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Rehman SU, Ali R, Zhang H, Zafar MH, Wang M. Research progress in the role and mechanism of Leucine in regulating animal growth and development. Front Physiol 2023; 14:1252089. [PMID: 38046946 PMCID: PMC10691278 DOI: 10.3389/fphys.2023.1252089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 11/08/2023] [Indexed: 12/05/2023] Open
Abstract
Leucine, a branched-chain amino acid, is essential in regulating animal growth and development. Recent research has uncovered the mechanisms underlying Leucine's anabolic effects on muscle and other tissues, including its ability to stimulate protein synthesis by activating the mTORC1 signaling pathway. The co-ingestion of carbohydrates and essential amino acids enhances Leucine's anabolic effects. Moreover, Leucine has been shown to benefit lipid metabolism, and insulin sensitivity, making it a promising strategy for preventing and treating metabolic diseases, including type 2 diabetes and obesity. While emerging evidence indicates that epigenetic mechanisms may mediate Leucine's effects on growth and development, more research is needed to elucidate its mechanisms of action fully. Specific studies have demonstrated that Leucine promotes muscle growth and metabolic health in animals and humans, making it a promising therapeutic agent. However, it is essential to note that Leucine supplementation may cause digestive issues or interact with certain medications, and More study is required to determine definitively optimal dosages. Therefore, it is important to understand how Leucine interacts with other nutrients, dietary factors, and lifestyle habits to maximize its benefits. Overall, Leucine's importance in human nutrition is far-reaching, and its potential to prevent muscle loss and enhance athletic performance warrants further investigation.
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Affiliation(s)
| | | | | | | | - Mengzhi Wang
- Laboratory of Metabolic Manipulation of Herbivorous Animal Nutrition, College of Animal Science and Technology, Yangzhou University, Yangzhou, China
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2
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Varshney N, Murmu S, Baral B, Kashyap D, Singh S, Kandpal M, Bhandari V, Chaurasia A, Kumar S, Jha HC. Unraveling the Aurora kinase A and Epstein-Barr nuclear antigen 1 axis in Epstein Barr virus associated gastric cancer. Virology 2023; 588:109901. [PMID: 37839162 DOI: 10.1016/j.virol.2023.109901] [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: 08/04/2023] [Revised: 09/18/2023] [Accepted: 09/29/2023] [Indexed: 10/17/2023]
Abstract
Aurora kinase A (AURKA) is one of the crucial cell cycle regulators associated with gastric cancer. Here, we explored Epstein Barr Virus-induced gastric cancer progression through EBV protein EBNA1 with AURKA. We found that EBV infection enhanced cell proliferation and migration of AGS cells and upregulation of AURKA levels. AURKA knockdown markedly reduced the proliferation and migration of the AGS cells even with EBV infection. Moreover, MD-simulation data deciphered the probable connection between EBNA1 and AURKA. The in-vitro analysis through the transcript and protein expression showed that AURKA knockdown reduces the expression of EBNA1. Moreover, EBNA1 alone can enhance AURKA protein expression in AGS cells. Co-immunoprecipitation and NMR analysis between AURKA and EBNA1 depicts the interaction between two proteins. In addition, AURKA knockdown promotes apoptosis in EBV-infected AGS cells through cleavage of Caspase-3, -9, and PARP1. This study demonstrates that EBV oncogenic modulators EBNA1 possibly modulate AURKA in EBV-mediated gastric cancer progression.
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Affiliation(s)
- Nidhi Varshney
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India
| | - Sneha Murmu
- Division of Agricultural Bioinformatics (DABin), ICAR-Indian Agricultural Statistics Research Institute (IASRI), India
| | - Budhadev Baral
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India
| | - Dharmendra Kashyap
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India
| | - Siddharth Singh
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India
| | - Meenakshi Kandpal
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India
| | - Vasundhra Bhandari
- Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research, Hyderabad, India
| | | | - Sunil Kumar
- Division of Agricultural Bioinformatics (DABin), ICAR-Indian Agricultural Statistics Research Institute (IASRI), India.
| | - Hem Chandra Jha
- Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, India.
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3
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Buschle A, Mrozek-Gorska P, Cernilogar FM, Ettinger A, Pich D, Krebs S, Mocanu B, Blum H, Schotta G, Straub T, Hammerschmidt W. Epstein-Barr virus inactivates the transcriptome and disrupts the chromatin architecture of its host cell in the first phase of lytic reactivation. Nucleic Acids Res 2021; 49:3217-3241. [PMID: 33675667 PMCID: PMC8034645 DOI: 10.1093/nar/gkab099] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/01/2021] [Accepted: 02/04/2021] [Indexed: 12/13/2022] Open
Abstract
Epstein-Barr virus (EBV), a herpes virus also termed HHV 4 and the first identified human tumor virus, establishes a stable, long-term latent infection in human B cells, its preferred host. Upon induction of EBV's lytic phase, the latently infected cells turn into a virus factory, a process that is governed by EBV. In the lytic, productive phase, all herpes viruses ensure the efficient induction of all lytic viral genes to produce progeny, but certain of these genes also repress the ensuing antiviral responses of the virally infected host cells, regulate their apoptotic death or control the cellular transcriptome. We now find that EBV causes previously unknown massive and global alterations in the chromatin of its host cell upon induction of the viral lytic phase and prior to the onset of viral DNA replication. The viral initiator protein of the lytic cycle, BZLF1, binds to >105 binding sites with different sequence motifs in cellular chromatin in a concentration dependent manner implementing a binary molar switch probably to prevent noise-induced erroneous induction of EBV's lytic phase. Concomitant with DNA binding of BZLF1, silent chromatin opens locally as shown by ATAC-seq experiments, while previously wide-open cellular chromatin becomes inaccessible on a global scale within hours. While viral transcripts increase drastically, the induction of the lytic phase results in a massive reduction of cellular transcripts and a loss of chromatin-chromatin interactions of cellular promoters with their distal regulatory elements as shown in Capture-C experiments. Our data document that EBV's lytic cycle induces discrete early processes that disrupt the architecture of host cellular chromatin and repress the cellular epigenome and transcriptome likely supporting the efficient de novo synthesis of this herpes virus.
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Affiliation(s)
- Alexander Buschle
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research (DZIF), Partner site Munich, Germany, Feodor-Lynen-Str. 21, D-81377 Munich, Germany
| | - Paulina Mrozek-Gorska
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research (DZIF), Partner site Munich, Germany, Feodor-Lynen-Str. 21, D-81377 Munich, Germany
| | - Filippo M Cernilogar
- Division of Molecular Biology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität (LMU) München, 82152 Planegg-Martinsried, Germany
| | - Andreas Ettinger
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, German Research Center for Environmental Health, Feodor-Lynen-Str. 21 D-81377 Munich, Germany
| | - Dagmar Pich
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research (DZIF), Partner site Munich, Germany, Feodor-Lynen-Str. 21, D-81377 Munich, Germany
| | - Stefan Krebs
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians-Universität (LMU) München, 81377 Munich, Germany
| | - Bianca Mocanu
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research (DZIF), Partner site Munich, Germany, Feodor-Lynen-Str. 21, D-81377 Munich, Germany
| | - Helmut Blum
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians-Universität (LMU) München, 81377 Munich, Germany
| | - Gunnar Schotta
- Division of Molecular Biology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität (LMU) München, 82152 Planegg-Martinsried, Germany
| | - Tobias Straub
- Bioinformatics Unit, Biomedical Center, Ludwig-Maximilians-Universität (LMU) München, 82152 Planegg-Martinsried, Germany
| | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research (DZIF), Partner site Munich, Germany, Feodor-Lynen-Str. 21, D-81377 Munich, Germany
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4
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The Epstein-Barr Virus Lytic Protein BMLF1 Induces Upregulation of GRP78 Expression through ATF6 Activation. Int J Mol Sci 2021; 22:ijms22084024. [PMID: 33919712 PMCID: PMC8070695 DOI: 10.3390/ijms22084024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/10/2021] [Accepted: 04/12/2021] [Indexed: 11/17/2022] Open
Abstract
The unfolded protein response (UPR) is an intracellular signaling pathway essential for alleviating the endoplasmic reticulum (ER) stress. To support the productive infection, many viruses are known to use different strategies to manipulate the UPR signaling network. However, it remains largely unclear whether the UPR signaling pathways are modulated in the lytic cycle of Epstein-Barr virus (EBV), a widely distributed human pathogen. Herein, we show that the expression of GRP78, a central UPR regulator, is up-regulated during the EBV lytic cycle. Our data further revealed that knockdown of GRP78 in EBV-infected cell lines did not substantially affect lytic gene expression; however, GRP78 knockdown in these cells markedly reduced the production of virus particles. Importantly, we identified that the early lytic protein BMLF1 is the key regulator critically contributing to the activation of the grp78 gene promoter. Mechanistically, we found that BMLF1 can trigger the proteolytic cleavage and activation of the UPR senor ATF6, which then transcriptionally activates the grp78 promoter through the ER stress response elements. Our findings therefore provide evidence for the connection between the EBV lytic cycle and the UPR, and implicate that the BMLF1-mediated ATF6 activation may play critical roles in EBV lytic replication.
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Stolz ML, McCormick C. The bZIP Proteins of Oncogenic Viruses. Viruses 2020; 12:v12070757. [PMID: 32674309 PMCID: PMC7412551 DOI: 10.3390/v12070757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/08/2020] [Accepted: 07/13/2020] [Indexed: 12/20/2022] Open
Abstract
Basic leucine zipper (bZIP) transcription factors (TFs) govern diverse cellular processes and cell fate decisions. The hallmark of the leucine zipper domain is the heptad repeat, with leucine residues at every seventh position in the domain. These leucine residues enable homo- and heterodimerization between ZIP domain α-helices, generating coiled-coil structures that stabilize interactions between adjacent DNA-binding domains and target DNA substrates. Several cancer-causing viruses encode viral bZIP TFs, including human T-cell leukemia virus (HTLV), hepatitis C virus (HCV) and the herpesviruses Marek’s disease virus (MDV), Epstein–Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV). Here, we provide a comprehensive review of these viral bZIP TFs and their impact on viral replication, host cell responses and cell fate.
