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Slack J, Nguyen C, Ibe-Enwo A. A Lac Repressor-Inducible Baculovirus Expression Vector for Controlling Adeno-Associated Virus Capsid Ratios. Viruses 2023; 16:51. [PMID: 38257750 PMCID: PMC10820722 DOI: 10.3390/v16010051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 12/19/2023] [Accepted: 12/23/2023] [Indexed: 01/24/2024] Open
Abstract
The baculovirus expression vector (BEV) system is an efficient, cost-effective, and scalable method to produce recombinant adeno-associated virus (rAAV) gene therapy vectors. Most BEV designs emulate the wild-type AAV transcriptome and translate the AAV capsid proteins, VP1, VP2, and VP3, from a single mRNA transcript with three overlapping open reading frames (ORFs). Non-canonical translation initiation codons for VP1 and VP2 reduce their abundances relative to VP3. Changing capsid ratios to improve rAAV vector efficacy requires a theoretical modification of the translational context. We have developed a Lac repressor-inducible system to empirically regulate the expression of VP1 and VP2 proteins relative to VP3 in the context of the BEV. We demonstrate the use of this system to tune the abundance, titer, and potency of a neurospecific rAAV9 serotype derivative. VP1:VP2:VP3 ratios of 1:1:8 gave optimal potency for this rAAV. It was discovered that the ratios of capsid proteins expressed were different than the ratios that ultimately were in purified capsids. Overexpressed VP1 did not become incorporated into capsids, while overexpressed VP2 did. Overabundance of VP2 correlated with reduced rAAV titers. This work demonstrates a novel technology for controlling the production of rAAV in the BEV system and shows a new perspective on the biology of rAAV capsid assembly.
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Affiliation(s)
- Jeffrey Slack
- Voyager Therapeutics, 64 Sidney St., Cambridge, MA 02139, USA;
| | | | - Amanda Ibe-Enwo
- Voyager Therapeutics, 64 Sidney St., Cambridge, MA 02139, USA;
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Nagamine T, Sako Y. A SLiM-dependent conformational change in baculovirus IE1 controls its focus formation ability. J Gen Virol 2023; 104. [PMID: 37877992 DOI: 10.1099/jgv.0.001910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023] Open
Abstract
The baculovirus IE1 gene encodes a multifunctional protein that is essential for both DNA replication and RNA transcription of the virus. Prior to viral DNA replication, IE1 promotes early gene transcription when localized in hr-dependent foci. During viral DNA replication, the IE1 foci expand and fuse to generate the virogenic stroma (VS) with IE1 found in the VS reticulum. To explore the IE1 structural features essential for this coordinated localization, we constructed various IE1 mutants based on three putative domains (N, I, and C). We determined that a BDI motif located in the intrinsic disorder region (IDR) between the N and I domains acts as a nuclear localization signal, whereas BDII and HLH in the C domain are required for VS localization in infected cells or for chromosomal association in uninfected mitotic cells. Deletion of the SLiM (short linear motif) located in the I domain restrains both nuclear- and VS localization. Intra-molecular fluorescence resonance energy transfer (FRET) probes of IE1 mutants revealed a conformational change of the I-C two-domain fragment during infection, which was inhibited by aphidicolin, suggesting that IE1 undergoes a stage-dependent conformational change. Further, homo-dimerization of the I domain and stage-dependent conformational changes require an intact SLiM. Mutational analysis of SLiM revealed that VS localization and chromosomal association were retained following S291A and S291E substitutions, but hr-dependent focus formation differed between the two mutations. These results suggest that coordinated IE1 localization is controlled by SLiM-dependent conformational changes that are potentially switched by the phosphorylation state of the SLiM.
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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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Hu ZG, Dong ZQ, Miao JH, Li KJ, Wang J, Chen P, Lu C, Pan MH. Identification of the Key Functional Domains of Bombyx mori Nucleopolyhedrovirus IE1 Protein. Int J Mol Sci 2022; 23:ijms231810276. [PMID: 36142194 PMCID: PMC9499007 DOI: 10.3390/ijms231810276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/22/2022] [Accepted: 08/29/2022] [Indexed: 11/28/2022] Open
Abstract
The immediate early protein 1 (IE1) acts as a transcriptional activator and is essential for viral gene transcription and viral DNA replication. However, the key regulatory domains of IE1 remain poorly understood. Here, we analyzed the sequence characteristics of Bombyx mori nucleopolyhedrovirus (BmNPV) IE1 and identified the key functional domains of BmNPV IE1 by stepwise truncation. Our results showed that BmNPV IE1 was highly similar to Autographa californica nucleopolyhedrovirus (AcMNPV) IE1, but was less conserved with IE1 of other baculoviruses, the C-terminus of IE1 was more conserved than the N-terminus, and BmNPV IE1 was also necessary for BmNPV proliferation. Moreover, we found that IE1158–208 was a major nuclear localization element, and IE11–157 and IE1539–559 were minor nuclear localization elements, but the combination of these two minor elements was equally sufficient to fully mediate the nuclear entry of IE1. Meanwhile, IE11–258, IE1560–584, and the association of amino acids 258 and 259 were indispensable for the transactivation activity of BmNPV IE1. These results systematically resolve the functional domains of BmNPV IE1, which contribute to the understanding of the mechanism of baculovirus infection and provide a possibility to synthesize a small molecule IE1-truncated mutant as an agonist or antagonist.
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Affiliation(s)
- Zhi-Gang Hu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Zhan-Qi Dong
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
- Key Laboratory for Sericultural Biology and Genetic Breeding, Ministry of Agriculture, Southwest University, Chongqing 400716, China
| | - Jiang-Hao Miao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Ke-Jie Li
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Jie Wang
- 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
- Key Laboratory for Sericultural Biology and Genetic Breeding, Ministry of Agriculture, Southwest University, Chongqing 400716, China
| | - Cheng Lu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
- Key Laboratory for Sericultural Biology and Genetic Breeding, Ministry of Agriculture, Southwest University, Chongqing 400716, China
- Correspondence: (C.L.); (M.-H.P.); Tel.: +86-023-68250076 (M.-H.P.)
| | - Min-Hui Pan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
- Key Laboratory for Sericultural Biology and Genetic Breeding, Ministry of Agriculture, Southwest University, Chongqing 400716, China
- Correspondence: (C.L.); (M.-H.P.); Tel.: +86-023-68250076 (M.-H.P.)
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5
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Chen N, Kong X, Zhao S, Xiaofeng W. Post-translational modification of baculovirus-encoded proteins. Virus Res 2020; 279:197865. [DOI: 10.1016/j.virusres.2020.197865] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 01/10/2020] [Accepted: 01/12/2020] [Indexed: 02/03/2023]
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6
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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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7
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Wang J, Hou D, Wang Q, Kuang W, Zhang L, Li J, Shen S, Deng F, Wang H, Hu Z, Wang M. Genome analysis of a novel Group I alphabaculovirus obtained from Oxyplax ochracea. PLoS One 2018; 13:e0192279. [PMID: 29390020 PMCID: PMC5794183 DOI: 10.1371/journal.pone.0192279] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/18/2018] [Indexed: 02/03/2023] Open
Abstract
Oxyplax ochracea (Moore) is a pest that causes severe damage to a wide range of crops, forests and fruit trees. The complete genome sequence of Oxyplax ochracea nucleopolyhedrovirus (OxocNPV) was determined using a Roche 454 pyrosequencing system. OxocNPV has a double-stranded DNA (dsDNA) genome of 113,971 bp with a G+C content of 31.1%. One hundred and twenty-four putative open reading frames (ORFs) encoding proteins of >50 amino acids in length and with minimal overlapping were predicted, which covered 92% of the whole genome. Six baculoviral typical homologous regions (hrs) were identified. Phylogenetic analysis and gene parity plot analysis showed that OxocNPV belongs to clade “a” of Group I alphabaculoviruses, and it seems to be close to the most recent common ancestor of Group I alphabaculoviruses. Three unique ORFs (with no homologs in the National Center for Biotechnology Information database) were identified. Interestingly, OxocNPV lacks three auxiliary genes (lef7, ie-2 and pcna) related to viral DNA replication and RNA transcription. In addition, OxocNPV has significantly different sequences for several genes (including ie1 and odv-e66) in comparison with those of other baculoviruses. However, three dimensional structure prediction showed that OxocNPV ODV-E66 contain the conserved catalytic residues, implying that it might possess polysaccharide lyase activity as AcMNPV ODV-E66. All these unique features suggest that OxocNPV represents a novel species of the Group I alphabaculovirus lineage.
