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Urbano AC, Ferreira N, Jordão N, Boinas F, Martins C, Ferreira F. Targeted mutagenesis of the β-strand DNA binding region of African swine fever virus histone-like protein (pA104R) impairs DNA-binding activity and antibody recognition. Antiviral Res 2024; 221:105784. [PMID: 38103699 DOI: 10.1016/j.antiviral.2023.105784] [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: 10/19/2023] [Revised: 12/11/2023] [Accepted: 12/13/2023] [Indexed: 12/19/2023]
Abstract
African Swine Fever (ASF) is a highly contagious disease caused by a double-stranded DNA virus (ASFV). Despite significant advances made over the last decade, issues such as residual virulence and absence of differentiating infected from vaccinated animals (DIVA) capacity remain an obstacle in the development of live attenuated vaccines (LAVs) against ASFV. It is, therefore, necessary to identify novel strategies to improve vaccine safety, by rational mutagenesis of virulence associated genes and generation of DIVA markers. ASFV encodes a HU (histone-like protein from E. coli strain U93) homolog protein, pA104R, which is involved in viral genome assembly and host immune recognition. A phylogenetic analysis revealed that pA104R is highly conserved among ASFV isolates, suggesting that it can be a good target for vaccine design. Thus, we selectively mutated the β-strand DNA binding region (BDR) of pA104R to attenuate its enzymatic activity, and identified and mutated several B-cell epitopes present in pA104R to generate a negative marker. Residues K64, K66, and R69 in the BDR were identified as relevant for pA104R activity, with double mutation of the first two showing additive attenuation. pA104R-reactive IgM and IgG epitopes were also identified in the bottom of the BDR, with selective mutagenesis drastically reducing antibody recognition and, when combined with mutations in the arm of the BDR, leading to a further reduction of DNA-binding activity. Interestingly, the immunodominant pA104R-reactive IgG epitope was mainly recognized by IgG1 suggesting that pA104R induces a dominant Th2 response. In sum, the rational mutagenesis can reduce pA104R-DNA binding activity and immune reactivity, providing a rationale for the development of an ASFV pA104R-based DIVA vaccine.
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Affiliation(s)
- Ana Catarina Urbano
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal
| | - Nicolas Ferreira
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal
| | - Nuno Jordão
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal
| | - Fernando Boinas
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal
| | - Carlos Martins
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal
| | - Fernando Ferreira
- CIISA - Centre for Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal; Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), Lisbon, Portugal.
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Chen Q, Li L, Guo S, Liu Z, Liu L, Tan C, Chen H, Wang X. African swine fever virus pA104R protein acts as a suppressor of type I interferon signaling. Front Microbiol 2023; 14:1169699. [PMID: 37089552 PMCID: PMC10119599 DOI: 10.3389/fmicb.2023.1169699] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 03/20/2023] [Indexed: 04/25/2023] Open
Abstract
This study evaluates the role of the late viral protein, pA104R, in African swine fever virus immunosuppression. ASFV-encoded pA104R is a putative histone-like protein that is highly conserved throughout different virulent and non-virulent isolates. Previous studies have demonstrated that pA104R plays a vital role in the ASFV replication cycle and is a potential target for antiviral therapy. Here, we demonstrated that pA104R is a potent antagonist of type I interferon signaling. IFN-stimulated response element activity and subsequent transcription of co-transfected and endogenous interferon-stimulated genes were attenuated by pA104R treatment in HEK-293 T cells. Immunoprecipitation assay and reciprocal pull-down showed that pA104R does not interact directly with STAT1, STAT2, or IRF9. However, pA104R could inhibit IFN signaling by attenuating STAT1 phosphorylation, and we identified the critical amino acid residues (R/H69,72 and K/R92,94,97) involved through the targeted mutation functional assays. Although pA104R is a histone-like protein localized to the nucleus, it did not inhibit IFN signaling through its DNA-binding capacity. In addition, activation of the ISRE promoter by IRF9-Stat2(TA), a STAT1-independent pathway, was inhibited by pA104R. Further results revealed that both the transcriptional activation and recruitment of transcriptional stimulators by interferon-stimulated gene factor 3 were not impaired. Although we failed to determine a mechanism for pA104R-mediated IFN signaling inhibition other than attenuating the phosphorylation of STAT1, these results might imply a possible involvement of epigenetic modification by ASFV pA104R. Taken together, these findings support that pA104R is an antagonist of type I interferon signaling, which may interfere with multiple signaling pathways.