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6
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Germini D, Sall FB, Shmakova A, Wiels J, Dokudovskaya S, Drouet E, Vassetzky Y. Oncogenic Properties of the EBV ZEBRA Protein. Cancers (Basel) 2020; 12:E1479. [PMID: 32517128 PMCID: PMC7352903 DOI: 10.3390/cancers12061479] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/03/2020] [Accepted: 06/04/2020] [Indexed: 12/14/2022] Open
Abstract
Epstein Barr Virus (EBV) is one of the most common human herpesviruses. After primary infection, it can persist in the host throughout their lifetime in a latent form, from which it can reactivate following specific stimuli. EBV reactivation is triggered by transcriptional transactivator proteins ZEBRA (also known as Z, EB-1, Zta or BZLF1) and RTA (also known as BRLF1). Here we discuss the structural and functional features of ZEBRA, its role in oncogenesis and its possible implication as a prognostic or diagnostic marker. Modulation of host gene expression by ZEBRA can deregulate the immune surveillance, allow the immune escape, and favor tumor progression. It also interacts with host proteins, thereby modifying their functions. ZEBRA is released into the bloodstream by infected cells and can potentially penetrate any cell through its cell-penetrating domain; therefore, it can also change the fate of non-infected cells. The features of ZEBRA described in this review outline its importance in EBV-related malignancies.
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Affiliation(s)
- Diego Germini
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
| | - Fatimata Bintou Sall
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
- Laboratory of Hematology, Aristide Le Dantec Hospital, Cheikh Anta Diop University, Dakar 12900, Senegal
| | - Anna Shmakova
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
| | - Joëlle Wiels
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
| | - Svetlana Dokudovskaya
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
| | - Emmanuel Drouet
- CIBB-IBS UMR 5075 Université Grenoble Alpes, 38044 Grenoble, France;
| | - Yegor Vassetzky
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, 94805 Villejuif, France; (D.G.); (F.B.S.); (A.S.); (J.W.); (S.D.)
- Koltzov Institute of Developmental Biology, 117334 Moscow, Russia
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7
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Schaeffner M, Mrozek-Gorska P, Buschle A, Woellmer A, Tagawa T, Cernilogar FM, Schotta G, Krietenstein N, Lieleg C, Korber P, Hammerschmidt W. BZLF1 interacts with chromatin remodelers promoting escape from latent infections with EBV. Life Sci Alliance 2019; 2:e201800108. [PMID: 30926617 PMCID: PMC6441497 DOI: 10.26508/lsa.201800108] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 03/17/2019] [Accepted: 03/18/2019] [Indexed: 12/16/2022] Open
Abstract
A hallmark of EBV infections is its latent phase, when all viral lytic genes are repressed. Repression results from a high nucleosome occupancy and epigenetic silencing by cellular factors such as the Polycomb repressive complex 2 (PRC2) and DNA methyltransferases that, respectively, introduce repressive histone marks and DNA methylation. The viral transcription factor BZLF1 acts as a molecular switch to induce transition from the latent to the lytic or productive phase of EBV's life cycle. It is unknown how BZLF1 can bind to the epigenetically silenced viral DNA and whether it directly reactivates the viral genome through chromatin remodeling. We addressed these fundamental questions and found that BZLF1 binds to nucleosomal DNA motifs both in vivo and in vitro. BZLF1 co-precipitates with cellular chromatin remodeler ATPases, and the knock-down of one of them, INO80, impaired lytic reactivation and virus synthesis. In Assay for Transposase-Accessible Chromatin-seq experiments, non-accessible chromatin opens up locally when BZLF1 binds to its cognate sequence motifs in viral DNA. We conclude that BZLF1 reactivates the EBV genome by directly binding to silenced chromatin and recruiting cellular chromatin-remodeling enzymes, which implement a permissive state for lytic viral transcription. BZLF1 shares this mode of action with a limited number of cellular pioneer factors, which are instrumental in transcriptional activation, differentiation, and reprogramming in all eukaryotic cells.
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Affiliation(s)
- Marisa Schaeffner
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Paulina Mrozek-Gorska
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Alexander Buschle
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Anne Woellmer
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Takanobu Tagawa
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
| | - Filippo M Cernilogar
- Biomedical Center, Molecular Biology, Ludwig-Maximilians-Universität Munich, Planegg, Germany
| | - Gunnar Schotta
- Biomedical Center, Molecular Biology, Ludwig-Maximilians-Universität Munich, Planegg, Germany
- Center for Integrated Protein Science Munich, Munich, Germany
| | - Nils Krietenstein
- Biomedical Center, Molecular Biology, Ludwig-Maximilians-Universität Munich, Planegg, Germany
| | - Corinna Lieleg
- Biomedical Center, Molecular Biology, Ludwig-Maximilians-Universität Munich, Planegg, Germany
| | - Philipp Korber
- Biomedical Center, Molecular Biology, Ludwig-Maximilians-Universität Munich, Planegg, Germany
| | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
- German Center for Infection Research (DZIF), Partner Site Munich, Munich, Germany
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8
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Chen LW, Hung CH, Wang SS, Yen JB, Liu AC, Hung YH, Chang PJ. Expression and regulation of the BKRF2, BKRF3 and BKRF4 genes of Epstein-Barr virus. Virus Res 2018; 256:76-89. [PMID: 30096410 DOI: 10.1016/j.virusres.2018.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 08/02/2018] [Accepted: 08/04/2018] [Indexed: 12/24/2022]
Abstract
The BKRF2, BKRF3 and BKRF4 genes of Epstein-Barr virus (EBV) are located close together in the viral genome, which encode glycoprotein L, uracil-DNA glycosylase and a tegument protein, respectively. Here, we demonstrate that the BKRF2 gene behaves as a true-late lytic gene, whereas the BKRF3 and BKRF4 genes belong to the early lytic gene family. Our results further reveal that both BKRF3 and BKRF4 promoters are new synergistic targets of Zta and Rta, two EBV latent-to-lytic switch transactivators. Multiple Rta- and Zta-responsive elements within the BKRF3 and BKRF4 promoters were identified and characterized experimentally. Importantly, we show that DNA methylation is absolutely required for activation of the BKRF4 promoter by Zta alone or in combination with Rta. Moreover, we find that sodium butyrate, an inducing agent of EBV reactivation, is capable of activating the BKRF4 promoter through a mechanism independent of Zta and Rta. Overall, our studies highlight the complexity of transcriptional regulation of lytic genes within the BKRF2-BKRF3-BKRF4 gene locus.
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Affiliation(s)
- Lee-Wen Chen
- Department of Respiratory Care, Chang-Gung University of Science and Technology, Chiayi 61363, Taiwan; Department of Pediatric Surgery, Chang-Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Chien-Hui Hung
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan 33302, Taiwan
| | - Shie-Shan Wang
- Department of Pediatric Surgery, Chang-Gung Memorial Hospital, Chiayi 61363, Taiwan; School of Traditional Chinese Medicine, College of Medicine, Chang-Gung University, Taoyuan 33302, Taiwan
| | - Ju-Bei Yen
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan 33302, Taiwan; Department of Pediatrics, Chang-Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Ann-Chi Liu
- Department of Respiratory Care, Chang-Gung University of Science and Technology, Chiayi 61363, Taiwan
| | - Ya-Hui Hung
- Department of Respiratory Care, Chang-Gung University of Science and Technology, Chiayi 61363, Taiwan
| | - Pey-Jium Chang
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan 33302, Taiwan; Department of Nephrology, Chang-Gung Memorial Hospital, Chiayi 61363, Taiwan.
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9
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Sall FB, Germini D, Kovina AP, Ribrag V, Wiels J, Toure AO, Iarovaia OV, Lipinski M, Vassetzky Y. Effect of Environmental Factors on Nuclear Organization and Transformation of Human B Lymphocytes. BIOCHEMISTRY (MOSCOW) 2018; 83:402-410. [DOI: 10.1134/s0006297918040119] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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10
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Kaposi's Sarcoma-Associated Herpesvirus K8 Is an RNA Binding Protein That Regulates Viral DNA Replication in Coordination with a Noncoding RNA. J Virol 2018; 92:JVI.02177-17. [PMID: 29321307 DOI: 10.1128/jvi.02177-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/03/2018] [Indexed: 12/16/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) lytic replication and constant primary infection of fresh cells are crucial for viral tumorigenicity. The virus-encoded bZIP family protein K8 plays an important role in viral DNA replication in both viral reactivation and de novo infection. The mechanism underlying the functional role of K8 in the viral life cycle is elusive. Here, we report that K8 is an RNA binding protein that also associates with many other proteins, including other RNA binding proteins. Many protein-protein interactions involving K8 are mediated by RNA. Using a UV cross-linking and immunoprecipitation (CLIP) procedure combined with high-throughput sequencing, RNAs that are associated with K8 in BCBL-1 cells were identified, including both viral (PAN, T1.4, T0.7, etc.) and cellular (MALAT-1, MRP, 7SK, etc.) RNAs. An RNA binding motif in K8 was defined, and mutation of the motif abolished the ability of K8 to bind to many noncoding RNAs, as well as viral DNA replication during de novo infection, suggesting that the K8 functions in viral replication are carried out through RNA association. The functions of K8 and associated T1.4 RNA were investigated in detail, and the results showed that T1.4 mediates the binding of K8 to ori-Lyt DNA. The T1.4-K8 complex physically bound to KSHV ori-Lyt DNA and recruited other proteins and cofactors to assemble a replication complex. Depletion of T1.4 abolished DNA replication in primary infection. These findings provide mechanistic insights into the role of K8 in coordination with T1.4 RNA in regulating KSHV DNA replication during de novo infection.IMPORTANCE Genomewide analyses of the mammalian transcriptome revealed that a large proportion of sequence previously annotated as noncoding regions is actually transcribed and gives rise to stable RNAs. The emergence of a large number of noncoding RNAs suggests that functional RNA-protein complexes, e.g., ribosomes or spliceosomes, are not ancient relics of the last ribo-organism but would be well adapted to a regulatory role in biology. K8 has been puzzling because of its unique characteristics, such as multiple regulatory roles in gene expression and DNA replication without DNA binding capability. This study reveals the mechanism underlying its regulatory role by demonstrating that K8 is an RNA binding protein that binds to DNA and initiates DNA replication in coordination with a noncoding RNA. It is suggested that many K8 functions, if not all, are carried out through its associated RNAs.
