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Singh D, Oudit O, Hajtovic S, Sarbaugh D, Salis R, Adebowale T, James J, Spatz LA. Antibodies to an Epstein Barr Virus protein that cross-react with dsDNA have pathogenic potential. Mol Immunol 2021; 132:41-52. [PMID: 33545624 DOI: 10.1016/j.molimm.2021.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/07/2021] [Accepted: 01/17/2021] [Indexed: 01/02/2023]
Abstract
Pathogens such as the Epstein Barr virus (EBV) have long been implicated in the etiology of systemic lupus erythematosus (SLE). The Epstein Barr virus nuclear antigen I (EBNA-1) has been shown to play a role in the development of anti-nuclear antibodies characteristic of SLE. One mechanism by which EBV may play a role in SLE is molecular mimicry. We previously generated two monoclonal antibodies (mAbs) to EBNA-1 and demonstrated that they cross-react with double-stranded DNA (dsDNA). In the present study, we demonstrate that these mAbs have pathogenic potential. We show that they can bind to isolated rat glomeruli and that binding can be greatly diminished by pretreatment of glomeruli with DNase I, suggesting that these mAbs bind dsDNA in the kidney. We also demonstrate that these antibodies can deposit in the kidney when injected into mice and can induce proteinuria and elicit histopathological alterations consistent with glomerulonephritis. Finally, we show that these antibodies can cross-react with laminin and collagen IV in the extracellular matrix suggesting that direct binding to the glomerular basement membrane or mesangial matrix may also contribute to the antibody deposition in the kidney. In summary, our results indicate that EBNA-1 can elicit antibodies that cross-react with dsDNA, that can deposit in the kidney, and induce kidney damage. These results are significant because they support the role of a viral protein in SLE and lupus nephritis.
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Affiliation(s)
- Divya Singh
- The Molecular, Cellular, and Biomedical Sciences Department, The CUNY School of Medicine, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Omar Oudit
- The Department of Chemistry & Biochemistry, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Sabastian Hajtovic
- The CUNY School of Medicine, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Dylan Sarbaugh
- The Department of Biology, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Rafatu Salis
- The Department of Biology, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Temitayo Adebowale
- The Department of Biology, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Justin James
- The CUNY School of Medicine, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA
| | - Linda A Spatz
- The Molecular, Cellular, and Biomedical Sciences Department, The CUNY School of Medicine, The City College of New York, 160 Convent Avenue, New York, NY, 10031, USA.
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STUB1 is targeted by the SUMO-interacting motif of EBNA1 to maintain Epstein-Barr Virus latency. PLoS Pathog 2020; 16:e1008447. [PMID: 32176739 PMCID: PMC7105294 DOI: 10.1371/journal.ppat.1008447] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/30/2020] [Accepted: 03/01/2020] [Indexed: 12/31/2022] Open
Abstract
Latent Epstein-Barr virus (EBV) infection is strongly associated with several malignancies, including B-cell lymphomas and epithelial tumors. EBNA1 is a key antigen expressed in all EBV-associated tumors during latency that is required for maintenance of the EBV episome DNA and the regulation of viral gene transcription. However, the mechanism utilized by EBV to maintain latent infection at the levels of posttranslational regulation remains largely unclear. Here, we report that EBNA1 contains two SUMO-interacting motifs (SIM2 and SIM3), and mutation of SIM2, but not SIM3, dramatically disrupts the EBNA1 dimerization, while SIM3 contributes to the polySUMO2 modification of EBNA1 at lysine 477 in vitro. Proteomic and immunoprecipitation analyses further reveal that the SIM3 motif is required for the EBNA1-mediated inhibitory effects on SUMO2-modified STUB1, SUMO2-mediated degradation of USP7, and SUMO1-modified KAP1. Deletion of the EBNASIM motif leads to functional loss of both EBNA1-mediated viral episome maintenance and lytic gene silencing. Importantly, hypoxic stress induces the SUMO2 modification of EBNA1, and in turn the dissociation of EBNA1 with STUB1, KAP1 and USP7 to increase the SUMO1 modification of both STUB1 and KAP1 for reactivation of lytic replication. Therefore, the EBNA1SIM motif plays an essential role in EBV latency and is a potential therapeutic target against EBV-associated cancers. The Small Ubiquitin-related modifier (SUMO) modification of proteins is a reversible post-translational regulation involved in control of gene transcription, among other functions. Epstein-Barr virus (EBV) infects most people worldwide and contributes to the development of several types of cancers due to its ability to induce cell proliferation and survival. EBNA1 is expressed in all forms of EBV-associated tumors. In this study, we found that EBNA1 contains a SUMO-interacting motif (SIM) named EBNA1SIM, which is required for EBNA1 to exert inhibitory effects on a SUMO2-modified complex (SC2) including STUB1, KAP1 and USP7. Disruption of EBNA1SIM leads to loss of both EBNA1-mediated viral episome maintenance and lytic gene silencing. Importantly, hypoxia-mediated reactivation of viral lytic replication induces the EBNA1 dissociation from STUB1 in the SC2 complex. This discovery not only opens a new insight on the interplay between host and virus, but it also provides a therapeutic target specific against EBV-associated cancers.
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Structural Basis for Cooperative Binding of EBNA1 to the Epstein-Barr Virus Dyad Symmetry Minimal Origin of Replication. J Virol 2019; 93:JVI.00487-19. [PMID: 31142669 DOI: 10.1128/jvi.00487-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 05/21/2019] [Indexed: 12/11/2022] Open
Abstract
Epstein-Barr virus is associated with several human malignancies, including nasopharyngeal carcinoma, gastric cancer, and lymphoma. Latently infected cells carry a circularized EBV episome where the origin of replication (oriP) is comprised of two elements: the family of repeats (FR) and dyad symmetry (DS). The viral protein Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) binds to FR and DS to promote EBV episome maintenance and DNA replication during latent infection in proliferating cells. EBNA1 binding to the DS constitutes a minimal origin of DNA replication. Here we report the crystal structure of two EBNA1 DNA-binding domain dimers bound to a DS half-site. This structure shows that the DNA is smoothly bent, allowing for stabilizing interactions between the dimers. The dimer-dimer interface requires an intricate hydrogen bonding network involving residues R491 and D581. When this interface is disrupted, we note loss of stable dimer-dimer complex formation on the DNA, compromised oriP-containing plasmid replication in cells, and impaired recruitment of the MCM3 complex to the oriP Surface conservation analysis reveals that these residues are part of a larger conserved surface that may be critical for recruitment of replication machinery to the oriP Our results reveal a new region of EBNA1 critical for its activity and one that may be exploited by targeted small molecules to treat EBV-associated disease.IMPORTANCE Epstein-Barr virus (EBV) is a causative agent of various malignancies and may also contribute to autoimmune disease. The latent and episomal form of the virus is known to drive EBV-associated oncogenesis. Persistence of the viral episome in proliferating tumor cells requires the interaction of Epstein-Barr virus nuclear antigen 1 (EBNA1) with the viral origin of plasmid replication (oriP). The dyad symmetry (DS) element in oriP is the essential minimal replicator of oriP Here we report the X-ray crystal structure of EBNA1 bound to DS. The structure reveals a previous unrecognized interface formed between dimers of EBNA1 necessary for cooperative DNA binding, recruitment of cellular replication machinery, and replication function. These findings provide new insights into the mechanism of EBNA1 function at the replication origin and new opportunities to inhibit EBV latent infection and pathogenesis.
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Jiang L, Xie C, Lung HL, Lo KW, Law GL, Mak NK, Wong KL. EBNA1-targeted inhibitors: Novel approaches for the treatment of Epstein-Barr virus-associated cancers. Am J Cancer Res 2018; 8:5307-5319. [PMID: 30555548 PMCID: PMC6276081 DOI: 10.7150/thno.26823] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 08/14/2018] [Indexed: 12/11/2022] Open
Abstract
Epstein-Barr virus (EBV) infects more than 90% of humans worldwide and establishes lifelong latent infection in the hosts. It is closely associated with endemic forms of a wide range of human cancers and directly contributes to the formation of some. Despite its critical role in cancer development, no EBV- or EBV latent protein-targeted therapy is available. The EBV-encoded latent protein, Epstein-Barr nuclear antigen 1 (EBNA1), is expressed in all EBV-associated tumors and acts as the only latent protein in some of these tumors. This versatile protein functions in the maintenance, replication, and segregation of the EBV genome and can therefore serve as an attractive therapeutic target to treat EBV-associated cancers. In the last decades, efforts have been made for designing specific EBNA1 inhibitors to decrease EBNA1 expression or interfere with EBNA1-dependent functions. In this review, we will briefly introduce the salient features of EBNA1, summarize its functional domains, and focus on the recent developments in the identification and design of EBNA1 inhibitors related to various EBNA1 domains as well as discuss their comparative merits.