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Affiliation(s)
- Qichao Chen
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Liang Li
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Shibang Guo
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Zhankui Liu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Lixinjie Liu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Chen Tan
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China
- International Research Center for Animal Disease, Ministry of Science and Technology of the People’s Republic of China, Wuhan, China
| | - Huanchun Chen
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China
- International Research Center for Animal Disease, Ministry of Science and Technology of the People’s Republic of China, Wuhan, China
| | - Xiangru Wang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
- Key Laboratory of Prevention & Control for African Swine Fever and Other Major Pig Diseases, Ministry of Agriculture and Rural Affairs, Wuhan, China
- International Research Center for Animal Disease, Ministry of Science and Technology of the People’s Republic of China, Wuhan, China
- *Correspondence: Xiangru Wang,
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Ramirez-Medina E, Vuono EA, Pruitt S, Rai A, Espinoza N, Valladares A, Silva E, Velazquez-Salinas L, Borca MV, Gladue DP. Deletion of African Swine Fever Virus Histone-like Protein, A104R from the Georgia Isolate Drastically Reduces Virus Virulence in Domestic Pigs. Viruses 2022; 14:v14051112. [PMID: 35632853 PMCID: PMC9146580 DOI: 10.3390/v14051112] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/10/2022] [Accepted: 05/17/2022] [Indexed: 02/06/2023] Open
Abstract
African swine fever virus (ASFV) is the etiological agent of a frequently lethal disease, ASF, affecting domestic and wild swine. Currently, ASF is causing a pandemic affecting pig production in Eurasia. There are no vaccines available, and therefore control of the disease is based on culling infected animals. We report here that deletion of the ASFV gene A104R, a virus histone-like protein, from the genome of the highly virulent ASFV-Georgia2010 (ASFV-G) strain induces a clear decrease in virus virulence when experimentally inoculated in domestic swine. A recombinant virus lacking the A104R gene, ASFV-G-∆A104R, was developed to assess the role of the A104R gene in disease production in swine. Domestic pigs were intramuscularly inoculated with 102 HAD50 of ASFV-G-∆A104R, and compared with animals that received a similar dose of virulent ASFV-G. While all ASFV-G inoculated animals developed a fatal form of the disease, animals receiving ASFV-G-∆A104R survived the challenge, remaining healthy during the 28-day observational period, with the exception of only one showing a protracted but fatal form of the disease. ASFV-G-∆A104R surviving animals presented protracted viremias with reduced virus titers when compared with those found in animals inoculated with ASFV-G, and all of them developed a strong virus-specific antibody response. This is the first report demonstrating that the A104R gene is involved in ASFV virulence in domestic swine, suggesting that A104R deletion may be used to increase the safety profile of currently experimental vaccines.
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Affiliation(s)
- Elizabeth Ramirez-Medina
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
| | - Elizabeth A. Vuono
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
- Department of Pathobiology and Population Medicine, Mississippi State University, P.O. Box 6100, Starkville, MS 39762, USA
| | - Sarah Pruitt
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
| | - Ayushi Rai
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
- Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN 37830, USA
| | - Nallely Espinoza
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
| | - Alyssa Valladares
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
- College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
| | - Ediane Silva
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
| | - Lauro Velazquez-Salinas
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
| | - Manuel V. Borca
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
- Correspondence: (M.V.B.); (D.P.G.)
| | - Douglas P. Gladue
- Plum Island Animal Disease Center, Agricultural Research Service, United States Department of Agriculture Greenport, Greenport, NY 11944, USA; (E.R.-M.); (E.A.V.); (S.P.); (A.R.); (N.E.); (A.V.); (E.S.); (L.V.-S.)
- Correspondence: (M.V.B.); (D.P.G.)
