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Aggarwal T, Kondabagil K. Assembly and Evolution of Poxviruses. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1451:35-54. [PMID: 38801570 DOI: 10.1007/978-3-031-57165-7_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Poxvirus assembly has been an intriguing area of research for several decades. While advancements in experimental techniques continue to yield fresh insights, many questions are still unresolved. Large genome sizes of up to 380 kbp, asymmetrical structure, an exterior lipid bilayer, and a cytoplasmic life cycle are some notable characteristics of these viruses. Inside the particle are two lateral bodies and a protein wall-bound-biconcave core containing the viral nucleocapsid. The assembly progresses through five major stages-endoplasmic reticulum (ER) membrane alteration and rupture, crescent formation, immature virion formation, genome encapsidation, virion maturation and in a subset of viruses, additional envelopment of the virion prior to its dissemination. Several large dsDNA viruses have been shown to follow a comparable sequence of events. In this chapter, we recapitulate our understanding of the poxvirus morphogenesis process while reviewing the most recent advances in the field. We also briefly discuss how virion assembly aids in our knowledge of the evolutionary links between poxviruses and other Nucleocytoplasmic Large DNA Viruses (NCLDVs).
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Affiliation(s)
- Tanvi Aggarwal
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India
| | - Kiran Kondabagil
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
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Giotis ES, Laidlaw SM, Bidgood SR, Albrecht D, Burden JJ, Robey RC, Mercer J, Skinner MA. Modulation of Early Host Innate Immune Response by an Avipox Vaccine Virus' Lateral Body Protein. Biomedicines 2020; 8:E634. [PMID: 33352813 PMCID: PMC7766033 DOI: 10.3390/biomedicines8120634] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 12/14/2022] Open
Abstract
The avian pathogen fowlpox virus (FWPV) has been successfully used as a vaccine vector in poultry and humans, but relatively little is known about its ability to modulate host antiviral immune responses in these hosts, which are replication-permissive and nonpermissive, respectively. FWPV is highly resistant to avian type I interferon (IFN) and able to completely block the host IFN-response. Microarray screening of host IFN-regulated gene expression in cells infected with 59 different, nonessential FWPV gene knockout mutants revealed that FPV184 confers immunomodulatory capacity. We report that the FPV184-knockout virus (FWPVΔ184) induces the cellular IFN response as early as 2 h postinfection. The wild-type, uninduced phenotype can be rescued by transient expression of FPV184 in FWPVΔ184-infected cells. Ectopic expression of FPV184 inhibited polyI:C activation of the chicken IFN-β promoter and IFN-α activation of the chicken Mx1 promoter. Confocal and correlative super-resolution light and electron microscopy demonstrated that FPV184 has a functional nuclear localisation signal domain and is packaged in the lateral bodies of the virions. Taken together, these results provide a paradigm for a late poxvirus structural protein packaged in the lateral bodies, capable of suppressing IFN induction early during the next round of infection.
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Affiliation(s)
- Efstathios S. Giotis
- Section of Virology, School of Medicine, St Mary’s Campus, Imperial College, London W2 1PG, UK; (S.M.L.); (R.C.R.); (M.A.S.)
- School of Life Sciences, University of Essex, Colchester C04 3SQ, UK
| | - Stephen M. Laidlaw
- Section of Virology, School of Medicine, St Mary’s Campus, Imperial College, London W2 1PG, UK; (S.M.L.); (R.C.R.); (M.A.S.)
| | - Susanna R. Bidgood
- Medical Research Council-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; (S.R.B.); (D.A.); (J.J.B.); (J.M.)
| | - David Albrecht
- Medical Research Council-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; (S.R.B.); (D.A.); (J.J.B.); (J.M.)
| | - Jemima J. Burden
- Medical Research Council-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; (S.R.B.); (D.A.); (J.J.B.); (J.M.)
| | - Rebecca C. Robey
- Section of Virology, School of Medicine, St Mary’s Campus, Imperial College, London W2 1PG, UK; (S.M.L.); (R.C.R.); (M.A.S.)
| | - Jason Mercer
- Medical Research Council-Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; (S.R.B.); (D.A.); (J.J.B.); (J.M.)
| | - Michael A. Skinner
- Section of Virology, School of Medicine, St Mary’s Campus, Imperial College, London W2 1PG, UK; (S.M.L.); (R.C.R.); (M.A.S.)