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El-Sharkawy A, Al Zaidan L, Malki A. Epstein-Barr Virus-Associated Malignancies: Roles of Viral Oncoproteins in Carcinogenesis. Front Oncol 2018; 8:265. [PMID: 30116721 PMCID: PMC6082928 DOI: 10.3389/fonc.2018.00265] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 06/27/2018] [Indexed: 12/19/2022] Open
Abstract
The Epstein–Barr virus (EBV) is the first herpesvirus identified to be associated with human cancers known to infect the majority of the world population. EBV-associated malignancies are associated with a latent form of infection, and several of the EBV-encoded latent proteins are known to mediate cellular transformation. These include six nuclear antigens and three latent membrane proteins (LMPs). In lymphoid and epithelial tumors, viral latent gene expressions have distinct pattern. In both primary and metastatic tumors, the constant expression of latent membrane protein 2A (LMP2A) at the RNA level suggests that this protein is the key player in the EBV-associated tumorigenesis. While LMP2A contributing to the malignant transformation possibly by cooperating with the aberrant host genome. This can be done in part by dysregulating signaling pathways at multiple points, notably in the cell cycle and apoptotic pathways. Recent studies also have confirmed that LMP1 and LMP2 contribute to carcinoma progression and that this may reflect the combined effects of these proteins on activation of multiple signaling pathways. This review article aims to investigate the aforementioned EBV-encoded proteins that reveal established roles in tumor formation, with a greater emphasis on the oncogenic LMPs (LMP1 and LMP2A) and their roles in dysregulating signaling pathways. It also aims to provide a quick look on the six members of the EBV nuclear antigens and their roles in dysregulating apoptosis.
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Affiliation(s)
- Ahmed El-Sharkawy
- Human Molecular Genetics Laboratory, Institute of Genetics and Biophysics "A. Buzzati-Traverso" (IGB)-CNR, Naples, Italy.,Biomolecular Science Programme, Università Degli Studi Della Campania "Luigi Vanvitelli", Naples, Italy
| | - Lobna Al Zaidan
- Biomedical Science Department, College of Health Sciences, Qatar University, Doha, Qatar
| | - Ahmed Malki
- Biomedical Science Department, College of Health Sciences, Qatar University, Doha, Qatar
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Structural and Functional Basis for an EBNA1 Hexameric Ring in Epstein-Barr Virus Episome Maintenance. J Virol 2017; 91:JVI.01046-17. [PMID: 28701406 DOI: 10.1128/jvi.01046-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 07/09/2017] [Indexed: 12/14/2022] Open
Abstract
Epstein-Barr virus (EBV) establishes a stable latent infection that can persist for the life of the host. EBNA1 is required for the replication, maintenance, and segregation of the latent episome, but the structural features of EBNA1 that confer each of these functions are not completely understood. Here, we have solved the X-ray crystal structure of an EBNA1 DNA-binding domain (DBD) and discovered a novel hexameric ring oligomeric form. The oligomeric interface pivoted around residue T585 as a joint that links and stabilizes higher-order EBNA1 complexes. Substitution mutations around the interface destabilized higher-order complex formation and altered the cooperative DNA-binding properties of EBNA1. Mutations had both positive and negative effects on EBNA1-dependent DNA replication and episome maintenance with OriP. We found that one naturally occurring polymorphism in the oligomer interface (T585P) had greater cooperative DNA binding in vitro, minor defects in DNA replication, and pronounced defects in episome maintenance. The T585P mutant was compromised for binding to OriP in vivo as well as for assembling the origin recognition complex subunit 2 (ORC2) and trimethylated histone 3 lysine 4 (H3K4me3) at OriP. The T585P mutant was also compromised for forming stable subnuclear foci in living cells. These findings reveal a novel oligomeric structure of EBNA1 with an interface subject to naturally occurring polymorphisms that modulate EBNA1 functional properties. We propose that EBNA1 dimers can assemble into higher-order oligomeric structures important for diverse functions of EBNA1.IMPORTANCE Epstein-Barr virus is a human gammaherpesvirus that is causally associated with various cancers. Carcinogenic properties are linked to the ability of the virus to persist in the latent form for the lifetime of the host. EBNA1 is a sequence-specific DNA-binding protein that is consistently expressed in EBV tumors and is the only viral protein required to maintain the viral episome during latency. The structural and biochemical mechanisms by which EBNA1 allows the long-term persistence of the EBV genome are currently unclear. Here, we have solved the crystal structure of an EBNA1 hexameric ring and characterized key residues in the interface required for higher-order complex formation and long-term plasmid maintenance.
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Yadav P, Carr MT, Yu R, Mumbey-Wafula A, Spatz LA. Mapping an epitope in EBNA-1 that is recognized by monoclonal antibodies to EBNA-1 that cross-react with dsDNA. IMMUNITY INFLAMMATION AND DISEASE 2016; 4:362-75. [PMID: 27621818 PMCID: PMC5004290 DOI: 10.1002/iid3.119] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 06/29/2016] [Accepted: 07/01/2016] [Indexed: 01/19/2023]
Abstract
Introduction The Epstein Barr Virus (EBV) has been associated with the autoimmune disease, Systemic Lupus Erythematosus (SLE). EBV nuclear antigen‐I (EBNA‐1) is the major nuclear protein of EBV. We previously generated an IgG monoclonal antibody (MAb) to EBNA‐1, 3D4, and demonstrated that it cross‐reacts with double stranded DNA (dsDNA) and binds the 148 amino acid viral binding site (VBS) in the carboxyl region of EBNA‐1. The aim of the present study was to characterize another antibody to EBNA‐1 that cross‐reacts with dsDNA, compare its immunoglobulin genes to 3D4, and finely map the epitope in EBNA‐1 that is recognized by these cross‐reactive antibodies. Methods We generated an IgM MAb to EBNA‐1, 16D2, from EBNA‐1 injected mice and demonstrated by ELISA that it cross‐reacts with dsDNA and binds the 148 amino acid VBS. We sequenced the variable heavy and light chain genes of 3D4 and 16D2 and compared V gene usage. To more finely map the epitope in EBNA‐1 recognized by these MAbs, we examined their binding by ELISA to 15 overlapping peptides spanning the 148 amino acid domain. Results Sequence analysis revealed that 3D4 and 16D2 utilize different VH and VL genes but identical JH and Jk regions with minimal junctional diversity. This accounts for similarities in their CDR3 regions and may explain their similar dual binding specificity. Epitope mapping revealed 3D4 and 16D2 bind the same peptide in the VBS. Based on the crystal structure of EBNA‐1, we observed that this peptide resides at the base of an exposed proline rich loop in EBNA‐1. Conclusion We have demonstrated that two MAbs that bind EBNA‐1 and cross‐react with dsDNA, recognize the same peptide in the VBS. This peptide may serve as a mimetope for dsDNA and may be of diagnostic and therapeutic value in SLE.
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Affiliation(s)
- Pragya Yadav
- Department of ChemistryCity College of New York160 Convent AvenueNew YorkNew York10031; Graduate Program in BiochemistryGraduate Center of the City University of New York160 Convent AvenueNew YorkNew York10031
| | - Matthew T Carr
- Department of ChemistryCity College of New York160 Convent AvenueNew YorkNew York10031; Graduate Program in BiochemistryGraduate Center of the City University of New York160 Convent AvenueNew YorkNew York10031
| | - Ruby Yu
- Department of Biology City College of New York 160 Convent Avenue New York New York 10031
| | - Alice Mumbey-Wafula
- Department of Pathobiology, Sophie Davis School of Biomedical Education City College of New York 160 Convent Avenue New York New York 10031
| | - Linda A Spatz
- Department of Pathobiology, Sophie Davis School of Biomedical Education City College of New York 160 Convent Avenue New York New York 10031
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Abstract
Latent Epstein–Barr virus (EBV) infection has a substantial role in causing many human disorders. The persistence of these viral genomes in all malignant cells, yet with the expression of limited latent genes, is consistent with the notion that EBV latent genes are important for malignant cell growth. While the EBV-encoded nuclear antigen-1 (EBNA-1) and latent membrane protein-2A (LMP-2A) are critical, the EBNA-leader proteins, EBNA-2, EBNA-3A, EBNA-3C and LMP-1, are individually essential for in vitro transformation of primary B cells to lymphoblastoid cell lines. EBV-encoded RNAs and EBNA-3Bs are dispensable. In this review, the roles of EBV latent genes are summarized.