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Affiliation(s)
- Jun Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Dianhai Hou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- School of Bioscience and Technology, Weifang Medical University, Weifang, China
| | - Qianran Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Wenhua Kuang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Lei Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Jiang Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Shu Shen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Fei Deng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Hualin Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Zhihong Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Manli Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- * E-mail:
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8
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Ono C, Sato M, Taka H, Asano SI, Matsuura Y, Bando H. Tightly regulated expression of Autographa californica multicapsid nucleopolyhedrovirus immediate early genes emerges from their interactions and possible collective behaviors. PLoS One 2015; 10:e0119580. [PMID: 25816136 PMCID: PMC4376880 DOI: 10.1371/journal.pone.0119580] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 01/29/2015] [Indexed: 11/18/2022] Open
Abstract
To infect their hosts, DNA viruses must successfully initiate the expression of viral genes that control subsequent viral gene expression and manipulate the host environment. Viral genes that are immediately expressed upon infection play critical roles in the early infection process. In this study, we investigated the expression and regulation of five canonical regulatory immediate-early (IE) genes of Autographa californica multicapsid nucleopolyhedrovirus: ie0, ie1, ie2, me53, and pe38. A systematic transient gene-expression analysis revealed that these IE genes are generally transactivators, suggesting the existence of a highly interactive regulatory network. A genetic analysis using gene knockout viruses demonstrated that the expression of these IE genes was tolerant to the single deletions of activator IE genes in the early stage of infection. A network graph analysis on the regulatory relationships observed in the transient expression analysis suggested that the robustness of IE gene expression is due to the organization of the IE gene regulatory network and how each IE gene is activated. However, some regulatory relationships detected by the genetic analysis were contradictory to those observed in the transient expression analysis, especially for IE0-mediated regulation. Statistical modeling, combined with genetic analysis using knockout alleles for ie0 and ie1, showed that the repressor function of ie0 was due to the interaction between ie0 and ie1, not ie0 itself. Taken together, these systematic approaches provided insight into the topology and nature of the IE gene regulatory network.
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Affiliation(s)
- Chikako Ono
- Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Masanao Sato
- National Institute for Basic Biology, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama, Myodaiji, Okazaki, Japan
| | - Hitomi Taka
- Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Shin-ichiro Asano
- Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Yoshiharu Matsuura
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Hisanori Bando
- Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
- * E-mail:
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9
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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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10
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Conserved structural motifs at the C-terminus of baculovirus protein IE0 are important for its functions in transactivation and supporting hr5-mediated DNA replication. Viruses 2012; 4:761-76. [PMID: 22754648 PMCID: PMC3386618 DOI: 10.3390/v4050761] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 04/23/2012] [Accepted: 04/27/2012] [Indexed: 11/16/2022] Open
Abstract
IE0 and IE1 are transactivator proteins of the most studied baculovirus, the Autographa californica multiple nucleopolyhedrovirus (AcMNPV). IE0 is a 72.6 kDa protein identical to IE1 with the exception of its 54 N-terminal amino acid residues. To gain some insight about important structural motifs of IE0, we expressed the protein and C‑terminal mutants of it under the control of the Drosophila heat shock promoter and studied the transactivation and replication functions of the transiently expressed proteins. IE0 was able to promote replication of a plasmid bearing the hr5 origin of replication of AcMNPV in transient transfections with a battery of eight plasmids expressing the AcMNPV genes dnapol, helicase, lef-1, lef-2, lef-3, p35, ie-2 and lef-7. IE0 transactivated expression of the baculovirus 39K promoter. Both functions of replication and transactivation were lost after introduction of selected mutations at the basic domain II and helix-loop-helix conserved structural motifs in the C-terminus of the protein. These IE0 mutants were unable to translocate to the cell nucleus. Our results point out the important role of some structural conserved motifs to the proper functioning of IE0.
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11
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A conserved N-terminal domain mediates required DNA replication activities and phosphorylation of the transcriptional activator IE1 of Autographa californica multicapsid nucleopolyhedrovirus. J Virol 2012; 86:6575-85. [PMID: 22496221 DOI: 10.1128/jvi.00373-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
IE1 is the principal transcriptional regulator of the baculoviruses. Like multifunctional transcription factors of other large DNA viruses, IE1 is an essential, site-specific DNA-binding phosphoprotein that activates virus gene expression and promotes genome replication. To define the poorly understood mechanisms by which IE1 achieves its diverse functions, we identified IE1 domains that contribute to productive infection of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), the baculovirus prototype. Site-directed mutagenesis revealed that the N-terminal 23 residues of IE1 are required for origin-specific DNA replication and AcMNPV propagation, but not for DNA-binding-dependent transcriptional activation. Within this defined replication domain, we identified an invariant TPXR/H motif that resembles a consensus cyclin-dependent kinase phosphorylation site. Amino acid substitutions of potential phosphorylation sites within or near this motif caused loss of IE1-mediated DNA replication activity. Remarkably, substitution of the single threonine (residue 15) within the TPXR/H motif caused complete loss of AcMNPV multiplication. The replication domain was required for IE1 phosphorylation. It was also sufficient for conferring phosphorylation of a heterologous protein. Importantly, IE1 hyperphosphorylation coincided exclusively with AcMNPV DNA replication. The temporal regulation of IE1 phosphorylation and the essential nature of the TPXR/H motif suggest that phosphorylation critically alters and possibly activates DNA replication activity of IE1 during infection. The striking conservation of the TPXR/H motif among IE1 proteins further suggests that this molecular switch may be a common mechanism by which the alphabaculoviruses coordinate DNA replication and gene expression by using a single regulator.
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Baculoviruses deficient in ie1 gene function abrogate viral gene expression in transduced mammalian cells. Virology 2010; 406:293-301. [PMID: 20705310 DOI: 10.1016/j.virol.2010.07.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 06/04/2010] [Accepted: 07/13/2010] [Indexed: 11/21/2022]
Abstract
One of the newest niches for baculoviruses-based technologies is their use as vectors for mammalian cell transduction and gene therapy applications. However, an outstanding safety issue related to such use is the residual expression of viral genes in infected mammalian cells. Here we show that infectious baculoviruses lacking the major transcriptional regulator, IE1, can be produced in insect host cells stably transformed with IE1 expression constructs lacking targets of homologous recombination that could promote the generation of wt-like revertants. Such ie1-deficient baculoviruses are unable to direct viral gene transcription to any appreciable degree and do not replicate in normal insect host cells. Most importantly, the residual viral gene expression, which occurs in mammalian cells infected with wt baculoviruses is reduced 10 to 100 fold in cells infected with ie1-deficient baculoviruses. Thus, ie1-deficient baculoviruses offer enhanced safety features to baculovirus-based vector systems destined for use in gene therapy applications.