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Structure-Based Deep Mining Reveals First-Time Annotations for 46 Percent of the Dark Annotation Space of the 9,671-Member Superproteome of the Nucleocytoplasmic Large DNA Viruses. J Virol 2020; 94:JVI.00854-20. [PMID: 32999026 DOI: 10.1128/jvi.00854-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 09/16/2020] [Indexed: 12/20/2022] Open
Abstract
We conducted an exhaustive search for three-dimensional structural homologs to the proteins of 20 key phylogenetically distinct nucleocytoplasmic DNA viruses (NCLDV). Structural matches covered 429 known protein domain superfamilies, with the most highly represented being ankyrin repeat, P-loop NTPase, F-box, protein kinase, and membrane occupation and recognition nexus (MORN) repeat. Domain superfamily diversity correlated with genome size, but a diversity of around 200 superfamilies appeared to correlate with an abrupt switch to paralogization. Extensive structural homology was found across the range of eukaryotic RNA polymerase II subunits and their associated basal transcription factors, with the coordinated gain and loss of clusters of subunits on a virus-by-virus basis. The total number of predicted endonucleases across the 20 NCLDV was nearly quadrupled from 36 to 132, covering much of the structural and functional diversity of endonucleases throughout the biosphere in DNA restriction, repair, and homing. Unexpected findings included capsid protein-transcription factor chimeras; endonuclease chimeras; enzymes for detoxification; antimicrobial peptides and toxin-antitoxin systems associated with symbiosis, immunity, and addiction; and novel proteins for membrane abscission and protein turnover.IMPORTANCE We extended the known annotation space for the NCLDV by 46%, revealing high-probability structural matches for fully 45% of the 9,671 query proteins and confirming up to 98% of existing annotations per virus. The most prevalent protein families included ankyrin repeat- and MORN repeat-containing proteins, many of which included an F-box, suggesting extensive host cell modulation among the NCLDV. Regression suggested a minimum requirement for around 36 protein structural superfamilies for a viable NCLDV, and beyond around 200 superfamilies, genome expansion by the acquisition of new functions was abruptly replaced by paralogization. We found homologs to herpesvirus surface glycoprotein gB in cytoplasmic viruses. This study provided the first prediction of an endonuclease in 10 of the 20 viruses examined; the first report in a virus of a phenolic acid decarboxylase, proteasomal subunit, or cysteine knot (defensin) protein; and the first report of a prokaryotic-type ribosomal protein in a eukaryotic virus.
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van Schalkwyk A, Kara P, Ebersohn K, Mather A, Annandale CH, Venter EH, Wallace DB. Potential link of single nucleotide polymorphisms to virulence of vaccine-associated field strains of lumpy skin disease virus in South Africa. Transbound Emerg Dis 2020; 67:2946-2960. [PMID: 32506755 PMCID: PMC9292827 DOI: 10.1111/tbed.13670] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/20/2020] [Accepted: 06/01/2020] [Indexed: 11/27/2022]
Abstract
South Africa is endemic for lumpy skin disease and is therefore reliant on various live attenuated vaccines for the control and prevention of the disease. In recent years, widespread outbreaks of vaccine‐like strains of lumpy skin disease virus (LSDV) were reported internationally, leading to an increase in the generation of full genome sequences from field isolates. In this study, the complete genomes of six LSDVs submitted during active outbreaks in the 1990s in South Africa were generated. Based on phylogenetic analysis, the six viruses clustered with vaccine strains in LSDV Subgroup 1.1 and are subsequently referred to as vaccine‐associated. The genetic differences between the phenotypically distinct vaccine and vaccine‐associated strains were 67 single nucleotide polymorphisms (SNPs). This study characterized the location and possible importance of each of these SNPs in their role during virulence and host specificity.
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Affiliation(s)
- Antoinette van Schalkwyk
- Vaccine and Diagnostic Development, Agricultural Research Council - Onderstepoort Veterinary Institute, Pretoria, South Africa
| | - Pravesh Kara
- Vaccine and Diagnostic Development, Agricultural Research Council - Onderstepoort Veterinary Institute, Pretoria, South Africa
| | - Karen Ebersohn
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Arshad Mather
- Vaccine and Diagnostic Development, Agricultural Research Council - Onderstepoort Veterinary Institute, Pretoria, South Africa
| | - Cornelius Henry Annandale
- Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Estelle Hildegard Venter
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.,College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville Queensland, Australia
| | - David Brian Wallace
- Vaccine and Diagnostic Development, Agricultural Research Council - Onderstepoort Veterinary Institute, Pretoria, South Africa.,Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
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Novy K, Kilcher S, Omasits U, Bleck CKE, Beerli C, Vowinckel J, Martin CK, Syedbasha M, Maiolica A, White I, Mercer J, Wollscheid B. Proteotype profiling unmasks a viral signalling network essential for poxvirus assembly and transcriptional competence. Nat Microbiol 2018; 3:588-599. [DOI: 10.1038/s41564-018-0142-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/07/2018] [Indexed: 11/09/2022]
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Hagen CJ, Titong A, Sarnoski EA, Verardi PH. Antibiotic-dependent expression of early transcription factor subunits leads to stringent control of vaccinia virus replication. Virus Res 2014; 181:43-52. [PMID: 24394294 DOI: 10.1016/j.virusres.2013.12.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 12/12/2013] [Accepted: 12/17/2013] [Indexed: 12/31/2022]
Abstract
The use of vaccinia virus (VACV) as the vaccine against variola virus resulted in the eradication of smallpox. VACV has since been used in the development of recombinant vaccine and therapeutic vectors, but complications associated with uncontrolled viral replication have constrained its use as a live viral vector. We propose to improve the safety of VACV as a live-replicating vector by using elements of the tet operon to control the transcription of genes that are essential for viral growth. Poxviruses encode all enzymes and factors necessary for their replication within the host cell cytoplasm. One essential VACV factor is the vaccinia early transcription factor (VETF) packaged into the viral core. This heterodimeric protein is required for expression of early VACV genes. VETF is composed of a large subunit encoded by the A7L gene and a small subunit encoded by the D6R gene. Two recombinant VACVs were generated in which either the A7L or D6R gene was placed under the control of tet operon elements to allow their transcription, and therefore viral replication, to be dependent on tetracycline antibiotics such as doxycycline. In the absence of inducers, no plaques were produced but abortively infected cells could be identified by expression of a reporter gene. In the presence of doxycycline, both recombinant viruses replicated indistinguishably from the wild-type strain. This stringent control of VACV replication can be used for the development of safer, next-generation VACV vaccines and therapeutic vectors. Such replication-inducible VACVs would only replicate when administered with tetracycline antibiotics, and if adverse events were to occur, treatment would be as simple as antibiotic cessation.