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Affiliation(s)
- Myung-Soo Kang
- 1] Samsung Advanced Institute for Health Sciences and Technology (SAIHST), Samsung Medical Center, Sungkyunkwan University, Seoul, Korea [2] Samsung Biomedical Research Institute (SBRI), Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
| | - Elliott Kieff
- Department of Medicine, Brigham and Women's Hospital, Program in Virology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA
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Abstract
Epstein-Barr nuclear antigen 1 (EBNA1) plays multiple important roles in EBV latent infection and has also been shown to impact EBV lytic infection. EBNA1 is required for the stable persistence of the EBV genomes in latent infection and activates the expression of other EBV latency genes through interactions with specific DNA sequences in the viral episomes. EBNA1 also interacts with several cellular proteins to modulate the activities of multiple cellular pathways important for viral persistence and cell survival. These cellular effects are also implicated in oncogenesis, suggesting a direct role of EBNA1 in the development of EBV-associated tumors.
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Affiliation(s)
- Lori Frappier
- Department of Molecular Genetics, University of Toronto, 1 Kings College Circle, Toronto, ON, M5S 1A8, Canada.
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Small molecule inhibition of Epstein-Barr virus nuclear antigen-1 DNA binding activity interferes with replication and persistence of the viral genome. Antiviral Res 2014; 104:73-83. [PMID: 24486954 DOI: 10.1016/j.antiviral.2014.01.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/12/2013] [Accepted: 01/06/2014] [Indexed: 11/20/2022]
Abstract
The replication and persistence of extra chromosomal Epstein-Barr virus (EBV) episome in latently infected cells are primarily dependent on the binding of EBV-encoded nuclear antigen 1 (EBNA1) to the cognate EBV oriP element. In continuation of the previous study, herein we characterized EBNA1 small molecule inhibitors (H20, H31) and their underlying inhibitory mechanisms. In silico docking analyses predicted that H20 fits into a pocket in the EBNA1 DNA binding domain (DBD). However, H20 did not significantly affect EBNA1 binding to its cognate sequence. A limited structure-relationship study of H20 identified a hydrophobic compound H31, as an EBNA1 inhibitor. An in vitro EBNA1 EMSA and in vivo EGFP-EBNA1 confocal microscopy analysis showed that H31 inhibited EBNA1-dependent oriP sequence-specific DNA binding activity, but not sequence-nonspecific chromosomal association. Consistent with this, H31 repressed the EBNA1-dependent transcription, replication, and persistence of an EBV oriP plasmid. Furthermore, H31 induced progressive loss of EBV episome. In addition, H31 selectively retarded the growth of EBV-infected LCL or Burkitt's lymphoma cells. These data indicate that H31 inhibition of EBNA1-dependent DNA binding decreases transcription from and persistence of EBV episome in EBV-infected cells. These new compounds might be useful probes for dissecting EBNA1 functions in vitro and in vivo.
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Domsic JF, Chen HS, Lu F, Marmorstein R, Lieberman PM. Molecular basis for oligomeric-DNA binding and episome maintenance by KSHV LANA. PLoS Pathog 2013; 9:e1003672. [PMID: 24146617 PMCID: PMC3798644 DOI: 10.1371/journal.ppat.1003672] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/16/2013] [Indexed: 12/20/2022] Open
Abstract
LANA is the KSHV-encoded terminal repeat binding protein essential for viral replication and episome maintenance during latency. We have determined the X-ray crystal structure of LANA C-terminal DNA binding domain (LANADBD) to reveal its capacity to form a decameric ring with an exterior DNA binding surface. The dimeric core is structurally similar to EBV EBNA1 with an N-terminal arm that regulates DNA binding and is required for replication function. The oligomeric interface between LANA dimers is dispensable for single site DNA binding, but is required for cooperative DNA binding, replication function, and episome maintenance. We also identify a basic patch opposite of the DNA binding surface that is responsible for the interaction with BRD proteins and contributes to episome maintenance function. The structural features of LANADBD suggest a novel mechanism of episome maintenance through DNA-binding induced oligomeric assembly. Kaposi's sarcoma-associated herpesvirus (KSHV) establishes latent infections that are associated with several cancers including Kaposi's sarcoma, pleural effusion lymphoma, and multicentric Caslteman's disease. One of the major viral proteins required for establishment and maintenance of the latent state is the latency-associated nuclear antigen (LANA). LANA binds to DNA sequences within the terminal repeats (TR) of the viral genome and stimulates both DNA replication and episome maintenance during latency. Here we present the X-ray crystal structure of the DNA binding domain of LANA (LANADBD) and show that it has the capacity to form oligomeric complexes upon DNA binding. We characterize structural features of LANADBD that are required for oligomerization, DNA binding, and interaction with host cell BET proteins, BRD2 and BRD4, which are important for mediating multiple functions of LANA, including episome maintenance.
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MESH Headings
- Antigens, Viral/chemistry
- Antigens, Viral/genetics
- Antigens, Viral/metabolism
- Cell Line, Tumor
- DNA Replication
- DNA, Viral/chemistry
- DNA, Viral/genetics
- DNA, Viral/metabolism
- Herpesvirus 8, Human/chemistry
- Herpesvirus 8, Human/genetics
- Herpesvirus 8, Human/metabolism
- Humans
- Nuclear Proteins/chemistry
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Plasmids/chemistry
- Plasmids/genetics
- Plasmids/metabolism
- Protein Binding
- Protein Multimerization
- Protein Structure, Quaternary
- Protein Structure, Tertiary
- Structure-Activity Relationship
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Affiliation(s)
- John F. Domsic
- Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, United States of America
| | - Horng-Shen Chen
- Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, United States of America
| | - Fang Lu
- Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, United States of America
| | - Ronen Marmorstein
- Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, United States of America
- * E-mail: (RM); (PML)
| | - Paul M. Lieberman
- Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, United States of America
- * E-mail: (RM); (PML)
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Frappier L. EBNA1 and host factors in Epstein-Barr virus latent DNA replication. Curr Opin Virol 2012; 2:733-9. [PMID: 23031715 DOI: 10.1016/j.coviro.2012.09.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/10/2012] [Accepted: 09/11/2012] [Indexed: 11/25/2022]
Abstract
Epstein-Barr virus episomes (EBV) replicate once per cell cycle during latent infection from the latent origin, oriP. This replication requires the viral EBNA1 protein, which specifically recognizes sequences in oriP and recruits cellular proteins to this origin. Replication from oriP requires the cellular origin recognition and MCM helicase complexes and also involves telomeric factors (including TRF2) that associate with repeated nonameric sequences at the origin. Replication from oriP occurs late in S-phase and this timing appears to be important for efficient replication. Replication from oriP has proven to be a valuable system for elucidating cellular proteins and mechanisms of origin activation.
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Affiliation(s)
- Lori Frappier
- Department of Molecular Genetics, University of Toronto, 1 Kings College Circle, Toronto, Ontario, Canada M5S 1A8.
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13
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Frappier L. The Epstein-Barr Virus EBNA1 Protein. SCIENTIFICA 2012; 2012:438204. [PMID: 24278697 PMCID: PMC3820569 DOI: 10.6064/2012/438204] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Accepted: 11/28/2012] [Indexed: 05/06/2023]
Abstract
Epstein-Barr virus (EBV) is a widespread human herpes virus that immortalizes cells as part of its latent infection and is a causative agent in the development of several types of lymphomas and carcinomas. Replication and stable persistence of the EBV genomes in latent infection require the viral EBNA1 protein, which binds specific DNA sequences in the viral DNA. While the roles of EBNA1 were initially thought to be limited to effects on the viral genomes, more recently EBNA1 has been found to have multiple effects on cellular proteins and pathways that may also be important for viral persistence. In addition, a role for EBNA1 in lytic infection has been recently identified. The multiple roles of EBNA1 in EBV infection are the subject of this paper.
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Affiliation(s)
- Lori Frappier
- Department of Molecular Genetics, University of Toronto, 1 Kings College Circle, Toronto, ON, Canada M5S 1A8
- *Lori Frappier:
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14
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Role of EBNA1 in NPC tumourigenesis. Semin Cancer Biol 2011; 22:154-61. [PMID: 22206863 DOI: 10.1016/j.semcancer.2011.12.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 11/29/2011] [Accepted: 12/09/2011] [Indexed: 12/12/2022]
Abstract
EBNA1 is expressed in all NPC tumours and is the only Epstein-Barr virus protein needed for the stable persistence of EBV episomes. EBNA1 binds to specific sequences in the EBV genome to facilitate the initiation of DNA synthesis, ensure the even distribution of the viral episomes to daughter cells during mitosis and to activate the transcription of other viral latency genes important for cell immortalization. In addition, EBNA1 has been found to alter cellular pathways in multiple ways that likely contribute to cell immortalization and malignant transformation. This chapter discusses the known functions and cellular effects of EBNA1, especially as pertains to NPC.