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Nie Y, Fang M, Theilmann DA. AcMNPV AC16 (DA26, BV/ODV-E26) regulates the levels of IE0 and IE1 and binds to both proteins via a domain located within the acidic transcriptional activation domain. Virology 2009; 385:484-95. [PMID: 19150105 DOI: 10.1016/j.virol.2008.12.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 11/20/2008] [Accepted: 12/10/2008] [Indexed: 11/19/2022]
Abstract
IE0 and IE1 are the primary viral regulatory proteins of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) involved in the transactivation of early genes, stimulation of late gene expression, and viral DNA replication. The protein interactions required for IE0 or IE1 to achieve these varied roles are not well defined, so to identify proteins that interact with IE0 and IE1, tandem affinity purification (TAP) and LC-MS/MS was used. Analysis of purified proteins identified AC16 (DA26, BV/ODV-E26) from TAP tagged IE0 virus infected Sf9 cells. Co-immunoprecipitation confirmed that AC16 interacts with both IE0 and IE1 and yeast 2-hybrid analysis mapped the domain required for interaction with AC16. Mutation of the AC16 binding domain enhanced BV production by viruses expressing only IE0 but had no effect if only IE1 is expressed. An ac16 deletion virus was constructed and was shown not to affect the temporal expression of IE0 and IE1; however the relative level of IE0 to IE1 was significantly increased.
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Affiliation(s)
- Yingchao Nie
- Plant Science, Faculty of Land and Food Systems, University of British Columbia, Vancouver, B.C., Canada V6T 1Z4
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14
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Transactivator IE1 is required for baculovirus early replication events that trigger apoptosis in permissive and nonpermissive cells. J Virol 2008; 83:262-72. [PMID: 18945761 DOI: 10.1128/jvi.01827-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Immediate early viral protein IE1 is a potent transcriptional activator encoded by baculoviruses. Although the requirement of IE1 for multiplication of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) is well established, the functional roles of IE1 during infection are unclear. Here, we used RNA interference to ablate IE1, plus its splice variant IE0, and thereby define in vivo activities of these early proteins, including gene-specific regulation and induction of host cell apoptosis. Confirming an essential replicative role, simultaneous ablation of IE1 and IE0 by gene-specific double-stranded RNAs inhibited AcMNPV late gene expression, reduced yields of budded virus by more than 1,000-fold, and blocked production of occluded virus particles. Depletion of IE1 and IE0 had no effect on early expression of the envelope fusion protein gene gp64 but abolished early expression of the caspase inhibitor gene p35, which is required for prevention of virus-induced apoptosis. Thus, IE1 is a positive, gene-specific transactivator. Whereas an AcMNPV p35 deletion mutant caused widespread apoptosis in permissive Spodoptera frugiperda cells, ablation of IE1 and IE0 prevented this apoptosis. Silencing of ie-1 also prevented AcMNPV-induced apoptosis in nonpermissive Drosophila melanogaster cells. Thus, de novo synthesis of IE1 is required for virus-induced apoptosis. We concluded that IE1 causes apoptosis directly or contributes indirectly by promoting virus replication events that subsequently trigger cell death. This study reveals that IE1 is a gene-selective transcriptional activator which is required not only for expedition of virus multiplication but also for blocking of its own proapoptotic activity by upregulation of baculovirus apoptotic suppressors.
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Transactivation, dimerization, and DNA-binding activity of white spot syndrome virus immediate-early protein IE1. J Virol 2008; 82:11362-73. [PMID: 18768963 DOI: 10.1128/jvi.01244-08] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immediate-early proteins from many viruses function as transcriptional regulators and exhibit transactivation activity, DNA binding activity, and dimerization. In this study, we investigated these characteristics in white spot syndrome virus (WSSV) immediate-early protein 1 (IE1) and attempted to map the corresponding functional domains. Transactivation was investigated by transiently expressing a protein consisting of the DNA binding domain of the yeast transactivator GAL4 fused to full-length IE1. This GAL4-IE1 fusion protein successfully activated the Autographa californica multicapsid nucleopolyhedrovirus p35 basal promoter when five copies of the GAL4 DNA binding site were inserted upstream of the TATA box. A deletion series of GAL4-IE1 fusion proteins suggested that the transactivation domain of WSSV IE1 was carried within its first 80 amino acids. A point mutation assay further showed that all 12 of the acidic residues in this highly acidic domain were important for IE1's transactivation activity. DNA binding activity was confirmed by an electrophoresis mobility shift assay using a probe with (32)P-labeled random oligonucleotides. The DNA binding region of WSSV IE1 was located in its C-terminal end (amino acids 81 to 224), but mutation of a putative zinc finger motif in this C-terminal region suggested that this motif was not directly involved in the DNA binding activity. A homotypic interaction between IE1 molecules was demonstrated by glutathione S-transferase pull-down assay and a coimmunoprecipitation analysis. A glutaraldehyde cross-linking experiment and gel filtration analysis showed that this self-interaction led to the formation of stable IE1 dimers.
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16
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Bilen MF, Pilloff MG, Belaich MN, Da Ros VG, Rodrigues JC, Ribeiro BM, Romanowski V, Lozano ME, Ghiringhelli PD. Functional and structural characterisation of AgMNPV ie1. Virus Genes 2007; 35:549-62. [PMID: 17682932 DOI: 10.1007/s11262-007-0150-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 11/20/2006] [Indexed: 11/25/2022]
Abstract
We have located and cloned the Anticarsia gemmatalis multicapsid nucleopolyhedrovirus isolate 2D (AgMNPV-2D) genomic DNA fragment containing the immediate early 1 ORF and its flanking regions. Computer assisted analysis of the complete ie1 locus nucleotide sequence information was used to locate regulatory signals in the upstream region and conserved nucleotide and amino acid sequences. Comparative studies led to the identification of several characteristic protein motifs and to the conclusion that AgMNPV-2D is more closely related to Choristoneura fumiferana defective NPV than to other Group I nucleopolyhedrovirus. We have also shown that the AgMNPV IE1 protein was able to transactivate an early Autographa californica MNPV promoter and its own promoter in transient expression assays. In order to investigate the biological functionality of the ie1 promoter, the ie1 upstream activating region (UAR) was molecularly dissected and cloned upstream of the E. coli lacZ ORF. The results obtained, after transfection of UFL-AG-286 insect cells, leading us to find that the -492 and -357 versions contains sequence motifs important for the level of the lacZ reporter gene expression.
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Affiliation(s)
- Marcos Fabián Bilen
- Laboratorio de Ingeniería Genética y Biología Celular y Molecular, Departamento de Ciencia y Tecnología, Centro de Estudios e Investigaciones, Universidad Nacional de Quilmes, Roque Saenz Peña 352, 1876 Bernal, Buenos Aires, Argentina
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17
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Carstens EB, Wu Y. No single homologous repeat region is essential for DNA replication of the baculovirus Autographa californica multiple nucleopolyhedrovirus. J Gen Virol 2007; 88:114-122. [PMID: 17170443 DOI: 10.1099/vir.0.82384-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The presence of homologous repeat (hr) regions in multiple locations within baculovirus genomes has led to the hypothesis that they represent origins of DNA replication. This hypothesis has been supported by transient replication assays where plasmids carrying hrs replicated in the presence of virus DNA replication. This study investigated whether any specific hr region was essential for viral DNA replication in vivo, by generating a series of recombinant Autographa californica multiple nucleopolyhedrovirus where the lacZ gene replaced hr1, hr1a, hr2, hr3, hr4a or hr4b. In addition, a double-hr knockout virus was constructed where both hr2 and hr3 were deleted. The successful construction of these knockout viruses indicated that no specific region was essential for virus production. These recombinant viruses were characterized by titrations of budded virus, expression of a variety of virus-specific proteins and the synthesis of viral DNA at various times after infection. The results demonstrated that each hr was dispensable for all of these properties and that no single region was absolutely essential for virus replication in cell culture. The functional significance of multiple origin regions is still unclear.
