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Shen Y, Li Y, Yan R. Structural basis for the inhibition mechanism of the DNA polymerase holoenzyme from mpox virus. Structure 2024; 32:654-661.e3. [PMID: 38579705 DOI: 10.1016/j.str.2024.03.004] [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: 11/05/2023] [Revised: 01/31/2024] [Accepted: 03/11/2024] [Indexed: 04/07/2024]
Abstract
There are three key components at the core of the mpox virus (MPXV) DNA polymerase holoenzyme: DNA polymerase F8, processivity factors A22, and the Uracil-DNA glycosylase E4. The holoenzyme is recognized as a vital antiviral target because MPXV replicates in the cytoplasm of host cells. Nucleotide analogs such as cidofovir and cytarabine (Ara-C) have shown potential in curbing MPXV replication and they also display promise against other poxviruses. However, the mechanism behind their inhibitory effects remains unclear. Here, we present the cryo-EM structure of the DNA polymerase holoenzyme F8/A22/E4 bound with its competitive inhibitor Ara-C-derived cytarabine triphosphate (Ara-CTP) at an overall resolution of 3.0 Å and reveal its inhibition mechanism. Ara-CTP functions as a direct chain terminator in proximity to the deoxycytidine triphosphate (dCTP)-binding site. The extra hydrogen bond formed with Asn665 makes it more potent in binding than dCTP. Asn665 is conserved among eukaryotic B-family polymerases.
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Affiliation(s)
- Yaping Shen
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, Zhejiang Province, China
| | - Yaning Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Renhong Yan
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Southern University of Science and Technology, Shenzhen 518055, Guangdong Province, China.
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2
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Lee W, Kim YJ, Lee SJ, Ahn DG, Kim SJ. Current Status of Epidemiology, Diagnosis, Therapeutics, and Vaccines for the Re-Emerging Human Monkeypox Virus. J Microbiol Biotechnol 2023; 33:981-991. [PMID: 37519276 PMCID: PMC10468680 DOI: 10.4014/jmb.2306.06033] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 07/18/2023] [Accepted: 07/22/2023] [Indexed: 08/01/2023]
Abstract
Monkeypox (Mpox) virus, a member of the Poxviridae family, causes a severe illness similar to smallpox, which is characterized by symptoms such as high fever, rash, and pustules. Human-to-human transmission cases have been reported but remained low since the first recorded case of human infection occurred in the Congo in 1970. Recently, Mpox has re-emerged, leading to an alarming surge in infections worldwide since 2022, originating in the United Kingdom. Consequently, the World Health Organization (WHO) officially declared the '2022-23 Mpox outbreak'. Currently, no specific therapy or vaccine is available for Mpox. Therefore, patients infected with Mpox are treated using conventional therapies developed for smallpox. However, the vaccines developed for smallpox have demonstrated only partial efficacy against Mpox, allowing viral transmission among humans. In this review, we discuss the current epidemiology of the ongoing Mpox outbreak and provide an update on the progress made in diagnosis, treatment, and development of vaccines for Mpox.
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Affiliation(s)
- Wooseong Lee
- Department of Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
| | - Yu-Jin Kim
- Department of Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
| | - Su Jin Lee
- Department of Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
| | - Dae-Gyun Ahn
- Department of Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
| | - Seong-Jun Kim
- Department of Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
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Byareddy SN, Sharma K, Sachdev S, Reddy AS, Acharya A, Klaustermeier KM, Lorson CL, Singh K. Potential therapeutic targets for Mpox: the evidence to date. Expert Opin Ther Targets 2023; 27:419-431. [PMID: 37368464 PMCID: PMC10722886 DOI: 10.1080/14728222.2023.2230361] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 06/07/2023] [Accepted: 06/23/2023] [Indexed: 06/28/2023]
Abstract
INTRODUCTION The global Mpox (MPX) disease outbreak caused by the Mpox virus (MPXV) in 2022 alarmed the World Health Organization (WHO) and health regulation agencies of individual countries leading to the declaration of MPX as a Public Health Emergency. Owing to the genetic similarities between smallpox-causing poxvirus and MPXV, vaccine JYNNEOS, and anti-smallpox drugs Brincidofovir and Tecovirimat were granted emergency use authorization by the United States Food and Drug Administration. The WHO also included cidofovir, NIOCH-14, and other vaccines as treatment options. AREAS COVERED This article covers the historical development of EUA-granted antivirals, resistance to these antivirals, and the projected impact of signature mutations on the potency of antivirals against currently circulating MPXV. Since a high prevalence of MPXV infections in individuals coinfected with HIV and MPXV, the treatment results among these individuals have been included. EXPERT OPINION All EUA-granted drugs have been approved for smallpox treatment. These antivirals show good potency against Mpox. However, conserved resistance mutation positions in MPXV and related poxviruses, and the signature mutations in the 2022 MPXV can potentially compromise the efficacy of the EUA-granted treatments. Therefore, MPXV-specific medications are required not only for the current but also for possible future outbreaks.
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Affiliation(s)
- Siddappa N Byareddy
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | | | - Shrikesh Sachdev
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Athreya S. Reddy
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
| | - Arpan Acharya
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | | | - Christian L Lorson
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
| | - Kamal Singh
- Department of Pharmaceutical Chemistry, DPSRU, New Delhi-110017
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
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Kannan SR, Sachdev S, Reddy AS, Kandasamy SL, Byrareddy SN, Lorson CL, Singh K. Mutations in the monkeypox virus replication complex: Potential contributing factors to the 2022 outbreak. J Autoimmun 2022; 133:102928. [PMID: 36252459 PMCID: PMC9562781 DOI: 10.1016/j.jaut.2022.102928] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/01/2022] [Accepted: 10/07/2022] [Indexed: 11/05/2022]
Abstract
Attributes contributing to the current monkeypox virus (MPXV) outbreak remain unknown. It has been established that mutations in viral proteins may alter phenotype and pathogenicity. To assess if mutations in the MPXV DNA replication complex (RC) contribute to the outbreak, we conducted a temporal analysis of available MPXV sequences to identify mutations, generated a DNA replication complex (RC) using structures of related viral and eukaryotic proteins, and structure prediction method AlphaFold. Ten mutations within the RC were identified and mapped onto the RC to infer role of mutations. Two mutations in F8L (RC catalytic subunit), and two in G9R (a processivity factor) were ∼100% prevalent in the 2022 sequences. F8L mutation L108F emerged in 2022, whereas W411L emerged in 2018, and persisted in 2022. L108 is topologically located to enhance DNA binding affinity of F8L. Therefore, mutation L108F can change the fidelity, sensitivity to nucleoside inhibitors, and processivity of F8L. Surface exposed W411L likely affects the binding of regulatory factor(s). G9R mutations S30L and D88 N in G9R emerged in 2022, and may impact the interaction of G9R with E4R (uracil DNA glycosylase). The remaining six mutations that appeared in 2001, reverted to the first (1965 Rotterdam) isolate. Two nucleoside inhibitors brincidofovir and cidofovir have been approved for MPXV treatment. Cidofovir resistance in vaccinia virus is achieved by A314T and A684V mutations. Both A314 and A684 are conserved in MPXV. Therefore, resistance to these drugs in MPXV may arise through similar mechanisms.