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Affiliation(s)
- Caitlin J Hagen
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, College of Agriculture and Natural Resources, University of Connecticut, Storrs, CT 06269, United States
| | - Allison Titong
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, College of Agriculture and Natural Resources, University of Connecticut, Storrs, CT 06269, United States
| | - Ethan A Sarnoski
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, College of Agriculture and Natural Resources, University of Connecticut, Storrs, CT 06269, United States
| | - Paulo H Verardi
- Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, College of Agriculture and Natural Resources, University of Connecticut, Storrs, CT 06269, United States.
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Abstract
The A19 protein of vaccinia virus (VACV) is conserved among chordopoxviruses, expressed late in infection, packaged in the virus core, and required for a late step in morphogenesis. Multiple-sequence alignments of A19 homologs indicated conservation of a series of lysines and arginines, which could represent a nuclear localization or nucleic acid binding motif, and a pair of CXXC motifs that suggested a zinc finger or redox active sites. The importance of the CXXC motif was confirmed by cysteine-to-serine substitutions, which rendered the altered protein unable to trans-complement infectivity of a null mutant. Nevertheless, the cysteines were not required for function of the poxvirus-specific redox pathway. Epitope-tagged A19 proteins were detected in the nucleus and cytoplasm in both infected and uninfected cells, but this distribution was unaffected by alanine substitutions of the arginine residues, which only partially reduced the ability of the mutated protein to trans-complement infectivity. Viral proteins specifically associated with affinity-purified A19 were identified by mass spectrometry as components of the transcription complex, including RNA polymerase subunits, RAP94 (RNA polymerase-associated protein 94), early transcription factors, capping enzyme, and nucleoside triphosphate phosphohydrolase I, and two core proteins required for morphogenesis. Further studies suggested that the interaction of A19 with the RNA polymerase did not require RAP94 or other intermediate or late viral proteins but was reduced by mutation of cysteines in the putative zinc finger domain. Although A19 was not required for incorporation of the transcription complex in virus particles, the transcriptional activity of A19-deficient virus particles was severely reduced.
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Vaccinia virus A19 protein participates in the transformation of spherical immature particles to barrel-shaped infectious virions. J Virol 2013; 87:10700-9. [PMID: 23885081 DOI: 10.1128/jvi.01258-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The A19L open reading frame of vaccinia virus encodes a 9-kDa protein that is conserved in all sequenced chordopoxviruses, yet until now it has not been specifically characterized in any species. We appended an epitope tag after the start codon of the A19L open reading frame without compromising infectivity. The protein was synthesized after viral DNA replication and was phosphorylated independently of the vaccinia virus F10 kinase. The A19 protein was present in purified virions and was largely resistant to nonionic detergent extraction, suggesting a location within the core. A conditional lethal mutant virus was constructed by placing the A19 open reading frame under the control of the Escherichia coli lac repressor system. A19 synthesis and infectious virus formation were dependent on inducer. In the absence of inducer, virion morphogenesis was interrupted, and spherical dense particles that had greatly reduced amounts of the D13 scaffold accumulated in place of barrel-shaped mature virions. The infectivity of purified A19-deficient particles was more than 2 log units less than that of A19-containing virions. Nevertheless, the A19-deficient particles contained DNA, and except for the absence of A19 and decreased core protein processing, they appeared to have a similar protein composition as A19-containing virions. Thus, the A19 protein participates in the maturation of immature vaccinia virus virions to infectious particles.
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Abstract
Most DNA viruses selfishly exploit the cellular transcription machinery of infected cells. Poxviruses are unique among DNA viruses in that they encode the majority of the enzymes required for RNA synthesis. Poxviruses are large DNA viruses that replicate entirely within the cytoplasmic compartment of the cell, and they encode their own multisubunit RNA polymerase and gene-specific transcription and termination factors. The virus-encoded RNA polymerase has sequence and structural homology to eukaryotic RNA polymerases. Virus-encoded and cellular proteins regulate promoter specificity by recruiting the viral RNA polymerase to one of three different classes of genes. Functional interplay between viral and cellular transcription factors in viral gene regulation represents a new frontier in poxvirus biology. Targeting these transcription systems may serve as an undeveloped and potent antiviral strategy to combat poxvirus infections.