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Yadav P, Tran H, Ebegbe R, Gottlieb P, Wei H, Lewis RH, Mumbey-Wafula A, Kaplan A, Kholdarova E, Spatz L. Antibodies elicited in response to EBNA-1 may cross-react with dsDNA. PLoS One 2011; 6:e14488. [PMID: 21245919 PMCID: PMC3014975 DOI: 10.1371/journal.pone.0014488] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 12/09/2010] [Indexed: 11/19/2022] Open
Abstract
Background Several genetic and environmental factors have been linked to Systemic Lupus Erythematosus (SLE). One environmental trigger that has a strong association with SLE is the Epstein Barr Virus (EBV). Our laboratory previously demonstrated that BALB/c mice expressing the complete EBNA-1 protein can develop antibodies to double stranded DNA (dsDNA). The present study was undertaken to understand why anti-dsDNA antibodies arise during the immune response to EBNA-1. Methodology/Principal Findings In this study, we demonstrated that mouse antibodies elicited in response to EBNA-1 cross-react with dsDNA. First, we showed that adsorption of sera reactive with EBNA-1 and dsDNA, on dsDNA cellulose columns, diminished reactivity with EBNA-1. Next, we generated mononclonal antibodies (MAbs) to EBNA-1 and showed, by several methods, that they also reacted with dsDNA. Examination of two cross-reactive MAbs—3D4, generated in this laboratory, and 0211, a commercial MAb—revealed that 3D4 recognizes the carboxyl region of EBNA-1, while 0211 recognizes both the amino and carboxyl regions. In addition, 0211 binds moderately well to the ribonucleoprotein, Sm, which has been reported by others to elicit a cross-reactive response with EBNA-1, while 3D4 binds only weakly to Sm. This suggests that the epitope in the carboxyl region may be more important for cross-reactivity with dsDNA while the epitope in the amino region may be more important for cross-reactivity with Sm. Conclusions/Significance In conclusion, our results demonstrate that antibodies to the EBNA-1 protein cross-react with dsDNA. This study is significant because it demonstrates a direct link between the viral antigen and the development of anti-dsDNA antibodies, which are the hallmark of SLE. Furthermore, it illustrates the crucial need to identify the epitopes in EBNA-1 responsible for this cross-reactivity so that therapeutic strategies can be designed to mask these regions from the immune system following EBV exposure.
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Affiliation(s)
- Pragya Yadav
- Department of Chemistry, The City College of New York and the Graduate Center of the City University of New York, New York, New York, United States of America
- The Ph.D. program in Biochemistry, The City College of New York and the Graduate Center of the City University of New York, New York, New York, United States of America
| | - Hoa Tran
- The Graduate School of Biology, The City College of New York, New York, New York, United States of America
| | - Roland Ebegbe
- The Graduate School of Biology, The City College of New York, New York, New York, United States of America
| | - Paul Gottlieb
- The Ph.D. program in Biochemistry, The City College of New York and the Graduate Center of the City University of New York, New York, New York, United States of America
- The Graduate School of Biology, The City College of New York, New York, New York, United States of America
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Hui Wei
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Rita H. Lewis
- The Graduate School of Biology, The City College of New York, New York, New York, United States of America
| | - Alice Mumbey-Wafula
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Atira Kaplan
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Elina Kholdarova
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Linda Spatz
- The Ph.D. program in Biochemistry, The City College of New York and the Graduate Center of the City University of New York, New York, New York, United States of America
- The Graduate School of Biology, The City College of New York, New York, New York, United States of America
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
- * E-mail:
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16
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Dellarole M, Sánchez IE, de Prat Gay G. Thermodynamics of cooperative DNA recognition at a replication origin and transcription regulatory site. Biochemistry 2010; 49:10277-86. [PMID: 21047141 PMCID: PMC3091369 DOI: 10.1021/bi1014908] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
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Binding cooperativity guides the formation of protein−nucleic acid complexes, in particular those that are highly regulated such as replication origins and transcription sites. Using the DNA binding domain of the origin binding and transcriptional regulator protein E2 from human papillomavirus type 16 as model, and through isothermal titration calorimetry analysis, we determined a positive, entropy-driven cooperativity upon binding of the protein to its cognate tandem double E2 site. This cooperativity is associated with a change in DNA structure, where the overall B conformation is maintained. Two homologous E2 domains, those of HPV18 and HPV11, showed that the enthalpic−entropic components of the reaction and DNA deformation can diverge. Because the DNA binding helix is almost identical in the three domains, the differences must lie dispersed throughout this unique dimeric β-barrel fold. This is in surprising agreement with previous results for this domain, which revealed a strong coupling between global dynamics and DNA recognition.
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Affiliation(s)
- Mariano Dellarole
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-Conicet, Patricias Argentinas 435, Buenos Aires, Argentina
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17
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d'Hérouël AF, Birgersdotter A, Werner M. FR-like EBNA1 binding repeats in the human genome. Virology 2010; 405:524-9. [DOI: 10.1016/j.virol.2010.06.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 02/15/2010] [Accepted: 06/22/2010] [Indexed: 10/19/2022]
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18
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Nayyar VK, Shire K, Frappier L. Mitotic chromosome interactions of Epstein-Barr nuclear antigen 1 (EBNA1) and human EBNA1-binding protein 2 (EBP2). J Cell Sci 2009; 122:4341-50. [PMID: 19887584 DOI: 10.1242/jcs.060913] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The Epstein-Barr nuclear antigen 1 (EBNA1) protein enables the stable persistence of Epstein-Barr virus episomal genomes during latent infection, in part by tethering the episomes to the cellular chromosomes in mitosis. A host nucleolar protein, EBNA1-binding protein 2 (EBP2), has been shown to be important for interactions between EBNA1 and chromosomes in metaphase and to associate with metaphase chromosomes. Here, we examine the timing of the chromosome associations of EBNA1 and EBP2 through mitosis and the regions of EBNA1 that mediate the chromosome interactions at each stage of mitosis. We show that EBP2 is localized to the nucleolus until late prophase, after which it relocalizes to the chromosome periphery, where it remains throughout telophase. EBNA1 is associated with chromosomes early in prophase through to telophase and partially colocalizes with chromosomal EBP2 in metaphase through to telophase. Using EBNA1 deletion mutants, the chromosome association of EBNA1 at each stage of mitosis was found to be mediated mainly by a central glycine-arginine region, and to a lesser degree by N-terminal sequences. These sequence requirements for chromosome interaction mirrored those for EBP2 binding. Our results suggest that interactions between EBNA1 and chromosomes involve at least two stages, and that the contribution of EBP2 to these interactions occurs in the second half of mitosis.
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Affiliation(s)
- Vipra Kapur Nayyar
- Department of Molecular Genetics, University of Toronto, Toronto, Canada M5S 1A8
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19
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EBNA1-mediated recruitment of a histone H2B deubiquitylating complex to the Epstein-Barr virus latent origin of DNA replication. PLoS Pathog 2009; 5:e1000624. [PMID: 19834552 PMCID: PMC2757719 DOI: 10.1371/journal.ppat.1000624] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Accepted: 09/17/2009] [Indexed: 12/24/2022] Open
Abstract
The EBNA1 protein of Epstein-Barr virus (EBV) plays essential roles in enabling the replication and persistence of EBV genomes in latently infected cells and activating EBV latent gene expression, in all cases by binding to specific recognition sites in the latent origin of replication, oriP. Here we show that EBNA1 binding to its recognition sites in vitro is greatly stimulated by binding to the cellular deubiquitylating enzyme, USP7, and that USP7 can form a ternary complex with DNA-bound EBNA1. Consistent with the in vitro effects, the assembly of EBNA1 on oriP elements in human cells was decreased by USP7 silencing, whereas assembly of an EBNA1 mutant defective in USP7 binding was unaffected. USP7 affinity column profiling identified a complex between USP7 and human GMP synthetase (GMPS), which was shown to stimulate the ability of USP7 to cleave monoubiquitin from histone H2B in vitro. Accordingly, silencing of USP7 in human cells resulted in a consistent increase in the level of monoubquitylated H2B. The USP7-GMPS complex formed a quaternary complex with DNA-bound EBNA1 in vitro and, in EBV infected cells, was preferentially detected at the oriP functional element, FR, along with EBNA1. Down-regulation of USP7 reduced the level of GMPS at the FR, increased the level of monoubiquitylated H2B in this region of the origin and decreased the ability of EBNA1, but not an EBNA1 USP7-binding mutant, to activate transcription from the FR. The results indicate that USP7 can stimulate EBNA1-DNA interactions and that EBNA1 can alter histone modification at oriP through recruitment of USP7. Epstein-Barr virus (EBV) infections persist for the lifetime of the host largely due to the actions of the EBNA1 viral protein. EBNA1 enables the replication and stable persistence of EBV genomes and activates the expression of other EBV genes by binding to specific DNA sequences in the EBV genome. We have shown that the cellular protein USP7 stimulates EBNA1 binding to its DNA sequences and that EBNA1 recruits USP7 to the EBV genome, which in turn recruits another cellular protein GMP synthetase. The complex of USP7 and GMP synthetase then functions to alter the chromatin structure at a region of the EBV genome that controls EBV persistence. These changes to the EBV genome are likely important for enabling the persistence of EBV genomes in infected cells.