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Affiliation(s)
| | - Shrikesh Sachdev
- Bond Life Sciences Center, University of Missouri, Columbia, MO, USA
| | - Athreya S. Reddy
- Bond Life Sciences Center, University of Missouri, Columbia, MO, USA
| | | | - Siddappa N. Byrareddy
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198, USA,Department of Genetics, Cell Biology, and Anatomy, University of Nebraska Medical Center, Omaha, NE, 68198, USA,Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198, USA,Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden
| | - Christian L. Lorson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA
| | - Kamal Singh
- Bond Life Sciences Center, University of Missouri, Columbia, MO, USA,Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA,Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden,Corresponding author. 471g, Bond Life Sciences Center, 1201 E Rollins Street, Columbia, MO, 65211, USA
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Templeton CW, Traktman P. UV Irradiation of Vaccinia Virus-Infected Cells Impairs Cellular Functions, Introduces Lesions into the Viral Genome, and Uncovers Repair Capabilities for the Viral Replication Machinery. J Virol 2022; 96:e0213721. [PMID: 35404095 PMCID: PMC9093118 DOI: 10.1128/jvi.02137-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 03/17/2022] [Indexed: 11/20/2022] Open
Abstract
Vaccinia virus (VV), the prototypic poxvirus, encodes a repertoire of proteins responsible for the metabolism of its large dsDNA genome. Previous work has furthered our understanding of how poxviruses replicate and recombine their genomes, but little is known about whether the poxvirus genome undergoes DNA repair. Our studies here are aimed at understanding how VV responds to exogenous DNA damage introduced by UV irradiation. Irradiation of cells prior to infection decreased protein synthesis and led to an ∼12-fold reduction in viral yield. On top of these cell-specific insults, irradiation of VV infections at 4 h postinfection (hpi) introduced both cyclobutene pyrimidine dimer (CPD) and 6,4-photoproduct (6,4-PP) lesions into the viral genome led to a nearly complete halt to further DNA synthesis and to a further reduction in viral yield (∼35-fold). DNA lesions persisted throughout infection and were indeed present in the genomes encapsidated into nascent virions. Depletion of several cellular proteins that mediate nucleotide excision repair (XP-A, -F, and -G) did not render viral infections hypersensitive to UV. We next investigated whether viral proteins were involved in combatting DNA damage. Infections performed with a virus lacking the A50 DNA ligase were moderately hypersensitive to UV irradiation (∼3-fold). More strikingly, when the DNA polymerase inhibitor cytosine arabinoside (araC) was added to wild-type infections at the time of UV irradiation (4 hpi), an even greater hypersensitivity to UV irradiation was seen (∼11-fold). Virions produced under the latter condition contained elevated levels of CPD adducts, strongly suggesting that the viral polymerase contributes to the repair of UV lesions introduced into the viral genome. IMPORTANCE Poxviruses remain of significant interest because of their continuing clinical relevance, their utility for the development of vaccines and oncolytic therapies, and their illustration of fundamental principles of viral replication and virus/cell interactions. These viruses are unique in that they replicate exclusively in the cytoplasm of infected mammalian cells, providing novel challenges for DNA viruses. How poxviruses replicate, recombine, and possibly repair their genomes is still only partially understood. Using UV irradiation as a form of exogenous DNA damage, we have examined how vaccinia virus metabolizes its genome following insult. We show that even UV irradiation of cells prior to infection diminishes viral yield, while UV irradiation during infection damages the genome, causes a halt in DNA accumulation, and reduces the viral yield more severely. Furthermore, we show that viral proteins, but not the cellular machinery, contribute to a partial repair of the viral genome following UV irradiation.
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Affiliation(s)
- Conor W. Templeton
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Paula Traktman
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
- Departments of Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina, USA
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6
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Andrei G, Fiten P, Krečmerová M, Opdenakker G, Topalis D, Snoeck R. Poxviruses Bearing DNA Polymerase Mutations Show Complex Patterns of Cross-Resistance. Biomedicines 2022; 10:biomedicines10030580. [PMID: 35327382 PMCID: PMC8945813 DOI: 10.3390/biomedicines10030580] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 02/08/2022] [Accepted: 02/11/2022] [Indexed: 01/06/2023] Open
Abstract
Despite the eradication of smallpox four decades ago, poxviruses continue to be a threat to humans and animals. The arsenal of anti-poxvirus agents is very limited and understanding mechanisms of resistance to agents targeting viral DNA polymerases is fundamental for the development of antiviral therapies. We describe here the phenotypic and genotypic characterization of poxvirus DNA polymerase mutants isolated under selective pressure with different acyclic nucleoside phosphonates, including HPMPC (cidofovir), cHPMPC, HPMPA, cHPMPA, HPMPDAP, HPMPO-DAPy, and PMEO-DAPy, and the pyrophosphate analogue phosphonoacetic acid. Vaccinia virus (VACV) and cowpox virus drug-resistant viral clones emerging under drug pressure were characterized phenotypically (drug-susceptibility profile) and genotypically (DNA polymerase sequencing). Different amino acid changes in the polymerase domain and in the 3′-5′ exonuclease domain were linked to drug resistance. Changes in the 3′-5′ domain emerged earlier than in the polymerase domain when viruses acquired a combination of mutations. Our study highlights the importance of poxvirus DNA polymerase residues 314, 613, 684, 688, and 851, previously linked to drug resistance, and identified several novel mutations in the 3′-5′ exonuclease domain (M313I, F354L, D480Y) and in the DNA polymerase domain (A632T, T831I, E856K, L924F) associated with different drug-susceptibility profiles. Furthermore, a combination of mutations resulted in complex patterns of cross-resistance. Modeling of the VACV DNA polymerase bearing the newly described mutations was performed to understand the effects of these mutations on the structure of the viral enzyme. We demonstrated the emergence of drug-resistant DNA polymerase mutations in complex patterns to be considered in case such mutations should eventually arise in the clinic.
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Affiliation(s)
- Graciela Andrei
- Laboratory of Virology and Chemotherapy, Department of Microbiology, Immunology, and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Box 1030, 3000 Leuven, Belgium; (D.T.); (R.S.)
- Correspondence: ; Tel.: +32-16-32-19-51
| | - Pierre Fiten
- Laboratory of Immunobiology, Department of Microbiology, Immunology, and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Box 1044, 3000 Leuven, Belgium; (P.F.); (G.O.)
| | - Marcela Krečmerová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Nám. 2, 166 10 Prague, Czech Republic;
| | - Ghislain Opdenakker
- Laboratory of Immunobiology, Department of Microbiology, Immunology, and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Box 1044, 3000 Leuven, Belgium; (P.F.); (G.O.)
| | - Dimitrios Topalis
- Laboratory of Virology and Chemotherapy, Department of Microbiology, Immunology, and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Box 1030, 3000 Leuven, Belgium; (D.T.); (R.S.)
| | - Robert Snoeck
- Laboratory of Virology and Chemotherapy, Department of Microbiology, Immunology, and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Box 1030, 3000 Leuven, Belgium; (D.T.); (R.S.)
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7
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Forsyth KS, Addison MM, Eisenlohr LC. Recombinant Poxviruses: Versatile Tools for Immunological Assays. Methods Mol Biol 2019; 1988:217-248. [PMID: 31147943 DOI: 10.1007/978-1-4939-9450-2_16] [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: 06/09/2023]
Abstract
The study of antigen processing and presentation is critical to our understanding of the mechanisms that govern immune surveillance. A typical requirement of assays designed to examine antigen processing and presentation is the de novo biosynthesis of a model antigen. Historically, Vaccinia virus, a poxvirus closely related to Cowpox virus, has enjoyed widespread use for this purpose. Recombinant poxvirus-based expression has a number of advantages over other systems. Poxviruses accommodate the insertion of large pieces of recombinant DNA into their genome, and recombination and selection are relatively efficient. Poxviruses readily infect a variety of cell types, and they drive rapid and high levels of antigen expression. Additionally, they can be utilized in a variety of assays to study both MHC class I restricted and MHC class II restricted antigen processing and presentation. Ultimately, the numerous advantages of poxvirus recombinants have made the Vaccinia expression system a mainstay in the study of processing and presentation over the past two decades. In an attempt to address one shortcoming of Vaccinia virus while simultaneously retaining the benefits inherent to poxviruses, our laboratory has begun to engineer recombinant Ectromelia viruses. Ectromelia virus, or mousepox, is a natural pathogen of murine cells and performing experiments in the context of a natural host-pathogen relationship may elucidate unknown factors that influence epitope generation and host response. This chapter will describe several recombinant poxvirus system protocols used to study both MHC class I and class II antigen processing and presentation, as well as provide insight and troubleshooting techniques to improve the reproducibility and fidelity of these experiments.
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Affiliation(s)
- Katherine S Forsyth
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Mary M Addison
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Laurence C Eisenlohr
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Children's Hospital of Philadelphia, PA, USA.