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Affiliation(s)
- Steven S Broyles
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Bruce A Knutson
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Seattle, WA 98109–1024, USA
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Boyd O, Strahl AL, Rodeffer C, Condit RC, Moussatche N. Temperature-sensitive mutant in the vaccinia virus E6 protein produce virions that are transcriptionally inactive. Virology 2010; 399:221-30. [PMID: 20116822 PMCID: PMC2830351 DOI: 10.1016/j.virol.2010.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 01/04/2010] [Accepted: 01/07/2010] [Indexed: 11/18/2022]
Abstract
The vaccinia virus E6R gene encodes a late protein that is packaged into virion cores. A temperature-sensitive mutant was used to study the role of this protein in viral replicative cycle. Cts52 has a P226L missense mutation in the E6R gene, shows a two-log reduction in plaque formation, but displays normal patterns of gene expression, late protein processing and DNA replication during infection. Mutant virions produced at 40 degrees C were similar in their morphology to wt virions grown at 40 degrees C. The particle to infectivity ratio was 50 times higher in purified Cts52 grown at 40 degrees C when compared to the mutant grown at permissive temperature. In vitro characterization of Cts-52 particles grown at 40 degrees C revealed no differences in protein composition or in DNA content and the mutant virions could bind and enter cells. However, core particles prepared from Cts52 grown at 40 degrees C failed to transcribe in vitro. Our results show that E6 in the virion has either a direct or an indirect role in viral transcription.
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Affiliation(s)
- Olga Boyd
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Audra L. Strahl
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Carson Rodeffer
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Richard C. Condit
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Nissin Moussatche
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
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11
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de Souza RF, Iyer LM, Aravind L. Diversity and evolution of chromatin proteins encoded by DNA viruses. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1799:302-18. [PMID: 19878744 PMCID: PMC3243496 DOI: 10.1016/j.bbagrm.2009.10.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 10/21/2009] [Accepted: 10/22/2009] [Indexed: 11/23/2022]
Abstract
Double-stranded DNA viruses display a great variety of proteins that interact with host chromatin. Using the wealth of available genomic and functional information, we have systematically surveyed chromatin-related proteins encoded by dsDNA viruses. The distribution of viral chromatin-related proteins is primarily influenced by viral genome size and the superkingdom to which the host of the virus belongs. Smaller viruses usually encode multifunctional proteins that mediate several distinct interactions with host chromatin proteins and viral or host DNA. Larger viruses additionally encode several enzymes, which catalyze manipulations of chromosome structure, chromatin remodeling and covalent modifications of proteins and DNA. Among these viruses, it is also common to encounter transcription factors and DNA-packaging proteins such as histones and IHF/HU derived from cellular genomes, which might play a role in constituting virus-specific chromatin states. Through all size ranges a subset of domains in viral chromatin proteins appears to have been derived from those found in host proteins. Examples include the Zn-finger domains of the E6 and E7 proteins of papillomaviruses, SET domain methyltransferases and Jumonji-related demethylases in certain nucleocytoplasmic large DNA viruses and BEN domains in poxviruses and polydnaviruses. In other cases, chromatin-interacting modules, such as the LXCXE motif, appear to have been widely disseminated across distinct viral lineages, resulting in similar retinoblastoma targeting strategies. Viruses, especially those with large linear genomes, have evolved a number of mechanisms to manipulate viral chromosomes in the process of replication-associated recombination. These include topoisomerases, Rad50/SbcC-like ABC ATPases and a novel recombinase system in bacteriophages utilizing RecA and Rad52 homologs. Larger DNA viruses also encode SWI2/SNF2 and A18-like ATPases which appear to play specialized roles in transcription and recombination. Finally, it also appears that certain domains of viral provenance have given rise to key functions in eukaryotic chromatin such as a HEH domain of chromosome tethering proteins and the TET/JBP-like cytosine and thymine hydroxylases.
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Affiliation(s)
- Robson F. de Souza
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, United States of America
| | - Lakshminarayan M. Iyer
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, United States of America
| | - L. Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, United States of America
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Interaction of the vaccinia virus RNA polymerase-associated 94-kilodalton protein with the early transcription factor. J Virol 2009; 83:12018-26. [PMID: 19759131 DOI: 10.1128/jvi.01653-09] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A multisubunit RNA polymerase (RPO) encoded by vaccinia virus (VACV), in conjunction with specific factors, transcribes early, intermediate, and late viral genes. However, an additional virus-encoded polypeptide referred to as the RPO-associated protein of 94 kDa (RAP94) is tightly bound to the RPO for the transcription of early genes. Unlike the eight RPO core subunits, RAP94 is synthesized exclusively at late times after infection. Furthermore, RAP94 is necessary for the packaging of RPO and other components needed for early transcription in assembling virus particles. The direct association of RAP94 with NPH I, a DNA-dependent ATPase required for transcription termination, and the multifunctional poly(A) polymerase small subunit/2'-O-methyltransferase/elongation factor was previously demonstrated. That RAP94 provides a structural and functional link between the core RPO and the VACV early transcription factor (VETF) has been suspected but not previously demonstrated. Using VACV recombinants that constitutively or inducibly express VETF subunits and RAP94 with affinity tags, we showed that (i) VETF associates only with RPO containing RAP94 in vivo and in vitro, (ii) the association of RAP94 with VETF requires both subunits of the latter, (iii) neither viral DNA nor other virus-encoded late proteins are required for the interaction of RAP94 with VETF and core RPO subunits, (iv) different domains of RAP94 bind VETF and core subunits of RPO, and (v) NPH I and VETF bind independently and possibly simultaneously to the N-terminal region of RAP94. Thus, RAP94 provides the bridge between the RPO and proteins needed for transcription initiation, elongation, and termination.