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20
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Nucleosome assembly proteins bind to Epstein-Barr virus nuclear antigen 1 and affect its functions in DNA replication and transcriptional activation. J Virol 2009; 83:11704-14. [PMID: 19726498 DOI: 10.1128/jvi.00931-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The EBNA1 protein of Epstein-Barr virus (EBV) plays several important roles in EBV latent infection, including activating DNA replication from the latent origin of replication (oriP) and activating the transcription of other latency genes within the EBV chromatin. These functions require EBNA1 binding to the DS and FR elements within oriP, respectively, although how these interactions activate these processes is not clear. We previously identified interactions of EBNA1 with the related nucleosome assembly proteins NAP1 and TAF-I, known to affect the replication and transcription of other chromatinized templates. We have further investigated these interactions, showing that EBNA1 binds directly to NAP1 and to the beta isoform of TAF-I (also called SET) and that these interactions greatly increase the solubility of EBNA1 in vitro. These interactions were confirmed in EBV-infected cells, and chromatin immunoprecipitation with these cells showed that NAP1 and TAF-I both localized with EBNA1 to the FR element, while only TAF-I was detected with EBNA1 at the DS element. In keeping with these observations, alteration of the NAP1 or TAF-Ibeta level by RNA interference and overexpression inhibited transcriptional activation by EBNA1 in FR reporter assays. In addition, EBNA1-mediated DNA replication was stimulated when TAF-I (but not NAP1) was downregulated and was inhibited by TAF-Ibeta overexpression. The results indicate that the interaction of EBNA1 with NAP1 and TAF-I is important for transcriptional activation and that EBNA1 recruits TAF-I to the DS element, where it negatively regulates DNA replication.
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21
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Freire E, Oddo C, Frappier L, de Prat-Gay G. Kinetically driven refolding of the hyperstable EBNA1 origin DNA-binding dimeric beta-barrel domain into amyloid-like spherical oligomers. Proteins 2008; 70:450-61. [PMID: 17680697 DOI: 10.1002/prot.21580] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The Epstein-Barr nuclear antigen 1 (EBNA1) is essential for DNA replication and episome segregation of the viral genome, and participates in other gene regulatory processes of the Epstein-Barr virus in benign and malignant diseases related to this virus. Despite the participation of other regions of the protein in evading immune response, its DNA binding, dimeric beta-barrel domain (residues 452-641) is necessary and sufficient for the main functions. This domain has an unusual topology only shared by another viral origin binding protein (OBP), the E2 DNA binding domain of papillomaviruses. Both the amino acid and DNA target sequences are completely different for these two proteins, indicating a link between fold conservation and function. In this work we investigated the folding and stability of the DNA binding domain of EBNA1 OBP and found it is extremely resistant to chemical, temperature, and pH denaturation. The thiocyanate salt of guanidine is required for obtaining a complete transition to a monomeric unfolded state. The unfolding reaction is extremely slow and shows a marked uncoupling between tertiary and secondary structure, indicating the presence of intermediate species. The Gdm.SCN unfolded protein refolds to fully soluble and spherical oligomeric species of 1.2 MDa molecular weight, with identical fluorescence centre of spectral mass but different intensity and different secondary structure. The refolded spherical oligomers are substantially less stable than the native recombinant dimer. In keeping with the substantial structural rearrangement in the oligomers, the spherical oligomers do not bind DNA, indicating that the DNA binding site is either disrupted or participates in the oligomerization interface. The puzzling extreme stability of a dimeric DNA binding domain from a protein from a human infecting virus in addition to a remarkable kinetically driven folding where all molecules do not return to the most stable original species suggests a co-translational and directional folding of EBNA1 in vivo, possibly assisted by folding accessory proteins. Finally, the oligomers bind Congo red and thioflavin-T, both characteristic of repetitive beta-sheet elements of structure found in amyloids and their soluble precursors. The stable nature of the "kinetically trapped" oligomers suggest their value as models for understanding amyloid intermediates, their toxic nature, and the progress to amyloid fibers in misfolding diseases. The possible role of the EBNA1 spherical oligomers in the virus biology is discussed.
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Affiliation(s)
- Eleonora Freire
- Instituto Leloir, Patricias Argentinas 435, (1405) Buenos Aires, Argentina
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22
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Lindner SE, Sugden B. The plasmid replicon of Epstein-Barr virus: mechanistic insights into efficient, licensed, extrachromosomal replication in human cells. Plasmid 2007; 58:1-12. [PMID: 17350094 PMCID: PMC2562867 DOI: 10.1016/j.plasmid.2007.01.003] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Accepted: 01/05/2007] [Indexed: 12/24/2022]
Abstract
The genome of Epstein-Barr Virus (EBV) and plasmid derivatives of it are among the most efficient extrachromosomal replicons in mammalian cells. The latent origin of plasmid replication (oriP), when supplied with the viral Epstein-Barr Nuclear Antigen 1 (EBNA1) in trans, provides efficient duplication, partitioning and maintenance of plasmids bearing it. In this review, we detail what is known about the viral cis and trans elements required for plasmid replication. In addition, we describe how the cellular factors that EBV usurps are used to complement the functions of the viral constituents. Finally, we propose a model for the sequential assembly of an EBNA1-dependent origin of DNA synthesis into a pre-Replicative Complex (pre-RC), which functions by making use only of cellular enzymatic activities to carry out the replication of the viral plasmid.
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Affiliation(s)
| | - Bill Sugden
- * To whom correspondence should be addressed: 1400 University Ave, Madison, WI 53706, Phone: 608.262.6697, Fax: 608.262.2824,
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23
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Oddo C, Freire E, Frappier L, de Prat-Gay G. Mechanism of DNA Recognition at a Viral Replication Origin. J Biol Chem 2006; 281:26893-903. [PMID: 16815848 DOI: 10.1074/jbc.m602083200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recognition of the DNA origin by the Epstein-Barr nuclear antigen 1 (EBNA1) protein is the primary event in latentphase genome replication of the Epstein-Barr virus, a model for replication initiation in eukaryotes. We carried out an extensive thermodynamic and kinetic characterization of the binding mechanism of the DNA binding domain of EBNA1, EBNA1452-641, to a DNA fragment containing a single specific origin site. The interaction displays a binding energy of 12.7 kcal mol-1, with 11.9 kcal mol-1 coming from the enthalpic change with a minimal entropic contribution. Formation of the EBNA1452-641.DNA complex is accompanied by a heat capacity change of -1.22 kcal mol-1 K-1, a very large value considering the surface area buried, which we assign to an unusually apolar protein-DNA interface. Kinetic dissociation experiments, including fluorescence anisotropy and a continuous native electrophoretic mobility shift assay, confirmed that two EBNA1.DNA complex conformers are in slow equilibrium; one dissociates slowly (t1/2 approximately 41 min) through an undissociated intermediate species and the other corresponds to a fast twostep dissociation route (t1/2 approximately 0.8 min). In line with this, at least two parallel association events from two populations of protein conformers are observed, with on-rates of 0.25-1.6x10(8) m-1 s-1, which occur differentially either in excess protein or DNA molecules. Both parallel complexes undergo subsequent firstorder rearrangements of approximately 2.0 s-1 to yield two consolidated complexes. These parallel association and dissociation routes likely allow additional flexible regulatory events for site recognition depending on site availability according to nucleus environmental conditions, which may lock a final recognition event, dissociate and re-bind, or slide along the DNA.
