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Li S, Liu B, Tan M, Juillard F, Szymula A, Álvarez Á, Van Sciver N, George A, Ramachandran A, Raina K, Tumuluri VS, Costa C, Simas J, Kaye K. Kaposi's sarcoma herpesvirus exploits the DNA damage response to circularize its genome. Nucleic Acids Res 2024; 52:1814-1829. [PMID: 38180827 PMCID: PMC10899755 DOI: 10.1093/nar/gkad1224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/05/2023] [Accepted: 12/16/2023] [Indexed: 01/07/2024] Open
Abstract
To establish lifelong, latent infection, herpesviruses circularize their linear, double-stranded, DNA genomes through an unknown mechanism. Kaposi's sarcoma (KS) herpesvirus (KSHV), a gamma herpesvirus, is tightly linked with KS, primary effusion lymphoma, and multicentric Castleman's disease. KSHV persists in latently infected cells as a multi-copy, extrachromosomal episome. Here, we show the KSHV genome rapidly circularizes following infection, and viral protein expression is unnecessary for this process. The DNA damage response (DDR) kinases, ATM and DNA-PKcs, each exert roles, and absence of both severely compromises circularization and latency. These deficiencies were rescued by expression of ATM and DNA-PKcs, but not catalytically inactive mutants. In contrast, γH2AX did not function in KSHV circularization. The linear viral genomic ends resemble a DNA double strand break, and non-homologous DNA end joining (NHEJ) and homologous recombination (HR) reporters indicate both NHEJ and HR contribute to KSHV circularization. Last, we show, similar to KSHV, ATM and DNA-PKcs have roles in circularization of the alpha herpesvirus, herpes simplex virus-1 (HSV-1), while γH2AX does not. Therefore, the DDR mediates KSHV and HSV-1 circularization. This strategy may serve as a general herpesvirus mechanism to initiate latency, and its disruption may provide new opportunities for prevention of herpesvirus disease.
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Affiliation(s)
- Shijun Li
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Bing Liu
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Min Tan
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Franceline Juillard
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Agnieszka Szymula
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Ángel L Álvarez
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Nicholas Van Sciver
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Athira George
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Akshaya Ramachandran
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Komal Raina
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Vinayak Sadasivam Tumuluri
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
| | - Catarina N Costa
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
- Universidade Católica Portuguesa, Católica Medical School, Católica Biomedical Research, Palma de Cima, 1649-023 Lisboa, Portugal
| | - J Pedro Simas
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
- Universidade Católica Portuguesa, Católica Medical School, Católica Biomedical Research, Palma de Cima, 1649-023 Lisboa, Portugal
| | - Kenneth M Kaye
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
- Program in Virology, Harvard Medical School, Boston, MA 02115, USA
- Broad Institute of Harvard University and Massachusetts Institute of Technology, Cambridge, MA 02142, USA
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Chung WC, Song MJ. Virus–Host Interplay Between Poly (ADP-Ribose) Polymerase 1 and Oncogenic Gammaherpesviruses. Front Microbiol 2022; 12:811671. [PMID: 35095818 PMCID: PMC8795711 DOI: 10.3389/fmicb.2021.811671] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 12/23/2021] [Indexed: 12/14/2022] Open
Abstract
The gammaherpesviruses, include the Epstein–Barr virus, Kaposi’s sarcoma-associated herpesvirus, and murine gammaherpesvirus 68. They establish latent infection in the B lymphocytes and are associated with various lymphoproliferative diseases and tumors. The poly (ADP-ribose) polymerase-1 (PARP1), also called ADP-ribosyltransferase diphtheria-toxin-like 1 (ARTD1) is a nuclear enzyme that catalyzes the transfer of the ADP-ribose moiety to its target proteins and participates in important cellular activities, such as the DNA-damage response, cell death, transcription, chromatin remodeling, and inflammation. In gammaherpesvirus infection, PARP1 acts as a key regulator of the virus life cycle: lytic replication and latency. These viruses also develop various strategies to regulate PARP1, facilitating their replication. This review summarizes the roles of PARP1 in the viral life cycle as well as the viral modulation of host PARP1 activity and discusses the implications. Understanding the interactions between the PARP1 and oncogenic gammaherpesviruses may lead to the identification of effective therapeutic targets for the associated diseases.
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Wang Y, Tibbetts SA, Krug LT. Conquering the Host: Determinants of Pathogenesis Learned from Murine Gammaherpesvirus 68. Annu Rev Virol 2021; 8:349-371. [PMID: 34586873 PMCID: PMC9153731 DOI: 10.1146/annurev-virology-011921-082615] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Gammaherpesviruses are an important class of oncogenic pathogens that are exquisitely evolved to their respective hosts. As such, the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi sarcoma herpesvirus (KSHV) do not naturally infect nonhuman primates or rodents. There is a clear need to fully explore mechanisms of gammaherpesvirus pathogenesis, host control, and immune evasion in the host. A gammaherpesvirus pathogen isolated from murid rodents was first reported in 1980; 40 years later, murine gammaherpesvirus 68 (MHV68, MuHV-4, γHV68) infection of laboratory mice is a well-established pathogenesis system recognized for its utility in applying state-of-the-art approaches to investigate virus-host interactions ranging from the whole host to the individual cell. Here, we highlight recent advancements in our understanding of the processes by which MHV68 colonizes the host and drives disease. Lessons that inform KSHV and EBV pathogenesis and provide future avenues for novel interventions against infection and virus-associated cancers are emphasized.