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The structural basis of African swine fever virus pA104R binding to DNA and its inhibition by stilbene derivatives. Proc Natl Acad Sci U S A 2020; 117:11000-11009. [PMID: 32358196 DOI: 10.1073/pnas.1922523117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
African swine fever virus (ASFV) is a highly contagious nucleocytoplasmic large DNA virus (NCLDV) that causes nearly 100% mortality in swine. The development of effective vaccines and drugs against this virus is urgently needed. pA104R, an ASFV-derived histone-like protein, shares sequence and functional similarity with bacterial HU/IHF family members and is essential for viral replication. Herein, we solved the crystal structures of pA104R in its apo state as well as in complex with DNA. Apo-pA104R forms a homodimer and folds into an architecture conserved in bacterial heat-unstable nucleoid proteins/integration host factors (HUs/IHFs). The pA104R-DNA complex structure, however, uncovers that pA104R has a DNA binding pattern distinct from its bacterial homologs, that is, the β-ribbon arms of pA104R stabilize DNA binding by contacting the major groove instead of the minor groove. Mutations of the basic residues at the base region of the β-strand DNA binding region (BDR), rather than those in the β-ribbon arms, completely abolished DNA binding, highlighting the major role of the BDR base in DNA binding. An overall DNA bending angle of 93.8° is observed in crystal packing of the pA104R-DNA complex structure, which is close to the DNA bending angle in the HU-DNA complex. Stilbene derivatives SD1 and SD4 were shown to disrupt the binding between pA104R and DNA and inhibit the replication of ASFV in primary porcine alveolar macrophages. Collectively, these results reveal the structural basis of pA104R binding to DNA highlighting the importance of the pA104R-DNA interaction in the ASFV replication cycle and provide inhibitor leads for ASFV chemotherapy.
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Karger A, Pérez-Núñez D, Urquiza J, Hinojar P, Alonso C, Freitas FB, Revilla Y, Le Potier MF, Montoya M. An Update on African Swine Fever Virology. Viruses 2019; 11:v11090864. [PMID: 31533244 PMCID: PMC6784044 DOI: 10.3390/v11090864] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/05/2019] [Accepted: 09/11/2019] [Indexed: 02/06/2023] Open
Abstract
Animal diseases constitute a continuing threat to animal health, food safety, national economy, and the environment. Among those, African swine fever (ASF) is one of the most devastating viruses affecting pigs and wild suids due to the lack of vaccine or effective treatment. ASF is endemic in countries in sub-Saharan Africa, but since its introduction to the Caucasus region in 2007, a highly virulent strain of ASF virus (ASFV) has continued to circulate and spread into Eastern Europe and Russia, and most recently into Western Europe, China, and various countries of Southeast Asia. Given the importance of this disease, this review will highlight recent discoveries in basic virology with special focus on proteomic analysis, replication cycle, and some recent data on genes involved in cycle progression and viral–host interactions, such as I215L (E2 ubiquitin-conjugating enzyme), EP402R (CD2v), A104R (histone-like protein), QP509L, and Q706L (RNA helicases) or P1192R (Topoisomerase II). Taking into consideration the large DNA genome of ASFV and its complex interactions with the host, more studies and new approaches are to be taken to understand the basic virus–host interaction for ASFV. Proteomic studies are just paving the way for future research.
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Affiliation(s)
- Axel Karger
- Institute of Molecular Virology and Cell Biology, Friedrich Loeffler Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany;
| | - Daniel Pérez-Núñez
- Virology Department, Centro Biología Molecular Severo Ochoa, CSIC-UAM, 28049 Madrid, Spain; (D.P.-N.); (Y.R.)
| | - Jesús Urquiza
- INIA, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28040 Madrid, Spain; (J.U.); (P.H.); (C.A.)
| | - Patricia Hinojar
- INIA, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28040 Madrid, Spain; (J.U.); (P.H.); (C.A.)
| | - Covadonga Alonso
- INIA, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28040 Madrid, Spain; (J.U.); (P.H.); (C.A.)
| | - Ferdinando B. Freitas
- Centre for Interdisciplinary Research in Animal Health (CIISA), Faculty of Veterinary Medicine, University of Lisbon, 1649-004 Lisboa, Portugal;
| | - Yolanda Revilla
- Virology Department, Centro Biología Molecular Severo Ochoa, CSIC-UAM, 28049 Madrid, Spain; (D.P.-N.); (Y.R.)