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11
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Lin SJ, Wu SW, Chou YC, Lin JH, Huang YC, Chen MR, Ma N, Tsai CH. Novel expression and regulation of TIMP-1 in Epstein Barr virus-infected cells and its impact on cell survival. Virology 2015; 481:24-33. [DOI: 10.1016/j.virol.2015.02.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 01/25/2015] [Accepted: 02/10/2015] [Indexed: 11/26/2022]
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12
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Viral genome methylation differentially affects the ability of BZLF1 versus BRLF1 to activate Epstein-Barr virus lytic gene expression and viral replication. J Virol 2012; 87:935-50. [PMID: 23135711 DOI: 10.1128/jvi.01790-12] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Epstein-Barr virus (EBV) immediate-early proteins BZLF1 and BRLF1 can both induce lytic EBV reactivation when overexpressed in latently infected cells. Although EBV genome methylation is required for BZLF1-mediated activation of lytic gene expression, the effect of viral genome methylation on BRLF1-mediated viral reactivation has not been well studied. Here, we have compared the effect of viral DNA methylation on BZLF1- versus BRLF1-mediated activation of lytic EBV gene transcription and viral genome replication. We show that most early lytic viral promoters are preferentially activated by BZLF1 in the methylated form, while methylation decreases the ability of BRLF1 to activate most early lytic promoters, as well as the BLRF2 late viral promoter. Moreover, methylation of bacmid constructs containing the EBV genome enhances BZLF1-mediated, but decreases BRLF1-mediated, early lytic gene expression. Methylation of viral promoter DNA does not affect BRLF1 binding to a variety of different CpG-containing BRLF1 binding motifs (RREs) in vitro or in vivo. However, BRLF1 preferentially induces H3K9 histone acetylation of unmethylated promoters in vivo. The methylated and unmethylated forms of an oriLyt-containing plasmid replicate with similar efficiency when transfected into EBV-positive cells that express the essential viral replication proteins in trans. Most importantly, we demonstrate that lytic viral gene expression and replication can be induced by BRLF1, but not BZLF1, expression in an EBV-positive telomerase-immortalized epithelial cell line (NOKs-Akata) in which lytic viral gene promoters remain largely unmethylated. These results suggest that the unmethylated form of the EBV genome can undergo viral reactivation and replication in a BRLF1-dependent manner.
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13
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Epstein-Barr virus transcription activator R upregulates BARF1 expression by direct binding to its promoter, independent of methylation. J Virol 2012; 86:11322-32. [PMID: 22896599 DOI: 10.1128/jvi.01161-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Epstein-Barr virus (EBV) BamHI-A rightward frame 1 (BARF1) is considered a major viral oncogene in epithelial cells and has immune-modulating properties. However, in B cells and lymphomas, BARF1 expression is restricted to the viral lytic replication cycle. In this report, the transcriptional regulation of BARF1 during lytic replication is unraveled. Bisulfite sequencing of various cell lines indicated a high level of methylation of the BARF1 gene control region. A BARF1 promoter luciferase reporter construct was created using a CpG-free vector, enabling true assessment of promoter methylation. Induction of the EBV lytic cycle is mediated by the immediate-early proteins BZLF1 (Z) and BRLF1 (R). R was found to activate expression of the BARF1 promoter up to 250-fold independently of Z and unaffected by BARF1 promoter methylation. Chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA), and specific mutagenesis of the R-responsive elements (RREs) demonstrated direct binding of R to RREs between nucleotides -554 and -327 relative to the BARF1 transcriptional ATG start site. The kinetics of BARF1 expression upon transactivation by R showed that BARF1 mRNA was expressed within 6 h in the context of the viral genome. In conclusion, expression of the BARF1 protein during lytic replication is regulated by direct binding of R to multiple RREs in the gene control region and is independent of the promoter methylation status. The early kinetics of BARF1 upon transactivation by R confirm its status as an early gene and emphasize the necessity of early immune modulation during lytic reactivation.
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Imajoh M, Hashida Y, Murakami M, Maeda A, Sato T, Fujieda M, Wakiguchi H, Daibata M. Characterization of Epstein-Barr virus (EBV) BZLF1 gene promoter variants and comparison of cellular gene expression profiles in Japanese patients with infectious mononucleosis, chronic active EBV infection, and EBV-associated hemophagocytic lymphohistioc. J Med Virol 2012; 84:940-6. [DOI: 10.1002/jmv.23299] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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SUMO binding by the Epstein-Barr virus protein kinase BGLF4 is crucial for BGLF4 function. J Virol 2012; 86:5412-21. [PMID: 22398289 DOI: 10.1128/jvi.00314-12] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
An Epstein-Barr virus (EBV) protein microarray was used to screen for proteins binding noncovalently to the small ubiquitin-like modifier SUMO2. Among the 11 SUMO binding proteins identified was the conserved protein kinase BGLF4. The mutation of potential SUMO interaction motifs (SIMs) in BGLF4 identified N- and C-terminal SIMs. The mutation of both SIMs changed the intracellular localization of BGLF4 from nuclear to cytoplasmic, while BGLF4 mutated in the N-terminal SIM remained predominantly nuclear. The mutation of the C-terminal SIM yielded an intermediate phenotype with nuclear and cytoplasmic staining. The transfer of BGLF4 amino acids 342 to 359 to a nuclear green fluorescent protein (GFP)-tagged reporter protein led to the relocalization of the reporter to the cytoplasm. Thus, the C-terminal SIM lies adjacent to a nuclear export signal, and coordinated SUMO binding by the N- and C-terminal SIMs blocks export and allows the nuclear accumulation of BGLF4. The mutation of either SIM prevented SUMO binding in vitro. The ability of BGLF4 to abolish the SUMOylation of the EBV lytic cycle transactivator ZTA was dependent on both BGLF4 SUMO binding and BGLF4 kinase activity. The global profile of SUMOylated cell proteins was also suppressed by BGLF4 but not by the SIM or kinase-dead BGLF4 mutant. The effective BGLF4-mediated dispersion of promyelocytic leukemia (PML) bodies was dependent on SUMO binding. The SUMO binding function of BGLF4 was also required to induce the cellular DNA damage response and to enhance the production of extracellular virus during EBV lytic replication. Thus, SUMO binding by BGLF4 modulates BGLF4 function and affects the efficiency of lytic EBV replication.
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Robinson AR, Kwek SS, Kenney SC. The B-cell specific transcription factor, Oct-2, promotes Epstein-Barr virus latency by inhibiting the viral immediate-early protein, BZLF1. PLoS Pathog 2012; 8:e1002516. [PMID: 22346751 PMCID: PMC3276558 DOI: 10.1371/journal.ppat.1002516] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 12/16/2011] [Indexed: 01/16/2023] Open
Abstract
The Epstein-Barr virus (EBV) latent-lytic switch is mediated by the BZLF1 immediate-early protein. EBV is normally latent in memory B cells, but cellular factors which promote viral latency specifically in B cells have not been identified. In this report, we demonstrate that the B-cell specific transcription factor, Oct-2, inhibits the function of the viral immediate-early protein, BZLF1, and prevents lytic viral reactivation. Co-transfected Oct-2 reduces the ability of BZLF1 to activate lytic gene expression in two different latently infected nasopharyngeal carcinoma cell lines. Furthermore, Oct-2 inhibits BZLF1 activation of lytic EBV promoters in reporter gene assays, and attenuates BZLF1 binding to lytic viral promoters in vivo. Oct-2 interacts directly with BZLF1, and this interaction requires the DNA-binding/dimerization domain of BZLF1 and the POU domain of Oct-2. An Oct-2 mutant (Δ262–302) deficient for interaction with BZLF1 is unable to inhibit BZLF1-mediated lytic reactivation. However, an Oct-2 mutant defective for DNA-binding (Q221A) retains the ability to inhibit BZLF1 transcriptional effects and DNA-binding. Importantly, shRNA-mediated knockdown of endogenous Oct-2 expression in several EBV-positive Burkitt lymphoma and lymphoblastoid cell lines increases the level of lytic EBV gene expression, while decreasing EBNA1 expression. Moreover, treatments which induce EBV lytic reactivation, such as anti-IgG cross-linking and chemical inducers, also decrease the level of Oct-2 protein expression at the transcriptional level. We conclude that Oct-2 potentiates establishment of EBV latency in B cells. Epstein-Barr virus (EBV) is a human herpesvirus associated with B-cell malignancies. EBV infection of cells can result in either lytic replication or latency. Memory B cells are the primary site of EBV latency within the human host, while oropharyngeal epithelial cells support the lytic form of infection. However, the cellular mechanism(s) that enable EBV to establish viral latency in a B-cell specific manner are not currently understood. In this report, we show that the B-cell specific cellular transcription factor, Oct-2, promotes viral latency by inhibiting the lytic form of infection. We find that Oct-2 interacts directly with the EBV immediate-early protein, BZLF1, and abrogates its ability to activate lytic viral gene transcription through protein-protein interactions off the DNA. Furthermore, knockdown of endogenous Oct-2 expression in several latently-infected Burkitt lymphoma B-cell lines increases EBV lytic protein expression. In addition, we show that certain stimuli which can prompt lytic EBV reactivation in B cells also decrease expression of endogenous Oct-2. Our results suggest that the cellular transcription factor, Oct-2, promotes EBV latency in a B-cell dependent manner.
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Affiliation(s)
- Amanda R. Robinson
- Department of Oncology, McArdle Laboratory for Cancer Research , University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
- Department of Cellular and Molecular Biology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Swee Sen Kwek
- Department of Oncology, McArdle Laboratory for Cancer Research , University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Shannon C. Kenney
- Department of Oncology, McArdle Laboratory for Cancer Research , University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
- * E-mail:
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Wu H, Li T, Zeng M, Peng T. Herpes simplex virus type 1 infection activates the Epstein-Barr virus replicative cycle via a CREB-dependent mechanism. Cell Microbiol 2012; 14:546-59. [PMID: 22188237 DOI: 10.1111/j.1462-5822.2011.01740.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reactivation of latent Epstein-Barr virus (EBV) to lytic replication is important in pathogenesis and requires virus-host cellular interactions. However, the mechanism underlying the reactivation of EBV is not yet fully understood. In the present study, herpes simplex virus type 1 (HSV-1) was shown to induce the reactivation of latent EBV by triggering BZLF1 expression. The BZLF1 promoter (Zp) was not activated by HSV-1 essential glycoprotein-induced membrane fusion. Nevertheless, Zp was activated within 6 h post HSV-1 infection in virus entry-dependent and replication-independent manners. Using a panel of Zp deletion mutants, HSV-1 was shown to promote Zp through a cyclic adenosine monophosphate (cAMP) response element (CRE) located in ZII. The phosphorylated cAMP response element-binding (phos-CREB) protein, the cellular transactivator that binds to CRE, also increased after HSV-1 infection. By transient transfection, cAMP-dependent protein kinase A and HSV-1 US3 protein were found to be capable of activating Zp in CREB- and CRE-dependent manners. The relationship between EBV activation and HSV-1 infection revealed a possible common mechanism that stimulated latent EBV into lytic cycles in vivo.