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Affiliation(s)
- Yiping Wang
- Department of Molecular Genetics and Microbiology, UF Health Cancer Center, College of Medicine, University of Florida, Gainesville, Florida 32610, USA
| | - Scott A Tibbetts
- Department of Molecular Genetics and Microbiology, UF Health Cancer Center, College of Medicine, University of Florida, Gainesville, Florida 32610, USA
| | - Laurie T Krug
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA;
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Deletion of Murine Gammaherpesvirus Gene M2 in Activation-Induced Cytidine Deaminase-Expressing B Cells Impairs Host Colonization and Viral Reactivation. J Virol 2020; 95:JVI.01933-20. [PMID: 33028711 DOI: 10.1128/jvi.01933-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 12/27/2022] Open
Abstract
Gammaherpesviruses (GHVs) are DNA tumor viruses that establish lifelong, chronic infections in lymphocytes of humans and other mammals. GHV infections are associated with numerous cancers, especially in immunocompromised hosts. While it is known that GHVs utilize host germinal center (GC) B cell responses during latency establishment, an understanding of how viral gene products function in specific B cell subsets to regulate this process is incomplete. Using murine gammaherpesvirus 68 (MHV68) as a small-animal model to define mechanisms of GHV pathogenesis in vivo, we generated a virus in which the M2 gene was flanked by loxP sites (M2.loxP), enabling the use of Cre-lox technology to define M2 function in specific cell types in infection and disease. The M2 gene encodes a protein that is highly expressed in GC B cells that promotes plasma cell differentiation and viral reactivation. M2 was efficiently deleted in Cre-expressing cells, and the presence of loxP sites flanking M2 did not alter viral replication or latency in mice that do not express Cre. In contrast, M2.loxP MHV68 exhibited a deficit in latency establishment and reactivation that resembled M2-null virus, following intranasal (IN) infection of mice that express Cre in all B cells (CD19-Cre). Nearly identical phenotypes were observed for M2.loxP MHV68 in mice that express Cre in germinal center (GC) B cells (AID-Cre). However, colonization of neither draining lymph nodes after IN infection nor the spleen after intraperitoneal (IP) infection required M2, although the reactivation defect was retained. Together, these data confirm that M2 function is B cell-specific and demonstrate that M2 primarily functions in AID-expressing cells to facilitate MHV68 dissemination to distal latency reservoirs within the host and reactivation from latency. Our study reveals that a viral latency gene functions within a distinct subset of cells to facilitate host colonization.IMPORTANCE Gammaherpesviruses establish lifelong chronic infections in cells of the immune system that can lead to lymphomas and other diseases. To facilitate colonization of a host, gammaherpesviruses encode gene products that manipulate processes involved in cellular proliferation and differentiation. Whether and how these viral gene products function in specific cells of the immune system is poorly defined. We report here the use of a viral genetic system that allows for deletion of specific viral genes in discrete populations of cells. We employ this system in an in vivo model to demonstrate cell-type-specific requirements for a particular viral gene. Our findings reveal that a viral gene product can function in distinct cellular subsets to direct gammaherpesvirus pathogenesis.
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Lotke R, Schneeweiß U, Pietrek M, Günther T, Grundhoff A, Weidner-Glunde M, Schulz TF. Brd/BET Proteins Influence the Genome-Wide Localization of the Kaposi's Sarcoma-Associated Herpesvirus and Murine Gammaherpesvirus Major Latency Proteins. Front Microbiol 2020; 11:591778. [PMID: 33193257 PMCID: PMC7642799 DOI: 10.3389/fmicb.2020.591778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 09/28/2020] [Indexed: 01/22/2023] Open
Abstract
The rhadinoviruses Kaposi’s Sarcoma-associated herpesvirus (KSHV) and murine gammaherpesvirus (MHV-68) persist in infected hosts in a latent state that is characterized by the absence of virus production and by restricted viral gene expression. Their major latency protein, the latency-associated nuclear antigen (kLANA for KSHV and mLANA for MHV-68), is essential for viral genome maintenance and replication and involved in transcriptional regulation. Both kLANA and mLANA interact with cellular chromatin-associated proteins, among them the Bromodomain and Extra Terminal domain (Brd/BET) proteins, which recruit cellular and viral proteins to acetylated histones through their bromodomains and modulate cellular gene expression. Brd/BET proteins also play a role in the tethering, replication, segregation or integration of a diverse group of viral DNA genomes. In this study we explored if Brd/BET proteins influence the localization of the LANAs to preferential regions in the host chromatin and thereby contribute to kLANA- or mLANA-mediated transcriptional regulation. Using ChIP-Seq, we revealed a genome-wide co-enrichment of kLANA with Brd2/4 near cellular and viral transcriptional start sites (TSS). Treatment with I-BET151, an inhibitor of Brd/BET, displaced kLANA and Brd2/4 from TSS in the viral and host chromatin, but did not affect the direct binding of kLANA to kLANA-binding sites (LBS) in the KSHV latent origin of replication. Similarly, mLANA, but not a mLANA mutant deficient for binding to Brd2/4, also associated with cellular TSS. We compared the transcriptome of KSHV-infected with uninfected and kLANA-expressing human B cell lines, as well as a murine B cell line expressing mLANA or a Brd2/4-binding deficient mLANA mutant. We found that only a minority of cellular genes, whose TSS are occupied by kLANA or mLANA, is transcriptionally regulated by these latency proteins. Our findings extend previous reports on a preferential deposition of kLANA on cellular TSS and show that this characteristic chromatin association pattern is at least partially determined by the interaction of these viral latency proteins with members of the Brd/BET family of chromatin modulators.