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Affiliation(s)
- Eric B Carstens
- Department of Microbiology and Immunology, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Yuntao Wu
- Department of Microbiology and Immunology, Queen's University, Kingston, ON K7L 3N6, Canada
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18
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Berretta MF, Passarelli AL. Function of Spodoptera exigua nucleopolyhedrovirus late gene expression factors in the insect cell line SF-21. Virology 2006; 355:82-93. [PMID: 16901524 DOI: 10.1016/j.virol.2006.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 06/13/2006] [Accepted: 07/10/2006] [Indexed: 12/01/2022]
Abstract
We used a well established transient expression assay to test the ability of the baculovirus Spodoptera exigua M nucleopolyhedrovirus (SeMNPV) homologs of Autographa californica MNPV (AcMNPV) late expression factors (lefs) to activate a late promoter-reporter gene cassette in SF-21 cells. This insect-derived cell line is fully permissive for AcMNPV infection but not for SeMNPV. In the assay, 19 AcMNPV lefs stimulate optimal levels of late gene promoter activity. SeMNPV lef-5 successfully replaced the corresponding AcMNPV gene in the context of the remaining set of AcMNPV lefs, whereas SeMNPV dnapol and 39k exhibited partial activity. When all the SeMNPV lefs were assayed together or in the presence of four lefs encoded only in AcMNPV, it resulted in background levels of late promoter-driven reporter gene activity. However, SeMNPV genomic DNA and the four AcMNPV-specific lefs stimulated low levels of reporter gene activity. Moreover, SeMNPV IE-1, but not AcMNPV IE-1, further stimulated late gene expression in the presence of SeMNPV DNA. AcMNPV IE-1 was able to mediate early gene expression cis-linked to homologous regions (hrs) derived from AcMNPV and SeMNPV. In contrast, SeMNPV IE-1 was more specific for SeMNPV-derived hr elements.
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Affiliation(s)
- Marcelo F Berretta
- Division of Biology, Molecular, Cellular, and Developmental Biology Program, Kansas State University, Manhattan, KS 66506-4901, USA
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19
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Lu L, Liqun L, Rivkin H, Chejanovsky N. The immediate-early protein IE0 of the Autographa californica nucleopolyhedrovirus is not essential for viral replication. J Virol 2005; 79:10077-82. [PMID: 16014970 PMCID: PMC1181591 DOI: 10.1128/jvi.79.15.10077-10082.2005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) immediate-early protein IE0 in the baculoviral infection is not clear. In this study, we constructed the recombinant virus vAcDeltaie0 null for ie0 expression by targeted mutagenesis replacing exon0 with the cat gene. We found that vAcDeltaie0 replicated efficiently in Spodoptera littoralis SL2 cells, which are poorly permissive for AcMNPV. In contrast, in Spodoptera frugiperda SF9 cells, which are fully permissive for AcMNPV, vAcDeltaie0 DNA replication and budded virus production were delayed. These results and recently published data (X. Dai et al., J. Virol. 78:9633-9644, 2004) indicate that ie0 is not essential for AcMNPV replication but enhances it in permissive SF9 cells.
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Affiliation(s)
- Liqun Lu
- Entomology Department, The Institute of Plant Protection, The Volcani Center, Bet Dagan, Israel
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20
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Stewart TM, Huijskens I, Willis LG, Theilmann DA. The Autographa californica multiple nucleopolyhedrovirus ie0-ie1 gene complex is essential for wild-type virus replication, but either IE0 or IE1 can support virus growth. J Virol 2005; 79:4619-29. [PMID: 15795248 PMCID: PMC1069578 DOI: 10.1128/jvi.79.8.4619-4629.2005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The immediate-early ie0-ie1 gene complex expresses the only baculovirus spliced gene that produces an alternate protein product. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) IE1 is a potent transcriptional transactivator that is essential for viral replication in transient assays. IE1 contains 582 amino acids that are arranged into different domains, including an acidic activation domain at the N terminus, a DNA binding domain, and an oligomerization domain at the C terminus. IE0 is a 52-amino-acid N-terminally elongated form of IE1. We investigated the functions of IE0 and IE1 in virus-infected cells by constructing the first ie1 open reading frame knockout virus. An infectious AcMNPV bacmid was used to generate the ie1 knockout, and the resulting virus, AcBacIE1KO, effectively deletes both ie0 and ie1. AcBacIE1KO does not infect Spodoptera frugiperda cells, showing that the ie0-ie1 gene complex is essential for viral infection. Rescue viruses of AcBacIE1KO were constructed that express only IE1, IE1 and IE0, or only IE0. Our results show that both IE0 and IE1 can function independently, but not equivalently, to support replication, producing infectious virus. Viruses expressing predominately, or only, IE0 produced significantly fewer cells with polyhedra than either the IE1 counterpart or wild-type virus. In addition, DNA replication was prolonged and budded virus and late gene expression were delayed. Viruses expressing only IE1 also produced fewer polyhedra, but replication was slightly faster and achieved higher levels than that of the wild-type virus. Both IE0 and IE1 are therefore required and must be expressed in the correct quantitative ratios to achieve a wild-type infection.
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Affiliation(s)
- Taryn M Stewart
- Faculty of Agricultural Sciences, University of British Columbia, Vancouver, Canada V0H 1Z0
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21
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Huijskens I, Li L, Willis LG, Theilmann DA. Role of AcMNPV IE0 in baculovirus very late gene activation. Virology 2004; 323:120-30. [PMID: 15165824 DOI: 10.1016/j.virol.2004.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2004] [Revised: 01/26/2004] [Accepted: 03/01/2004] [Indexed: 10/26/2022]
Abstract
IE0 is the only known baculovirus protein that is produced by splicing. In this study, we have explored the role of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) IE0 and its interaction with IE1 in the activation of very late gene expression from the polyhedrin promoter using transient assays. IE0 is co-expressed with IE1 throughout infection up to late times post-infection (p.i.) but shows peak levels of expression at early times. Significant changes in the ratios of the relative levels of IE0 to IE1 were observed throughout the course of infection. To study IE0 in the absence of IE1, we constructed a plasmid pAc-IE0(M-->A) that expressed only IE0. This was due to a mutation of the internal AUG that prevented translation of IE1 from the ie0 mRNA. Both IE0 and IE0(M-->A) were able to replace IE1 in transient assays, showing that IE0 is functional for very late gene activation and should be considered the 20th late gene expression factor (lef). In transient assays, IE0 showed that maximum very late gene expression is achieved at very low relative levels of protein. In contrast, IE1 requires higher levels of protein to obtain maximum very late gene expression. Furthermore, when the levels of IE0 become too high, very late gene expression rapidly declines. Interestingly, co-expression of IE0 and IE1 results in a mutually antagonistic affect on very late gene expression.
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Affiliation(s)
- Ilse Huijskens
- Department of Agroecology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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22
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Abstract
Autographa californica nuclear polyhedrosis virus, or AcMNPV, is the type member of the baculoviruses, a family of double-stranded DNA viruses with large circular genomes. The successive and concomitant expression of an assortment of early, late and very late genes is instrumental for successful baculovirus infection, and requires a switch from early dependence on a host cell-derived polymerase II to a novel virus-encoded RNA polymerase that is required for transcription later on in infection. A series of repetitive and highly conserved sequences known as homologous regions, or hrs, function both as origins of DNA replication as well as transcriptional enhancers of late gene expression. An array of AcMNPV genes produced early on in infection, known as late expression factors, or LEFs, are essential for both replication and late gene expression. In this review, an overview of baculovirus LEFs and their roles in viral replication and late gene expression is presented. The role of LEFs in determining baculovirus host range is described. Finally, we compare baculovirus replication and transcription machinery with other viral systems.