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Remakus S, Ma X, Tang L, Xu RH, Knudson C, Melo-Silva CR, Rubio D, Kuo YM, Andrews A, Sigal LJ. Cutting Edge: Protection by Antiviral Memory CD8 T Cells Requires Rapidly Produced Antigen in Large Amounts. THE JOURNAL OF IMMUNOLOGY 2018; 200:3347-3352. [PMID: 29643193 DOI: 10.4049/jimmunol.1701568] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 03/20/2018] [Indexed: 11/19/2022]
Abstract
Numerous attempts to produce antiviral vaccines by harnessing memory CD8 T cells have failed. A barrier to progress is that we do not know what makes an Ag a viable target of protective CD8 T cell memory. We found that in mice susceptible to lethal mousepox (the mouse homolog of human smallpox), a dendritic cell vaccine that induced memory CD8 T cells fully protected mice when the infecting virus produced Ag in large quantities and with rapid kinetics. Protection did not occur when the Ag was produced in low amounts, even with rapid kinetics, and protection was only partial when the Ag was produced in large quantities but with slow kinetics. Hence, the amount and timing of Ag expression appear to be key determinants of memory CD8 T cell antiviral protective immunity. These findings may have important implications for vaccine design.
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Affiliation(s)
- Sanda Remakus
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107; and.,Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Xueying Ma
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Lingjuan Tang
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107; and
| | - Ren-Huan Xu
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Cory Knudson
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107; and
| | - Carolina R Melo-Silva
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107; and
| | - Daniel Rubio
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Yin-Ming Kuo
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Andrew Andrews
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Luis J Sigal
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107; and
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Tarbouriech N, Ducournau C, Hutin S, Mas PJ, Man P, Forest E, Hart DJ, Peyrefitte CN, Burmeister WP, Iseni F. The vaccinia virus DNA polymerase structure provides insights into the mode of processivity factor binding. Nat Commun 2017; 8:1455. [PMID: 29129932 PMCID: PMC5682278 DOI: 10.1038/s41467-017-01542-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 09/26/2017] [Indexed: 11/12/2022] Open
Abstract
Vaccinia virus (VACV), the prototype member of the Poxviridae, replicates in the cytoplasm of an infected cell. The catalytic subunit of the DNA polymerase E9 binds the heterodimeric processivity factor A20/D4 to form the functional polymerase holoenzyme. Here we present the crystal structure of full-length E9 at 2.7 Å resolution that permits identification of important poxvirus-specific structural insertions. One insertion in the palm domain interacts with C-terminal residues of A20 and thus serves as the processivity factor-binding site. This is in strong contrast to all other family B polymerases that bind their co-factors at the C terminus of the thumb domain. The VACV E9 structure also permits rationalization of polymerase inhibitor resistance mutations when compared with the closely related eukaryotic polymerase delta–DNA complex. The catalytic subunit E9 of the vaccinia virus DNA polymerase forms a functional polymerase holoenzyme by interacting with the heterodimeric processivity factor A20/D4. Here the authors present the structure of full-length E9 and show that an insertion within its palm domain binds A20, in a mode different from other family B polymerases.
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Affiliation(s)
- Nicolas Tarbouriech
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CNRS, CEA, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Corinne Ducournau
- Unité de Virologie, Institut de Recherche Biomédicale des Armées, BP 73, 91223, Brétigny-sur-Orge Cedex, France
| | - Stephanie Hutin
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CNRS, CEA, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Philippe J Mas
- Integrated Structural Biology Grenoble (ISBG) CNRS, CEA, Université Grenoble Alpes, EMBL, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Petr Man
- BioCeV-Institute of Microbiology, Czech Academy of Sciences, Prumyslova 595, 252 50, Vestec, Czech Republic.,Faculty of Science, Charles University, Hlavova 8, 128 43, Prague 2, Czech Republic
| | - Eric Forest
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CNRS, CEA, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Darren J Hart
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CNRS, CEA, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Christophe N Peyrefitte
- Unité de Virologie, Institut de Recherche Biomédicale des Armées, BP 73, 91223, Brétigny-sur-Orge Cedex, France.,Emerging Pathogens Laboratory, Fondation Mérieux, 21 Avenue Tony Garnier, 69007, Lyon, France
| | - Wim P Burmeister
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CNRS, CEA, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Frédéric Iseni
- Unité de Virologie, Institut de Recherche Biomédicale des Armées, BP 73, 91223, Brétigny-sur-Orge Cedex, France.
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10
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Leite FGG, Bergthaler A, Skern T. Vaccinia virus G1 protein: absence of autocatalytic self-processing. Arch Virol 2017; 162:2803-2808. [PMID: 28523522 DOI: 10.1007/s00705-017-3409-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 05/08/2017] [Indexed: 11/30/2022]
Abstract
Vaccinia virus relies on a series of proteolytic cleavage events involving two viral proteins, I7 and G1, to complete its life cycle. Furthermore, G1 itself is cleaved during vaccinia virus infection. However, convincing evidence is lacking to show whether G1 participates in autoproteolysis or is a substrate of another protease. We employed both biochemical and cell-based approaches to investigate G1 cleavage. G1, when expressed in bacteria, rabbit reticulocyte lysates or HeLa cells, was not processed. Moreover, G1 was cleaved in infected cells, but only in the presence of virus late gene expression; cleavage was strongly inhibited by proteasome inhibitors. Thus, these results imply a more complex G1 cleavage reaction than previously envisaged.
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Affiliation(s)
- F G G Leite
- Max F. Perutz Laboratories, Medical University of Vienna, Dr. Bohr-Gasse 9/3, 1030, Vienna, Austria. .,Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
| | - A Bergthaler
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090, Vienna, Austria
| | - T Skern
- Max F. Perutz Laboratories, Medical University of Vienna, Dr. Bohr-Gasse 9/3, 1030, Vienna, Austria
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11
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Teferi WM, Desaulniers MA, Noyce RS, Shenouda M, Umer B, Evans DH. The vaccinia virus K7 protein promotes histone methylation associated with heterochromatin formation. PLoS One 2017; 12:e0173056. [PMID: 28257484 PMCID: PMC5336242 DOI: 10.1371/journal.pone.0173056] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 02/14/2017] [Indexed: 12/12/2022] Open
Abstract
It has been well established that many vaccinia virus proteins suppress host antiviral pathways by targeting the transcription of antiviral proteins, thus evading the host innate immune system. However, whether viral proteins have an effect on the host’s overall cellular transcription is less understood. In this study we investigated the regulation of heterochromatin during vaccinia virus infection. Heterochromatin is a highly condensed form of chromatin that is less transcriptionally active and characterized by methylation of histone proteins. We examined the change in methylation of two histone proteins, H3 and H4, which are major markers of heterochromatin, during the course of viral infection. Using immunofluorescence microscopy and flow cytometry we were able to track the overall change in the methylated levels of H3K9 and H4K20. Our results suggest that there is significant increase in methylation of H3K9 and H4K20 during Orthopoxviruses infection compared to mock-infected cells. However, this effect was not seen when we infected cells with Leporipoxviruses. We further screened several vaccinia virus single and multi-gene deletion mutant and identified the vaccinia virus gene K7R as a contributor to the increase in cellular histone methylation during infection.
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Affiliation(s)
- Wondimagegnehu M. Teferi
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
| | - Megan A. Desaulniers
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
| | - Ryan S. Noyce
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
| | - Mira Shenouda
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
| | - Brittany Umer
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
| | - David H. Evans
- Department of Medical Microbiology & Immunology, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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Czarnecki MW, Traktman P. The vaccinia virus DNA polymerase and its processivity factor. Virus Res 2017; 234:193-206. [PMID: 28159613 DOI: 10.1016/j.virusres.2017.01.027] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 01/29/2017] [Indexed: 10/20/2022]
Abstract
Vaccinia virus is the prototypic poxvirus. The 192 kilobase double-stranded DNA viral genome encodes most if not all of the viral replication machinery. The vaccinia virus DNA polymerase is encoded by the E9L gene. Sequence analysis indicates that E9 is a member of the B family of replicative polymerases. The enzyme has both polymerase and 3'-5' exonuclease activities, both of which are essential to support viral replication. Genetic analysis of E9 has identified residues and motifs whose alteration can confer temperature-sensitivity, drug resistance (phosphonoacetic acid, aphidicolin, cytosine arabinsode, cidofovir) or altered fidelity. The polymerase is involved both in DNA replication and in recombination. Although inherently distributive, E9 gains processivity by interacting in a 1:1 stoichiometry with a heterodimer of the A20 and D4 proteins. A20 binds to both E9 and D4 and serves as a bridge within the holoenzyme. The A20/D4 heterodimer has been purified and can confer processivity on purified E9. The interaction of A20 with D4 is mediated by the N'-terminus of A20. The D4 protein is an enzymatically active uracil DNA glycosylase. The DNA-scanning activity of D4 is proposed to keep the holoenzyme tethered to the DNA template but allow polymerase translocation. The crystal structure of D4, alone and in complex with A201-50 and/or DNA has been solved. Screens for low molecular weight compounds that interrupt the A201-50/D4 interface have yielded hits that disrupt processive DNA synthesis in vitro and/or inhibit plaque formation. The observation that an active DNA repair enzyme is an integral part of the holoenzyme suggests that DNA replication and repair may be coupled.