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Abstract
Poxviruses comprise a large family of viruses characterized by a large, linear dsDNA genome, a cytoplasmic site of replication and a complex virion morphology. The most notorious member of the poxvirus family is variola, the causative agent of smallpox. The laboratory prototype virus used for the study of poxviruses is vaccinia, the virus that was used as a live, naturally attenuated vaccine for the eradication of smallpox. Both the morphogenesis and structure of poxvirus virions are unique among viruses. Poxvirus virions apparently lack any of the symmetry features common to other viruses such as helical or icosahedral capsids or nucleocapsids. Instead poxvirus virions appear as "brick shaped" or "ovoid" membrane-bound particles with a complex internal structure featuring a walled, biconcave core flanked by "lateral bodies." The virion assembly pathway involves a remarkable fabrication of membrane-containing crescents and immature virions, which evolve into mature virions in a process that is unparalleled in virology. As a result of significant advances in poxvirus genetics and molecular biology during the past 15 years, we can now positively identify over 70 specific gene products contained in poxvirus virions, and we can describe the effects of mutations in over 50 specific genes on poxvirus assembly. This review summarizes these advances and attempts to assemble them into a comprehensible and thoughtful picture of poxvirus structure and assembly.
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Affiliation(s)
- Richard C Condit
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, 32610, USA
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14
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Scott MS, Oomen R, Thomas DY, Hallett MT. Predicting the subcellular localization of viral proteins within a mammalian host cell. Virol J 2006; 3:24. [PMID: 16595001 PMCID: PMC1475561 DOI: 10.1186/1743-422x-3-24] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 04/04/2006] [Indexed: 11/19/2022] Open
Abstract
Background The bioinformatic prediction of protein subcellular localization has been extensively studied for prokaryotic and eukaryotic organisms. However, this is not the case for viruses whose proteins are often involved in extensive interactions at various subcellular localizations with host proteins. Results Here, we investigate the extent of utilization of human cellular localization mechanisms by viral proteins and we demonstrate that appropriate eukaryotic subcellular localization predictors can be used to predict viral protein localization within the host cell. Conclusion Such predictions provide a method to rapidly annotate viral proteomes with subcellular localization information. They are likely to have widespread applications both in the study of the functions of viral proteins in the host cell and in the design of antiviral drugs.
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Affiliation(s)
- MS Scott
- McGill Center for Bioinformatics, McGill University, 3775 University Street, Montreal, Quebec, Canada
| | - R Oomen
- Integrated Genomics, Sanofi Pasteur, 1755 Steeles Avenue West, Toronto, Ontario, Canada
| | - DY Thomas
- Biochemistry Department, McGill University, McIntyre Medical Sciences Building, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada
| | - MT Hallett
- McGill Center for Bioinformatics, McGill University, 3775 University Street, Montreal, Quebec, Canada
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15
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Abstract
Vaccinia virus replication takes place in the cytoplasm of the host cell. The nearly 200 kbp genome owes part of its complexity to encoding most of the proteins involved in genome and mRNA synthesis. The multisubunit vaccinia virus RNA polymerase requires a separate set of virus-encoded proteins for the transcription of the early, intermediate and late classes of genes. Cell fractionation studies have provided evidence for a role for host cell proteins in the initiation and termination of vaccinia virus intermediate and late gene transcription. Vaccinia virus resembles nuclear DNA viruses in the integration of viral and host proteins for viral mRNA synthesis, yet is markedly less reliant on host proteins than its nuclear counterparts.
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Affiliation(s)
- Steven S Broyles
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907-1153, USA
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16
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Damaso CRA, Oliveira MF, Massarani SM, Moussatché N. Azathioprine inhibits vaccinia virus replication in both BSC-40 and RAG cell lines acting on different stages of virus cycle. Virology 2002; 300:79-91. [PMID: 12202208 DOI: 10.1006/viro.2002.1534] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In the present study we demonstrate that azathioprine (AZA) inhibits vaccinia virus (VV) replication in both BSC-40 and RAG cell lines, acting on different stages of virus cycle. In BSC-40 cells, early protein synthesis was not significantly affected, but late gene expression was severely impaired. In RAG cells all stages of gene expression were completed during synchronous infection in the presence of the drug. The onset of DNA replication was not affected in RAG cells, but a severe inhibition was observed in BSC-40 cells. Electron microscopic analysis of VV-infected RAG cells treated with AZA revealed brick-shaped particles presenting abnormal definition of the internal structure. Purified virions from AZA-treated RAG cells presented several modifications of the protein content, a lesser amount of DNA, and a lower PFU:particle ratio. Our results suggest that in VV-infected RAG cells AZA interfered with virus morphogenesis, whereas in BSC-40 cells the replicative cycle was inhibited at the DNA replication stage.