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Affiliation(s)
- Hongling Wu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
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Katsumura KR, Maruo S, Takada K. EBV lytic infection enhances transformation of B-lymphocytes infected with EBV in the presence of T-lymphocytes. J Med Virol 2012; 84:504-10. [DOI: 10.1002/jmv.23208] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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19
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Toyooka T, Hisatomi O, Takahashi F, Kataoka H, Terazima M. Photoreactions of aureochrome-1. Biophys J 2011; 100:2801-9. [PMID: 21641326 DOI: 10.1016/j.bpj.2011.02.043] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/22/2011] [Accepted: 02/24/2011] [Indexed: 10/18/2022] Open
Abstract
Aureochrome is a recently discovered blue light photosensor that controls a light-dependent morphology change. As a photosensor, it has a unique DNA binding domain (bZIP). Although the biological functions of aureochrome have been revealed, the fundamental photochemistry of this protein has not been elucidated. The photochemical reaction dynamics of the LOV (light, oxygen, or voltage) domain of aureochrome-1 (AUREO1-LOV) and the LOV domain with the bZIP domain (AUREO1-ZL) were studied by employing the transient-grating (TG) technique, using size-exclusion chromatography to verify results. For both samples, adduct formation takes place with a time constant of 2.8 μs. Although significant diffusion changes were observed for both AUREO1-LOV and AUREO1-ZL after adduct formation, the origins of these changes were significantly different. The TG signal of AUREO1-LOV was strongly concentration-dependent. From analysis of the signal, it was concluded that AUREO1-LOV exists in equilibrium between the monomer and dimer, and dimerization of the monomer is the main reaction, i.e., irradiation with blue light enhances the strength of the interdomain interaction. On the other hand, the reaction of AUREO1-ZL is independent of concentration, suggesting that an intraprotein conformational change occurs in the bZIP domain with a time constant of 160 ms. These results revealed the different reactions and roles of the two domains; the LOV domain acts as a photosensor, leading to a subsequent conformational change in the bZIP domain, which should change its ability to bind to DNA. A model is proposed that demonstrates how aureochrome uses blue light to control its affinity for DNA.
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Affiliation(s)
- Tsuguyoshi Toyooka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
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Epstein-Barr virus Zta-induced immunomodulators from nasopharyngeal carcinoma cells upregulate interleukin-10 production from monocytes. J Virol 2011; 85:7333-42. [PMID: 21543473 DOI: 10.1128/jvi.00182-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
During lytic infection with Epstein-Barr virus (EBV), several viral lytic proteins function to evade immune recognition or to actively suppress immune cells. An EBV lytic transactivator, Zta, induces an immunosuppressive cytokine interleukin 10 (IL-10) in B cells, but whether it regulates IL-10 in the context of epithelial cells is unclear. In this study, we tested nasopharyngeal carcinoma (NPC) cell lines and found that Zta did not induce IL-10 in these epithelial cells. Interestingly, the conditioned medium of Zta-expressing NPC cells enhanced IL-10 production from monocytes. We further revealed that the IL-10-inducing effect involved at least two immunomodulators that were upregulated by Zta and secreted from NPC cells: granulocyte-macrophage colony-stimulating factor (GM-CSF) and prostaglandin E(2) (PGE(2)). Zta was recruited to and activated the GM-CSF promoter, thus upregulating GM-CSF expression. Zta also activated the promoter of cyclooxygenase-2 (COX-2), and Zta-induced COX-2 increased downstream PGE(2) production. Cotreatment with GM-CSF and PGE(2) synergistically induced IL-10 production from monocytes. The IL-10-inducing effect of the Zta-conditioned medium was reduced when GM-CSF or the COX-2/PGE(2) pathway was blocked. The conditioned medium of NPC cells with EBV lytic infection showed a similar increase of GM-CSF and PGE(2) levels as well as the IL-10-inducing effect on monocytes, and knockdown of Zta abolished all the effects. Therefore, through Zta-induced immunomodulators, EBV lytic infection in NPC cells can direct bystander monocytes to produce IL-10, which may be a novel way of EBV to promote local immunosuppression.
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Park R, Wang'ondu R, Heston L, Shedd D, Miller G. Efficient induction of nuclear aggresomes by specific single missense mutations in the DNA-binding domain of a viral AP-1 homolog. J Biol Chem 2011; 286:9748-62. [PMID: 21233201 DOI: 10.1074/jbc.m110.198325] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nuclear aggresomes induced by proteins containing an expanded polyglutamine (polyQ) tract are pathologic hallmarks of certain neurodegenerative diseases. Some GFP fusion proteins lacking a polyQ tract may also induce nuclear aggresomes in cultured cells. Here we identify single missense mutations within the basic DNA recognition region of Bam HI Z E B virus replication activator (ZEBRA), an Epstein-Barr virus (EBV)-encoded basic zipper protein without a polyQ tract, that efficiently induced the formation of nuclear aggresomes. Wild-type (WT) ZEBRA was diffusely distributed within the nucleus. Four non-DNA-binding mutants, Z(R179E), Z(R183E), Z(R190E), and Z(K178D) localized to the periphery of large intranuclear spheres, to discrete nuclear aggregates, and to the cytoplasm. Other non-DNA-binding mutants, Z(N182K), Z(N182E), and Z(S186E), did not exhibit this phenotype. The interior of the spheres contained promyelocytic leukemia and HSP70 proteins. ZEBRA mutants directly induced the nuclear aggresome pathway in cells with and without EBV. Specific cellular proteins (SC35 and HDAC6) and viral proteins (WT ZEBRA, Rta, and BMLF1) but not other cellular or viral proteins were recruited to nuclear aggresomes. Co-transfection of WT ZEBRA with aggresome-inducing mutants Z(R183E) and Z(R179E) inhibited late lytic viral protein expression and lytic viral DNA amplification. This is the first reported instance in which nuclear aggresomes are induced by single missense mutations in a viral or cellular protein. We discuss conformational changes in the mutant viral AP-1 proteins that may lead to formation of nuclear aggresomes.
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Affiliation(s)
- Richard Park
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Chen CC, Yang YC, Wang WH, Chen CS, Chang LK. Enhancement of Zta-activated lytic transcription of Epstein-Barr virus by Ku80. J Gen Virol 2010; 92:661-8. [DOI: 10.1099/vir.0.026302-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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The nuclear and adherent junction complex component protein ubinuclein negatively regulates the productive cycle of Epstein-Barr virus in epithelial cells. J Virol 2010; 85:784-94. [PMID: 21084479 DOI: 10.1128/jvi.01397-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Epstein-Barr Virus (EBV) productive cycle is initiated by the expression of the viral trans-activator EB1 (also called Zebra, Zta, or BZLF1), which belongs to the basic leucine zipper transcription factor family. We have previously identified the cellular NACos (nuclear and adherent junction complex components) protein ubinuclein (Ubn-1) as a partner for EB1, but the function of this complex has never been studied. Here, we have evaluated the consequences of this interaction on the EBV productive cycle and find that Ubn-1 overexpression represses the EBV productive cycle whereas Ubn-1 downregulation by short hairpin RNA (shRNA) increases virus production. By a chromatin immunoprecipitation (ChIP) assay, we show that Ubn-1 blocks EB1-DNA interaction. We also show that in epithelial cells, relocalization and sequestration of Ubn-1 to the tight junctions of nondividing cells allow increased activation of the productive cycle. We propose a model in which Ubn-1 is a modulator of the EBV productive cycle: in proliferating epithelial cells, Ubn-1 is nuclear and inhibits activation of the productive cycle, whereas in differentiated cells, Ubn-1 is sequestrated to tight junctions, thereby allowing EB1 to fully function in the nucleus.
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The Epstein-Barr virus BZLF1 protein inhibits tumor necrosis factor receptor 1 expression through effects on cellular C/EBP proteins. J Virol 2010; 84:12362-74. [PMID: 20861254 DOI: 10.1128/jvi.00712-10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The Epstein-Barr virus immediate-early protein, BZLF1 (Z), initiates the switch between latent and lytic infection and plays an essential role in mediating viral replication. Z also inhibits expression of the major receptor for tumor necrosis factor (TNF), TNFR1, thus repressing TNF cytokine signaling, but the mechanism for this effect is unknown. Here, we demonstrate that Z prevents both C/EBPα- and C/EBPβ-mediated activation of the TNFR1 promoter (TNFR1p) by interacting directly with both C/EBP family members. We show that Z interacts directly with C/EBPα and C/EBPβ in vivo and that a Z mutant altered at alanine residue 204 in the bZIP domain is impaired for the ability to interact with both C/EBP proteins. Furthermore, we find that the Z(A204D) mutant is attenuated in the ability to inhibit the TNFR1p but mediates lytic viral reactivation and replication in vitro in 293 cells as well as wild-type Z. Although Z does not bind directly to the TNFR1p in EMSA studies, chromatin immunoprecipitation studies indicate that Z is complexed with this promoter in vivo. The Z(A204D) mutant has reduced interaction with the TNFR1p in vivo but is similar to wild-type Z in its ability to complex with the IL-8 promoter. Finally, we show that the effect of Z on C/EBPα- and C/EBPβ-mediated activation is promoter dependent. These results indicate that Z modulates the effects of C/EBPα and C/EBPβ in a promoter-specific manner and that in some cases (including that of the TNFR1p), Z inhibits C/EBPα- and C/EBPβ-mediated activation.
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Cellular microRNAs 200b and 429 regulate the Epstein-Barr virus switch between latency and lytic replication. J Virol 2010; 84:10329-43. [PMID: 20668090 DOI: 10.1128/jvi.00923-10] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously showed that the cellular proteins ZEB1 and ZEB2/SIP1 both play key roles in regulating the latent-lytic switch of Epstein-Barr Virus (EBV) by repressing BZLF1 gene expression. We investigated here the effects of cellular microRNA (miRNA) 200 (miR200) family members on the EBV infection status of cells. We show that miR200b and miR429, but not miR200a, can induce EBV-positive cells into lytic replication by downregulating expression of ZEB1 and ZEB2, leading to production of infectious virus. The levels of miR200 family members in EBV-infected cells strongly negatively correlated with the levels of the ZEBs (e.g., -0.89 [P < 0.001] for miR429 versus ZEB1) and positively correlated with the degree of EBV lytic gene expression (e.g., 0.73 [P < 0.01] for miR429 versus BZLF1). The addition of either miR200b or miR429 to EBV-positive cells led to EBV lytic reactivation in a ZEB-dependent manner; inhibition of these miRNAs led to decreased EBV lytic gene expression. The degree of latent infection by an EBV mutant defective in the primary ZEB-binding site of the EBV BZLF1 promoter was not affected by the addition of these miRNAs. Furthermore, EBV infection of primary blood B cells led to downregulation of these miRNAs and upregulation of ZEB levels. Thus, we conclude that miRNAs 200b and 429 are key regulators via their effects on expression of ZEB1 and ZEB2 of the switch between latent and lytic infection by EBV and, therefore, potential targets for development of new lytic induction therapeutics with which to treat patients with EBV-associated malignancies.