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Affiliation(s)
- Maciej W Czarnecki
- Departments of Biochemistry & Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Paula Traktman
- Departments of Biochemistry & Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Departments of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 29425, United States; Departments of the Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29425, United States; Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
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Quantitative Analysis of MicroRNAs in Vaccinia virus Infection Reveals Diversity in Their Susceptibility to Modification and Suppression. PLoS One 2015; 10:e0131787. [PMID: 26161560 PMCID: PMC4498801 DOI: 10.1371/journal.pone.0131787] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2015] [Accepted: 06/08/2015] [Indexed: 12/26/2022] Open
Abstract
Vaccinia virus (VACV) is a large cytoplasmic DNA virus that causes dramatic alterations to many cellular pathways including microRNA biogenesis. The virus encodes a poly(A) polymerase which was previously shown to add poly(A) tails to the 3’ end of cellular miRNAs, resulting in their degradation by 24 hours post infection (hpi). Here we used small RNA sequencing to quantify the impact of VACV infection on cellular miRNAs in human cells at both early (6 h) and late (24 h) times post infection. A detailed quantitative analysis of individual miRNAs revealed marked diversity in the extent of their modification and relative change in abundance during infection. Some miRNAs became highly modified (e.g. miR-29a-3p, miR-27b-3p) whereas others appeared resistant (e.g. miR-16-5p). Furthermore, miRNAs that were highly tailed at 6 hpi were not necessarily among the most reduced at 24 hpi. These results suggest that intrinsic features of human cellular miRNAs cause them to be differentially polyadenylated and altered in abundance during VACV infection. We also demonstrate that intermediate and late VACV gene expression are required for optimal repression of some miRNAs including miR-27-3p. Overall this work reveals complex and varied consequences of VACV infection on host miRNAs and identifies miRNAs which are largely resistant to VACV-induced polyadenylation and are therefore present at functional levels during the initial stages of infection and replication.
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Abstract
UNLABELLED Recombination plays a critical role in virus evolution. It helps avoid genetic decline and creates novel phenotypes. This promotes survival, and genome sequencing suggests that recombination has facilitated the evolution of human pathogens, including orthopoxviruses such as variola virus. Recombination can also be used to map genes, but although recombinant poxviruses are easily produced in culture, classical attempts to map the vaccinia virus (VACV) genome this way met with little success. We have sequenced recombinants formed when VACV strains TianTan and Dryvax are crossed under different conditions. These were a single round of growth in coinfected cells, five rounds of sequential passage, or recombinants obtained using leporipoxvirus-mediated DNA reactivation. Our studies showed that recombinants contain a patchwork of DNA, with the number of exchanges increasing with passage. Further passage also selected for TianTan DNA and correlated with increased plaque size. The recombinants produced through a single round of coinfection contain a disproportionate number of short conversion tracks (<1 kbp) and exhibited 1 exchange per 12 kbp, close to the ∼1 per 8 kbp in the literature. One by-product of this study was that rare mutations were also detected; VACV replication produces ∼1×10(-8) mutation per nucleotide copied per cycle of replication and ∼1 large (21 kbp) deletion per 70 rounds of passage. Viruses produced using DNA reactivation appeared no different from recombinants produced using ordinary methods. An attractive feature of this approach is that when it is combined with selection for a particular phenotype, it provides a way of mapping and dissecting more complex virus traits. IMPORTANCE When two closely related viruses coinfect the same cell, they can swap genetic information through a process called recombination. Recombination produces new viruses bearing different combinations of genes, and it plays an important role in virus evolution. Poxviruses are a family of viruses that includes variola (or smallpox) virus, and although poxviruses are known to recombine, no one has previously mapped the patterns of DNAs exchanged between viruses. We coinfected cells with two different vaccinia poxviruses, isolated the progeny, and sequenced them. We show that poxvirus recombination is a very accurate process that assembles viruses containing DNA copied from both parents. In a single round of infection, DNA is swapped back and forth ∼18 times per genome to make recombinant viruses that are a mosaic of the two parental DNAs. This mixes many different genes in complex combinations and illustrates how recombination can produce viruses with greatly altered disease potential.
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Ibrahim N, Wicklund A, Jamin A, Wiebe MS. Barrier to autointegration factor (BAF) inhibits vaccinia virus intermediate transcription in the absence of the viral B1 kinase. Virology 2013; 444:363-73. [PMID: 23891157 DOI: 10.1016/j.virol.2013.07.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/01/2013] [Accepted: 07/02/2013] [Indexed: 11/16/2022]
Abstract
Barrier to autointegration factor (BAF/BANF1) is a cellular DNA-binding protein found in the nucleus and cytoplasm. Cytoplasmic BAF binds to foreign DNA and can act as a defense against vaccinia DNA replication. To evade BAF, vaccinia expresses the B1 kinase, which phosphorylates BAF and blocks its ability to bind DNA. Interestingly, B1 is also needed for viral intermediate gene expression via an unknown mechanism. Therefore, we evaluated the impact of B1-BAF signaling on vaccinia transcription. Strikingly, the decrease in vaccinia transcription caused by loss of B1 can be rescued by depletion of BAF. The repressive action of BAF is greatest on a viral promoter, and is more modest when non-vaccinia promoters are employed, which suggests BAF acts in a gene specific manner. These studies expand our understanding of the role of the B1 kinase during infection and provide the first evidence that BAF is a defense against viral gene expression.
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Affiliation(s)
- Nouhou Ibrahim
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
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Siciliano NA, Huang L, Eisenlohr LC. Recombinant poxviruses: versatile tools for immunological assays. Methods Mol Biol 2013; 960:219-245. [PMID: 23329491 DOI: 10.1007/978-1-62703-218-6_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The study of antigen processing and presentation is critical to our understanding of the mechanisms that govern immune surveillance. A typical requirement of assays designed to examine antigen processing and presentation is the de novo biosynthesis of a model antigen. Historically, Vaccinia virus (VACV), a poxvirus closely related to Cowpox, has enjoyed widespread use for this purpose. Recombinant poxvirus-based expression has a number of advantages over other systems. Poxviruses accommodate the insertion of large pieces of recombinant DNA into their genome, and recombination and selection are relatively efficient. Poxviruses readily infect a variety of cell types, and they drive rapid and high levels of antigen expression. Additionally, they can be utilized in a variety of assays to study both MHC class I-restricted and MHC class II-restricted antigen processing and presentation. Ultimately, the numerous advantages of poxvirus recombinants have made the Vaccinia expression system a mainstay in the study of processing and presentation over the past two decades. In an attempt to address one shortcoming of VACV while simultaneously retaining the benefits inherent to poxviruses, our laboratory has begun to engineer recombinant Ectromelia viruses. Ectromelia virus, or mousepox, is a natural pathogen of murine cells and performing experiments in the context of a natural host-pathogen relationship may elucidate unknown factors that influence epitope generation and host response. This chapter describes several recombinant poxvirus system protocols used to study both MHC class I and class II antigen processing and presentation, as well as provides insight and troubleshooting techniques to improve the reproducibility and fidelity of these experiments.
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Affiliation(s)
- Nicholas A Siciliano
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
| | - Lan Huang
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
| | - Laurence C Eisenlohr
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA.