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Affiliation(s)
- Cristian Oddo
- Instituto Leloir, Patricias Argentinas 435, 1405 Buenos Aires, Argentina
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24
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Kapoor P, Lavoie BD, Frappier L. EBP2 plays a key role in Epstein-Barr virus mitotic segregation and is regulated by aurora family kinases. Mol Cell Biol 2005; 25:4934-45. [PMID: 15923612 PMCID: PMC1140579 DOI: 10.1128/mcb.25.12.4934-4945.2005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 03/26/2005] [Accepted: 03/29/2005] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr virus (EBV) genomes persist indefinitely in latently infected human cells, in part due to their ability to stably segregate during cell division. This process is mediated by the viral EBNA1 protein, which tethers the viral episomes to the cellular mitotic chromosomes. We have previously identified a mitotic chromosomal protein, human EBNA1 binding protein 2 (hEBP2), which binds to EBNA1 and enables EBNA1 to partition EBV-based plasmids in Saccharomyces cerevisiae. Using an RNA silencing approach, we show that hEBP2 is essential for the proliferation of human cells and that repression of hEBP2 severely decreases the ability of EBNA1 and EBV-based plasmids to bind mitotic chromosomes. When expressed in yeast, hEBP2 undergoes the same cell cycle-regulated association with the mitotic chromatin as in human cells, and using yeast temperature-sensitive mutant strains, we found that the attachment of hEBP2 to mitotic chromosomes was dependent on the Ipl1 kinase. Both RNA silencing of the Ipl1 orthologue in human cells (Aurora B) and specific inhibition of the Aurora B kinase activity with a small molecule confirmed a role for this kinase in enabling hEBP2 binding to human mitotic chromosomes, suggesting that this kinase can regulate EBV segregation.
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Affiliation(s)
- Priya Kapoor
- Department of Medical Genetics and Microbiology, University of Toronto, 1 Kings College Circle, Toronto M5S 1A8, Canada
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25
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Habel ME, Drouin M, Jung D. Maintenance of Epstein-Barr virus-derived episomal vectors in the murine Sp2/0 myeloma cell line is dependent upon exogenous expression of human EBP2. Biochem Cell Biol 2005; 82:375-80. [PMID: 15181471 DOI: 10.1139/o04-037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vectors carrying the origin of replication (oriP) and driving expression of the EBNA-1 protein from Epstein-Barr virus (EBV) replicate as extrachromosomal episomes in human cells. Whether these vectors can be maintained as episomes in murine cells is still controversial. Here we demonstrate that EBNA-1 expression alone was unable to maintain episomal expression of an EBV-based vector in the murine Sp2/0 cell line. However, we were able to obtain long-term episome maintenance in Sp2/0 cells after exogenously expressing human EBP2 by genetic engineering. Our results provide further evidence for the fundamental role of human EBP2 in episomal maintenance of EBV-based vectors. Moreover, we demonstrate that EBV-based vectors can be successfully used in cells presumably incompetent for episomal maintenance.
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Affiliation(s)
- Marie-Eve Habel
- Héma-Québec, Recherche et développement, Pavillion Héma-Québec, 1009 Route du Vallon, Sainte Foy, QC G1V 4C3, Canada
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26
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Garber AC, Hu J, Renne R. Latency-associated nuclear antigen (LANA) cooperatively binds to two sites within the terminal repeat, and both sites contribute to the ability of LANA to suppress transcription and to facilitate DNA replication. J Biol Chem 2002; 277:27401-11. [PMID: 12015325 DOI: 10.1074/jbc.m203489200] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus is a multifunctional protein with important roles in both transcriptional regulation and episomal maintenance. LANA is also a DNA-binding protein and has been shown to specifically bind to a region within the terminal repeat. Here, we have performed a detailed analysis of the DNA-binding activity of LANA and show that it binds two sites separated by 22 bp. We used electrophoretic mobility shift assay to quantitatively analyze the binding sites and determined that the K(d) of the high affinity site is 1.51 +/- 0.16 nm. Examination of the contribution of nucleotides near the ends of the site showed that the core binding site consists of 16 bp, 13 of which are conserved between both sites. Analysis of the affinity of each site alone and in tandem revealed that the binding to the second site is primarily due to cooperativity with the first site. Using deletion and point mutations, we show that both sites contribute to the ability of LANA to suppress transcription and to facilitate DNA replication. In addition, we show that the ability of LANA to carry out these functions is directly proportional to its affinity for the sites in this region. The affinities, spacing, and cooperative binding between the two sites is similar to that of the Epstein-Barr virus dyad symmetry element oriP, suggesting a requirement for such an element in latent replication of these related DNA tumor viruses.
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Affiliation(s)
- Alexander C Garber
- Division of Hematology/Oncology, Department of Molecular Biology and Microbiology, Case Western Reserve University, 2109 Adelbert Road, Cleveland, OH 44106, USA
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27
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Wu H, Kapoor P, Frappier L. Separation of the DNA replication, segregation, and transcriptional activation functions of Epstein-Barr nuclear antigen 1. J Virol 2002; 76:2480-90. [PMID: 11836426 PMCID: PMC135949 DOI: 10.1128/jvi.76.5.2480-2490.2002] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Accepted: 11/12/2001] [Indexed: 11/20/2022] Open
Abstract
In latent Epstein-Barr virus infection, the viral EBNA1 protein binds to specific sites in the viral origin of DNA replication, oriP, to activate the initiation of DNA replication, enhance the expression of other viral latency proteins, and partition the viral episomes during cell division. The DNA binding domain of EBNA1 is required for all three function, and a Gly-Arg-rich sequence between amino acids 325 and 376 is required for both the transcriptional activation and partitioning functions. We have used mutational analysis to identify additional EBNA1 sequences that contribute to EBNA1 functions. We show that EBNA1 amino acids 8 to 67 contribute to, but are not absolutely required for, EBNA1 replication, partitioning, and transcriptional activation functions. A Gly-Arg-rich sequence (amino acids 33 to 53) that is similar to that of amino acids 325 to 376 and lies within the 8-to-67 region was not responsible for the functional contributions of residues 8 to 67, since deletion of amino acids 34 to 52 alone did not affect EBNA1 functions. We also found that deletion of amino acids 61 to 83 eliminated the transcriptional activity of EBNA1 without affecting partitioning. This mutant also exhibited an increased replication efficiency that resulted in the maintenance of oriP plasmids at a copy number approximately fourfold higher than for wild-type EBNA1. The results indicate that the three EBNA1 functions have overlapping but different sequence requirements. Transcriptional activation requires residues 61 to 83 and 325 to 376 and is stimulated by residues 8 to 67; partitioning requires residues 325 to 376 and is stimulated by residues 8 to 67; and replication involves redundant contributions of both the 325-to-376 and 8-to-67 regions.
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Affiliation(s)
- Hong Wu
- Department of Medical Genetics and Microbiology, University of Toronto, 1 Kings College Circle, Toronto, Ontario, Canada M5S 1A8
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28
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Koons MD, Van Scoy S, Hearing J. The replicator of the Epstein-Barr virus latent cycle origin of DNA replication, oriP, is composed of multiple functional elements. J Virol 2001; 75:10582-92. [PMID: 11602700 PMCID: PMC114640 DOI: 10.1128/jvi.75.22.10582-10592.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2001] [Accepted: 08/09/2001] [Indexed: 11/20/2022] Open
Abstract
Replication of the Epstein-Barr virus genome initiates at one of several sites in latently infected, dividing cells. One of these replication origins is close to the viral DNA maintenance element, and, together, this replication origin and the maintenance element are referred to as oriP. The replicator of oriP contains four binding sites for Epstein-Barr virus nuclear antigen 1 (EBNA-1), the sole viral protein required for the replication and maintenance of oriP plasmids. We showed previously that these EBNA-1 sites function in pairs and that mutational inactivation of one pair does not eliminate replicator function. In this study we characterized the contribution of each EBNA-1 site within the replicator and flanking sequences through the use of an internally controlled replication assay. We present evidence that shows that all four EBNA-1 sites are required for an oriP plasmid to be replicated in every cell cycle. Results from these experiments also show that the paired EBNA-1 binding sites are not functionally equivalent and that the low affinity of sites 2 and 3 compared to that of sites 1 and 4 is not essential for replicator function. Our results suggest that a host cell protein(s) binds sequences flanking the EBNA-1 sites and that interactions between EBNA-1 and this protein(s) are critical for replicator function. Finally, we present evidence that shows that the minimal replicator of oriP consists of EBNA-1 sites 3 and 4 and two copies of a 14-bp repeat that is present in inverse orientation flanking these EBNA-1 sites. EBNA-1 sites 1 and 2, together with an element(s) within nucleotides 9138 to 9516, are ancillary elements required for full replicator activity.
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Affiliation(s)
- M D Koons
- Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, New York 11794-5222, USA
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29
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Bashaw JM, Yates JL. Replication from oriP of Epstein-Barr virus requires exact spacing of two bound dimers of EBNA1 which bend DNA. J Virol 2001; 75:10603-11. [PMID: 11602702 PMCID: PMC114642 DOI: 10.1128/jvi.75.22.10603-10611.2001] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
oriP is a 1.7-kb region of the Epstein-Barr virus (EBV) chromosome that supports replication and stable maintenance of plasmids in human cells that contain EBV-encoded protein EBNA1. Plasmids that depend on oriP are replicated once per cell cycle by cellular factors. The replicator of oriP is an approximately 120-bp region called DS which depends on either of two pairs of closely spaced EBNA1 binding sites. Here we report that changing the distance between the EBNA1 sites of a functional pair by inserting or deleting 1 or 2 bp abolished replication activity. The results indicated that, while the distance separating the binding sites is critical, the specific nucleotide sequence between them is unlikely to be important. The use of electrophoretic mobility shift assays to investigate binding by EBNA1 to the sites with normal or altered spacing revealed that EBNA1 induces DNA to bend significantly when it binds, with the center of bending coinciding with the center of binding. EBNA1 binding to a functional pair of sites which are spaced 21 bp apart center to center and which thus are in helical phase induces a larger symmetrical bend, which based on electrophoretic mobility approximates the sum of two separate EBNA1-induced DNA bends. The results imply that replication from oriP requires a precise structure in which DNA forms a large bend around two EBNA1 dimers.