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Affiliation(s)
- Rishikesh Lotke
- Institut für Virologie, Medizinische Hochschule Hannover, Hanover, Germany.,German Center for Infection Research, Hannover-Braunschweig and Hamburg Sites, Hanover, Germany
| | - Ulrike Schneeweiß
- Institut für Virologie, Medizinische Hochschule Hannover, Hanover, Germany
| | - Marcel Pietrek
- Institut für Virologie, Medizinische Hochschule Hannover, Hanover, Germany
| | - Thomas Günther
- Heinrich-Pette-Institut, Leibniz-Institut für Experimentelle Virologie, Hamburg, Germany
| | - Adam Grundhoff
- German Center for Infection Research, Hannover-Braunschweig and Hamburg Sites, Hanover, Germany.,Heinrich-Pette-Institut, Leibniz-Institut für Experimentelle Virologie, Hamburg, Germany
| | - Magdalena Weidner-Glunde
- Institut für Virologie, Medizinische Hochschule Hannover, Hanover, Germany.,German Center for Infection Research, Hannover-Braunschweig and Hamburg Sites, Hanover, Germany
| | - Thomas F Schulz
- Institut für Virologie, Medizinische Hochschule Hannover, Hanover, Germany.,German Center for Infection Research, Hannover-Braunschweig and Hamburg Sites, Hanover, Germany
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6
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Günther T, Fröhlich J, Herrde C, Ohno S, Burkhardt L, Adler H, Grundhoff A. A comparative epigenome analysis of gammaherpesviruses suggests cis-acting sequence features as critical mediators of rapid polycomb recruitment. PLoS Pathog 2019; 15:e1007838. [PMID: 31671162 PMCID: PMC6932816 DOI: 10.1371/journal.ppat.1007838] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 12/26/2019] [Accepted: 09/18/2019] [Indexed: 12/23/2022] Open
Abstract
Latent Kaposi sarcoma-associated herpesvirus (KSHV) genomes rapidly acquire distinct patterns of the activating histone modification H3K4-me3 as well as repressive H3K27-me3 marks, a modification linked to transcriptional silencing by polycomb repressive complexes (PRC). Interestingly, PRCs have recently been reported to restrict viral gene expression in a number of other viral systems, suggesting they may play a broader role in controlling viral chromatin. If so, it is an intriguing possibility that latency establishment may result from viral subversion of polycomb-mediated host responses to exogenous DNA. To investigate such scenarios we sought to establish whether rapid repression by PRC constitutes a general hallmark of herpesvirus latency. For this purpose, we performed a comparative epigenome analysis of KSHV and the related murine gammaherpesvirus 68 (MHV-68). We demonstrate that, while latently replicating MHV-68 genomes readily acquire distinct patterns of activation-associated histone modifications upon de novo infection, they fundamentally differ in their ability to efficiently attract H3K27-me3 marks. Statistical analyses of ChIP-seq data from in vitro infected cells as well as in vivo latency reservoirs furthermore suggest that, whereas KSHV rapidly attracts PRCs in a genome-wide manner, H3K27-me3 acquisition by MHV-68 genomes may require spreading from initial seed sites to which PRC are recruited as the result of an inefficient or stochastic recruitment, and that immune pressure may be needed to select for latency pools harboring PRC-silenced episomes in vivo. Using co-infection experiments and recombinant viruses, we also show that KSHV's ability to rapidly and efficiently acquire H3K27-me3 marks does not depend on the host cell environment or unique properties of the KSHV-encoded LANA protein, but rather requires specific cis-acting sequence features. We show that the non-canonical PRC1.1 component KDM2B, a factor which binds to unmethylated CpG motifs, is efficiently recruited to KSHV genomes, indicating that CpG island characteristics may constitute these features. In accord with the fact that, compared to MHV-68, KSHV genomes exhibit a fundamentally higher density of CpG motifs, we furthermore demonstrate efficient acquisition of H2AK119-ub by KSHV and H3K36-me2 by MHV-68 (but not vice versa), furthermore supporting the notion that KSHV genomes rapidly attract PRC1.1 complexes in a genome-wide fashion. Collectively, our results suggest that rapid PRC silencing is not a universal feature of viral latency, but that some viruses may rather have adopted distinct genomic features to specifically exploit default host pathways that repress epigenetically naive, CpG-rich DNA.