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Identification of a pyridopyrimidinone inhibitor of orthopoxviruses from a diversity-oriented synthesis library. J Virol 2011; 86:2632-40. [PMID: 22205744 DOI: 10.1128/jvi.05416-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Orthopoxviruses include the prototypical vaccinia virus, the emerging infectious agent monkeypox virus, and the potential biothreat variola virus (the causative agent of smallpox). There is currently no FDA-approved drug for humans infected with orthopoxviruses. We screened a diversity-oriented synthesis library for new scaffolds with activity against vaccinia virus. This screen identified a nonnucleoside analog that blocked postreplicative intermediate and late gene expression. Viral genome replication was unaffected, and inhibition could be elicited late in infection and persisted upon drug removal. Sequencing of drug-resistant viruses revealed mutations predicted to be on the periphery of the highly conserved viral RNA polymerase large subunit. Consistent with this, the compound had broad-spectrum activity against orthopoxviruses in vitro. These findings indicate that novel chemical synthesis approaches are a potential source for new infectious disease therapeutics and identify a potentially promising candidate for development to treat orthopoxvirus-infected individuals.
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Boyle KA, Stanitsa ES, Greseth MD, Lindgren JK, Traktman P. Evaluation of the role of the vaccinia virus uracil DNA glycosylase and A20 proteins as intrinsic components of the DNA polymerase holoenzyme. J Biol Chem 2011; 286:24702-13. [PMID: 21572084 PMCID: PMC3137046 DOI: 10.1074/jbc.m111.222216] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 05/09/2011] [Indexed: 01/04/2023] Open
Abstract
The vaccinia virus DNA polymerase is inherently distributive but acquires processivity by associating with a heterodimeric processivity factor comprised of the viral A20 and D4 proteins. D4 is also an enzymatically active uracil DNA glycosylase (UDG). The presence of an active repair protein as an essential component of the polymerase holoenzyme is a unique feature of the replication machinery. We have shown previously that the A20-UDG complex has a stoichiometry of ∼1:1, and our data suggest that A20 serves as a bridge between polymerase and UDG. Here we show that conserved hydrophobic residues in the N' terminus of A20 are important for its binding to UDG. Our data argue against the assembly of D4 into higher order multimers, suggesting that the processivity factor does not form a toroidal ring around the DNA. Instead, we hypothesize that the intrinsic, processive DNA scanning activity of UDG tethers the holoenzyme to the DNA template. The inclusion of UDG as an essential holoenzyme component suggests that replication and base excision repair may be coupled. Here we show that the DNA polymerase can utilize dUTP as a substrate in vitro. Moreover, uracil moieties incorporated into the nascent strand during holoenzyme-mediated DNA synthesis can be excised by the viral UDG present within this holoenzyme, leaving abasic sites. Finally, we show that the polymerase stalls upon encountering an abasic site in the template strand, indicating that, like many replicative polymerases, the poxviral holoenzyme cannot perform translesion synthesis across an abasic site.
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Affiliation(s)
- Kathleen A. Boyle
- From the Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Eleni S. Stanitsa
- From the Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Matthew D. Greseth
- From the Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jill K. Lindgren
- From the Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Paula Traktman
- From the Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Gammon DB, Gowrishankar B, Duraffour S, Andrei G, Upton C, Evans DH. Vaccinia virus-encoded ribonucleotide reductase subunits are differentially required for replication and pathogenesis. PLoS Pathog 2010; 6:e1000984. [PMID: 20628573 PMCID: PMC2900304 DOI: 10.1371/journal.ppat.1000984] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 06/03/2010] [Indexed: 11/19/2022] Open
Abstract
Ribonucleotide reductases (RRs) are evolutionarily-conserved enzymes that catalyze the rate-limiting step during dNTP synthesis in mammals. RR consists of both large (R1) and small (R2) subunits, which are both required for catalysis by the R12R22 heterotetrameric complex. Poxviruses also encode RR proteins, but while the Orthopoxviruses infecting humans [e.g. vaccinia (VACV), variola, cowpox, and monkeypox viruses] encode both R1 and R2 subunits, the vast majority of Chordopoxviruses encode only R2 subunits. Using plaque morphology, growth curve, and mouse model studies, we investigated the requirement of VACV R1 (I4) and R2 (F4) subunits for replication and pathogenesis using a panel of mutant viruses in which one or more viral RR genes had been inactivated. Surprisingly, VACV F4, but not I4, was required for efficient replication in culture and virulence in mice. The growth defects of VACV strains lacking F4 could be complemented by genes encoding other Chordopoxvirus R2 subunits, suggesting conservation of function between poxvirus R2 proteins. Expression of F4 proteins encoding a point mutation predicted to inactivate RR activity but still allow for interaction with R1 subunits, caused a dominant negative phenotype in growth experiments in the presence or absence of I4. Co-immunoprecipitation studies showed that F4 (as well as other Chordopoxvirus R2 subunits) form hybrid complexes with cellular R1 subunits. Mutant F4 proteins that are unable to interact with host R1 subunits failed to rescue the replication defect of strains lacking F4, suggesting that F4-host R1 complex formation is critical for VACV replication. Our results suggest that poxvirus R2 subunits form functional complexes with host R1 subunits to provide sufficient dNTPs for viral replication. Our results also suggest that R2-deficient poxviruses may be selective oncolytic agents and our bioinformatic analyses provide insights into how poxvirus nucleotide metabolism proteins may have influenced the base composition of these pathogens. Efficient genome replication is central to the virulence of all DNA viruses, including poxviruses. To ensure replication efficiency, many of the more virulent poxviruses encode their own nucleotide metabolism machinery, including ribonucleotide reductase (RR) enzymes, which act to provide ample DNA precursors for replication. RR enzymes require both large (R1) and small (R2) subunit proteins for activity. Curiously, some poxviruses only encode R2 subunits. Other poxviruses, such as the smallpox vaccine strain, vaccinia virus (VACV), encode both R1 and R2 subunits. We report here that the R2, but not the R1, subunit of VACV RR is required for efficient replication and virulence. We also provide evidence that several poxvirus R2 proteins form novel complexes with host R1 subunits and this interaction is required for efficient VACV replication in primate cells. Our study explains why some poxviruses only encode R2 subunits and identifies a role for these proteins in poxvirus pathogenesis. Furthermore, we provide evidence that mutant poxviruses unable to generate R2 proteins may become entirely dependent upon host RR activity. This may restrict their replication to cells that over-express RR proteins such as cancer cells, making them potential therapeutics for human malignancies.
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Affiliation(s)
- Don B. Gammon
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Branawan Gowrishankar
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Sophie Duraffour
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Graciela Andrei
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Chris Upton
- Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - David H. Evans
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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Attenuation of vaccinia virus by the expression of human Flt3 ligand. Virol J 2010; 7:109. [PMID: 20504356 PMCID: PMC2883979 DOI: 10.1186/1743-422x-7-109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 05/26/2010] [Indexed: 11/10/2022] Open
Abstract
Background Vaccinia virus, one of the best known members of poxvirus family, has a wide host range both in vivo and in vitro. The expression of Flt3 ligand (FL) by recombinant vaccinia virus (rVACV) highly influenced properties of the virus in dependence on the level of expression. Results High production of FL driven by the strong synthetic promoter decreased the growth of rVACV in macrophage cell line J774.G8 in vitro as well as its multiplication in vivo when inoculated in mice. The inhibition of replication in vivo was mirrored in low levels of antibodies against vaccinia virus (anti-VACV) which nearly approached to the negative serum level in non-infected mice. Strong FL expression changed not only the host range of the recombinant but also the basic protein contents of virions. The major proteins - H3L and D8L - which are responsible for the virus binding to the cells, and 28 K protein that serves as a virulence factor, were changed in the membrane portion of P13-E/L-FL viral particles. The core virion fraction contained multiple larger, uncleaved proteins and a higher amount of cellular proteins compared to the control virus. The overexpression of FL also resulted in its incorporation into the viral core of P13-E/L-FL IMV particles. In contrary to the equimolar ratio of glycosylated and nonglycosylated FL forms found in cells transfected with the expression plasmid, the recombinant virus incorporated mainly the smaller, nonglycosylated FL. Conclusions It has been shown that the overexpression of the Flt3L gene in VACV results in the attenuation of the virus in vivo.