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Evidence for DNA hairpin recognition by Zta at the Epstein-Barr virus origin of lytic replication. J Virol 2010; 84:7073-82. [PMID: 20444899 DOI: 10.1128/jvi.02666-09] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Epstein-Barr virus immediate-early protein (Zta) plays an essential role in viral lytic activation and pathogenesis. Zta is a basic zipper (b-Zip) domain-containing protein that binds multiple sites in the viral origin of lytic replication (OriLyt) and is required for lytic-cycle DNA replication. We present evidence that Zta binds to a sequence-specific, imperfect DNA hairpin formed by an inverted repeat within the upstream essential element (UEE) of OriLyt. Mutations in the OriLyt sequence that are predicted to disrupt hairpin formation also disrupt Zta binding in vitro. Restoration of the hairpin rescues the defect. We also show that OriLyt DNA isolated from replicating cells contains a nuclease-sensitive region that overlaps with the inverted-repeat region of the UEE. Furthermore, point mutations in Zta that disrupt specific recognition of the UEE hairpin are defective for activation of lytic replication. These data suggest that Zta acts by inducing and/or stabilizing a DNA hairpin structure during productive infection. The DNA hairpin at OriLyt with which Zta interacts resembles DNA structures formed at other herpesvirus origins and may therefore represent a common secondary structure used by all herpesvirus family members during the initiation of DNA replication.
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Reinke AW, Grigoryan G, Keating AE. Identification of bZIP interaction partners of viral proteins HBZ, MEQ, BZLF1, and K-bZIP using coiled-coil arrays. Biochemistry 2010; 49:1985-97. [PMID: 20102225 DOI: 10.1021/bi902065k] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Basic-region leucine-zipper transcription factors (bZIPs) contain a segment rich in basic amino acids that can bind DNA, followed by a leucine zipper that can interact with other leucine zippers to form coiled-coil homo- or heterodimers. Several viruses encode proteins containing bZIP domains, including four that encode bZIPs lacking significant homology to any human protein. We investigated the interaction specificity of these four viral bZIPs by using coiled-coil arrays to assess self-associations as well as heterointeractions with 33 representative human bZIPs. The arrays recapitulated reported viral-human interactions and also uncovered new associations. MEQ and HBZ interacted with multiple human partners and had unique interaction profiles compared to any human bZIPs, whereas K-bZIP and BZLF1 displayed homospecificity. New interactions detected included HBZ with MAFB, MAFG, ATF2, CEBPG, and CREBZF and MEQ with NFIL3. These were confirmed in solution using circular dichroism. HBZ can heteroassociate with MAFB and MAFG in the presence of MARE-site DNA, and this interaction is dependent on the basic region of HBZ. NFIL3 and MEQ have different yet overlapping DNA-binding specificities and can form a heterocomplex with DNA. Computational design considering both affinity for MEQ and specificity with respect to other undesired bZIP-type interactions was used to generate a MEQ dimerization inhibitor. This peptide, anti-MEQ, bound MEQ both stably and specifically, as assayed using coiled-coil arrays and circular dichroism in solution. Anti-MEQ also inhibited MEQ binding to DNA. These studies can guide further investigation of the function of viral and human bZIP complexes.
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Affiliation(s)
- Aaron W Reinke
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Either ZEB1 or ZEB2/SIP1 can play a central role in regulating the Epstein-Barr virus latent-lytic switch in a cell-type-specific manner. J Virol 2010; 84:6139-52. [PMID: 20375168 DOI: 10.1128/jvi.02706-09] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously reported that the cellular protein ZEB1 can repress expression of the Epstein-Barr virus (EBV) BZLF1 gene in transient transfection assays by directly binding its promoter, Zp. We also reported that EBV containing a 2-bp substitution mutation in the ZEB-binding ZV element of Zp spontaneously reactivated out of latency into lytic replication at a higher frequency than did wild-type EBV. Here, using small interfering RNA (siRNA) and short hairpin RNA (shRNA) technologies, we definitively show that ZEB1 is, indeed, a key player in maintaining EBV latency in some epithelial and B-lymphocytic cell lines. However, in other EBV-positive epithelial and B-cell lines, another zinc finger E-box-binding protein, ZEB2/SIP1, is the key player. Both ZEB1 and ZEB2 can bind Zp via the ZV element. In EBV-positive cells containing only ZEB1, knockdown of ZEB1 led to viral reactivation out of latency, with synthesis of EBV immediate-early and early lytic gene products. However, in EBV-positive cells containing both ZEBs, ZEB2, not ZEB1, was the primary ZEB family member bound to Zp. Knockdown of ZEB2, but not ZEB1, led to EBV lytic reactivation. Thus, we conclude that either ZEB1 or ZEB2 can play a central role in the maintenance of EBV latency, doing so in a cell-type-dependent manner.
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Evaluation of a prediction protocol to identify potential targets of epigenetic reprogramming by the cancer associated Epstein Barr virus. PLoS One 2010; 5:e9443. [PMID: 20195470 PMCID: PMC2829078 DOI: 10.1371/journal.pone.0009443] [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] [Received: 10/14/2009] [Accepted: 12/02/2009] [Indexed: 12/15/2022] Open
Abstract
Background Epstein Barr virus (EBV) infects the majority of the human population, causing fatal diseases in a small proportion in conjunction with environmental factors. Following primary infection, EBV remains latent in the memory B cell population for life. Recurrent reactivation of the virus occurs, probably due to activation of the memory B-lymphocytes, resulting in viral replication and re-infection of B-lymphocytes. Methylation of the viral DNA at CpG motifs leads to silencing of viral gene expression during latency. Zta, the key viral protein that mediates the latency/reactivation balance, interacts with methylated DNA. Zta is a transcription factor for both viral and host genes. A sub-set of its DNA binding sites (ZREs) contains a CpG motif, which is recognised in its methylated form. Detailed analysis of the promoter of the viral gene BRLF1 revealed that interaction with a methylated CpG ZRE (RpZRE3) is key to overturning the epigenetic silencing of the gene. Methodology and Principal Findings Here we question whether we can use this information to identify which host genes contain promoters with similar response elements. A computational search of human gene promoters identified 274 targets containing the 7-nucleotide RpZRE3 core element. DNA binding analysis of Zta with 17 of these targets revealed that the flanking context of the core element does not have a profound effect on the ability of Zta to interact with the methylated sites. A second juxtaposed ZRE was observed for one promoter. Zta was able to interact with this site, although co-occupancy with the RpZRE3 core element was not observed. Conclusions/Significance This research demonstrates 274 human promoters have the potential to be regulated by Zta to overturn epigenetic silencing of gene expression during viral reactivation from latency.
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Sumoylation of the Epstein-Barr virus BZLF1 protein inhibits its transcriptional activity and is regulated by the virus-encoded protein kinase. J Virol 2010; 84:4383-94. [PMID: 20181712 DOI: 10.1128/jvi.02369-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Epstein-Barr virus (EBV) immediate-early protein BZLF1 (Z) mediates the switch between latent and lytic EBV infection. Z not only activates early lytic viral gene transcription but also plays a direct role in lytic viral genome replication. Although a small fraction of Z is known to be sumoylated, the effects of this posttranslational modification on various different Z functions have not been well defined. In this report, we show that only the lysine at amino acid residue 12 is required for the sumoylation of Z, and that Z can be sumoylated by SUMO isoforms 1, 2, and 3. We also demonstrate that the sumo-defective Z mutants ZK12A and ZK12R have enhanced transcriptional activity. The sumoylated and nonsumoylated forms of Z were found to have a similar cellular location, both being localized primarily within the nuclear matrix. The Z sumo-defective mutants were, however, partially defective for disrupting promyelocytic leukemia (PML) bodies compared to the ability of wild-type Z. In addition, we show that lytic viral genome replication does not require the sumoylation of Z, although a Z mutant altered at both amino acids 12 and 13 is replication defective. Furthermore, we show that the sumoylation of Z is greatly increased (from less than 1 to about 11%) in lytically induced 293 cells infected with an EBV mutant virus deleted for the EBV-encoded protein kinase (EBV-PK) compared to that of 293 cells infected with wild-type EBV, and that the overexpression of EBV-PK leads to the reduced sumoylation of Z in EBV-negative cells. Our results suggest that the sumoylation of Z helps to promote viral latency, and that EBV-PK inhibits Z sumoylation during viral reactivation.
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Rennekamp AJ, Lieberman PM. Initiation of lytic DNA replication in Epstein-Barr virus: search for a common family mechanism. Future Virol 2010; 5:65-83. [PMID: 22468146 PMCID: PMC3314400 DOI: 10.2217/fvl.09.69] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Herpesviruses are a complex family of dsDNA viruses that are a major cause of human disease. All family members share highly related viral replication proteins, such as DNA polymerase, ssDNA-binding proteins and processivity factors. Consequently, it is generally thought that lytic replication occurs through a common and conserved mechanism. However, considerable evidence indicates that proteins controlling initiation of DNA replication vary greatly among the herepesvirus subfamilies. In this article, we focus on some of the known mechanisms that regulate Epstein-Barr virus lytic-cycle replication, and compare this to other herpesvirus family members. Our reading of the literature leads us to conclude that diverse viral mechanisms generate a common nucleoprotein prereplication structure that can be recognized by a highly conserved family of viral replication enzymes.
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Affiliation(s)
- Andrew J Rennekamp
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA and The University of Pennsylvania, Biomedical Graduate Program in Cell & Molecular Biology, The School of Medicine, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9523, Fax: +1 251 898 0663,
| | - Paul M Lieberman
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9491, Fax: +1 215 898 0663,
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Qian L, Li D, Yang Z, Hu M, Yu M, Shi M, Shen B, Guo N. Construction and expression of a spliced variant of Epstein-Barr virus bzlf1 and preparation of its polyclonal antibody. Prep Biochem Biotechnol 2009; 40:46-56. [PMID: 20024794 DOI: 10.1080/10826060903392780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The BZLF1 gene-encoded protein, Zta (EB1, ZEBRA), is a key transcriptional activator of induction of the lytic cycle of EBV. Zta; it contains a basic region with homology to the DNA binding domains of the AP-1 family. In this study, an alternatively spliced BZLF1 (Delta BZLF1) cDNA lacking exon 2, which encodes the DNA-binding domain of Zta, was isolated from B95-8 marmoset cell line releasing EBV. The cDNA was inserted into a prokaryotic expression vector pET-28a+. The His-tagged recombinant protein was overproduced in E. coli BL21(DE3) and purified by nickel affinity chromatography. The purified fraction was characterized by Western blot and MALDI-TOF-MS analysis and used as an antigen to immunize mice. The antibody against Delta Zta can recognize both denatured and natural Zta protein. The Delta Zta protein and its antibody can be used to further investigate its unknown functions.