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Gray CE, Coates CJ. High-level gene expression in Aedes albopictus cells using a baculovirus Hr3 enhancer and IE1 transactivator. BMC Mol Biol 2004; 5:8. [PMID: 15251037 PMCID: PMC487899 DOI: 10.1186/1471-2199-5-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Accepted: 07/13/2004] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Aedes aegypti is the key vector of both the Yellow Fever and Dengue Fever viruses throughout many parts of the world. Low and variable transgene expression levels due to position effect and position effect variegation are problematic to efforts to create transgenic laboratory strains refractory to these viruses. Transformation efficiencies are also less than optimal, likely due to failure to detect expression from all integrated transgenes and potentially due to limited expression of the transposase required for transgene integration. RESULTS Expression plasmids utilizing three heterologous promoters and three heterologous enhancers, in all possible combinations, were tested. The Hr3/IE1 enhancer-transactivator in combination with each of the constitutive heterologous promoters tested increased reporter gene expression significantly in transiently transfected Aedes albopictus C7-10 cells. CONCLUSIONS The addition of the Hr3 enhancer to expression cassettes and concomitant expression of the IE1 transactivator gene product is a potential method for increasing the level of transgene expression in insect systems. This mechanism could also potentially be used to increase the level of transiently-expressed transposase in order to increase the number of integration events in transposon-mediated transformation experiments.
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Affiliation(s)
- Christine E Gray
- Department of Entomology, MS 2475, Texas A&M University, College Station, TX 77843-2475 USA
- Genetics Interdisciplinary Program, MS 2475, Texas A&M University, College Station, TX 77843-2475 USA
| | - Craig J Coates
- Department of Entomology, MS 2475, Texas A&M University, College Station, TX 77843-2475 USA
- Genetics Interdisciplinary Program, MS 2475, Texas A&M University, College Station, TX 77843-2475 USA
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24
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Dai X, Willis LG, Huijskens I, Palli SR, Theilmann DA. The acidic activation domains of the baculovirus transactivators IE1 and IE0 are functional for transcriptional activation in both insect and mammalian cells. J Gen Virol 2004; 85:573-582. [PMID: 14993640 DOI: 10.1099/vir.0.19747-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The acidic activation domains (AADs) of the baculovirus transactivators IE1 and IE0 are essential for transcriptional transactivation. To compare the relative transcriptional activation potentials of IE1 and IE0 AADs of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Orgyia pseudotsugata MNPV (OpMNPV), we constructed two ecdysone receptor (EcR)-based inducible expression systems to analyse six baculovirus AADs in two insect cell lines (Ld652Y and Sf9) and two mammalian cell lines (NIH-3T3 and CHO). For insect cell expression, the AADs were fused to the C, D, E and F domains of the spruce budworm Choristoneura fumiferana EcR. For mammalian cell expression the AADs were fused to the E and F domains of mammalian Mus musculus retinoid X receptor. In Ld652Y and Sf9 cells, chimeric proteins containing the AcMNPV AADs activated gene expression to higher levels than those containing the OpMNPV AADs. In NIH-3T3 cells, chimeras containing AcMNPV IE1 and IE0 AADs consistently activated gene expression to higher levels than the archetypal mammalian herpesvirus VP16 AAD. In contrast, OpMNPV AADs only activated expression by 5-15 % relative to the VP16 AAD. In CHO cells, both AcMNPV and OpMNPV AADs exhibited intermediate transactivation levels relative to VP16 AAD. These results show that the baculovirus AADs are functional for transcriptional activation in mammalian cells and that AcMNPV AADs generally appear to be more potent than OpMNPV AADs in both insect and mammalian cells.
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Affiliation(s)
- Xiaojiang Dai
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada V0H 1Z0
| | - Leslie G Willis
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada V0H 1Z0
| | - Ilse Huijskens
- Department of Plant Science, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Subba R Palli
- Department of Entomology, College of Agriculture, University of Kentucky, Lexington, KY 40546, USA
| | - David A Theilmann
- Department of Plant Science, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada V0H 1Z0
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25
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Olson VA, Wetter JA, Friesen PD. The highly conserved basic domain I of baculovirus IE1 is required for hr enhancer DNA binding and hr-dependent transactivation. J Virol 2003; 77:5668-77. [PMID: 12719559 PMCID: PMC153999 DOI: 10.1128/jvi.77.10.5668-5677.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The immediate-early protein IE1 is the principal transcriptional regulator of the baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV). Transactivation by IE1 is dramatically stimulated by cis linkage of the affected promoter to AcMNPV homologous region (hr) elements that contain palindromic 28-bp repeats (28-mers) with enhancer activity. This hr-dependent transcriptional enhancement requires binding of the 28-mer by dimeric IE1. Here, we have defined IE1 domains required for this DNA binding in order to investigate the mechanism of IE1 function. Analysis of a panel of IE1 insertion mutations indicated that disruption of a highly conserved domain (residues 152 to 161) consisting of mostly positive-charged residues (basic domain I) abolished hr-dependent transactivation. Targeted mutagenesis of basic residues within basic domain I caused loss of hr-dependent transactivation but had no effect on IE1 oligomerization, nuclear localization, or hr-independent transactivation of viral promoters. Alanine substitutions of K(152) and K(154) or K(160) and K(161) impaired IE1 binding to 28-mer DNA as a homodimer, indicating that these basic residues are required for enhancer binding. Consistent with a DNA-binding defect, 28-mer interaction was improved by heterodimerization with wild-type IE1 or by increasing mutated IE1 concentrations. DNA binding mediated by basic domain I was also required for IE1 transactivation that occurred through physically separated, unlinked hr elements. We concluded that basic domain I is the enhancer-binding domain for IE1. Our data also suggest that DNA binding activates IE1 for transcriptional enhancement, possibly through a conformational change involving basic domain I.
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Affiliation(s)
- Victoria A Olson
- Institute for Molecular Virology and Department of Biochemistry, Graduate School and College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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26
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Lu L, Du Q, Chejanovsky N. Reduced expression of the immediate-early protein IE0 enables efficient replication of Autographa californica multiple nucleopolyhedrovirus in poorly permissive Spodoptera littoralis cells. J Virol 2003; 77:535-45. [PMID: 12477858 PMCID: PMC140604 DOI: 10.1128/jvi.77.1.535-545.2003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infection of Spodoptera littoralis SL2 cells with the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) results in apoptosis and low yields of viral progeny, in contrast to infection with S. littoralis nucleopolyhedrovirus (SlNPV). By cotransfecting SL2 cells with AcMNPV genomic DNA and a cosmid library representing the complete SlNPV genome, we were able to rescue AcMNPV replication and to isolate recombinant virus vAcSL2, which replicated efficiently in SL2 cells. Moreover, vAcSL2 showed enhanced infectivity for S. littoralis larvae compared to AcMNPV. The genome of vAcSL2 carried a 519-bp insert fragment that increased the distance between the TATA element and the transcriptional initiation site (CAGT) of immediate-early gene ie0. This finding correlated with low steady-state levels of IE0 and higher steady-state levels of IE1 (the product of the ie1 gene, a major AcMNPV transactivator, and a multifunctional protein) than of IE0. Mutagenesis of the ie0 promoter locus by insertion of the chloramphenical acetyltransferase (cat) gene yielded a new recombinant AcMNPV with replication properties identical to those of vAcSL2. Thus, the analysis indicated that increasing the steady-state levels of IE1 relative to IE0 should enable AcMNPV replication in SL2 cells. This suggestion was confirmed by constructing a recombinant AcMNPV bearing an extra copy of the ie1 gene under the control of the Drosophila hsp70 promoter. These results suggest that IE0 plays a role in the regulation of AcMNPV infection and show, for the first time, that significant improvement in the ability of AcMNPV to replicate in a poorly permissive cell line and organism can be achieved by increasing the expression of the main multiple functional protein, IE1.