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Bhat S, Vaino AR, Szarek WA. Targeting of phosphonoacetate to the liver: Synthesis of a phosphonoacetate-trilactoside conjugate. Isr J Chem 2010. [DOI: 10.1560/8qka-dfyf-fj70-e1cx] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Mechanism of antiviral drug resistance of vaccinia virus: identification of residues in the viral DNA polymerase conferring differential resistance to antipoxvirus drugs. J Virol 2008; 82:12520-34. [PMID: 18842735 DOI: 10.1128/jvi.01528-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The acyclic nucleoside phosphonate (ANP) family of drugs shows promise as therapeutics for treating poxvirus infections. However, it has been questioned whether the utility of these compounds could be compromised through the intentional genetic modification of viral sequences by bioterrorists or the selection of drug resistance viruses during the course of antiviral therapy. To address these concerns, vaccinia virus (strain Lederle) was passaged 40 times in medium containing an escalating dose of (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)-2,6-diaminopurine [(S)-HPMPDAP], which selected for mutant viruses exhibiting a approximately 15-fold-increased resistance to the drug. (S)-HPMPDAP-resistant viruses were generated because this compound was shown to be one of the most highly selective and effective ANPs for the treatment of poxvirus infections. DNA sequence analysis revealed that these viruses encoded mutations in the E9L (DNA polymerase) gene, and marker rescue studies showed that the phenotype was produced by a combination of two (A684V and S851Y) substitution mutations. The effects of these mutations on drug resistance were tested against various ANPs, both separately and collectively, and compared with E9L A314T and A684V mutations previously isolated using selection for resistance to cidofovir, i.e., (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)cytosine]. These studies demonstrated a complex pattern of resistance, although as a general rule, the double-mutant viruses exhibited greater resistance to the deoxyadenosine than to deoxycytidine nucleotide analogs. The S851Y mutant virus exhibited a low level of resistance to dCMP analogues but high-level resistance to dAMP analogues and to 6-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine, which is considered to mimic the purine ring system. Notably, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-3-deazaadenine retained marked activity against most of these mutant viruses. In vitro studies showed that the A684V mutation partially suppressed a virus growth defect and mutator phenotype created by the S851Y mutation, but all of the mutant viruses still exhibited a variable degree of reduced virulence in a mouse intranasal challenge model. Infections caused by these drug-resistant viruses in mice were still treatable with higher concentrations of the ANPs. These studies have identified a novel mechanism for the development of mutator DNA polymerases and provide further evidence that antipoxviral therapeutic strategies would not readily be undermined by selection for resistance to ANP drugs.
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Becker MN, Obraztsova M, Kern ER, Quenelle DC, Keith KA, Prichard MN, Luo M, Moyer RW. Isolation and characterization of cidofovir resistant vaccinia viruses. Virol J 2008; 5:58. [PMID: 18479513 PMCID: PMC2397383 DOI: 10.1186/1743-422x-5-58] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Accepted: 05/14/2008] [Indexed: 12/04/2022] Open
Abstract
Background The emergence of drug resistant viruses, together with the possibility of increased virulence, is an important concern in the development of new antiviral compounds. Cidofovir (CDV) is a phosphonate nucleotide that is approved for use against cytomegalovirus retinitis and for the emergency treatment of smallpox or complications following vaccination. One mode of action for CDV has been demonstrated to be the inhibition of the viral DNA polymerase. Results We have isolated several CDV resistant (CDVR) vaccinia viruses through a one step process, two of which have unique single mutations within the DNA polymerase. An additional resistant virus isolate provides evidence of a second site mutation within the genome involved in CDV resistance. The CDVR viruses were 3–7 fold more resistant to the drug than the parental viruses. The virulence of the CDVR viruses was tested in mice inoculated intranasally and all were found to be attenuated. Conclusion Resistance to CDV in vaccinia virus can be conferred individually by at least two different mutations within the DNA polymerase gene. Additional genes may be involved. This one step approach for isolating resistant viruses without serial passage and in the presence of low doses of drug minimizes unintended secondary mutations and is applicable to other potential antiviral agents.
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Identification of novel antipoxviral agents: mitoxantrone inhibits vaccinia virus replication by blocking virion assembly. J Virol 2007; 81:13392-402. [PMID: 17928345 DOI: 10.1128/jvi.00770-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The bioterror threat of a smallpox outbreak in an unvaccinated population has mobilized efforts to develop new antipoxviral agents. By screening a library of known drugs, we identified 13 compounds that inhibited vaccinia virus replication at noncytotoxic doses. The anticancer drug mitoxantrone is unique among the inhibitors identified in that it has no apparent impact on viral gene expression. Rather, it blocks processing of viral structural proteins and assembly of mature progeny virions. The isolation of mitoxantrone-resistant vaccinia strains underscores that a viral protein is the likely target of the drug. Whole-genome sequencing of mitoxantrone-resistant viruses pinpointed missense mutations in the N-terminal domain of vaccinia DNA ligase. Despite its favorable activity in cell culture, mitoxantrone administered intraperitoneally at the maximum tolerated dose failed to protect mice against a lethal intranasal infection with vaccinia virus.
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Kornbluth RS, Smee DF, Sidwell RW, Snarsky V, Evans DH, Hostetler KY. Mutations in the E9L polymerase gene of cidofovir-resistant vaccinia virus strain WR are associated with the drug resistance phenotype. Antimicrob Agents Chemother 2006; 50:4038-43. [PMID: 16982794 PMCID: PMC1694007 DOI: 10.1128/aac.00380-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 05/08/2006] [Accepted: 09/07/2006] [Indexed: 11/20/2022] Open
Abstract
Cidofovir (CDV) is an effective drug against viruses of the Orthopoxviridae family and is active in vitro against variola virus, the cause of smallpox. However, CDV-resistant poxviruses can be generated by repeated in vitro passage in the presence of suboptimal concentrations of CDV. To determine if mutations in the E9L polymerase gene could confer resistance to this nucleoside analog, this gene was sequenced from CDV-resistant vaccinia virus and found to encode five amino acid changes, centered on an N-terminal region associated with 3'-->5' exonuclease activity. Transfer of this mutant E9L gene into wild-type vaccinia virus by marker rescue sufficed to confer the resistance phenotype. E9L polymerase mutations occurred sequentially during passage in CDV, and an H296Y/S338F double mutant that conferred an intermediate CDV resistance phenotype was identified. In vitro, the marker-rescued CDV-resistant vaccinia virus containing all five mutations grew nearly as well as wild-type vaccinia virus. However, the virulence of this virus for mice was reduced, as 10- to 30-fold more CDV-resistant virus than wild-type virus was required for lethality following intranasal challenge. Cidofovir and hexadecyloxypropyl-cidofovir gave partial protection to mice infected with the virus when used at 50 and 100 mg/kg of body weight given as single treatments 24 h after virus exposure, whereas 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl]purine (compound S2242) was completely protective at 25, 50, and 100 mg/kg/day when given daily for 5 days. These findings suggest that drug therapy for poxviruses may be complicated by drug resistance but that treatment of the infection with currently known compounds is possible.
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Affiliation(s)
- Richard S Kornbluth
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0676, USA
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Boyle KA, Arps L, Traktman P. Biochemical and genetic analysis of the vaccinia virus d5 protein: Multimerization-dependent ATPase activity is required to support viral DNA replication. J Virol 2006; 81:844-59. [PMID: 17093187 PMCID: PMC1797480 DOI: 10.1128/jvi.02217-06] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The vaccinia virus-encoded D5 protein is an essential ATPase involved in viral DNA replication. We have expanded the genotypic and phenotypic analysis of six temperature-sensitive (ts) D5 mutants (Cts17, Cts24, Ets69, Dts6389 [also referred to as Dts38], Dts12, and Dts56) and shown that at nonpermissive temperature all of the tsD5 viruses exhibit a dramatic reduction in DNA synthesis and virus production. For Cts17 and Cts24, this restriction reflects the thermolability of the D5 proteins. The Dts6389, Dts12, and Dts56 D5 proteins become insoluble at 39.7 degrees C, while the Ets69 D5 protein remains stable and soluble and retains the ability to oligomerize and hydrolyze ATP when synthesized at 39.7 degrees C. To investigate which structural features of D5 are important for its biological and biochemical activities, we generated targeted mutations in invariant residues positioned within conserved domains found within D5. Using a transient complementation assay that assessed the ability of D5 variants to sustain ongoing DNA synthesis during nonpermissive Cts24 infections, only a wtD5 allele supported DNA synthesis. Alleles of D5 containing targeted mutations within the Walker A or B domains, the superfamily III helicase motif C, or the AAA+ motif lacked biological competency. Furthermore, purified preparations of these variant proteins revealed that they all were defective in ATP hydrolysis. Multimerization of D5 appeared to be a prerequisite for enzymatic activity and required the Walker B domain, the AAA+ motif, and a region located upstream of the catalytic core. Finally, although multimerization and enzymatic activity are necessary for the biological competence of D5, they are not sufficient.