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Affiliation(s)
- Lu Qian
- Institute of Basic Medical Sciences, Beijing, PR China
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Katsumura KR, Maruo S, Wu Y, Kanda T, Takada K. Quantitative evaluation of the role of Epstein-Barr virus immediate-early protein BZLF1 in B-cell transformation. J Gen Virol 2009; 90:2331-2341. [PMID: 19553389 DOI: 10.1099/vir.0.012831-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The Epstein-Barr virus (EBV) immediate-early transactivator BZLF1 plays a key role in switching EBV infection from the latent to the lytic form by stimulating the expression cascade of lytic genes; it also regulates the expression of several cellular genes. Recently, we reported that BZLF1 is expressed in primary human B cells early after EBV infection. To investigate whether this BZLF1 expression early after infection plays a role in the EBV-induced growth transformation of primary B cells, we generated BZLF1-knockout EBV and quantitatively evaluated its transforming ability compared with that of wild-type EBV. We found that the 50% transforming dose of BZLF1-knockout EBV was quite similar to that of wild-type EBV. Established lymphoblastoid cell lines (LCLs) harbouring BZLF1-knockout EBV were indistinguishable from LCLs harbouring wild-type EBV in their pattern of latent gene expression and in their growth in vitro. Furthermore, the copy numbers of EBV episomes were very similar in the LCLs harbouring BZLF1-knockout EBV and in those harbouring wild-type EBV. These data indicate that disrupting BZLF1 expression in the context of the EBV genome, and the resultant inability to enter lytic replication, have little impact on the growth of LCLs and the steady-state copy number of EBV episomes in established LCLs.
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Affiliation(s)
- Koichi Ricardo Katsumura
- Department of Tumor Virology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
| | - Seiji Maruo
- Department of Tumor Virology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
| | - Yi Wu
- Department of Tumor Virology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
| | - Teru Kanda
- Research Center for Infection-Associated Cancer, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
| | - Kenzo Takada
- Department of Tumor Virology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan
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Dickerson SJ, Xing Y, Robinson AR, Seaman WT, Gruffat H, Kenney SC. Methylation-dependent binding of the epstein-barr virus BZLF1 protein to viral promoters. PLoS Pathog 2009; 5:e1000356. [PMID: 19325883 PMCID: PMC2654727 DOI: 10.1371/journal.ppat.1000356] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 02/27/2009] [Indexed: 11/19/2022] Open
Abstract
The switch between latent and lytic Epstein-Barr virus (EBV) infection is mediated by the viral immediate-early (IE) protein, BZLF1 (Z). Z, a homologue of c-jun that binds to AP1-like motifs (ZREs), induces expression of the BRLF1 (R) and BRRF1 (Na) viral proteins, which cooperatively activate transcription of the Z promoter and thereby establish a positive autoregulatory loop. A unique feature of Z is its ability to preferentially bind to, and activate, the methylated form of the BRLF1 promoter (Rp). To date, however, Rp is the only EBV promoter known to be regulated in this unusual manner. We now demonstrate that the promoter driving transcription of the early BRRF1 gene (Nap) has two CpG-containing ZREs (ACGCTCA and TCGCCCG) that are only bound by Z in the methylated state. Both Nap ZREs are highly methylated in cells with latent EBV infection. Z efficiently activates the methylated, but not unmethylated, form of Nap in reporter gene assays, and both ZREs are required. Z serine residue 186, which was previously shown to be required for Z binding to methylated ZREs in Rp, but not for Z binding to the AP1 site, is required for Z binding to methylated Nap ZREs. The Z(S186A) mutant cannot activate methylated Nap in reporter gene assays and does not induce Na expression in cells with latent EBV infection. Molecular modeling studies of Z bound to the methylated Nap ZREs help to explain why methylation is required for Z binding, and the role of the Z Ser186 residue. Methylation-dependent Z binding to critical viral promoters may enhance lytic reactivation in latently infected cells, where the viral genome is heavily methylated. Conversely, since the incoming viral genome is initially unmethylated, methylation-dependent Z activation may also help the virus to establish latency following infection. In cells with long-term latent Epstein-Barr virus (EBV) infection, the majority of the EBV genome becomes highly methylated. Methylation of cytosines plays a critical role in inhibiting the expression of cellular genes. In contrast, our laboratory previously showed that the EBV protein, BZLF1 (Z), which mediates viral reactivation and replication, preferentially binds to, and activates, the methylated form of the viral BRLF1 promoter. To date, however, BRLF1 is the only EBV promoter known to be activated by Z in this unusual manner. Here, we show that another EBV promoter (Nap, driving transcription of the BRRF1 gene) likewise has two methylation-dependent Z binding sites, and that Z only activates the Nap efficiently in the methylated form. Molecular modeling studies suggest why methylation of the Nap enhances Z binding. Since the BRLF1 and BRRF1 genes encode essential viral transcription factors that work cooperatively with Z to induce the lytic form of viral infection, our results indicate that methylation of the EBV genome enhances Z-mediated disruption of viral latency.
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Affiliation(s)
- Sarah J. Dickerson
- McArdle Laboratory, Departments of Oncology and Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Yongna Xing
- McArdle Laboratory, Departments of Oncology and Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Amanda R. Robinson
- McArdle Laboratory, Departments of Oncology and Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - William T. Seaman
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Henri Gruffat
- Laboratoire de Virologie U758, ENS-Lyon, INSERM, Lyon, France
| | - Shannon C. Kenney
- McArdle Laboratory, Departments of Oncology and Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
- * E-mail:
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Epstein-Barr virus lytic transactivator Zta enhances chemotactic activity through induction of interleukin-8 in nasopharyngeal carcinoma cells. J Virol 2008; 82:3679-88. [PMID: 18234802 DOI: 10.1128/jvi.02301-07] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Epstein-Barr virus (EBV)-associated, undifferentiated type of nasopharyngeal carcinoma (NPC) is characterized by intensive leukocyte infiltration. Interaction between the infiltrating cells and the tumor cells has been considered crucial for NPC development. Recruitment of the infiltrates can be directed by certain chemokines present in the NPC tissues. It is unknown whether and how EBV lytic infection regulates expression of the chemokines. Using an antibody array, we first found that several chemokines secreted from EBV-infected NPC cells are increased upon EBV reactivation into the lytic cycle, and interleukin-8 (IL-8) is the chemokine upregulated most significantly and consistently. Further studies showed that the EBV lytic transactivator Zta is a potent inducer of IL-8 in NPC cells, augmenting secreted and intracellular IL-8 proteins, as well as IL-8 RNA. Zta upregulates Egr-1, a cellular transcription factor that has been involved in upregulation of IL-8, but the Zta-induced IL-8 expression is independent of Egr-1. The ability of Zta to transactivate the IL-8 promoter is important for the induction of IL-8, and we have identified two Zta-responsive elements in the promoter. Zta can bind to these two elements in vitro and can also be recruited to the IL-8 promoter in vivo. DNA-binding-defective Zta mutants can neither activate the IL-8 promoter nor induce IL-8 production. In addition, Zta-expressing NPC cells exert enhanced chemotactic activity that is mainly mediated by IL-8. Since IL-8 may contribute to not only leukocyte infiltration but also multiple oncogenic processes, the present study provides a potential link between EBV lytic infection and pathogenesis of NPC.
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Schelcher C, Al Mehairi S, Verrall E, Hope Q, Flower K, Bromley B, Woolfson DN, West MJ, Sinclair AJ. Atypical bZIP domain of viral transcription factor contributes to stability of dimer formation and transcriptional function. J Virol 2007; 81:7149-55. [PMID: 17459922 PMCID: PMC1933325 DOI: 10.1128/jvi.00215-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Epstein-Barr virus transcription factor Zta (encoded by BZLF1) is a bZIP protein containing an alpha-helical coiled-coil homodimerization motif (zipper). The Zta zipper forms less-stable dimers than other bZIP proteins, and an adjacent region (CT) interacts with the zipper to form a novel structure that is proposed to strengthen the dimer. Here we question the role of the CT region for Zta function. Cross-linking experiments demonstrate that the entire CT region lies adjacent to the zipper. Detailed analyses of Zta truncation mutations identify an involvement of the proximal CT region (221 to 230) in dimer formation with a further contribution from the distal region (236 to 243). Biophysical analyses reveal that residues 221 to 230 enhance the stability of the coiled coil. The ability of the Zta truncation mutants to interact with three Zta-binding sites also requires the proximal CT region. Fine mapping of DNA-binding requirements highlighted the contribution of these amino acids for Zta function. Thus, the proximal part of the CT region is required to aid the dimerization of Zta and thereby its DNA-binding ability. In contrast, although the distal part of the CT region aids dimerization, it promotes only a modest increase in DNA binding. To probe this further, we defined the contribution from the CT region for Zta to transactivate a promoter embedded within the viral genome. From this we conclude that the proximal part of the CT region is absolutely required, whereas the distal part is dispensable.
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Affiliation(s)
- Celine Schelcher
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom
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37
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Heston L, El-Guindy A, Countryman J, Dela Cruz C, Delecluse HJ, Miller G. Amino acids in the basic domain of Epstein-Barr virus ZEBRA protein play distinct roles in DNA binding, activation of early lytic gene expression, and promotion of viral DNA replication. J Virol 2006; 80:9115-33. [PMID: 16940523 PMCID: PMC1563939 DOI: 10.1128/jvi.00909-06] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The ZEBRA protein of Epstein-Barr virus (EBV) drives the viral lytic cycle cascade. The capacity of ZEBRA to recognize specific DNA sequences resides in amino acids 178 to 194, a region in which 9 of 17 residues are either lysine or arginine. To define the basic domain residues essential for activity, a series of 46 single-amino-acid-substitution mutants were examined for their ability to bind ZIIIB DNA, a high-affinity ZEBRA binding site, and for their capacity to activate early and late EBV lytic cycle gene expression. DNA binding was obligatory for the protein to activate the lytic cascade. Nineteen mutants that failed to bind DNA were unable to disrupt latency. A single acidic replacement of a basic amino acid destroyed DNA binding and the biologic activity of the protein. Four mutants that bound weakly to DNA were defective at stimulating the expression of Rta, the essential first target of ZEBRA in lytic cycle activation. Four amino acids, R183, A185, C189, and R190, are likely to contact ZIIIB DNA specifically, since alanine or valine substitutions at these positions drastically weakened or eliminated DNA binding. Twenty-three mutants were proficient in binding to ZIIIB DNA. Some DNA binding-proficient mutants were refractory to supershift by BZ-1 monoclonal antibody (epitope amino acids 214 to 230), likely as the result of the increased solubility of the mutants. Mutants competent to bind DNA could be separated into four functional groups: the wild-type group (eight mutants), a group defective at activating Rta (five mutants, all with mutations at the S186 site), a group defective at activating EA-D (three mutants with the R179A, S186T, and K192A mutations), and a group specifically defective at activating late gene expression (seven mutants). Three late mutants, with a Y180A, Y180E, or K188A mutation, were defective at stimulating EBV DNA replication. This catalogue of point mutants reveals that basic domain amino acids play distinct functions in binding to DNA, in activating Rta, in stimulating early lytic gene expression, and in promoting viral DNA replication and viral late gene expression. These results are discussed in relationship to the recently solved crystal structure of ZEBRA bound to an AP-1 site.