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Affiliation(s)
- Clarissa R A Damaso
- Laboratório de Biologia Molecular de Vi;rus, Instituto de Biofi;sica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590, Rio de Janeiro, Brazil
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17
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Shchelkunov SN, Totmenin AV, Safronov PF, Mikheev MV, Gutorov VV, Ryazankina OI, Petrov NA, Babkin IV, Uvarova EA, Sandakhchiev LS, Sisler JR, Esposito JJ, Damon IK, Jahrling PB, Moss B. Analysis of the monkeypox virus genome. Virology 2002; 297:172-94. [PMID: 12083817 PMCID: PMC9534300 DOI: 10.1006/viro.2002.1446] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Monkeypox virus (MPV) belongs to the orthopoxvirus genus of the family Poxviridae, is endemic in parts of Africa, and causes a human disease that resembles smallpox. The 196,858-bp MPV genome was analyzed with regard to structural features and open reading frames. Each end of the genome contains an identical but oppositely oriented 6379-bp terminal inverted repetition, which similar to that of other orthopoxviruses, includes a putative telomere resolution sequence and short tandem repeats. Computer-assisted analysis was used to identify 190 open reading frames containing >/=60 amino acid residues. Of these, four were present within the inverted terminal repetition. MPV contained the known essential orthopoxvirus genes but only a subset of the putative immunomodulatory and host range genes. Sequence comparisons confirmed the assignment of MPV as a distinct species of orthopoxvirus that is not a direct ancestor or a direct descendent of variola virus, the causative agent of smallpox.
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Affiliation(s)
- S N Shchelkunov
- State Research Center of Virology and Biotechnology Vector, Koltsovo, Novosibirsk Region, Russia
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18
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Sodeik B, Krijnse-Locker J. Assembly of vaccinia virus revisited: de novo membrane synthesis or acquisition from the host? Trends Microbiol 2002; 10:15-24. [PMID: 11755081 DOI: 10.1016/s0966-842x(01)02256-9] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In 1968 it was proposed that the first membrane structures that assemble in vaccinia virus-infected cells, the crescents, are formed by a unique viral mechanism in which a single membrane bilayer is synthesized de novo. 25 years later it was suggested that the vaccinia membranes are derived from an organelle that is part of the host cell's secretory pathway, the intermediate compartment (IC), and that the viral crescents are made of two tightly apposed membranes rather than a single bilayer. Several independent studies have subsequently shown that membrane proteins of the intracellular mature virus (IMV) insert co-translationally into endoplasmic reticulum (ER) membranes, and are targeted to and retained in the IC, the compartment from which the virus acquires its membranes. Furthermore, a recent study on the entry of both the IMV and extracellular enveloped virus (EEV) suggests that these viruses do not enter by a simple fusion mechanism, consistent with the idea that both are surrounded by more than one lipid bilayer.
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Affiliation(s)
- Beate Sodeik
- Institute of Biochemistry, Hannover Medical School, OE 4310, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
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19
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Heljasvaara R, Rodríguez D, Risco C, Carrascosa JL, Esteban M, Rodríguez JR. The major core protein P4a (A10L gene) of vaccinia virus is essential for correct assembly of viral DNA into the nucleoprotein complex to form immature viral particles. J Virol 2001; 75:5778-95. [PMID: 11390580 PMCID: PMC114294 DOI: 10.1128/jvi.75.13.5778-5795.2001] [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] [Received: 07/28/2000] [Accepted: 04/02/2001] [Indexed: 11/20/2022] Open
Abstract
The vaccinia virus (VV) A10L gene codes for a major core protein, P4a. This polypeptide is synthesized at late times during viral infection and is proteolytically cleaved during virion assembly. To investigate the role of P4a in the virus life cycle and morphogenesis, we have generated an inducer-dependent conditional mutant (VVindA10L) in which expression of the A10L gene is under the control of the Escherichia coli lacI operator/repressor system. Repression of the A10L gene severely impairs virus growth, as observed by both the inability of the virus to form plaques and the 2-log reduction of viral yields. This defect can be partially overcome by addition of the inducer isopropyl-beta-D-thiogalactopyranoside (IPTG). Synthesis of viral proteins other than P4a occurred, although early shutoff of host protein synthesis and expression of viral late polypeptides are clearly delayed, both in the absence and in the presence of IPTG, compared with cells infected with the parental virus. Viral DNA replication and concatemer resolution appeared to proceed normally in the absence of the A10L gene product. In cells infected with VVindA10L in the absence of the inducer virion assembly is blocked, as defined by electron microscopy. Numerous spherical immature viral particles that appear devoid of dense viroplasmic material together with highly electron-dense regular structures are abundant in VVindA10L-infected cells. These regularly spaced structures can be specifically labeled with anti-DNA antibodies as well as with a DNase-gold conjugate, indicating that they contain DNA. Some images suggest that these DNA structures enter into spherical immature viral particles. In this regard, although it has not been firmly established, it has been suggested that DNA uptake occurs after formation of spherical immature particles. Overall, our results showed that P4a and/or its cleaved products are essential for the correct assembly of the nucleoprotein complex within immature viral particles.