| | - Marie-Frédérique Le Potier
- ANSES, Laboratoire de Ploufragan/Plouzané/Niort, Unité Virologie Immunologie Porcines, Anses, 22440 Ploufragan, France;
| | - Maria Montoya
- Centro de Investigaciones Biológicas (CIB-CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
- Correspondence:
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Freitas FB, Simões M, Frouco G, Martins C, Ferreira F. Towards the Generation of an ASFV-pA104R DISC Mutant and a Complementary Cell Line-A Potential Methodology for the Production of a Vaccine Candidate. Vaccines (Basel) 2019; 7:E68. [PMID: 31323824 PMCID: PMC6789577 DOI: 10.3390/vaccines7030068] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/06/2019] [Accepted: 07/15/2019] [Indexed: 12/13/2022] Open
Abstract
African swine fever (ASF) is a fatal viral disease of domestic swine and wild boar, considered one of the main threats for global pig husbandry. Despite enormous efforts, to date, neither the classical vaccine formulations nor the use of protein subunits proved to be efficient to prevent this disease. Under this scenario, new strategies have been proposed including the development of disabled infectious single cycle (DISC) or replication-defective mutants as potential immunizing agents against the ASF virus (ASFV). In this study, we describe the methodology to generate an ASFV-DISC mutant by homologous recombination, lacking the A104R gene, which was replaced by the selection marker (GUS gene). The recombinant viruses were identified when the infected cells acquired a blue color in the presence of X-Gluc (100 µg/mL), which is the substrate for the GUS gene. Since these viral particles result from loss-of-function mutations, being unable to replicate, helper-cell lines expressing the viral pA104R protein were produced. Vero and COS-1 cell lines were transfected by different methods, both physical and chemical, in order to stably express the ASFV-pA104R. Best results were obtained by using Lipofectamine 2000 and Nucleofection methodology of Vero with the pIRESneo vector and by using Flp-FRT site-directed recombination technology system in Flp-In CV-1 cells (transformed COS-1 cells with a single integration site in a transcriptional active region). In order to ensure an efficient and stable integration of the viral ORF on the host cellular genome, the maintenance of the insert was verified by PCR and its expression by immunofluorescence and immunoblot analysis. Although the isolation of the recombinant virus was not achieved, the confirmation of ASFV-ΔA104R sequence, and the detection of the recombinant mutant through three passages, suggest that this approach is feasible and could be a potential strategy to generate safe and efficient DISC vaccine candidates.
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Affiliation(s)
- Ferdinando B Freitas
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Margarida Simões
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
- Laboratório de Virologia, Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Quinta do Marquês, 2780-157 Oeiras, Portugal
| | - Gonçalo Frouco
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Carlos Martins
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Fernando Ferreira
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
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DNA-Binding Properties of African Swine Fever Virus pA104R, a Histone-Like Protein Involved in Viral Replication and Transcription. J Virol 2017; 91:JVI.02498-16. [PMID: 28381576 DOI: 10.1128/jvi.02498-16] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 03/28/2017] [Indexed: 12/14/2022] Open
Abstract
African swine fever virus (ASFV) codes for a putative histone-like protein (pA104R) with extensive sequence homology to bacterial proteins that are implicated in genome replication and packaging. Functional characterization of purified recombinant pA104R revealed that it binds to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) over a wide range of temperatures, pH values, and salt concentrations and in an ATP-independent manner, with an estimated binding site size of about 14 to 16 nucleotides. Using site-directed mutagenesis, the arginine located in pA104R's DNA-binding domain, at position 69, was found to be relevant for efficient DNA-binding activity. Together, pA104R and ASFV topoisomerase II (pP1192R) display DNA-supercoiling activity, although none of the proteins by themselves do, indicating that the two cooperate in this process. In ASFV-infected cells, A104R transcripts were detected from 2 h postinfection (hpi) onward, reaching a maximum concentration around 16 hpi. pA104R was detected from 12 hpi onward, localizing with viral DNA replication sites and being found exclusively in the Triton-insoluble fraction. Small interfering RNA (siRNA) knockdown experiments revealed that pA104R plays a critical role in viral DNA replication and gene expression, with transfected cells showing lower viral progeny numbers (up to a reduction of 82.0%), lower copy numbers of viral genomes (-78.3%), and reduced transcription of a late viral gene (-47.6%). Taken together, our results strongly suggest that pA104R participates in the modulation of viral DNA topology, probably being involved in viral DNA replication, transcription, and packaging, emphasizing that ASFV mutants lacking the