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Affiliation(s)
- Lee Heston
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520, USA
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Chang Y, Lee HH, Chen YT, Lu J, Wu SY, Chen CW, Takada K, Tsai CH. Induction of the early growth response 1 gene by Epstein-Barr virus lytic transactivator Zta. J Virol 2006; 80:7748-55. [PMID: 16840354 PMCID: PMC1563714 DOI: 10.1128/jvi.02608-05] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Early growth response 1 (Egr-1) is a cellular transcription factor involved in diverse biologic functions. Egr-1 has been associated with Epstein-Barr virus (EBV) infection, but it is still unknown whether any EBV protein regulates Egr-1 expression. In this study, we first showed that EBV reactivation is involved in upregulation of Egr-1 and that Egr-1 can be induced by Zta, an EBV lytic transactivator. Zta not only binds to the Egr-1 promoter but also activates the ERK signaling pathway to trigger binding of Elk-1 to the Egr-1 promoter. In addition, knockdown of Egr-1 significantly reduces the spontaneous expression of Zta and Rta in EBV-infected 293 cells, suggesting that a positive-feedback network involving Egr-1 is required for EBV reactivation. This study also implies that Zta has the potential to affect expression of certain genes through Egr-1.
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Affiliation(s)
- Yao Chang
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Number 1, Section 1 Jen-Ai Road, Taipei, Taiwan
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Bernasconi M, Berger C, Sigrist JA, Bonanomi A, Sobek J, Niggli FK, Nadal D. Quantitative profiling of housekeeping and Epstein-Barr virus gene transcription in Burkitt lymphoma cell lines using an oligonucleotide microarray. Virol J 2006; 3:43. [PMID: 16756670 PMCID: PMC1533810 DOI: 10.1186/1743-422x-3-43] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Accepted: 06/06/2006] [Indexed: 11/10/2022] Open
Abstract
Background The Epstein-Barr virus (EBV) is associated with lymphoid malignancies, including Burkitt's lymphoma (BL), and can transform human B cells in vitro. EBV-harboring cell lines are widely used to investigate lymphocyte transformation and oncogenesis. Qualitative EBV gene expression has been extensively described, but knowledge of quantitative transcription is lacking. We hypothesized that transcription levels of EBNA1, the gene essential for EBV persistence within an infected cell, are similar in BL cell lines. Results To compare quantitative gene transcription in the BL cell lines Namalwa, Raji, Akata, Jijoye, and P3HR1, we developed an oligonucleotide microarray chip, including 17 housekeeping genes, six latent EBV genes (EBNA1, EBNA2, EBNA3A, EBNA3C, LMP1, LMP2), and four lytic EBV genes (BZLF1, BXLF2, BKRF2, BZLF2), and used the cell line B95.8 as a reference for EBV gene transcription. Quantitative polymerase chain reaction assays were used to validate microarray results. We found that transcription levels of housekeeping genes differed considerably among BL cell lines. Using a selection of housekeeping genes with similar quantitative transcription in the tested cell lines to normalize EBV gene transcription data, we showed that transcription levels of EBNA1 were quite similar in very different BL cell lines, in contrast to transcription levels of other EBV genes. As demonstrated with Akata cells, the chip allowed us to accurately measure EBV gene transcription changes triggered by treatment interventions. Conclusion Our results suggest uniform EBNA1 transcription levels in BL and that microarray profiling can reveal novel insights on quantitative EBV gene transcription and its impact on lymphocyte biology.
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Affiliation(s)
- Michele Bernasconi
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
| | - Christoph Berger
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
| | - Jürg A Sigrist
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
| | - Athos Bonanomi
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
| | - Jens Sobek
- Functional Genomics Center of the University of Zurich, Winterthurerstrasse 190CH-8057 Zurich, Switzerland
| | - Felix K Niggli
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
| | - David Nadal
- Division of Infectious Diseases and Division of Oncology, University Children's Hospital of Zurich, August Forel-Strasse 1, CH-8008 Zurich, Switzerland
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Petosa C, Morand P, Baudin F, Moulin M, Artero JB, Müller CW. Structural basis of lytic cycle activation by the Epstein-Barr virus ZEBRA protein. Mol Cell 2006; 21:565-72. [PMID: 16483937 DOI: 10.1016/j.molcel.2006.01.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 11/14/2005] [Accepted: 01/03/2006] [Indexed: 12/12/2022]
Abstract
Epstein-Barr virus (EBV) causes infectious mononucleosis and is linked to several human malignancies. EBV has a biphasic infection cycle consisting of a latent and a lytic, replicative phase. The switch from latent to lytic infection is triggered by the EBV immediate-early transcription factor ZEBRA (BZLF1, Zta, Z, EB1). We present the crystal structure of ZEBRA's DNA binding domain bound to an EBV lytic gene promoter element. ZEBRA exhibits a variant of the basic-region leucine zipper (bZIP) fold in which a C-terminal moiety stabilizes the coiled coil involved in dimer formation. The structure provides insights into ZEBRA's broad target site specificity, preferential activation of specific EBV promoters in their methylated state, ability to dimerize despite lacking a leucine zipper motif, and failure to heterodimerize with cellular bZIP proteins. The structure will allow for the design of new therapeutic agents that block activation of the EBV lytic cycle.
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Affiliation(s)
- Carlo Petosa
- European Molecular Biology Laboratory, Grenoble Outstation, B.P. 181, 38042 Grenoble Cedex 9, France
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41
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Morand P, Budayova-Spano M, Perrissin M, Müller CW, Petosa C. Expression, purification, crystallization and preliminary X-ray analysis of a C-terminal fragment of the Epstein-Barr virus ZEBRA protein. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:210-4. [PMID: 16511303 PMCID: PMC2197177 DOI: 10.1107/s1744309106002971] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Accepted: 01/24/2006] [Indexed: 11/10/2022]
Abstract
A C-terminal fragment of the Epstein-Barr virus immediate-early transcription factor ZEBRA has been expressed as a recombinant protein in Escherichia coli and purified to homogeneity. The fragment behaves as a dimer in solution, consistent with the presence of a basic region leucine-zipper (bZIP) domain. Crystals of the fragment in complex with a DNA duplex were grown by the hanging-drop vapour-diffusion technique using polyethylene glycol 4000 and magnesium acetate as crystallization agents. Crystals diffract to better than 2.5 A resolution using synchrotron radiation (lambda = 0.976 A). Crystals belong to space group C2, with unit-cell parameters a = 94.2, b = 26.5, c = 98.1 A, beta = 103.9 degrees.
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Affiliation(s)
- Patrice Morand
- European Molecular Biology Laboratory, Grenoble Outstation, BP 181, 38042 Grenoble CEDEX 9, France
- Laboratoire de Virologie Moléculaire et Structurale, EA 2939, Université Joseph Fourier, Grenoble, France
| | - Monika Budayova-Spano
- European Molecular Biology Laboratory, Grenoble Outstation, BP 181, 38042 Grenoble CEDEX 9, France
| | - Monique Perrissin
- Laboratoire de Virologie Moléculaire et Structurale, EA 2939, Université Joseph Fourier, Grenoble, France
| | - Christoph W. Müller
- European Molecular Biology Laboratory, Grenoble Outstation, BP 181, 38042 Grenoble CEDEX 9, France
- Correspondence e-mail:
| | - Carlo Petosa
- European Molecular Biology Laboratory, Grenoble Outstation, BP 181, 38042 Grenoble CEDEX 9, France
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El-Guindy AS, Paek SY, Countryman J, Miller G. Identification of constitutive phosphorylation sites on the Epstein-Barr virus ZEBRA protein. J Biol Chem 2005; 281:3085-95. [PMID: 16321978 DOI: 10.1074/jbc.m506076200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ZEBRA, the product of the Epstein-Barr virus gene bzlf1, and a member of the AP-1 subfamily of basic zipper (bZIP) transcription factors, is necessary and sufficient to disrupt viral latency and to initiate the viral lytic cycle. Two serine residues of ZEBRA, Ser167 and Ser173, are substrates for casein kinase 2 (CK2) and are constitutively phosphorylated in vivo. Phosphorylation of ZEBRA at its CK2 sites is required for proper temporal regulation of viral gene expression. Phosphopeptide analysis indicated that ZEBRA contains additional constitutive phosphorylation sites. Here we employed a co-migration strategy to map these sites in vivo. The cornerstone of this strategy was to correlate the migration of 32P- and 35S-labeled tryptic peptides of ZEBRA. The identity of the peptides was revealed by mutagenesis of methionine and cysteine residues present in each peptide. Phosphorylation sites within the peptide were identified by mutagenesis of serines and threonines. ZEBRA was shown to be phosphorylated at serine and threonine residues, but not tyrosine. Two previously unrecognized phosphorylation sites of ZEBRA were identified in the NH2-terminal region of the transactivation domain: a cluster of weak phosphorylation sites at Ser6, Thr7, and Ser8 and a strong phosphorylation site at Thr14. Thr14 was embedded in a MAP kinase consensus sequence and could be phosphorylated in vitro by JNK, despite the absence of a canonical JNK docking site. Thus ZEBRA is now known to be constitutively phosphorylated at three distinct sites.