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Affiliation(s)
- Liqun Lu
- Entomology Department, Institute of Plant Protection, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
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27
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Yamada Y, Matsuyama T, Quan GX, Kanda T, Tamura T, Sahara K, Asano SI, Bando H. Use of an N-terminal half truncated IE1 as an antagonist of IE1, an essential regulatory protein in baculovirus. Virus Res 2002; 90:253-61. [PMID: 12457979 DOI: 10.1016/s0168-1702(02)00229-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An immediate-early gene product of baculovirus, IE1, is essential for viral gene expression and for viral DNA replication. It has been demonstrated for Autographa californica nuclear polyhedrosis virus (AcNPV) that the C-terminal region of IE1 is required for dimerization. And the acidic N-terminal region of IE1 has been identified as the activation domain. We constructed an N-terminal 267 amino acid (a.a.) truncated mutant of Bombyx mori nuclear polyhedrosis virus (BmNPV) IE1, which was defective as a transactivator of a viral early gene (p35) promoter. We then examined possible IE1 antagonistic functions of this defective IE1, IE1TN, in BmNPV-infected cells. A transient expression experiment demonstrated that IE1TN strongly repressed the activation of the hr5-dependent p35 promoter derived from BmNPV infection. In addition, DpnI assay elucidated an inhibitory effect of IE1TN on the hr5-dependent replication of plasmid in BmN cells induced by NPV infection. A marked reduction in the production of virus was observed when the BmN cells were infected with BmNPV after transfection with IE1TN-expression plasmids. These results suggested that IE1TN could act as an IE1 antagonist in silkworm cells infected with BmNPV. We then analyzed the ability of IE1TN to inhibit the multiplication of BmNPV using transgenic silkworms. The BmNPV-resistance of the transgenic silkworms was very weak, suggesting insufficient expression of the transgene product, IE1TN.
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Affiliation(s)
- Yoji Yamada
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan
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28
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Olson VA, Wetter JA, Friesen PD. Baculovirus transregulator IE1 requires a dimeric nuclear localization element for nuclear import and promoter activation. J Virol 2002; 76:9505-15. [PMID: 12186932 PMCID: PMC136476 DOI: 10.1128/jvi.76.18.9505-9515.2002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immediate-early protein IE1 is a principal regulator of viral transcription and a contributor to origin-specific DNA replication of the baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Since these viral functions involve interaction of dimeric IE1 with palindromic homologous region (hr) enhancer-origin elements of the AcMNPV genome within the nucleus, it is presumed that proper nuclear transport of IE1 is essential for productive infection. To investigate the mechanisms of IE1 nuclear import, we analyzed the effect of site-directed mutations on IE1 subcellular distribution. As demonstrated by fluorescence microscopy and biochemical fractionation of plasmid-transfected cells, wild-type IE1 localized predominantly to the nucleus. Substitution or deletion of amino acid residues within a positively charged domain (residues 534 to 538) adjacent to IE1's oligomerization motif impaired nuclear import and caused loss of transactivation. Moreover, upon coexpression, these import-defective mutations prevented nuclear entry of wild-type IE1. In contrast, double-mutated IE1 defective for both nuclear import and dimerization failed to block nuclear entry or transactivation by wild-type IE1. Thus, import-defective IE1 dominantly interfered with wild-type IE1 by direct interaction and cytosolic trapping. Collectively, our data indicate that the small basic domain encompassing residues R(537) and R(538) constitutes a novel nuclear localization element that functions only upon IE1 dimerization. These findings support a model wherein IE1 oligomerizes within the cytosol as a prerequisite for nuclear entry and subsequent high-affinity interaction with the symmetrical binding sites comprising AcMNPV hr enhancer-origin elements.
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Affiliation(s)
- Victoria A Olson
- Institute for Molecular Virology and Department of Biochemistry, Graduate School and College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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29
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Pathakamuri JA, Theilmann DA. The acidic activation domain of the baculovirus transactivator IE1 contains a virus-specific domain essential for DNA replication. J Virol 2002; 76:5598-604. [PMID: 11991988 PMCID: PMC137056 DOI: 10.1128/jvi.76.11.5598-5604.2002] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
IE1 is a potent transcriptional transactivator of the baculovirus Orgyia pseudotsugata multiple nucleopolyhedrovirus (OpMNPV) and has been shown to be essential for viral DNA replication. IE1 contains an acidic activation domain (AAD) at the N terminus that is essential for transcriptional transactivation, but its role in viral DNA replication is unknown. In this study the role of the IE1 AAD in DNA replication is investigated. We have determined that deletion of the AAD eliminates the ability of IE1 to support DNA replication, showing that the AAD is essential for DNA replication as well as transcriptional transactivation. Replacement of the AAD with the archetype domain from herpesvirus VP16 and the evolutionarily related domain from Autographa californica MNPV (AcMNPV) IE1 produces chimeric proteins that are potent transactivators. Surprisingly, however, these chimeric proteins were unable to support DNA replication, indicating that there is a host- or virus-specific replication subdomain in the AAD that was not functionally replaced by the VP16 or AcMNPV AAD. Using N- and C-terminal deletion mutants, the region of the AAD that was essential for DNA replication was mapped to amino acids 1 to 65. AAD deletion mutants also showed that an IE1 that is functional for transcriptional transactivation is not required for viral DNA replication. The IE1 AAD therefore contains an essential replication domain that is separable from the transcriptional activation domains. Our results suggest that IE1 specifically interacts with a component of the viral replication complex, supporting the view that it acts as a nucleating factor by binding to the viral replication origins.
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Affiliation(s)
- Joseph A Pathakamuri
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada V0H 1Z0
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30
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Carstens EB, Liu JJ, Dominy C. Identification and molecular characterization of the baculovirus CfMNPV early genes: ie-1, ie-2 and pe38. Virus Res 2002; 83:13-30. [PMID: 11864738 DOI: 10.1016/s0168-1702(01)00401-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Three early virus genes, ie-1, ie-2 and pe38, were identified and localized in the XbaI G region (91.2-98.6 m.u.) of the genome of Choristoneura fumiferana nucleopolyhedrovirus (CfMNPV), a baculovirus pathogenic to spruce budworm. Nucleotide sequence analysis indicated that these genes share varied sequence similarity with their homologues in other baculoviruses where they are involved in regulating virus gene expression and DNA replication. Sequence motifs characteristic of DNA binding and transactivation found in other baculovirus regulatory genes were conserved in the CfMNPV genes. Northern analysis demonstrated that all three CfMNPV genes were transcriptionally active in virus infected cells and followed the temporal expression pattern of immediate early baculovirus genes. Primer extension experiments revealed that typical baculovirus early transcription start sites (CAGT) were used for ie-1 and pe38 transcription initiation. Two regions of highly repetitive DNA were found in the odv-e56 to ie-2 and ie-2 and pe38 intergenic regions. These sequences are predicted to function as transcriptional enhancers and viral origins of DNA replication.
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Affiliation(s)
- Eric B Carstens
- Department of Microbiology and Immunology, Queen's University, Kingston Ont., Canada K7L 3N6.