A104R gene could be used as a strategy to develop a vaccine against ASFV.IMPORTANCE Recently reintroduced in Europe, African swine fever virus (ASFV) causes a fatal disease in domestic pigs, causing high economic losses in affected countries, as no vaccine or treatment is currently available. Remarkably, ASFV is the only known mammalian virus that putatively codes for a histone-like protein (pA104R) that shares extensive sequence homology with bacterial histone-like proteins. In this study, we characterized the DNA-binding properties of pA104R, analyzed the functional importance of two conserved residues, and showed that pA104R and ASFV topoisomerase II cooperate and display DNA-supercoiling activity. Moreover, pA104R is expressed during the late phase of infection and accumulates in viral DNA replication sites, and its downregulation revealed that pA104R is required for viral DNA replication and transcription. These results suggest that pA104R participates in the modulation of viral DNA topology and genome packaging, indicating that A104R deletion mutants may be a good strategy for vaccine development against ASFV.
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Ghodsi S, Gharavi S, Ghadam P. Cloning the hbs gene from Bacillus subtilis and expression of the HBsu protein in Escherichia coli. IRANIAN JOURNAL OF MICROBIOLOGY 2010; 2:152-6. [PMID: 22347565 PMCID: PMC3279786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVES Bacillus subtilis HBsu is a 10 kD heat-stable protein shown to be involved in binding to DNA and is encoded by the hbs gene. Large-scale production for biochemical analysis is achieved through cloning and expression of the recombinant protein. MATERIALS AND METHODS This gene was amplified from B. subtilis ATCC 6633 using PCR and cloned into pET28a (+) expression vector. The construct was used to transform Escherichia coli BL21 (DE3). The expression of the protein was induced by the addition of 1mM IPTG. To confirm the expression of the cloned gene, SDS-PAGE was carried out and production of an approximately 11 KD recombinant tagged protein was confirmed for the cloned hbs gene. RESULTS AND CONCLUSION The identity of the recombinant HBsu was verified and characterized by SDS-PAGE which can then be utilized for further applications.
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Affiliation(s)
| | - S Gharavi
- Corresponding author: Sara Gharavi Ph.D. Address: Biology Department, Faculty of Sciences, Alzahra University, Vanak, Tehran, IR Iran. Tel: +98-2188044052-2709 (Ext), Fax: +98-2188058912, E-mail:
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9
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Berg CP, Schlosser SF, Neukirchen DKH, Papadakis C, Gregor M, Wesselborg S, Stein GM. Hepatitis C virus core protein induces apoptosis-like caspase independent cell death. Virol J 2009; 6:213. [PMID: 19951438 PMCID: PMC3224943 DOI: 10.1186/1743-422x-6-213] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 12/01/2009] [Indexed: 12/16/2022] Open
Abstract
Background Hepatitis C virus (HCV) associated liver diseases may be related to apoptotic processes. Thus, we investigated the role of different HCV proteins in apoptosis induction as well as their potency to interact with different apoptosis inducing agents. Methods and Results The use of a tightly adjustable tetracycline (Tet)-dependent HCV protein expression cell system with the founder osteosarcoma cell line U-2 OS allowed switch-off and on of the endogenous production of HCV proteins. Analyzed were cell lines expressing the HCV polyprotein, the core protein, protein complexes of the core, envelope proteins E1, E2 and p7, and non-structural proteins NS3 and NS4A, NS4B or NS5A and NS5B. Apoptosis was measured mainly by the detection of hypodiploid apoptotic nuclei in the absence or presence of mitomycin C, etoposide, TRAIL and an agonistic anti-CD95 antibody. To further characterize cell death induction, a variety of different methods like fluorescence microscopy, TUNEL (terminal deoxynucleotidyl transferase (TdT)-catalyzed deoxyuridinephosphate (dUTP)-nick end labeling) assay, Annexin V staining, Western blot and caspase activation assays were included into our analysis. Two cell lines expressing the core protein but not the total polyprotein exerted a strong apoptotic effect, while the other cell lines did not induce any or only a slight effect by measuring the hypodiploid nuclei. Cell death induction was caspase-independent since it could not be blocked by zVAD-fmk. Moreover, caspase activity was absent in Western blot analysis and fluorometric assays while typical apoptosis-associated morphological features like the membrane blebbing and nuclei condensation and fragmentation could be clearly observed by microscopy. None of the HCV proteins influenced the apoptotic effect mediated via the mitochondrial apoptosis pathway while only the core protein enhanced death-receptor-mediated apoptosis. Conclusion Our data showed a caspase-independent apoptosis-like effect of the core protein, which seems to be inhibited in the presence of further HCV proteins like the non structural (NS) proteins. This observation could be of relevance for the viral spread since induction of an apoptosis-like cell death by the core protein may have some impact on the release of the HCV particles from the host cell.