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Affiliation(s)
- J M Bashaw
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
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30
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Avolio-Hunter TM, Lewis PN, Frappier L. Epstein-Barr nuclear antigen 1 binds and destabilizes nucleosomes at the viral origin of latent DNA replication. Nucleic Acids Res 2001; 29:3520-8. [PMID: 11522821 PMCID: PMC55891 DOI: 10.1093/nar/29.17.3520] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2001] [Revised: 07/09/2001] [Accepted: 07/17/2001] [Indexed: 11/12/2022] Open
Abstract
The EBNA1 protein of Epstein-Barr virus (EBV) activates latent-phase DNA replication by an unknown mechanism that involves binding to four recognition sites in the dyad symmetry (DS) element of the viral latent origin of DNA replication. Since EBV episomes are assembled into nucleosomes, we have examined the ability of Epstein-Barr virus nuclear antigen 1 (EBNA1) to interact with the DS element when it is assembled into a nucleosome core particle. EBNA1 bound to its recognition sites within this nucleosome, forming a ternary complex, and displaced the histone octamer upon competitor DNA challenge. The DNA binding and dimerization region of EBNA1 was sufficient for nucleosome binding and destabilization. Although EBNA1 was able to bind to nucleosomes containing two recognition sites from the DS element positioned at the edge of the nucleosome, nucleosome destabilization was only observed when all four sites of the DS element were present. Our results indicate that the presence of a nucleosome at the viral origin will not prevent EBNA1 binding to its recognition sites. In addition, since four EBNA1 recognition sites are required for both nucleosome destabilization and efficient origin activation, our findings also suggest that nucleosome destabilization by EBNA1 is important for origin activation.
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Affiliation(s)
- T M Avolio-Hunter
- Department of Medical Genetics and Microbiology, University of Toronto, 1 Kings College Circle, Toronto, Ontario M5S 1A8, Canada
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31
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Kapoor P, Shire K, Frappier L. Reconstitution of Epstein-Barr virus-based plasmid partitioning in budding yeast. EMBO J 2001; 20:222-30. [PMID: 11226172 PMCID: PMC140207 DOI: 10.1093/emboj/20.1.222] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The EBNA1 protein of Epstein-Barr virus (EBV) mediates the partitioning of EBV episomes and EBV-based plasmids during cell division by a mechanism that appears to involve binding to the cellular EBP2 protein on human chromosomes. We have investigated the ability of EBNA1 and the EBV segregation element (FR) to mediate plasmid partitioning in Saccharomyces cerevisiae. EBNA1 expression alone did not enable the stable segregation of FR-containing plasmids in yeast, but segregation was rescued by human EBP2. The reconstituted segregation system required EBNA1, human EBP2 and the FR element, and functionally replaced a CEN element. An EBP2 binding mutant of EBNA1 and an EBNA1 binding mutant of EBP2 each failed to support FR-plasmid partitioning, indicating that an EBNA1-EBP2 interaction is required. The results provide direct evidence of the role of hEBP2 in EBNA1-mediated segregation and demonstrate that heterologous segregation systems can be reconstituted in yeast.
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Affiliation(s)
- P Kapoor
- Department of Medical Genetics and Microbiology, University of Toronto, 1 Kings College Circle, Toronto, Canada M5S 1A8.
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32
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Cameron MJ, Strathdee CA, Holmes KD, Arreaza GA, Dekaban GA, Delovitch TL. Biolistic-mediated interleukin 4 gene transfer prevents the onset of type 1 diabetes. Hum Gene Ther 2000; 11:1647-56. [PMID: 10954899 DOI: 10.1089/10430340050111304] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We tested the efficacy of biolistic-mediated gene transfer as a noninvasive therapy for type 1 diabetes (T1D) in nonobese diabetic (NOD) mice by expression of murine interleukin 4 (mIL-4) cDNA. Epidermal delivery of 2 microg of DNA yielded transient detection of serum mIL-4, using a conventional cDNA expression vector. A vector stabilized by incorporation of the Epstein-Barr virus (EBV) EBNA1/oriP episomal maintenance replicon produced higher levels of serum mIL-4 that persisted for 12 days after inoculation. Although biolistic inoculation of either vector reduced insulitis and prevented diabetes, the protracted mIL-4 expression afforded by the EBV vector resulted in Th2-type responses in the periphery and pancreas and more significant protection from the onset of diabetes. Our studies demonstrate the efficacy of biolistic gene delivery of stabilized cytokine expression as a viable therapeutic approach to prevent the onset of T1D.
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Affiliation(s)
- M J Cameron
- Autoimmunity/Diabetes Group, John P. Robarts Research Institute, London, Ontario, Canada. Canada
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33
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Cruickshank J, Shire K, Davidson AR, Edwards AM, Frappier L. Two domains of the epstein-barr virus origin DNA-binding protein, EBNA1, orchestrate sequence-specific DNA binding. J Biol Chem 2000; 275:22273-7. [PMID: 10801810 DOI: 10.1074/jbc.m001414200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The EBNA1 (for Epstein-Barr nuclear antigen 1) protein of Epstein-Barr virus governs the replication and partitioning of the viral genomes during latent infection by binding to specific recognition sites in the viral origin of DNA replication. The crystal structure of the DNA binding portion of the EBNA1 protein revealed that this region comprises two structural motifs; a core domain, which mediates protein dimerization and is structurally homologous to the DNA binding domain of the papillomavirus E2 protein, and a flanking domain, which mediated all the observed sequence-specific contacts. To test the possibility that the EBNA1 core domain plays a role in sequence-specific DNA binding not revealed in the crystal structure, we examined the effects of point mutations in potential hydrogen bond donors located in an alpha-helix of the EBNA1 core domain whose structural homologue in E2 mediates sequence-specific DNA binding. We show that these mutations severely reduce the affinity of EBNA1 for its recognition site, and that the core domain, when expressed in the absence of the flanking domain, has sequence-specific DNA binding activity. Flanking domain residues were also found to contribute to the DNA binding activity of EBNA1. Thus, both the core and flanking domains of EBNA1 play direct roles in DNA recognition.
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Affiliation(s)
- J Cruickshank
- Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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34
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Ceccarelli DF, Frappier L. Functional analyses of the EBNA1 origin DNA binding protein of Epstein-Barr virus. J Virol 2000; 74:4939-48. [PMID: 10799567 PMCID: PMC110845 DOI: 10.1128/jvi.74.11.4939-4948.2000] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The EBNA1 protein of Epstein-Barr virus (EBV) governs the replication and segregation of the viral episomes in latently infected cells and transactivates the expression of other EBV latency proteins through direct interactions with DNA sequences in the EBV latent origin of replication, oriP. To better understand how EBNA1 controls these processes, we have assessed the contribution of various EBNA1 sequences to its replication, segregation, and transactivation functions. Here we show that EBNA1 residues 325 to 376 are responsible for the transactivation activity of EBNA1. This region coincides with the DNA looping domain previously shown to mediate interactions at a distance between DNA-bound EBNA1 molecules. The same residues mediate DNA segregation but have no apparent role in DNA replication, indicating that the replication and transcription activation activities of EBNA1 are distinct. The acidic C-terminal tail of EBNA1 was not found to contribute to replication, transactivation, or segregation. We have also investigated the functional significance of two structural motifs within the DNA binding and dimerization domains of EBNA1, the proline loop and the WF motif. Although the amino acids in these motifs do not directly contact the DNA, both of these motifs were found to contribute to EBNA1 functions by increasing the DNA-binding ability of EBNA1. Mechanisms by which DNA binding is stimulated by these motifs are discussed.