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Affiliation(s)
- Kathleen A Boyle
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Rd., BSB-273, Milwaukee, WI 53226, USA
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Andrei G, Gammon DB, Fiten P, De Clercq E, Opdenakker G, Snoeck R, Evans DH. Cidofovir resistance in vaccinia virus is linked to diminished virulence in mice. J Virol 2006; 80:9391-401. [PMID: 16973545 PMCID: PMC1617232 DOI: 10.1128/jvi.00605-06] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cidofovir [(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC)] is recognized as a promising drug for the treatment of poxvirus infections, but drug resistance can arise by a mechanism that is poorly understood. We show here that in vitro selection for high levels of resistance to HPMPC produces viruses encoding two substitution mutations in the virus DNA polymerase (E9L) gene. These mutations are located within the regions of the gene encoding the 3'-5' exonuclease (A314T) and polymerase (A684V) catalytic domains. These mutant viruses exhibited cross-resistance to other nucleoside phosphonate drugs, while they remained sensitive to other unrelated DNA polymerase inhibitors. Marker rescue experiments were used to transfer A314T and/or A684V alleles into a vaccinia virus Western Reserve strain. Either mutation alone could confer a drug resistance phenotype, although the degree of resistance was significantly lower than when virus encoded both mutations. The A684V substitution, but not the A314T change, also conferred a spontaneous mutator phenotype. All of the HPMPC-resistant recombinant viruses exhibited reduced virulence in mice, demonstrating that these E9L mutations are inextricably linked to reduced fitness in vivo. HPMPC, at a dose of 50 mg/kg of body weight/day for 5 days, still protected mice against intranasal challenge with the drug-resistant virus with A314T and A684V mutations. Our studies show that proposed drug therapies offer a reasonable likelihood of controlling orthopoxvirus infections, even if the viruses encode drug resistance markers.
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Affiliation(s)
- Graciela Andrei
- Laboratory of Virology, Katholieke Universiteit Leuven, Leuven B-3000, Belgium
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29
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Deng L, Dai P, Ding W, Granstein RD, Shuman S. Vaccinia virus infection attenuates innate immune responses and antigen presentation by epidermal dendritic cells. J Virol 2006; 80:9977-87. [PMID: 17005676 PMCID: PMC1617288 DOI: 10.1128/jvi.00354-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Accepted: 07/05/2006] [Indexed: 11/20/2022] Open
Abstract
Langerhans cells (LCs) are antigen-presenting cells in the skin that play sentinel roles in host immune defense by secreting proinflammatory molecules and activating T cells. Here we studied the interaction of vaccinia virus with XS52 cells, a murine epidermis-derived dendritic cell line that serves as a surrogate model for LCs. We found that vaccinia virus productively infects XS52 cells, yet this infection displays an atypical response to anti-poxvirus agents. Whereas adenosine N1-oxide blocked virus production and viral protein synthesis during a synchronous infection, cytosine arabinoside had no effect at concentrations sufficient to prevent virus replication in BSC40 monkey kidney cells. Vaccinia virus infection of XS52 cells not only failed to elicit the production of various cytokines, including tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, IL-10, IL-12 p40, alpha interferon (IFN-alpha), and IFN-gamma, it actively inhibited the production of proinflammatory cytokines TNF-alpha and IL-6 by XS52 cells in response to exogenous lipopolysaccharide (LPS) or poly(I:C). Infection with a vaccinia virus mutant lacking the E3L gene resulted in TNF-alpha secretion in the absence of applied stimuli. Infection of XS52 cells or BSC40 cells with the DeltaE3L virus, but not wild-type vaccinia virus, triggered proteolytic decay of IkappaBalpha. These results suggest a novel role for the E3L protein as an antagonist of the NF-kappaB signaling pathway. DeltaE3L-infected XS52 cells secreted higher levels of TNF-alpha and IL-6 in response to LPS and poly(I:C) than did cells infected with the wild-type virus. XS52 cells were productively infected by a vaccinia virus mutant lacking the K1L gene. DeltaK1L-infected cells secreted higher levels of TNF-alpha and IL-6 in response to LPS than wild-type virus-infected cells. Vaccinia virus infection of primary LCs harvested from mouse epidermis was nonpermissive, although a viral reporter protein was expressed in the infected LCs. Vaccinia virus infection of primary LCs strongly inhibited their capacity for antigen-specific activation of T cells. Our results highlight suppression of the skin immune response as a feature of orthopoxvirus infection.
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Affiliation(s)
- Liang Deng
- Molecular Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10021, USA
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30
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Luttge BG, Moyer RW. Suppressors of a host range mutation in the rabbitpox virus serpin SPI-1 map to proteins essential for viral DNA replication. J Virol 2005; 79:9168-79. [PMID: 15994811 PMCID: PMC1168772 DOI: 10.1128/jvi.79.14.9168-9179.2005] [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: 01/14/2023] Open
Abstract
The orthopoxvirus serpin SPI-1 is an intracellular serine protease inhibitor that is active against cathepsin G in vitro. Rabbitpox virus (RPV) mutants with deletions of the SPI-1 gene grow on monkey kidney cells (CV-1) but do not plaque on normally permissive human lung carcinoma cells (A549). This reduced-host-range (hr) phenotype suggests that SPI-1 may interact with cellular and/or other viral proteins. We devised a genetic screen for suppressors of SPI-1 hr mutations by first introducing a mutation into SPI-1 (T309R) at residue P14 of the serpin reactive center loop. The SPI-1 T309R serpin is inactive as a protease inhibitor in vitro. Introduction of the mutation into RPV leads to the same restricted hr phenotype as deletion of the SPI-1 gene. Second-site suppressors were selected by restoration of growth of the RPV SPI-1 T309R hr mutant on A549 cells. Both intragenic and extragenic suppressors of the T309R mutation were identified. One novel intragenic suppressor mutation, T309C, restored protease inhibition by SPI-1 in vitro. Extragenic suppressor mutations were mapped by a new procedure utilizing overlapping PCR products encompassing the entire genome in conjunction with marker rescue. One suppressor mutation, which also rendered the virus temperature sensitive for growth, mapped to the DNA polymerase gene (E9L). Several other suppressors mapped to gene D5R, an NTPase required for DNA replication. These results unexpectedly suggest that the host range function of SPI-1 may be associated with viral DNA replication by an as yet unknown mechanism.
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Affiliation(s)
- Benjamin G Luttge
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, P.O. Box 100266, Gainesville, FL 32610.