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Affiliation(s)
- Christoph P Berg
- Department of Internal Medicine I, Medical Clinic, University of Tübingen, Germany.
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10
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Abstract
African swine fever virus (ASFV) is a large, intracytoplasmically-replicating DNA arbovirus and the sole member of the family Asfarviridae. It is the etiologic agent of a highly lethal hemorrhagic disease of domestic swine and therefore extensively studied to elucidate the structures, genes, and mechanisms affecting viral replication in the host, virus-host interactions, and viral virulence. Increasingly apparent is the complexity with which ASFV replicates and interacts with the host cell during infection. ASFV encodes novel genes involved in host immune response modulation, viral virulence for domestic swine, and in the ability of ASFV to replicate and spread in its tick vector. The unique nature of ASFV has contributed to a broader understanding of DNA virus/host interactions.
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Affiliation(s)
- E R Tulman
- Department of Pathobiology and Veterinary Science, Center of Excellence for Vaccine Research, University of Connecticut, Storrs 06269, USA.
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11
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Kamashev D, Balandina A, Mazur AK, Arimondo PB, Rouviere-Yaniv J. HU binds and folds single-stranded DNA. Nucleic Acids Res 2007; 36:1026-36. [PMID: 18096614 PMCID: PMC2241890 DOI: 10.1093/nar/gkm667] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The nucleoid-associated protein HU plays an important role in bacterial nucleoid organization and is involved in numerous processes including transposition, recombination and DNA repair. We show here that HU binds specifically DNA containing mismatched region longer than 3 bp as well as DNA bulges. HU binds single-stranded DNA (ssDNA) in a binding mode that is reminiscent but different from earlier reported specific HU interactions with double-helical DNA lesions. An HU dimer requires 24 nt of ssDNA for initial binding, and 12 nt of ssDNA for each additional dimer binding. In the presence of equimolar amounts of HU dimer and DNA, the ssDNA molecule forms an U-loop (hairpin-like) around the protein, providing contacts with both sides of the HU body. This mode differs from the binding of the single-strand-binding protein (SSB) to ssDNA: in sharp contrast to SSB, HU binds ssDNA non-cooperatively and does not destabilize double-helical DNA. Furthermore HU has a strong preference for poly(dG), while binding to poly(dA) is the weakest. HU binding to ssDNA is probably important for its capacity to cover and protect bacterial DNA both intact and carrying lesions.