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31
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Wang W, Leat N, Fielding B, Davison S. Identification, sequence analysis, and phylogeny of the immediate early gene 1 of the Trichoplusia ni single nucleocapsid polyhedrosis virus. Virus Genes 2002; 23:53-62. [PMID: 11556402 DOI: 10.1023/a:1011183313021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Substantial research has been conducted on the immediate early I (ie-1) genes from the prototype baculovirus Auographa californica multicapsid nuclear polyhedrosis virus (AcMNPV) and the Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus (OpMNPV). In both cases ie-1 gene products have been implicated in transcriptional activation and repression. In this study an ie-1 homolog was identified from Trichoplusia ni single nucleocapsid polyhedrosis virus (TniSNPV). Nucleotide sequence analysis indicated that the TniSNPV ie-1 gene consists of a 2,217 nucleotide open reading frame (ORF), encoding a protein with a molecular mass of 84.464 kDa. This represents the largest baculovirus ie-1 gene characterised to date. Of the seven ie-1 homologs identified to date, the TniSNPV ie-1 shared most sequence similarity with the ie-1 gene of Spodoptera exigua MNPV (SeMNPV) (41%). At the nucleotide level, expected TATA and CAGT motifs were found to precede each ie-1 ORE. At the protein level, it was confirmed that the N-termini are poorly conserved, but share the characteristic of having a high proportion of acidic amino acids. In addition it was found that N-terminal regions significantly matched the SET domain in the Swiss-Prot prosite database. The C-terminal regions of the deduced IE-1 sequences were found to be substantially more conserved than the N-termini. Several conserved motifs were identified in the C-terminal sequences. A phylogenetic tree of nine baculovirus IE-1 proteins was constructed using maximum parsimony analysis. The phylogenetic estimation of the ie-1 genes shows that TniSNPV is a member of the previously described lepidopteran NPV group II and it is most closely related to SeMNPV.
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Affiliation(s)
- W Wang
- Department of Microbiology, University of the Western Cape, Bellville, South Africa
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Slack JM, Blissard GW. Measurement of membrane fusion activity from viral membrane fusion proteins based on a fusion-dependent promoter induction system in insect cells. J Gen Virol 2001; 82:2519-2529. [PMID: 11562545 PMCID: PMC3754798 DOI: 10.1099/0022-1317-82-10-2519] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A number of viral membrane fusion proteins can be expressed alone on the surface of host cells, and then triggered to induce cell-to-cell fusion or syncytium formation. Although rapid and easily observed, syncytium formation is not easily quantified and differences in fusion activity are not easily distinguished or measured. To address this problem, we developed a rapid and quantitative cell-to-cell fusion system that is useful for comparative analysis and may be suitable for high throughput screening. In this system, expression of a reporter protein, enhanced green fluorescent protein (EGFP), is dependent on cell-to-cell fusion. Spodoptera frugiperda (Sf9) insect cells expressing a chimeric Lac repressor-IE1 protein were fused to Sf9 cells containing an EGFP reporter construct under the control of a responsive lac operator-containing promoter. Membrane fusion efficiency was measured from the resulting EGFP fluorescence activity. Sf9 cells expressing the Orgyia pseudotsugata multicapsid nucleopolyhedrovirus (OpMNPV) GP64 envelope fusion protein were used as a model to test this fusion assay. Subtle changes in fusion activities of GP64 proteins containing single amino acid substitutions in a putative membrane fusion domain were distinguished, and decreases in EGFP fluorescence corresponded to decreases in the hydrophobicity in the small putative membrane fusion domain.
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Affiliation(s)
| | - G. W. Blissard
- To whom correspondence should be addressed, G. W. Blissard, Boyce Thompson Institute, Cornell University, Tower Road, Ithaca, New York 14853-1801, Phone: 607-254-1366 Fax: 607-254-1366,
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33
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Slack JM, Dougherty EM, Lawrence SD. A study of the Autographa californica multiple nucleopolyhedrovirus ODV envelope protein p74 using a GFP tag. J Gen Virol 2001; 82:2279-2287. [PMID: 11514740 DOI: 10.1099/0022-1317-82-9-2279] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) protein p74 is associated with the occlusion-derived virus (ODV) envelope. p74 is essential for oral infectivity of ODV and has been proposed to play a role in midgut attachment and/or fusion. In this study, p74 protein was expressed in-frame with green fluorescent protein (GFP) to create a p74-GFP chimera. The C-terminal GFP portion of the chimera facilitated visualization of the trafficking of p74 in baculovirus-infected Spodoptera frugiperda (Sf-9) cells. p74-GFP chimeric proteins localized in the intranuclear ring zone of the nucleus and were found to co-precipitate with the microvesicle fraction of cell lysates. A series of truncations of p74 was expressed as p74-GFP chimeras in recombinant baculoviruses. When C-terminal region S580-F645 was deleted from p74, p74-GFP chimera localization became non-specific and chimeras became soluble. p74 region S580-F645 directed GFP to the intranuclear ring zone in a similar pattern to full-length p74. The hydrophobic C terminus of p74 plays a role in protein localization and possibly in transmembrane anchoring and insertion.
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Affiliation(s)
- Jeffrey M Slack
- United State Department of Agriculture, Agriculture Research Service, Plant Sciences Institute, Insect Biocontrol Laboratory, Bldg 011A, Rm 214, BARC-West, Beltsville, MD 20705-2350, USA1
| | - Edward M Dougherty
- United State Department of Agriculture, Agriculture Research Service, Plant Sciences Institute, Insect Biocontrol Laboratory, Bldg 011A, Rm 214, BARC-West, Beltsville, MD 20705-2350, USA1
| | - Susan D Lawrence
- United State Department of Agriculture, Agriculture Research Service, Plant Sciences Institute, Insect Biocontrol Laboratory, Bldg 011A, Rm 214, BARC-West, Beltsville, MD 20705-2350, USA1
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Olson VA, Wetter JA, Friesen PD. Oligomerization mediated by a helix-loop-helix-like domain of baculovirus IE1 is required for early promoter transactivation. J Virol 2001; 75:6042-51. [PMID: 11390606 PMCID: PMC114320 DOI: 10.1128/jvi.75.13.6042-6051.2001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
IE1 is a principal transcriptional regulator of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Transactivation by IE1 is stimulated when early viral promoters are cis linked to homologous-region (hr) enhancer sequences of AcMNPV. This transcriptional enhancement is correlated with the binding of IE1 as a dimer to the 28-bp palindromic repeats comprising the hr enhancer. To define the role of homophilic interactions in IE1 transactivation, we have mapped the IE1 domains required for oligomerization. We report here that IE1 oligomerizes by a mechanism independent of enhancer binding, as demonstrated by in vitro pull-down assays using fusions of IE1 (582 residues) to the C terminus of glutathione S-transferase. In vivo oligomerization of IE1 was verified by immunoprecipitation of IE1 complexes from extracts of plasmid-transfected SF21 cells. Analyses of a series of site-directed IE1 insertion mutations indicated that a helix-loop-helix (HLH)-like domain extending from residue 543 to residue 568 is the primary determinant of oligomerization. Replacement of residues within the hydrophobic face of the putative dimerization domain disrupted IE1 homophilic interactions and caused loss of IE1 transactivation of hr-dependent promoters in plasmid transfection assays. Thus, oligomerization is required for IE1 transcriptional stimulation. HLH mutations also reduced IE1 stability and abrogated transactivation of non-hr-dependent promoters. These data support a model wherein IE1 oligomerizes prior to DNA binding to facilitate proper interaction with the symmetrical recognition sites within the hr enhancer and thereby promote the transcription of early viral genes.
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Affiliation(s)
- V A Olson
- Institute for Molecular Virology, Graduate School and College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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Leisy DJ, Rohrmann GF. The Autographa californica nucleopolyhedrovirus IE-1 protein complex has two modes of specific DNA binding. Virology 2000; 274:196-202. [PMID: 10936100 DOI: 10.1006/viro.2000.0452] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Missing contact footprinting with formic acid as a modifying reagent was used to examine specific IE-1 binding contacts to double-stranded oligonucleotides that contained either a consensus hr repeat sequence or a sequence from the pe38 promoter, which is down regulated by IE-1. The hr repeat sequences contain two consensus IE-1 binding motifs (IBMs) flanking a central EcoRI site that are oriented in opposite directions with respect to each other. IE-1 was found to contact regions including both IBMs. The bases footprinted in the top strand included the left IBM (IBM-A), whereas bases in the bottom strand were footprinted in a region that included IBM-B and part of IBM-A. When substitution mutations were introduced into either IBM, bases on both strands of the remaining IBM were strongly footprinted. As with the hr IBM-mutant constructs, bases footprinted in the pe38 promoter construct included both strands of the single IBM.