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Affiliation(s)
- Thomas Günther
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Jacqueline Fröhlich
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Christina Herrde
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Shinji Ohno
- Comprehensive Pneumology Center, Research Unit Lung Repair and Regeneration, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Munich, Germany
| | - Lia Burkhardt
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Heiko Adler
- Comprehensive Pneumology Center, Research Unit Lung Repair and Regeneration, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Munich, Germany
- German Center of Lung Research (DZL), Giessen, Germany
- * E-mail: (HA); (AG)
| | - Adam Grundhoff
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
- * E-mail: (HA); (AG)
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A Gammaherpesvirus MicroRNA Targets EWSR1 (Ewing Sarcoma Breakpoint Region 1) In Vivo To Promote Latent Infection of Germinal Center B Cells. mBio 2019; 10:mBio.00996-19. [PMID: 31363027 PMCID: PMC6667617 DOI: 10.1128/mbio.00996-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Gammaherpesviruses, including the human pathogens Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), directly contribute to the genesis of multiple types of malignancies. In vivo, these viruses infect B cells and manipulate B cell biology to establish lifelong infection. To accomplish this, gammaherpesviruses employ an array of gene products, including miRNAs, short noncoding RNAs that bind to and repress protein synthesis from specific target mRNAs. The in vivo relevance of repression of targets of gammaherpesvirus miRNAs remains highly elusive. Here, we identified a murine gammaherpesvirus miRNA as critical for in vivo infection and validated the host mRNA EWSR1 (Ewing sarcoma breakpoint region 1) as the predominant target for this miRNA. Using a novel technology, we demonstrated that repression of EWSR1 was essential for in vivo infection of the critical B cell reservoir. These findings provide the first in vivo demonstration of the significance of repression of a specific host mRNA by a gammaherpesvirus miRNA. Gammaherpesviruses, including the human pathogens Epstein-Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV), directly contribute to the genesis of multiple types of malignancies, including B cell lymphomas. In vivo, these viruses infect B cells and manipulate B cell biology to establish lifelong latent infection. To accomplish this, gammaherpesviruses employ an array of gene products, including microRNAs (miRNAs). Although numerous host mRNA targets of gammaherpesvirus miRNAs have been identified, the in vivo relevance of repression of these targets remains elusive due to species restriction. Murine gammaherpesvirus 68 (MHV68) provides a robust virus-host system to dissect the in vivo function of conserved gammaherpesvirus genetic elements. We identified here MHV68 mghv-miR-M1-7-5p as critical for in vivo infection and then validated host EWSR1 (Ewing sarcoma breakpoint region 1) as the predominant target for this miRNA. Using novel, target-specific shRNA-expressing viruses, we determined that EWSR1 repression in vivo was essential for germinal center B cell infection. These findings provide the first in vivo demonstration of the biological significance of repression of a specific host mRNA by a gammaherpesvirus miRNA.
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Sorel O, Dewals BG. The Critical Role of Genome Maintenance Proteins in Immune Evasion During Gammaherpesvirus Latency. Front Microbiol 2019; 9:3315. [PMID: 30687291 PMCID: PMC6333680 DOI: 10.3389/fmicb.2018.03315] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 12/20/2018] [Indexed: 12/25/2022] Open
Abstract
Gammaherpesviruses are important pathogens that establish latent infection in their natural host for lifelong persistence. During latency, the viral genome persists in the nucleus of infected cells as a circular episomal element while the viral gene expression program is restricted to non-coding RNAs and a few latency proteins. Among these, the genome maintenance protein (GMP) is part of the small subset of genes expressed in latently infected cells. Despite sharing little peptidic sequence similarity, gammaherpesvirus GMPs have conserved functions playing essential roles in latent infection. Among these functions, GMPs have acquired an intriguing capacity to evade the cytotoxic T cell response through self-limitation of MHC class I-restricted antigen presentation, further ensuring virus persistence in the infected host. In this review, we provide an updated overview of the main functions of gammaherpesvirus GMPs during latency with an emphasis on their immune evasion properties.
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Affiliation(s)
- Océane Sorel
- Immunology-Vaccinology, Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine-FARAH, University of Liège, Liège, Belgium.,Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Benjamin G Dewals
- Immunology-Vaccinology, Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine-FARAH, University of Liège, Liège, Belgium
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In Vivo Persistence of Chimeric Virus after Substitution of the Kaposi's Sarcoma-Associated Herpesvirus LANA DNA Binding Domain with That of Murid Herpesvirus 4. J Virol 2018; 92:JVI.01251-18. [PMID: 30111565 PMCID: PMC6189500 DOI: 10.1128/jvi.01251-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 08/09/2018] [Indexed: 01/12/2023] Open
Abstract
The latency-associated nuclear antigen from Kaposi's sarcoma-associated herpesvirus (KSHV), kLANA, and its homolog from the murid herpesvirus 4 (MuHV-4), mLANA, are essential for viral latency. kLANA is nearly four times the size of mLANA, mainly due to an extensive central repeat region that is absent in mLANA. Both proteins harbor a C-terminal DNA binding domain (DBD). The DBD binds the terminal repeat (TR) DNA sequences of the viral genome to mediate persistence. Despite structural conservation, the kLANA and mLANA DBDs differ in sequence and mode of oligomerization. kLANA DBD oligomers are flexible and bent, while mLANA DBD oligomers bind DNA in a rigid, linear conformation. We previously reported that kLANA and mLANA acted reciprocally on TR sequences. Furthermore, a MuHV-4 expressing kLANA instead of mLANA (v-kLANA) established latency in mice, albeit at a lower magnitude than the wild-type (WT) virus. Here, we asked if kLANA can accommodate the mLANA DBD and generated a fusion protein which contains kLANA but with the mLANA C-terminal region in place of that of kLANA. We report a recombinant MuHV-4 (v-KM) encoding this LANA fusion protein instead of mLANA. The fusion protein was expressed in lytic infection in vitro and assembled nuclear LANA dots in infected splenocytes. Results demonstrated that kLANA functionally accommodated mLANA's mode of DNA binding, allowing MuHV-4 chimeric virus to establish latency in vivo Notably, v-KM established latency in germinal center B cells more efficiently than did v-kLANA, although levels were reduced compared to WT MuHV-4.IMPORTANCE KSHV is a human oncogenic virus for which there is no tractable, immunocompetent animal model of infection. MuHV-4, a related rodent gammaherpesvirus, enables pathogenesis studies in mice. In latency, both viruses persist as extrachromosomal, circular genomes (episomes). LANA proteins encoded by KSHV (kLANA) and MuHV-4 (mLANA) contain a C-terminal DNA binding domain (DBD) that acts on the virus terminal repeats to enable episome persistence. mLANA is a smaller protein than kLANA. Their DBDs are structurally conserved but differ strikingly in the conformation of DNA binding. We report a recombinant, chimeric MuHV-4 which contains kLANA in place of mLANA, but in which the DBD is replaced with that of mLANA. Results showed that kLANA functionally accommodated mLANA's mode of DNA binding. In fact, the new chimeric virus established latency in vivo more efficiently than MuHV-4 expressing full-length kLANA.