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Affiliation(s)
- Dmitri Kamashev
- Laboratoire de Physiologie Bacterienne, CNRS UPR 9073, Laboratoire de Biochimie Théorique, CNRS UPR 9080, Paris, France
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12
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Reis AL, Parkhouse RME, Penedos AR, Martins C, Leitão A. Systematic analysis of longitudinal serological responses of pigs infected experimentally with African swine fever virus. J Gen Virol 2007; 88:2426-2434. [PMID: 17698651 DOI: 10.1099/vir.0.82857-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The protective immune response to African swine fever virus (ASFV) includes both cellular and serological components. In this study, the role of antibodies in the pathogenicity and diagnosis of African swine fever (ASF) was explored. Accordingly, total and Ig isotype antibody responses against the 12 viral proteins previously demonstrated to be the main targets of serological immunity were evaluated in longitudinally collected sera from pigs infected experimentally with the non-pathogenic ASFV/NH/P68 isolate. Strong total IgG antibody responses were observed against viral proteins E183L/p54, K205R/'unassigned', A104R/histone-like and B602L/'unassigned'; therefore, IgM, IgG1 and IgG2 responses to these proteins were also determined. One protein stimulating IgM (K205R) may have practical potential for the detection of recently infected animals. There was a clear trend towards an IgG1 response to all of the proteins. This may reflect a dominant Th2-controlled immune response. In order to identify possible correlations between these serological responses and the pathogenesis of ASF, total IgG responses to the 12 recombinant proteins were compared in asymptomatic and chronically infected animals. For the proteins NP419L/DNA ligase, CP312R, B646L/p73, K196R/thymidine kinase and K205R, the antibody titres were significantly higher in animals developing lesions. One exception was the antibody response to the A104R/histone-like protein, which was higher in asymptomatic than in chronically infected pigs, suggesting that antibodies against this protein might be an indicator of an effective immune response or that this response is somehow involved in protection.
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Affiliation(s)
- Ana Luísa Reis
- Instituto Gulbenkian de Ciência, Apartado 14, 2781-901 Oeiras, Portugal
| | - R M E Parkhouse
- Instituto Gulbenkian de Ciência, Apartado 14, 2781-901 Oeiras, Portugal
| | | | - Carlos Martins
- Laboratório de Doenças Infecciosas, CIISA, Faculdade de Medicina Veterinária, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
| | - Alexandre Leitão
- Instituto de Investigação Científica Tropical, CVZ, CIISA, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal
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13
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Moore DM, Zsak L, Neilan JG, Lu Z, Rock DL. The African swine fever virus thymidine kinase gene is required for efficient replication in swine macrophages and for virulence in swine. J Virol 1998; 72:10310-5. [PMID: 9811782 PMCID: PMC110620 DOI: 10.1128/jvi.72.12.10310-10315.1998] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/1998] [Accepted: 09/02/1998] [Indexed: 11/20/2022] Open
Abstract
African swine fever virus (ASFV) replicates in the cytoplasm of infected cells and contains genes encoding a number of enzymes needed for DNA synthesis, including a thymidine kinase (TK) gene. Recombinant TK gene deletion viruses were produced by using two highly pathogenic isolates of ASFV through homologous recombination with an ASFV p72 promoter-beta-glucuronidase indicator cassette (p72GUS) flanked by ASFV sequences targeting the TK region. Attempts to isolate double-crossover TK gene deletion mutants on swine macrophages failed, suggesting a growth deficiency of TK- ASFV on macrophages. Two pathogenic ASFV isolates, ASFV Malawi and ASFV Haiti, partially adapted to Vero cells, were used successfully to construct TK deletion viruses on Vero cells. The selected viruses grew well on Vero cells, but both mutants exhibited a growth defect on swine macrophages at low multiplicities of infection (MOI), yielding 0.1 to 1.0% of wild-type levels. At high MOI, the macrophage growth defect was not apparent. The Malawi TK deletion mutant showed reduced virulence for swine, producing transient fevers, lower viremia titers, and reduced mortality. In contrast, 100% mortality was observed for swine inoculated with the TK+ revertant virus. Swine surviving TK- ASFV infection remained free of clinical signs of African swine fever following subsequent challenge with the parental pathogenic ASFV. The data indicate that the TK gene of ASFV is important for growth in swine macrophages in vitro and is a virus virulence factor in swine.
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Affiliation(s)
- D M Moore
- Plum Island Animal Disease Center, Agricultural Research Service, U. S. Department of Agriculture, Greenport, New York 11944-0848, USA.