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31
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Boyle KA, Traktman P. Members of a novel family of mammalian protein kinases complement the DNA-negative phenotype of a vaccinia virus ts mutant defective in the B1 kinase. J Virol 2004; 78:1992-2005. [PMID: 14747564 PMCID: PMC369515 DOI: 10.1128/jvi.78.4.1992-2005.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Temperature-sensitive (ts) mutants of vaccinia virus defective in the B1 kinase demonstrate a conditionally lethal defect in DNA synthesis. B1 is the prototypic member of a new family of protein kinases (vaccinia virus-related kinases, or VRK) that possess distinctive B1-like sequence features within their catalytic motifs (R. J. Nichols and P. Traktman, J. Biol. Chem., in press). Given the striking sequence similarity between B1 and the VRK enzymes, we proposed that they might share overlapping substrate specificity. We therefore sought to determine whether the human and mouse VRK1 enzymes (hVRK1 and mVRK1, respectively) could complement a B1 deficiency in vivo. Recombinant ts2 viruses expressing hVRK1, mVRK1, or wild-type B1 were able to synthesize viral DNA at high temperature, but those expressing the more distantly related human casein kinase 1 alpha 2 could not. Complementation required the enzymatic activity of hVRK1, since a catalytically inactive allele of hVRK1 was unable to confer a temperature-insensitive phenotype. Interestingly, rescue of viral DNA synthesis was not coupled to the ability to phosphorylate H5, the only virus-encoded protein shown to be a B1 substrate in vivo. Expression of hVRK1 during nonpermissive ts2 infections restored virus production and plaque formation, whereas expression of mVRK1 resulted in an intermediate level of rescue. Taken together, these observations indicate that enzymatically active cellular VRK1 kinases can perform the function(s) of B1 required for genome replication, most likely due to overlapping specificity for cellular and/or viral substrates.
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Affiliation(s)
- Kathleen A Boyle
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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32
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Smee DF, Sidwell RW, Kefauver D, Bray M, Huggins JW. Characterization of wild-type and cidofovir-resistant strains of camelpox, cowpox, monkeypox, and vaccinia viruses. Antimicrob Agents Chemother 2002; 46:1329-35. [PMID: 11959564 PMCID: PMC127179 DOI: 10.1128/aac.46.5.1329-1335.2002] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cidofovir ([(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine] [HPMPC])-resistant forms of camelpox, cowpox, monkeypox, and vaccinia viruses were developed by prolonged passage in Vero 76 cells in the presence of drug. Eight- to 27-fold-higher concentrations of cidofovir were required to inhibit the resistant viruses than were needed to inhibit the wild-type (WT) viruses. Resistant viruses were characterized by determining their cross-resistance to other antiviral compounds, examining their different replication abilities in two cell lines, studying the biochemical basis of their drug resistance, and assessing the degrees of their virulence in mice. These viruses were cross resistant to cyclic HPMPC and, with the exception of vaccinia virus, to (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)adenine. Three of the four resistant cowpox and monkeypox viruses exhibited reduced abilities to infect and replicate in 3T3 cells compared to their abilities in Vero 76 cells. Compared to the WT virus polymers the resistant cowpox virus DNA polymerase was 8.5-fold less sensitive to inhibition by cidofovir diphosphate, the active form of the drug. Intracellular phosphorylation of [3H]cidofovir was not stimulated or inhibited by infection with resistant cowpox virus. In intranasally infected BALB/c mice, WT cowpox virus was 80-fold more virulent than the resistant virus. Cidofovir treatment (100 mg/kg of body weight, given one time only as early as 5 min after virus challenge) of a resistant cowpox virus infection could not protect mice from mortality. However, the drug prevented mortality in 80 to 100% of the mice treated with a single 100-mg/kg dose at 1, 2, 3, or 4 days after WT virus challenge. By application of these results to human orthopoxvirus infections, it is anticipated that resistant viruses may be untreatable with cidofovir but their virulence may be attenuated. Studies will need to be conducted with cidofovir-resistant monkeypox virus in monkeys to further support these hypotheses.
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Affiliation(s)
- Donald F Smee
- Institute for Antiviral Research, Utah State University, Logan, Utah 84322-5600, USA.
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Punjabi A, Boyle K, DeMasi J, Grubisha O, Unger B, Khanna M, Traktman P. Clustered charge-to-alanine mutagenesis of the vaccinia virus A20 gene: temperature-sensitive mutants have a DNA-minus phenotype and are defective in the production of processive DNA polymerase activity. J Virol 2001; 75:12308-18. [PMID: 11711621 PMCID: PMC116127 DOI: 10.1128/jvi.75.24.12308-12318.2001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the vaccinia virus DNA polymerase is inherently distributive, a highly processive form of the enzyme exists within the cytoplasm of infected cells (W. F. McDonald, N. Klemperer, and P. Traktman, Virology 234:168-175, 1997). In the accompanying report we outline the purification of the 49-kDa A20 protein as a stoichiometric component of the processive polymerase complex (N. Klemperer, W. McDonald, K. Boyle, B. Unger, and P. Traktman, J. Virol. 75:12298-12307, 2001). To complement this biochemical analysis, we undertook a genetic approach to the analysis of the structure and function of the A20 protein. Here we report the application of clustered charge-to-alanine mutagenesis of the A20 gene. Eight mutant viruses containing altered A20 alleles were isolated using this approach; two of these, tsA20-6 and tsA20-ER5, have tight temperature-sensitive phenotypes. At the nonpermissive temperature, neither virus forms macroscopic plaques and the yield of infectious virus is <1% of that obtained at the permissive temperature. Both viruses show a profound defect in the accumulation of viral DNA at the nonpermissive temperature, although both the A20 protein and DNA polymerase accumulate to wild-type levels. Cytoplasmic extracts prepared from cells infected with the tsA20 viruses show a defect in processive polymerase activity; they are unable to direct the formation of RFII product using a singly primed M13 template. In sum, these data indicate that the A20 protein plays an essential role in the viral life cycle and that viruses with A20 lesions exhibit a DNA(-) phenotype that is correlated with a loss in processive polymerase activity as assayed in vitro. The vaccinia virus A20 protein can, therefore, be considered a new member of the family of proteins (E9, B1, D4, and D5) with essential roles in vaccinia virus DNA replication.
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Affiliation(s)
- A Punjabi
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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McDonald WF, Klemperer N, Traktman P. Characterization of a processive form of the vaccinia virus DNA polymerase. Virology 1997; 234:168-75. [PMID: 9234958 DOI: 10.1006/viro.1997.8639] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have previously shown that the purified, 116-kDa DNA polymerase encoded by vaccinia virus is inherently distributive, synthesizing only a few nucleotides per template binding event under moderate reaction conditions (W. F. McDonald and P. Traktman, J. Biol. Chem. 269, 31190-31197). These properties would be incompatible with efficient DNA replication in vivo and suggest that the polymerase most probably interacts with accessory proteins that stabilize the template/polymerase interaction. Here we show that a highly processive form of the enzyme is indeed present with cytoplasmic lysates prepared from infected cells, and demonstrate that this form of the enzyme is likely to comprise the DNA polymerase in association with an early viral protein with a native molecular weight of approximately 48K.
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Affiliation(s)
- W F McDonald
- Department of Cell Biology, Cornell University Medical College, New York, New York 10021, USA
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Gardner J, Khanna R, Sherritt MA, Suhrbier A. Use of recombinant vaccinia to restimulate antigen specific human peripheral blood cytotoxic T lymphocytes. J Virol Methods 1997; 65:105-9. [PMID: 9128867 DOI: 10.1016/s0166-0934(96)02173-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A simple method is described for using recombinant vaccinia virus for restimulating human peripheral blood mononuclear cells (PBMC) to generate antigen specific CD8 + alpha beta cytotoxic T cell (CTL) effector populations. Effector PBMC were restimulated in vitro with a subpopulation of PBMC, which had been infected with recombinant vaccinia at very low multiplicities of infection in the absence of serum. This protocol avoided the vaccinia mediated overt cytopathic effects on the effector PBMC and generated bulk CTL cultures, which could be used for the identification of epitopes recognised by antigen specific CTL.
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Affiliation(s)
- J Gardner
- Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Australia
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Abstract
Comparison of the genomic organization of variola and vaccinia viruses has been carried out. Molecular factors of virulence of these viruses is the focus of this review. Possible roles of the genes of soluble cytokine receptors, complement control proteins, factors of virus replication, and dissemination in vivo for variola virus pathogenesis are discussed. The existence of "buffer" genes in the vaccinia virus genome is proposed.
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Affiliation(s)
- S N Shchelkunov
- Institute of Molecular Biology, State Research Center of Virology and Biotechnology, Vector, Koltsovo, Russia
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37
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McDonald WF, Traktman P. Vaccinia virus DNA polymerase. In vitro analysis of parameters affecting processivity. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47408-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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38
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Weisshart K, Kuo A, Hwang C, Kumura K, Coen D. Structural and functional organization of herpes simplex virus DNA polymerase investigated by limited proteolysis. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31714-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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