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10
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Salinas E, Gupta A, Sifford JM, Oldenburg DG, White DW, Forrest JC. Conditional mutagenesis in vivo reveals cell type- and infection stage-specific requirements for LANA in chronic MHV68 infection. PLoS Pathog 2018; 14:e1006865. [PMID: 29364981 PMCID: PMC5798852 DOI: 10.1371/journal.ppat.1006865] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 02/05/2018] [Accepted: 01/09/2018] [Indexed: 12/14/2022] Open
Abstract
Gammaherpesvirus (GHV) pathogenesis is a complex process that involves productive viral replication, dissemination to tissues that harbor lifelong latent infection, and reactivation from latency back into a productive replication cycle. Traditional loss-of-function mutagenesis approaches in mice using murine gammaherpesvirus 68 (MHV68), a model that allows for examination of GHV pathogenesis in vivo, have been invaluable for defining requirements for specific viral gene products in GHV infection. But these approaches are insufficient to fully reveal how viral gene products contribute when the encoded protein facilitates multiple processes in the infectious cycle and when these functions vary over time and from one host tissue to another. To address this complexity, we developed an MHV68 genetic platform that enables cell-type-specific and inducible viral gene deletion in vivo. We employed this system to re-evaluate functions of the MHV68 latency-associated nuclear antigen (mLANA), a protein with roles in both viral replication and latency. Cre-mediated deletion in mice of loxP-flanked ORF73 demonstrated the necessity of mLANA in B cells for MHV68 latency establishment. Impaired latency during the transition from draining lymph nodes to blood following mLANA deletion also was observed, supporting the hypothesis that B cells are a major conduit for viral dissemination. Ablation of mLANA in infected germinal center (GC) B cells severely impaired viral latency, indicating the importance of viral passage through the GC for latency establishment. Finally, induced ablation of mLANA during latency resulted in complete loss of affected viral genomes, indicating that mLANA is critically important for maintenance of viral genomes during stable latency. Collectively, these experiments provide new insights into LANA homolog functions in GHV colonization of the host and highlight the potential of a new MHV68 genetic platform to foster a more complete understanding of viral gene functions at discrete stages of GHV pathogenesis. Gammaherpesviruses (GHVs), including the human pathogens Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus, establish lifelong infections that can lead to cancer. Defining the functions of viral gene products in acute replication and chronic infection is important for understanding how these viruses cause disease. Infection of mice with the related GHV, murine gammaherpesvirus 68 (MHV68), provides a tractable small animal model for defining how viral gene products function in chronic infection and understanding how host factors limit disease. Here we describe the development of a new viral genetic platform that enables the targeted deletion of specific genes from the viral genome in discrete host cells or at distinct times during infection. We utilize this system to better define requirements for the conserved latency-associated nuclear antigen in MHV68 lytic replication and latency in mice. This work highlights the utility of this MHV68 genetic platform for defining mechanisms of GHV infection and disease.
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Affiliation(s)
- Eduardo Salinas
- Department of Microbiology and Immunology and Center for Microbial Pathogenesis and Host Inflammatory Responses, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Arundhati Gupta
- Department of Microbiology and Immunology and Center for Microbial Pathogenesis and Host Inflammatory Responses, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Jeffrey M. Sifford
- Department of Microbiology and Immunology and Center for Microbial Pathogenesis and Host Inflammatory Responses, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | | | - Douglas W. White
- Gundersen Health System, La Crosse, Wisconsin, United States of America
| | - J. Craig Forrest
- Department of Microbiology and Immunology and Center for Microbial Pathogenesis and Host Inflammatory Responses, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
- * E-mail:
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11
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Habison AC, de Miranda MP, Beauchemin C, Tan M, Cerqueira SA, Correia B, Ponnusamy R, Usherwood EJ, McVey CE, Simas JP, Kaye KM. Cross-species conservation of episome maintenance provides a basis for in vivo investigation of Kaposi's sarcoma herpesvirus LANA. PLoS Pathog 2017; 13:e1006555. [PMID: 28910389 PMCID: PMC5599060 DOI: 10.1371/journal.ppat.1006555] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/27/2017] [Indexed: 12/26/2022] Open
Abstract
Many pathogens, including Kaposi's sarcoma herpesvirus (KSHV), lack tractable small animal models. KSHV persists as a multi-copy, nuclear episome in latently infected cells. KSHV latency-associated nuclear antigen (kLANA) binds viral terminal repeat (kTR) DNA to mediate episome persistence. Model pathogen murine gammaherpesvirus 68 (MHV68) mLANA acts analogously on mTR DNA. kLANA and mLANA differ substantially in size and kTR and mTR show little sequence conservation. Here, we find kLANA and mLANA act reciprocally to mediate episome persistence of TR DNA. Further, kLANA rescued mLANA deficient MHV68, enabling a chimeric virus to establish latent infection in vivo in germinal center B cells. The level of chimeric virus in vivo latency was moderately reduced compared to WT infection, but WT or chimeric MHV68 infected cells had similar viral genome copy numbers as assessed by immunofluorescence of LANA intranuclear dots or qPCR. Thus, despite more than 60 Ma of evolutionary divergence, mLANA and kLANA act reciprocally on TR DNA, and kLANA functionally substitutes for mLANA, allowing kLANA investigation in vivo. Analogous chimeras may allow in vivo investigation of genes of other human pathogens.
