymes. The composition of this virus RNA polymerase is known. The virus replication process culminates in the very high level expression of both polyhedrin and p10 gene products in the latter stages of infection. It has also been realized that the insect host cell has innate defenses against baculoviruses in the form of an apoptotic response to virus invasion. Baculoviruses counter this by encoding apoptotic-suppressors, which also appear to have a role in determining the host range of the virus. Also of importance to our understanding of baculovirus expression systems is how the virus can accumulate mutations within genes that affect recombinant protein yield in cell culture. The summary in this chapter is not exhaustive, but should provide a good preparation to those wishing to use this highly successful gene expression system.
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48
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Mikhailov VS, Vanarsdall AL, Rohrmann GF. Isolation and characterization of the DNA-binding protein (DBP) of the Autographa californica multiple nucleopolyhedrovirus. Virology 2007; 370:415-29. [PMID: 17935748 DOI: 10.1016/j.virol.2007.09.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 08/29/2007] [Accepted: 09/05/2007] [Indexed: 11/24/2022]
Abstract
DNA-binding protein (DBP) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) was expressed as an N-terminal His(6)-tag fusion using a recombinant baculovirus and purified to near homogeneity. Purified DBP formed oligomers that were crosslinked by redox reagents resulting in predominantly protein dimers and tetramers. In gel retardation assays, DBP showed a high affinity for single-stranded oligonucleotides and was able to compete with another baculovirus SSB protein, LEF-3, for binding sites. DBP binding protected ssDNA against hydrolysis by a baculovirus alkaline nuclease AN/LEF-3 complex. Partial proteolysis by trypsin revealed a domain structure of DBP that is required for interaction with DNA and that can be disrupted by thermal treatment. Binding to ssDNA, but not to dsDNA, changed the pattern of proteolytic fragments of DBP indicating adjustments in protein structure upon interaction with ssDNA. DBP was capable of unwinding short DNA duplexes and also promoted the renaturation of long complementary strands of ssDNA into duplexes. The unwinding and renaturation activities of DBP, as well as the DNA binding activity, were sensitive to sulfhydryl reagents and were inhibited by oxidation of thiol groups with diamide or by alkylation with N-ethylmaleimide. A high affinity of DBP for ssDNA and its unwinding and renaturation activities confirmed identification of DBP as a member of the SSB/recombinase family. These activities and a tight association with subnuclear structures suggests that DBP is a component of the virogenic stroma that is involved in the processing of replicative intermediates.
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Affiliation(s)
- Victor S Mikhailov
- Department of Microbiology, Oregon State University, Corvallis, OR 97331-3804, USA.
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Wang Y, Wu W, Li Z, Yuan M, Feng G, Yu Q, Yang K, Pang Y. ac18 is not essential for the propagation of Autographa californica multiple nucleopolyhedrovirus. Virology 2007; 367:71-81. [PMID: 17573091 DOI: 10.1016/j.virol.2007.05.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 03/10/2007] [Accepted: 05/09/2007] [Indexed: 10/23/2022]
Abstract
orf18 (ac18) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved gene in lepidopteran nucleopolyhedroviruses, but its function remains unknown. In this study, an ac18 knockout AcMNPV bacmid was generated to determine the role of ac18 in baculovirus life cycle. After transfection of Sf-9 cells, the ac18-null mutant showed similar infection pattern to the parent virus and the ac18 repair virus with respect to the production of infectious budded virus, occlusion bodies, or the formation of nucleocapsids as visualized by electron microscopy. The deletion mutant did not reduce AcMNPV infectivity for Trichoplusia ni in LD(50) bioassay; however, it did take 24 h longer for deleted mutant to kill T. ni larvae than wild-type virus in LT(50) bioassay. Our results demonstrate that ac18 is not essential for viral propagation both in vitro and in vivo, but it may play a role in efficient virus infection in T. ni larvae.
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Affiliation(s)
- Yanjie Wang
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, China
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50
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Vanarsdall AL, Mikhailov VS, Rohrmann GF. Characterization of a baculovirus lacking the DBP (DNA-binding protein) gene. Virology 2007; 364:475-85. [PMID: 17449080 PMCID: PMC2697660 DOI: 10.1016/j.virol.2007.03.024] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 03/12/2007] [Accepted: 03/16/2007] [Indexed: 11/28/2022]
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) encodes two proteins that possess properties typical of single-stranded DNA-binding proteins (SSBs), late expression factor-3 (LEF-3), and a protein referred to as DNA-binding protein (DBP). Whereas LEF-3 is a multi-functional protein essential for viral DNA replication, transporting helicase into the nucleus, and forms a stable complex with the baculovirus alkaline nuclease, the role for DBP in baculovirus replication remains unclear. Therefore, to better understand the functional role of DBP in viral replication, a DBP knockout virus was generated from an AcMNPV bacmid and analyzed. The results of a growth curve analysis indicated that the dbp knockout construct was unable to produce budded virus indicating that dbp is essential. The lack of DBP does not cause a general shutdown of the expression of viral genes, as was revealed by accumulation of early (LEF-3), late (VP39), and very late (P10) proteins in cells transfected with the dbp knockout construct. To investigate the role of DBP in DNA replication, a real-time PCR-based assay was employed and showed that, although viral DNA synthesis occurred in cells transfected with the dbp knockout, the levels were less than that of the control virus suggesting that DBP is required for normal levels of DNA synthesis or for stability of nascent viral DNA. In addition, analysis of the viral DNA replicated by the dbp knockout by using field inversion gel electrophoresis failed to detect the presence of genome-length DNA. Furthermore, analysis of DBP from infected cells indicated that similar to LEF-3, DBP was tightly bound to viral chromatin. Assessment of the cellular localization of DBP relative to replicated viral DNA by immunoelectron microscopy indicated that, at 24 h post-infection, DBP co-localized with nascent DNA at distinct electron-dense regions within the nucleus. Finally, immunoelectron microscopic analysis of cells transfected with the dbp knockout revealed that DBP is required for the production of normal-appearing nucleocapsids and for the generation of the virogenic stroma.
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Affiliation(s)
- Adam L. Vanarsdall
- Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Victor S. Mikhailov
- Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
- N. K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 117808, Russia
| | - George F. Rohrmann
- Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
- Address Correspondence regarding publication to: George F. Rohrmann, Department of Microbiology, Nash Hall Room 220, Oregon State University, Corvallis, Oregon 97331-3804, phone: 541 737 1793, FAX 541 737 0496,
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