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Affiliation(s)
- Ayman S El-Guindy
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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43
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Bhende PM, Seaman WT, Delecluse HJ, Kenney SC. BZLF1 activation of the methylated form of the BRLF1 immediate-early promoter is regulated by BZLF1 residue 186. J Virol 2005; 79:7338-48. [PMID: 15919888 PMCID: PMC1143640 DOI: 10.1128/jvi.79.12.7338-7348.2005] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Epstein-Barr virus (EBV) genome is highly methylated in latently infected cells. We recently reported that the EBV immediate-early (IE) protein BZLF1 (Z) preferentially binds to and activates transcription from the methylated form of the BRLF1 IE gene promoter (Rp). We now report that serine residue 186 in the Z DNA-binding domain plays an important role in the ability of Z to bind to and activate methylated Rp. A Z mutant containing an alanine residue at position 186 [Z(S186A)] was significantly defective in binding to methylated, as well as unmethylated, ZREs (Z-responsive elements) in Rp and was unable to activate lytic EBV gene transcription from the methylated or demethylated form of the viral genome. A Z mutant containing threonine at residue 186 [Z(S186T)] bound only to the methylated form of the ZRE-2 site in Rp and induced lytic EBV gene transcription from the methylated, but not demethylated, form of the viral genome. The defect in both of these mutants was primarily due to an inability to activate the Rp in the context of the viral genome. Finally, a Z mutant containing an aspartic acid at position 186 [Z(S186D)] did not bind to either the consensus AP-1 site or to the methylated or unmethylated Rp ZRE-2 site and did not induce lytic gene transcription. These results indicate that replacement of serine with threonine at residue 186 in the Z DNA-binding domain differentially affects its ability to reactivate the unmethylated, versus methylated, viral genome.
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Affiliation(s)
- Prasanna M Bhende
- Lineberger Comprehensive Cancer Center, CB# 7295, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Abstract
Epstein-Barr virus (EBV) is a human herpesvirus that causes infectious mononucleosis and is associated with several types of cancers, including nasopharyngeal carcinoma and Burkitt's lymphoma. An EBV protein that plays an integral role during lytic replication is the immediate-early protein BZLF1. Our laboratory has found that BZLF1 (Z) localizes to host chromosomes during mitosis. Two Z-interacting proteins are also found localized to mitotic chromosomes in the presence of Z. The association between Z and mitotic chromosomes may lead to the sequestering of Z-interacting proteins within the cell and potentially cause an alteration of chromosome compaction or chromatin structure.
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Affiliation(s)
- Amy L Adamson
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, USA.
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45
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Dias LC, Melgar GZ, Jardim LS. A short approach to the bicyclo[4.3.0]nonane fragment of stawamycin. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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46
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Colletti KS, Xu Y, Yamboliev I, Pari GS. Human cytomegalovirus UL84 is a phosphoprotein that exhibits UTPase activity and is a putative member of the DExD/H box family of proteins. J Biol Chem 2005; 280:11955-60. [PMID: 15778228 DOI: 10.1074/jbc.c400603200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human cytomegalovirus (HCMV) UL84 is required for lytic DNA replication and is proposed to be the key factor in initiation of viral DNA synthesis. We now show that UL84 has a high degree of homology to the DExD/H (where x can be any amino acid) box family of helicases, displays UTPase activity, and is phosphorylated at serine residues. Affinity column-purified UL84-FLAG fusion protein was used in an in vitro nucleoside triphosphatase (NTPase) assay to show that UL84 has NTPase activity, preferring UTP. This UTPase activity was linear with respect to enzyme concentration and slightly enhanced by the addition of nucleic acid substrates. UL84 UTPase was the highest at low salt concentrations, a pH of 7.5, and a temperature of 45 degrees C. The enzyme preferred Mg2+ as the divalent cation but was also able to catalyze the UTPase reaction in the presence of Mn2+, Ca2+, and Zn2+ albeit at lower levels. The evidence presented here suggests that the UL84 UTPase activity may be part of an energy-generating system for helicase activity associated with the initiation of HCMV DNA replication.
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Affiliation(s)
- Kelly S Colletti
- University of Nevada-Reno, Department of Microbiology & Immunology and the Cell and Molecular Biology Program, Reno, Nevada 89557, USA
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47
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Morrison TE, Kenney SC. BZLF1, an Epstein-Barr virus immediate-early protein, induces p65 nuclear translocation while inhibiting p65 transcriptional function. Virology 2004; 328:219-32. [PMID: 15464842 DOI: 10.1016/j.virol.2004.07.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Revised: 05/27/2004] [Accepted: 07/14/2004] [Indexed: 10/26/2022]
Abstract
We have previously demonstrated that the Epstein-Barr virus immediate-early BZLF1 protein interacts with, and is inhibited by, the NF-kappaB family member p65. However, the effects of BZLF1 on NF-kappaB activity have not been intensively studied. Here we show that BZLF1 inhibits p65-dependent gene expression. BZLF1 inhibited the ability of IL-1, as well as transfected p65, to activate the expression of two different NF-kappaB-responsive genes, ICAM-1 and IkappaB-alpha. BZLF1 also reduced the constitutive level of IkappaB-alpha protein in HeLa and A549 cells, and increased the amount of nuclear NF-kappaB to a similar extent as tumor necrosis factor-alpha (TNF-alpha) treatment. In spite of this BZLF1-associated increase in the nuclear form of NF-kappaB, BZLF1 did not induce binding of NF-kappaB to NF-kappaB responsive promoters (as determined by chromatin immunoprecipitation assay) in vivo, although TNF-alpha treatment induced NF-kappaB binding as expected. Overexpression of p65 dramatically inhibited the lytic replication cycle of EBV in 293-EBV cells, confirming that NF-kappaB also inhibits BZLF1 transcriptional function. Our results are consistent with a model in which BZLF1 inhibits the transcriptional function of p65, resulting in decreased transcription of IkappaB-alpha, decreased expression of IkappaB-alpha protein, and subsequent translocation of NF-kappaB to the nucleus. This nuclear translocation of NF-kappaB may promote viral latency by negatively regulating BZLF1 transcriptional activity. In situations where p65 activity is limiting in comparison to BZLF1, the ability of BZLF1 to inhibit p65 transcriptional function may protect the virus from the host immune system during the lytic form of infection.
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Affiliation(s)
- Thomas E Morrison
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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48
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Colletti KS, Xu Y, Cei SA, Tarrant M, Pari GS. Human cytomegalovirus UL84 oligomerization and heterodimerization domains act as transdominant inhibitors of oriLyt-dependent DNA replication: evidence that IE2-UL84 and UL84-UL84 interactions are required for lytic DNA replication. J Virol 2004; 78:9203-14. [PMID: 15308715 PMCID: PMC506931 DOI: 10.1128/jvi.78.17.9203-9214.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus (HCMV) UL84 encodes a 75-kDa protein required for oriLyt-dependent DNA replication and interacts with IE2 in infected and transfected cells. UL84 localizes to the nucleus of transfected and infected cells and is found in viral replication compartments. In transient assays it was shown that UL84 can interfere with the IE2-mediated transactivation of the UL112/113 promoter of HCMV. To determine whether UL84 protein-protein interactions are necessary for lytic DNA synthesis, we purified UL84 and used this protein to generate a monoclonal antibody. Using this antibody, we now show that UL84 forms a stable interaction with itself in vivo. The point of self-interaction maps to a region of the protein between amino acids 151 and 200, a domain that contains a series of highly charged amino acid residues. Coimmunoprecipitation assays determined that UL84 interacts with a protein domain present within the first 215 amino acids of IE2. We also show that an intact leucine zipper domain of UL84 is required for a stable interaction with IE2 and UL84 leucine zipper mutants fail to complement oriLyt-dependent DNA replication. UL84 leucine zipper mutants no longer interfere with IE2-mediated transactivation of the UL112/113 promoter, confirming that the leucine zipper is essential for a functional interaction with IE2. In addition, we demonstrate that both the leucine zipper and oligomerization domains of UL84 can act as transdominant-negative inhibitors of lytic replication in the transient assay, strongly suggesting that both an IE2-UL84 and a UL84-UL84 interaction are required for DNA synthesis.
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Affiliation(s)
- Kelly S Colletti
- Department of Microbiology and Immunology, University of Nevada-Reno, Reno, Nevada, USA
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Bhende PM, Seaman WT, Delecluse HJ, Kenney SC. The EBV lytic switch protein, Z, preferentially binds to and activates the methylated viral genome. Nat Genet 2004; 36:1099-104. [PMID: 15361873 DOI: 10.1038/ng1424] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2004] [Accepted: 08/09/2004] [Indexed: 11/08/2022]
Abstract
DNA methylation promotes gene silencing, yet the Epstein-Barr virus immediate-early protein, BZLF1 (Z), converts the virus from the latent to the lytic form of infection even when the viral genome is highly methylated. Here we show that methylation of CpG motifs in Z-responsive elements of the viral BRLF1 immediate-early promoter enhances Z binding to, and activation of, this promoter. Demethylation of the viral genome impairs Z activation of lytic viral genes. Z is the first transcription factor that preferentially binds to, and activates, a methylated promoter. These results identify an unexpected mechanism by which Epstein-Barr virus circumvents the inhibitory effects of viral genome methylation.
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Affiliation(s)
- Prasanna M Bhende
- Department of Medicine, and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina, USA
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50
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El-Guindy AS, Miller G. Phosphorylation of Epstein-Barr virus ZEBRA protein at its casein kinase 2 sites mediates its ability to repress activation of a viral lytic cycle late gene by Rta. J Virol 2004; 78:7634-44. [PMID: 15220438 PMCID: PMC434091 DOI: 10.1128/jvi.78.14.7634-7644.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
ZEBRA, a member of the bZIP family, serves as a master switch between latent and lytic cycle Epstein-Barr virus (EBV) gene expression. ZEBRA influences the activity of another viral transactivator, Rta, in a gene-specific manner. Some early lytic cycle genes, such as BMRF1, are activated in synergy by ZEBRA and Rta. However, ZEBRA suppresses Rta's ability to activate a late gene, BLRF2. Here we show that this repressive activity is dependent on the phosphorylation state of ZEBRA. We find that two residues of ZEBRA, S167 and S173, that are phosphorylated by casein kinase 2 (CK2) in vitro are also phosphorylated in vivo. Inhibition of ZEBRA phosphorylation at the CK2 substrate motif, either by serine-to-alanine substitutions or by use of a specific inhibitor of CK2, abolished ZEBRA's capacity to repress Rta activation of the BLRF2 gene, but did not alter its ability to initiate the lytic cycle or to synergize with Rta in activation of the BMRF1 early-lytic-cycle gene. These studies illustrate how the phosphorylation state of a transcriptional activator can modulate its behavior as an activator or repressor of gene expression. Phosphorylation of ZEBRA at its CK2 sites is likely to play an essential role in proper temporal control of the EBV lytic life cycle.
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Affiliation(s)
- Ayman S El-Guindy
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520-8064, USA
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