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Affiliation(s)
- D F Ceccarelli
- Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5
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35
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Shire K, Ceccarelli DF, Avolio-Hunter TM, Frappier L. EBP2, a human protein that interacts with sequences of the Epstein-Barr virus nuclear antigen 1 important for plasmid maintenance. J Virol 1999; 73:2587-95. [PMID: 10074103 PMCID: PMC104013 DOI: 10.1128/jvi.73.4.2587-2595.1999] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The replication and stable maintenance of latent Epstein-Barr virus (EBV) DNA episomes in human cells requires only one viral protein, Epstein-Barr nuclear antigen 1 (EBNA1). To gain insight into the mechanisms by which EBNA1 functions, we used a yeast two-hybrid screen to detect human proteins that interact with EBNA1. We describe here the isolation of a protein, EBP2 (EBNA1 binding protein 2), that specifically interacts with EBNA1. EBP2 was also shown to bind to DNA-bound EBNA1 in a one-hybrid system, and the EBP2-EBNA1 interaction was confirmed by coimmunoprecipitation from insect cells expressing these two proteins. EBP2 is a 35-kDa protein that is conserved in a variety of organisms and is predicted to form coiled-coil interactions. We have mapped the region of EBNA1 that binds EBP2 and generated internal deletion mutants of EBNA1 that are deficient in EBP2 interactions. Functional analyses of these EBNA1 mutants show that the ability to bind EBP2 correlates with the ability of EBNA1 to support the long-term maintenance in human cells of a plasmid containing the EBV origin, oriP. An EBNA1 mutant lacking amino acids 325 to 376 was defective for EBP2 binding and long-term oriP plasmid maintenance but supported the transient replication of oriP plasmids at wild-type levels. Thus, our results suggest that the EBNA1-EBP2 interaction is important for the stable segregation of EBV episomes during cell division but not for the replication of the episomes.
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Affiliation(s)
- K Shire
- Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Ontario M5S 1A8
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36
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Bochkarev A, Bochkareva E, Frappier L, Edwards AM. The 2.2 A structure of a permanganate-sensitive DNA site bound by the Epstein-Barr virus origin binding protein, EBNA1. J Mol Biol 1998; 284:1273-8. [PMID: 9878348 DOI: 10.1006/jmbi.1998.2247] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epstein-Barr nuclear antigen 1 (EBNA1) binds to four recognition sites in the minimal origin of latent DNA replication of Epstein-Barr virus and activates latent-phase replication of the viral genomes. Two of these EBNA1 binding sites become sensitive to permanganate oxidation when bound by the DNA binding and dimerization domains of EBNA1. We have previously solved the co-crystal structure of this EBNA1 fragment bound to a consensus recognition site that is not sensitive to permanganate oxidation (CS). To understand the structural difference that underlies the permanganate sensitivity of EBNA1 binding sites, we have now solved the crystal structure of the EBNA1 DNA-binding and dimerization domains bound to a permanganate-sensitive site (CSA/T). Comparisons of permanganate-sensitive and insensitive EBNA1-DNA complexes have revealed only minor differences in protein and DNA structures. In the EBNA1-CSA/T structure, interstrand H-bonds for three consecutive base-pairs centered over the permanganate-sensitive thymine base are lengthened relative to the corresponding bonds in the EBNA1-CS complex, and three potential intrastrand H-bonds were observed between adjacent bases. We also observed that both the CS and CSA/T sequences are overwound by EBNA1 in the vicinity of the permanganate-sensitive thymine base. Finally, we show that the permanganate-sensitive thymine base in the CSA/T-EBNA1 complex is more accessible to solvent than the corresponding T in the EBNA-CS complex.
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Affiliation(s)
- A Bochkarev
- Department of Medical Genetics and Microbiology, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
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37
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Abstract
The first step in DNA replication involves the recognition of origin DNA sequences by origin-binding proteins. The three-dimensional structures of three different origin DNA-binding proteins have recently been solved. These proteins form a structural class distinct from other DNA-binding proteins. One of the origin-binding proteins, Epstein-Barr virus nuclear antigen 1, most likely has two modes of DNA binding; the sequential use of these modes may be important for the initiation of DNA replication.
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Affiliation(s)
- A M Edwards
- Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
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38
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Summers H, Fleming A, Frappier L. Requirements for Epstein-Barr nuclear antigen 1 (EBNA1)-induced permanganate sensitivity of the epstein-barr virus latent origin of DNA replication. J Biol Chem 1997; 272:26434-40. [PMID: 9334219 DOI: 10.1074/jbc.272.42.26434] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Epstein-Barr nuclear antigen 1 (EBNA1) activates DNA replication from the Epstein-Barr virus latent origin of DNA replication, oriP. EBNA1 binds cooperatively to four recognition sites in the dyad symmetry (DS) element of oriP, causing alterations in the origin DNA structure, which can be detected by the increased sensitivity of one Thy residue in two of the binding sites to permanganate oxidation. To better understand the significance of this EBNA1-induced origin distortion, we have investigated the DNA sequence and EBNA1 amino acid requirements for permanganate sensitivity. We have shown that the EBNA1 DNA binding and dimerization domains are sufficient to induce permanganate sensitivity and that amino acids 463-467, which form an extended chain that travels along the minor groove of the EBNA1 recognition site, play an important role in generating the DNA distortion. The EBNA1-induced permanganate sensitivity is independent of cooperative interactions between EBNA1 molecules on the origin and requires a specific sequence within the EBNA1 binding site. Using synthetic EBNA1 binding sites, we found that the inversion of a single AT base pair in the EBNA1 recognition sequence is sufficient to confer EBNA1-induced permanganate sensitivity. These studies indicate that permanganate oxidation can detect very minor alterations in DNA structure.
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Affiliation(s)
- H Summers
- Cancer Research Group, Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
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39
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Ermakova OV, Frappier L, Schildkraut CL. Role of the EBNA-1 protein in pausing of replication forks in the Epstein-Barr virus genome. J Biol Chem 1996; 271:33009-17. [PMID: 8955146 DOI: 10.1074/jbc.271.51.33009] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have previously shown that replication forks stall at a family of repeated sequences (FR) within the Epstein-Barr virus latent origin of replication oriP, both in a small plasmid and in the intact Epstein-Barr virus genome. Each of the 20 repeated sequences within the FR contains a binding site for Epstein-Barr nuclear antigen 1 (EBNA-1), the only viral protein required for latent replication. We showed that the EBNA-1 protein enhances the accumulation of paused replication forks at the FR. In this study, we have investigated a series of truncated EBNA-1 proteins to determine the portion of the EBNA-1 protein that is responsible for pausing of forks at the FR. Two-dimensional agarose gel electrophoresis was performed on the products of in vitro replication reactions in the presence of full-length EBNA-1 or proteins with various deletions to assess the extent of fork pausing at the FR. We conclude that a portion of the DNA binding domain is important for fork pausing. We also present evidence indicating that phosphorylation of the EBNA-1 protein or EBNA-1-truncated derivatives is not essential for pausing. To investigate the mechanism of EBNA-1-mediated pausing of replication forks, we asked whether EBNA-1 could inhibit the DNA unwinding activity of replicative helicases. We found that EBNA-1, when bound to the FR, inhibits DNA unwinding in vitro by SV40 T antigen and Escherichia coli dnaB helicases in an orientation-independent manner.
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Affiliation(s)
- O V Ermakova
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York 10461, USA
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40
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Abstract
Recent structural studies of the Epstein-Barr virus EBNA1 protein bound to DNA suggest that it binds to DNA replication origins in a two-step process; the first step involves recognition of the correct sequence and the second initiates structural changes in the DNA.
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Affiliation(s)
- F B Dean
- Microbiology Department, Hearst Research Foundation and Howard Hughes Medical Institute, Cornell University Medical College, 1300 York Avenue, New York, New York 10021, USA
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Bochkarev A, Barwell JA, Pfuetzner RA, Bochkareva E, Frappier L, Edwards AM. Crystal structure of the DNA-binding domain of the Epstein-Barr virus origin-binding protein, EBNA1, bound to DNA. Cell 1996; 84:791-800. [PMID: 8625416 DOI: 10.1016/s0092-8674(00)81056-9] [Citation(s) in RCA: 174] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The Epstein-Barr virus nuclear antigen 1 (EBNA1) protein binds to and activates DNA replication from oriP, the latent origin of DNA replication in Epstein-Barr virus. The crystal structure of the DNA-binding domain of EBNA1 bound to an 18 bp binding site was solved at 2.4 A resolution. EBNA1 comprises two domains, a flanking and a core domain. The flanking domain, which includes a helix that projects into the major groove and an extended chain that travels along the minor groove, makes all of the sequence-determining contacts with the DNA. The core domain, which is structurally homologous to the complete DNA-binding domain of the bovine papilloma virus E2 protein, makes no direct contacts with the DNA bases. A model for origin unwinding is proposed that incorporates the known biochemical and structural features of the EBNA1-origin interaction.
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Affiliation(s)
- A Bochkarev
- Institute for Molecular Biology and Biotechnology, Cancer Research Group, Department of Pathology, McMaster University, Hamilton, Ontario Canada
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