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Affiliation(s)
- R Heljasvaara
- Departments of Molecular and Cellular Biology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientifícas, Campus Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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20
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Wheeler MD, Kono H, Rusyn I, Arteel GE, McCarty D, Samulski RJ, Thurman RG. Chronic ethanol increases adeno-associated viral transgene expression in rat liver via oxidant and NFkappaB-dependent mechanisms. Hepatology 2000; 32:1050-9. [PMID: 11050056 DOI: 10.1053/jhep.2000.19339] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Recombinant adeno-associated virus (rAAV) transduction is limited in vivo, yet can be enhanced by hydroxyurea, ultraviolet-irradiation, or adenovirus coinfection, possibly via mechanisms involving stress in the host cell. Because chronic ethanol induces oxidative stress, it was hypothesized that chronic ethanol would increase rAAV transduction in vivo. To test this hypothesis, rAAV encoding beta-galactosidase was given to Wistar rats that later received either ethanol diet or high-fat control diet via an enteral-feeding protocol for 3 weeks. Expression and activity of beta-galactosidase in the liver were increased nearly 5-fold by ethanol. The increase in transgene expression was inhibited by antioxidant diphenylene iodonium (DPI), which is consistent with the hypothesis that ethanol causes an increase in rAAV transduction via oxidative stress. Ethanol increased DNA synthesis only slightly; however, it increased the nuclear transcription factor kappaB (NFkappaB) 4-fold, a phenomenon also sensitive to DPI. Moreover, a 6-fold increase in rAAV transgene expression was observed in an acute ischemia-reperfusion model of oxidative stress. Transgene expression was transiently increased 24 hours after ischemia-reperfusion 3 days and 3 weeks after rAAV infection. Further, adenoviral expression of superoxide dismutase or IkappaBalpha superrepressor inhibited rAAV transgene expression caused by ischemia-reperfusion. Therefore, it is concluded that ethanol increases rAAV transgene expression via mechanisms dependent on oxidative stress, and NFkappaB likely through enhancement of cytomegaloviral (CMV) promoter elements. Alcoholic liver disease is an attractive target for gene therapy because consumption of ethanol could theoretically increase expression of therapeutic genes (e.g., superoxide dismutase). Moreover, this study has important implications for rAAV gene therapy and potential enhancement and regulation of transgene expression in liver.
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Affiliation(s)
- M D Wheeler
- Laboratory of Hepatobiology and Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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21
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Yeh WW, Moss B, Wolffe EJ. The vaccinia virus A9L gene encodes a membrane protein required for an early step in virion morphogenesis. J Virol 2000; 74:9701-11. [PMID: 11000242 PMCID: PMC112402 DOI: 10.1128/jvi.74.20.9701-9711.2000] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The A9L open reading frame of vaccinia virus was predicted to encode a membrane-associated protein. A transcriptional analysis of the A9L gene indicated that it was expressed at late times in vaccinia virus-infected cells. Late expression, as well as virion membrane association, was demonstrated by the construction and use of a recombinant vaccinia virus encoding an A9L protein with a C-terminal epitope tag. Immunoelectron microscopy revealed that the A9L protein was associated with both immature and mature virus particles and was oriented in the membrane with its C terminus exposed on the virion surface. To determine whether the A9L protein functions in viral assembly or infectivity, we made a conditional-lethal inducible recombinant vaccinia virus. In the absence of inducer, A9L expression and virus replication were undetectable. Under nonpermissive conditions, viral late protein synthesis occurred, but maturational proteolytic processing was inhibited, and there was an accumulation of membrane-coated electron-dense bodies, crescents, and immature virus particles, many of which appeared abnormal. We concluded that the product of the A9L gene is a viral membrane-associated protein and functions at an early stage in virion morphogenesis.
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Affiliation(s)
- W W Yeh
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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22
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Lin CL, Chung CS, Heine HG, Chang W. Vaccinia virus envelope H3L protein binds to cell surface heparan sulfate and is important for intracellular mature virion morphogenesis and virus infection in vitro and in vivo. J Virol 2000; 74:3353-65. [PMID: 10708453 PMCID: PMC111837 DOI: 10.1128/jvi.74.7.3353-3365.2000] [Citation(s) in RCA: 219] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An immunodominant antigen, p35, is expressed on the envelope of intracellular mature virions (IMV) of vaccinia virus. p35 is encoded by the viral late gene H3L, but its role in the virus life cycle is not known. This report demonstrates that soluble H3L protein binds to heparan sulfate on the cell surface and competes with the binding of vaccinia virus, indicating a role for H3L protein in IMV adsorption to mammalian cells. A mutant virus defective in expression of H3L (H3L(-)) was constructed; the mutant virus has a small plaque phenotype and 10-fold lower IMV and extracellular enveloped virion titers than the wild-type virus. Virion morphogenesis is severely blocked and intermediate viral structures such as viral factories and crescents accumulate in cells infected with the H3L(-) mutant virus. IMV from the H3L(-) mutant virus are somewhat altered and less infectious than wild-type virions. However, cells infected by the mutant virus form multinucleated syncytia after low pH treatment, suggesting that H3L protein is not required for cell fusion. Mice inoculated intranasally with wild-type virus show high mortality and severe weight loss, whereas mice infected with H3L(-) mutant virus survive and recover faster, indicating that inactivation of the H3L gene attenuates virus virulence in vivo. In summary, these data indicate that H3L protein mediates vaccinia virus adsorption to cell surface heparan sulfate and is important for vaccinia virus infection in vitro and in vivo. In addition, H3L protein plays a role in virion assembly.