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Affiliation(s)
- Aline C. Habison
- Departments of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marta Pires de Miranda
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Chantal Beauchemin
- Departments of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Min Tan
- Departments of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Sofia A. Cerqueira
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Bruno Correia
- Instituto de Tecnologia Quimica e Bioliogica Antonio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Rajesh Ponnusamy
- Instituto de Tecnologia Quimica e Bioliogica Antonio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Edward J. Usherwood
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Colin E. McVey
- Instituto de Tecnologia Quimica e Bioliogica Antonio Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - J. Pedro Simas
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
- * E-mail: (KMK); (JPS)
| | - Kenneth M. Kaye
- Departments of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (KMK); (JPS)
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12
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Murine Gammaherpesvirus 68 Expressing Kaposi Sarcoma-Associated Herpesvirus Latency-Associated Nuclear Antigen (LANA) Reveals both Functional Conservation and Divergence in LANA Homologs. J Virol 2017; 91:JVI.00992-17. [PMID: 28747501 DOI: 10.1128/jvi.00992-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 07/18/2017] [Indexed: 12/12/2022] Open
Abstract
Latency-associated nuclear antigen (LANA) is a multifunctional protein encoded by members of the Rhadinovirus genus of gammaherpesviruses. Studies using murine gammaherpesvirus 68 (MHV68) demonstrated that LANA is important for acute replication, latency establishment, and reactivation in vivo Despite structural similarities in their DNA-binding domains (DBDs), LANA homologs from Kaposi sarcoma-associated herpesvirus (KSHV) and MHV68 exhibit considerable sequence divergence. We sought to determine if KSHV and MHV68 LANA homologs are functionally interchangeable. We generated an MHV68 virus that encodes KSHV LANA (kLANA) in place of MHV68 LANA (mLANA) and evaluated the virus's capacity to replicate, establish and maintain latency, and reactivate. kLANA knock-in (KLKI) MHV68 was replication competent in vitro and in vivo but exhibited slower growth kinetics and lower titers than wild-type (WT) MHV68. Following inoculation of mice, KLKI MHV68 established and maintained latency in splenocytes and peritoneal cells but did not reactivate efficiently ex vivo kLANA repressed the MHV68 promoter for ORF50, the gene that encodes the major lytic transactivator protein RTA, while mLANA did not, suggesting a likely mechanism for the KLKI MHV68 phenotypes. Bypassing this repression by providing MHV68 RTA in trans rescued KLKI MHV68 replication in tissue culture and enabled detection of KLKI MHV68 reactivation ex vivo These data demonstrate that kLANA and mLANA are functionally interchangeable for establishment and maintenance of latency and suggest that repression of lytic replication by kLANA, as previously shown with KSHV, is a kLANA-specific function that is transferable to MHV68.IMPORTANCE Kaposi sarcoma-associated herpesvirus (KSHV) and murine gammaherpesvirus 68 (MHV68) are members of the Rhadinovirus genus of gammaherpesviruses. These viruses establish lifelong infections that place their respective human and murine hosts at risk for cancer. Latency-associated nuclear antigen (LANA) is a conserved Rhadinovirus protein that is necessary for long-term chronic infection by these viruses. To better understand the conserved functions performed by LANA homologs, we generated a recombinant MHV68 virus that encodes the KSHV LANA protein in place of the MHV68 LANA homolog. We determined that the KSHV LANA protein is capable of supporting MHV68 latency in a mouse model of chronic infection but also functions to repress viral replication. This work describes an in vivo model system for defining evolutionarily conserved and divergent functions of LANA homologs in Rhadinovirus infection and disease.
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13
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Lomonte P. Herpesvirus Latency: On the Importance of Positioning Oneself. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2017; 223:95-117. [PMID: 28528441 DOI: 10.1007/978-3-319-53168-7_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The nucleus is composed of multiple compartments and domains, which directly or indirectly influence many cellular processes including gene expression, RNA splicing and maturation, protein post-translational modifications, and chromosome segregation. Nuclear-replicating viruses, especially herpesviruses, have co-evolved with the cell, adopting strategies to counteract and eventually hijack this hostile environment for their own benefit. This allows them to persist in the host for the entire life of an individual and to ensure their maintenance in the target species. Herpesviruses establish latency in dividing or postmitotic cells from which they can efficiently reactivate after sometimes years of a seemingly dormant state. Therefore, herpesviruses circumvent the threat of permanent silencing by reactivating their dormant genomes just enough to escape extinction, but not too much to avoid life-threatening damage to the host. In addition, herpesviruses that establish latency in dividing cells must adopt strategies to maintain their genomes in the daughter cells to avoid extinction by dilution of their genomes following multiple cell divisions. From a biochemical point of view, reactivation and maintenance of viral genomes in dividing cells occur successfully because the viral genomes interact with the nuclear architecture in a way that allows the genomes to be transmitted faithfully and to benefit from the nuclear micro-environments that allow reactivation following specific stimuli. Therefore, spatial positioning of the viral genomes within the nucleus is likely to be essential for the success of the latent infection and, beyond that, for the maintenance of herpesviruses in their respective hosts.