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14
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Borca MV, Irusta PM, Kutish GF, Carillo C, Afonso CL, Burrage AT, Neilan JG, Rock DL. A structural DNA binding protein of African swine fever virus with similarity to bacterial histone-like proteins. Arch Virol 1996; 141:301-13. [PMID: 8634022 DOI: 10.1007/bf01718401] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Here we describe an African swine fever virus (ASFV) protein encoded by the open reading frame 5-AR that shares structural and functional similarities with the family of bacterial histone-like proteins which include histone-like DNA binding proteins, integration host factor, and Bacillus phage SPO1 transcription factor, TF1. The ASFV 5-AR gene was cloned by PCR and expressed in E. coli. Monospecific antiserum prepared to the 5-AR bacterial expression product specifically immunoprecipitated a protein of approximately 11.6 kDa from ASFV infected swine macrophages at late times post infection. Additionally, the 5-AR expression product was strongly recognized by ASFV convalescent pig serum, indicating its antigenicity during natural infection. Cloned p11.6 bound both double and single stranded DNA-cellulose columns. Consistent with a DNA binding function, immunoelectronmicroscopy localized p11.6 to the virion nucleoid, To our knowledge, p11.6 is the first bacterial histone-like DNA-binding protein found in an animal virus or eukaryotic cell system.
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Affiliation(s)
- M V Borca
- ARS, USDA, Plum Island Animal Disease Center, Greenport, New York 11944-0848, U.S.A
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15
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Oberto J, Rouviere-Yaniv J. Serratia marcescens contains a heterodimeric HU protein like Escherichia coli and Salmonella typhimurium. J Bacteriol 1996; 178:293-7. [PMID: 8550432 PMCID: PMC177653 DOI: 10.1128/jb.178.1.293-297.1996] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Homologs of the dimeric HU protein of Escherichia coli can be found in every prokaryotic organism that has been analyzed. In this work, we demonstrate that Serratia marcescens synthesizes two distinct HU subunits, like E. coli and Salmonella typhimurium, suggesting that the heterodimeric HU protein could be a common feature of enteric bacteria. A phylogenetic analysis of the HU-type proteins (HU and IHF) is presented, and a scheme for the origin of the hup genes and the onset of HU heterodimericity is suggested.
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Affiliation(s)
- J Oberto
- Laboratoire de Physiologie Bactérienne, Institut de Biologie Physico-chimique, Paris, France
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16
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Andera L, Geiduschek EP. Determinants of affinity and mode of DNA binding at the carboxy terminus of the bacteriophage SPO1-encoded type II DNA-binding protein, TF1. J Bacteriol 1994; 176:1364-73. [PMID: 8113176 PMCID: PMC205201 DOI: 10.1128/jb.176.5.1364-1373.1994] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The role of the carboxy-terminal amino acids of the bacteriophage SPO1-encoded type II DNA-binding protein, TF1, in DNA binding was analyzed. Chain-terminating mutations truncating the normally 99-amino-acid TF1 at amino acids 96, 97, and 98 were constructed, as were missense mutations substituting cysteine, arginine, and serine for phenylalanine at amino acid 97 and tryptophan for lysine at amino acid 99. The binding of the resulting proteins to a synthetic 44-bp binding site in 5-(hydroxymethyl)uracil DNA, to binding sites in larger SPO1 [5-(hydroxymethyl)uracil-containing] DNA fragments, and to thymine-containing homologous DNA was analyzed by gel retardation and also by DNase I and hydroxy radical footprinting. We conclude that the C tail up to and including phenylalanine at amino acid 97 is essential for DNA binding and that the two C-terminal amino acids, 98 and 99, are involved in protein-protein interactions between TF1 dimers bound to DNA.
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Affiliation(s)
- L Andera
- Department of Biology, University of California, San Diego, La Jolla 92093-0634
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17
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Abstract
In this review article we present a compilation of the proteins homologous to Escherichia coli HU: the HU-like family. Two of these, HU and IHF from E coli have been extensively characterized genetically and biochemically. Due to their DNA binding activities, these proteins confer a condensed shape to the chromosome and regulate the transcription of selected sets of its genes. The parallel between the dual function of the HU-like proteins and the roles described for eukaryotic histone and HMG proteins is striking, especially in the view that they are evolutionary unrelated.
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Affiliation(s)
- J Oberto
- Institut de Biologie Physico-Chimique, Paris, France
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