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Affiliation(s)
- C L Lin
- Graduate Institute of Life Science, National Defense Medical Center and Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
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23
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Traktman P, Liu K, DeMasi J, Rollins R, Jesty S, Unger B. Elucidating the essential role of the A14 phosphoprotein in vaccinia virus morphogenesis: construction and characterization of a tetracycline-inducible recombinant. J Virol 2000; 74:3682-95. [PMID: 10729144 PMCID: PMC111878 DOI: 10.1128/jvi.74.8.3682-3695.2000] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously reported the construction and characterization of vindH1, an inducible recombinant in which expression of the vaccinia virus H1 phosphatase is regulated experimentally by IPTG (isopropyl-beta-D-thiogalactopyranoside) (35). In the absence of H1 expression, the transcriptional competence and infectivity of nascent virions are severely compromised. We have sought to identify H1 substrates by characterizing proteins that are hyperphosphorylated in H1-deficient virions. Here, we demonstrate that the A14 protein, a component of the virion membrane, is indeed an H1 phosphatase substrate in vivo and in vitro. A14 is hyperphosphorylated on serine residues in the absence of H1 expression. To enable a genetic analysis of A14's function during the viral life cycle, we have adopted the regulatory components of the tetracycline (TET) operon and created new reagents for the construction of TET-inducible vaccinia virus recombinants. In the context of a virus expressing the TET repressor (tetR), insertion of the TET operator between the transcriptional and translational start sites of a late viral gene enables its expression to be tightly regulated by TET. We constructed a TET-inducible recombinant for the A14 gene, vindA14. In the absence of TET, vindA14 fails to form plaques and the 24-h yield of infectious progeny is reduced by 3 orders of magnitude. The infection arrests early during viral morphogenesis, with the accumulation of large numbers of vesicles and the appearance of "empty" crescents that appear to adhere only loosely to virosomes. This phenotype corresponds closely to that observed for an IPTG-inducible A14 recombinant whose construction and characterization were reported while our work was ongoing (47). The consistency in the phenotypes seen for the IPTG- and TET-inducible recombinants confirms the efficacy of the TET-inducible system and reinforces the value of having a second, independent system available for generating inducible recombinants.
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Affiliation(s)
- P Traktman
- Department of Microbiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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24
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Broyles SS, Liu X, Zhu M, Kremer M. Transcription factor YY1 is a vaccinia virus late promoter activator. J Biol Chem 1999; 274:35662-7. [PMID: 10585445 DOI: 10.1074/jbc.274.50.35662] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vaccinia virus has a DNA genome, yet replicates in the cytoplasmic compartment of the cell. We previously described the identification of a cellular protein having high affinity for vaccinia virus late promoter DNA. Sequence substitutions in the vaccinia I1L promoter were used to define a 5-nucleotide block at the transcription initiation site as essential for interaction with the protein. Within this sequence is the recognition motif for the nuclear transcription factor YY1. This factor regulates a multitude of cellular promoters, as an activator of transcription, as a repressor, or as an initiator element-binding protein. Antibodies directed against YY1 were used to show that YY1 copurified with the vaccinia late promoter-binding protein and was present in late promoter-protein complexes in gel supershift assays. Bacterially expressed YY1 also bound specifically to late promoter DNA. A dinucleotide replacement within the YY1 recognition motif directly adjacent to the transcription start site severely reduced the affinity of YY1 for the I1L promoter in vitro and impaired I1L promoter-dependent transcription in vivo. The intracellular localization of YY1 was shown by immunofluorescence microscopy to shift from primarily nuclear to the cytoplasm after vaccinia infection. These results indicate that YY1 has a positive role in the regulation of vaccinia virus late gene transcription and suggest that poxviruses have adapted cellular initiator elements as a means of regulating viral gene expression. This is the first identifiable cellular protein implicated in poxvirus transcription.
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Affiliation(s)
- S S Broyles
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA.
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25
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Williams O, Wolffe EJ, Weisberg AS, Merchlinsky M. Vaccinia virus WR gene A5L is required for morphogenesis of mature virions. J Virol 1999; 73:4590-9. [PMID: 10233918 PMCID: PMC112500 DOI: 10.1128/jvi.73.6.4590-4599.1999] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The vaccinia virus WR A5L open reading frame (corresponding to open reading frame A4L in vaccinia virus Copenhagen) encodes an immunodominant late protein found in the core of the vaccinia virion. To investigate the role of this protein in vaccinia virus replication, we have constructed a recombinant virus, vA5Li, in which the endogenous gene has been deleted and an inducible copy of the A5 gene dependent on isopropyl-beta-D-thiogalactopyranoside (IPTG) for expression has been inserted into the genome. In the absence of inducer, the yield of infectious virus was dramatically reduced. However, DNA synthesis and processing, viral protein expression (except for A5), and early stages in virion formation were indistinguishable from the analogous steps in a normal infection. Electron microscopy revealed that the major vaccinia virus structural form present in cells infected with vA5Li in the absence of inducer was immature virions. Viral particles were purified from vA5Li-infected cells in the presence and absence of inducer. Both particles contained viral DNA and the full complement of viral proteins, except for A5, which was missing from particles prepared in the absence of inducer. The particles prepared in the presence of IPTG were more infectious than those prepared in its absence. The A5 protein appears to be required for the immature virion to form the brick-shaped intracellular mature virion.
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Affiliation(s)
- O Williams
- Laboratory of Viral Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, Maryland 20852, USA
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