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Affiliation(s)
- Patrick Lomonte
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, LabEx DEVweCAN, Institut NeuroMyoGène (INMG), team Chromatin Assembly, Nuclear Domains, Virus, 69008, Lyon, France.
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14
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Latency-Associated Nuclear Antigen E3 Ubiquitin Ligase Activity Impacts Gammaherpesvirus-Driven Germinal Center B Cell Proliferation. J Virol 2016; 90:7667-83. [PMID: 27307564 DOI: 10.1128/jvi.00813-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 06/06/2016] [Indexed: 12/28/2022] Open
Abstract
UNLABELLED Viruses have evolved mechanisms to hijack components of cellular E3 ubiquitin ligases, thus modulating the ubiquitination pathway. However, the biological relevance of such mechanisms for viral pathogenesis in vivo remains largely unknown. Here, we utilized murid herpesvirus 4 (MuHV-4) infection of mice as a model system to address the role of MuHV-4 latency-associated nuclear antigen (mLANA) E3 ligase activity in gammaherpesvirus latent infection. We show that specific mutations in the mLANA SOCS box (V199A, V199A/L202A, or P203A/P206A) disrupted mLANA's ability to recruit Elongin C and Cullin 5, thereby impairing the formation of the Elongin BC/Cullin 5/SOCS (EC5S(mLANA)) complex and mLANA's E3 ligase activity on host NF-κB and Myc. Although these mutations resulted in considerably reduced mLANA binding to viral terminal repeat DNA as assessed by electrophoretic mobility shift assay (EMSA), the mutations did not disrupt mLANA's ability to mediate episome persistence. In vivo, MuHV-4 recombinant viruses bearing these mLANA SOCS box mutations exhibited a deficit in latency amplification in germinal center (GC) B cells. These findings demonstrate that the E3 ligase activity of mLANA contributes to gammaherpesvirus-driven GC B cell proliferation. Hence, pharmacological inhibition of viral E3 ligase activity through targeting SOCS box motifs is a putative strategy to control gammaherpesvirus-driven lymphoproliferation and associated disease. IMPORTANCE The gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) cause lifelong persistent infection and play causative roles in several human malignancies. Colonization of B cells is crucial for virus persistence, and access to the B cell compartment is gained by virus-driven proliferation in germinal center (GC) B cells. Infection of B cells is predominantly latent, with the viral genome persisting as a multicopy episome and expressing only a small subset of viral genes. Here, we focused on latency-associated nuclear antigen (mLANA) encoded by murid herpesvirus-4 (MuHV-4), which exhibits homology in sequence, structure, and function to KSHV LANA (kLANA), thereby allowing the study of LANA-mediated pathogenesis in mice. Our experiments show that mLANA's E3 ubiquitin ligase activity is necessary for efficient expansion of latency in GC B cells, suggesting that the development of pharmacological inhibitors of LANA E3 ubiquitin ligase activity may allow strategies to interfere with gammaherpesvirus-driven lymphoproliferation and associated disease.
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15
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Cieniewicz B, Santana AL, Minkah N, Krug LT. Interplay of Murine Gammaherpesvirus 68 with NF-kappaB Signaling of the Host. Front Microbiol 2016; 7:1202. [PMID: 27582728 PMCID: PMC4987367 DOI: 10.3389/fmicb.2016.01202] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 07/19/2016] [Indexed: 11/13/2022] Open
Abstract
Herpesviruses establish a chronic infection in the host characterized by intervals of lytic replication, quiescent latency, and reactivation from latency. Murine gammaherpesvirus 68 (MHV68) naturally infects small rodents and has genetic and biologic parallels with the human gammaherpesviruses (gHVs), Kaposi's sarcoma-associated herpesvirus and Epstein-Barr virus. The murine gammaherpesvirus model pathogen system provides a platform to apply cutting-edge approaches to dissect the interplay of gammaherpesvirus and host determinants that enable colonization of the host, and that shape the latent or lytic fate of an infected cell. This knowledge is critical for the development of novel therapeutic interventions against the oncogenic gHVs. The nuclear factor kappa B (NF-κB) signaling pathway is well-known for its role in the promotion of inflammation and many aspects of B cell biology. Here, we review key aspects of the virus lifecycle in the host, with an emphasis on the route that the virus takes to gain access to the B cell latency reservoir. We highlight how the murine gammaherpesvirus requires components of the NF-κB signaling pathway to promote replication, latency establishment, and maintenance of latency. These studies emphasize the complexity of gammaherpesvirus interactions with NF-κB signaling components that direct innate and adaptive immune responses of the host. Importantly, multiple facets of NF-κB signaling have been identified that might be targeted to reduce the burden of gammaherpesvirus-associated diseases.