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Affiliation(s)
- D J Leisy
- Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA.
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Abstract
While studying apoptosis induced by baculovirus transactivator IE1 in SF-21 cells, we found that the levels of IE1-induced apoptosis were increased approximately twofold upon cotransfection with the baculovirus early pe38 gene. However, no apoptotic activity was observed in cells transfected with pe38 alone, even when placed under the control of a constitutive promoter. Thus, pe38 was able to augment IE1-induced apoptosis but was unable to induce apoptosis when expressed in SF-21 cells alone. PE38, the full-length product of pe38, is a nuclear protein with RING finger and leucine zipper motifs. Deletion of the amino-terminal region, which contains a putative nuclear localization motif, resulted in cytoplasmic localization of the PE38 mutants. These N-terminal deletion mutants were unable to enhance IE1-induced apoptosis. Mutation of a single conserved leucine (L242) of the leucine zipper motif also eliminated the ability of PE38 to augment apoptosis induced by IE1. In contrast, PE38 mutants with alanine substitutions for conserved cysteine residues (C109 or C138) of the RING finger motif were able to increase IE1-induced apoptosis to levels equivalent to those of wild-type PE38. We propose that PE38 is one of at least two viral factors which collectively evoke a cellular apoptotic response during baculovirus infection.
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Affiliation(s)
- E A Prikhod'ko
- Departments of Entomology and Genetics, The University of Georgia, Athens, Georgia 30602, USA
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Chang MJ, Kuzio J, Blissard GW. Modulation of translational efficiency by contextual nucleotides flanking a baculovirus initiator AUG codon. Virology 1999; 259:369-83. [PMID: 10388661 DOI: 10.1006/viro.1999.9787] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In a previous study of translational regulation of a baculovirus gene, we observed that translation initiated at an unexpectedly high efficiency from an AUG codon found in what was believed to be a poor context (M.-J. Chang and G. W. Blissard, 1997, J. Virol. 71, 7448-7460). In the current study, we examined the roles of nucleotides flanking a baculovirus AUG initiator codon in modulating translation initiation in lepidopteran insect cells. The roles of nucleotides flanking the AcMNPV gp64 initiator codon were examined by site-directed mutagenesis and functional assays in transfected Sf9 cells. To eliminate potential cis-acting sequences and effects, the gp64 initiator context was cloned in-frame with a chloramphenicol acetyl transferase reporter gene and under the control of a heterologous promoter. All possible single-nucleotide substitutions were generated in positions -6 to -1 and +4 to +6, relative to the A of the initiator AUG codon, which was designated +1. Constructs were transfected into lepidopteran cells and translation products were quantified by an enzyme-linked immunosorbent assay procedure. Substitutions of pyrimidines or other nucleotides at the -3 position resulted in little or no detectable effect on translation efficiency. In contrast, specific substitutions at the +4 and +5 positions resulted in approximately 2- to 3-fold increases in translation. Substitution of A in the +4 position resulted in an approximately 3-fold increase in translation, and substitution of any nucleotide for T in the +5 position resulted in approximately 1.9- to 2.8-fold increases. Substitutions at other positions (-6 to -1 and +6) resulted in no detectable increase or decrease in translation efficiency. These experimental results suggest an optimal initiator context of 5'-N N N N N N A U G A a/c/g N-3' for efficient translation initiation in lepidopteran cells. Consensus translation initiation contexts were generated from baculovirus genes and lepidopteran genes, then compared with the experimental results from the gp64 initiator context.
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Affiliation(s)
- M J Chang
- Boyce Thompson Institute at Cornell University, Tower Road, Ithaca, New York, 14853-1801, USA
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Forsythe IJ, Shippam CE, Willis LG, Stewart S, Grigliatti T, Theilmann DA. Characterization of the acidic domain of the IE1 regulatory protein from Orgyia pseudotsugata multicapsid nucleopolyhedrovirus. Virology 1998; 252:65-81. [PMID: 9875318 DOI: 10.1006/viro.1998.9415] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study presents a detailed analysis of the acidic N-terminal region of the Orgyia pseudotsugata multicapsid nucleopolyhedrovirus (OpMNPV) transactivator IE1. The N-terminal region of IE1 is rich in acidic amino acids and has been hypothesized to be an acidic activation domain. Removal of the N-terminal 126 amino acids containing the acidic domain of IE1 resulted in complete loss of transactivation activity, indicating that this region is essential for transactivation. The OpMNPV acidic domain was replaced with the archetype acidic activation domain from VP16 and the acid-rich region of Autographa californica multicapsid NPV (AcMNPV) IE1. These chimeric constructs were fully capable of transactivation in transient assays. The chimeric OpMNPV IE1s containing the herpes simplex virus VP16 and AcMNPV IE1 acidic activation domains consistently transactivated a reporter gene to higher levels than the OpMNPV IE1 acidic activation domain. Transactivation by the chimeric constructs is enhanced synergistically when cotransfected with IE2 into Lymantria dispar and Spodoptera frugiperda cells. Both N- to C-terminal and C- to N-terminal deletions of the OpMNPV acidic activation domain were constructed to define functional domains within the OpMNPV IE1 acidic activation domain. At least two potential activation domains were identified. Within each of these domains, two core regions at amino acids 28-43 and amino acids 113-124 were identified that were similar to core regions of VP16 and GAL4, which contain predominately acidic and bulky hydrophobic amino acids.
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Affiliation(s)
- I J Forsythe
- Department of Zoology, University of British Columbia, Vancouver, Canada
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Abstract
Stable transformed insect cell lines have been used for producing many highly processed heterologous proteins. Current research has focused on development of new expression and selection systems, and enhancement of vector stability. Defining the variation of modification and processing capabilities between cell lines will further enhance complex protein production from insect cells.
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Affiliation(s)
- T A Pfeifer
- Department of Zoology, University of British Columbia, Vancouver, Canada.
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Kremer A, Knebel-Mörsdorf D. The early baculovirus he65 promoter: On the mechanism of transcriptional activation by IE1. Virology 1998; 249:336-51. [PMID: 9791025 DOI: 10.1006/viro.1998.9288] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have initiated studies on the mechanism of early transcriptional activation of the early he65 promoter during infection with Autographa californica multicapsid nuclear polyhedrosis virus. This analysis is based on a comparison of the sequences required for he65 promoter activation with those sequences that support specific protein binding. The he65 promoter is located immediately downstream of the homologous region (hr) 4a. The sequences of hr4a are characterized by two imperfect palindromes of 24 bp. The results of transient expression assays indicate promoter activation in the presence of both the proximal palindrome and the known viral trans-regulator IE1. The results of mobility shift assays and DNaseI footprinting analyses reveal differences in specific protein binding at and close to the proximal palindrome depending on whether the nuclear protein extracts are prepared from uninfected or infected cells. The analysis of the protein binding complex at the proximal inverted repeat with extracts from infected cells suggests the involvement of both IE1 and IE0 as oligomers. The minimal protein binding sequences include the left half-site of the 24 bp repeat with 9 additional bp of the flanking sequences. The right half-site of the repeat also directs binding although with lower affinity as confirmed by phenanthroline-copper footprinting assays. Both half-sites of the repeat are thus essential for he65 promoter activation, suggesting that IE1 acts via cooperative binding. We conclude that the proximal inverted repeat is able to interact with both IE1 and IE0 although IE1 is sufficient for activation at least in transient expression assays.
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Affiliation(s)
- A Kremer
- Institute of Genetics, University of Cologne, Cologne, D-50931, Germany
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