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Affiliation(s)
- Brandon Cieniewicz
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Alexis L Santana
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Nana Minkah
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
| | - Laurie T Krug
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook NY, USA
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16
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Juillard F, Tan M, Li S, Kaye KM. Kaposi's Sarcoma Herpesvirus Genome Persistence. Front Microbiol 2016; 7:1149. [PMID: 27570517 PMCID: PMC4982378 DOI: 10.3389/fmicb.2016.01149] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 07/11/2016] [Indexed: 12/17/2022] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV) has an etiologic role in Kaposi’s sarcoma, primary effusion lymphoma, and multicentric Castleman’s disease. These diseases are most common in immunocompromised individuals, especially those with AIDS. Similar to all herpesviruses, KSHV infection is lifelong. KSHV infection in tumor cells is primarily latent, with only a small subset of cells undergoing lytic infection. During latency, the KSHV genome persists as a multiple copy, extrachromosomal episome in the nucleus. In order to persist in proliferating tumor cells, the viral genome replicates once per cell cycle and then segregates to daughter cell nuclei. KSHV only expresses several genes during latent infection. Prominent among these genes, is the latency-associated nuclear antigen (LANA). LANA is responsible for KSHV genome persistence and also exerts transcriptional regulatory effects. LANA mediates KSHV DNA replication and in addition, is responsible for segregation of replicated genomes to daughter nuclei. LANA serves as a molecular tether, bridging the viral genome to mitotic chromosomes to ensure that KSHV DNA reaches progeny nuclei. N-terminal LANA attaches to mitotic chromosomes by binding histones H2A/H2B at the surface of the nucleosome. C-terminal LANA binds specific KSHV DNA sequence and also has a role in chromosome attachment. In addition to the essential roles of N- and C-terminal LANA in genome persistence, internal LANA sequence is also critical for efficient episome maintenance. LANA’s role as an essential mediator of virus persistence makes it an attractive target for inhibition in order to prevent or treat KSHV infection and disease.
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Affiliation(s)
- Franceline Juillard
- Departments of Medicine, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA
| | - Min Tan
- Departments of Medicine, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA
| | - Shijun Li
- Departments of Medicine, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA
| | - Kenneth M Kaye
- Departments of Medicine, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA
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17
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Identification of Viral and Host Proteins That Interact with Murine Gammaherpesvirus 68 Latency-Associated Nuclear Antigen during Lytic Replication: a Role for Hsc70 in Viral Replication. J Virol 2015; 90:1397-413. [PMID: 26581985 DOI: 10.1128/jvi.02022-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/10/2015] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Latency-associated nuclear antigen (LANA) is a conserved, multifunctional protein encoded by members of the rhadinovirus subfamily of gammaherpesviruses, including Kaposi sarcoma-associated herpesvirus (KSHV) and murine gammaherpesvirus 68 (MHV68). We previously demonstrated that MHV68 LANA (mLANA) is required for efficient lytic replication. However, mechanisms by which mLANA facilitates viral replication, including interactions with cellular and viral proteins, are not known. Thus, we performed a mass spectrometry-based interaction screen that defined an mLANA protein-protein interaction network for lytic viral replication consisting of 15 viral proteins and 191 cellular proteins, including 19 interactions previously reported in KSHV LANA interaction studies. We also employed a stable-isotope labeling technique to illuminate high-priority mLANA-interacting host proteins. Among the top prioritized mLANA-binding proteins was a cellular chaperone, heat shock cognate protein 70 (Hsc70). We independently validated the mLANA-Hsc70 interaction through coimmunoprecipitation and in vitro glutathione S-transferase (GST) pulldown assays. Immunofluorescence and cellular fractionation analyses comparing wild-type (WT) to mLANA-null MHV68 infections demonstrated mLANA-dependent recruitment of Hsc70 to nuclei of productively infected cells. Pharmacologic inhibition and small hairpin RNA (shRNA)-mediated knockdown of Hsc70 impaired MHV68 lytic replication, which functionally correlated with impaired viral protein expression, reduced viral DNA replication, and failure to form viral replication complexes. Replication of mLANA-null MHV68 was less affected than that of WT virus by Hsc70 inhibition, which strongly suggests that Hsc70 function in MHV68 lytic replication is at least partially mediated by its interaction with mLANA. Together these experiments identify proteins engaged by mLANA during the MHV68 lytic replication cycle and define a previously unknown role for Hsc70 in facilitating MHV68 lytic replication. IMPORTANCE Latency-associated nuclear antigen (LANA) is a conserved gamma-2-herpesvirus protein important for latency maintenance and pathogenesis. For MHV68, this includes regulating lytic replication and reactivation. While previous studies of KSHV LANA defined interactions with host cell proteins that impact latency, interactions that facilitate productive viral replication are not known. Thus, we performed a differential proteomics analysis to identify and prioritize cellular and viral proteins that interact with the MHV68 LANA homolog during lytic infection. Among the proteins identified was heat shock cognate protein 70 (Hsc70), which we determined is recruited to host cell nuclei in an mLANA-dependent process. Moreover, Hsc70 facilitates MHV68 protein expression and DNA replication, thus contributing to efficient MHV68 lytic replication. These experiments expand the known LANA-binding proteins to include MHV68 lytic replication and demonstrate a previously unappreciated role for Hsc70 in regulating viral replication.
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18
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Ponnusamy R, Petoukhov MV, Correia B, Custodio TF, Juillard F, Tan M, Pires de Miranda M, Carrondo MA, Simas JP, Kaye KM, Svergun DI, McVey CE. KSHV but not MHV-68 LANA induces a strong bend upon binding to terminal repeat viral DNA. Nucleic Acids Res 2015; 43:10039-54. [PMID: 26424851 PMCID: PMC4787769 DOI: 10.1093/nar/gkv987] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/16/2015] [Indexed: 12/20/2022] Open
Abstract
Latency-associated nuclear antigen (LANA) is central to episomal tethering, replication and transcriptional regulation of γ2-herpesviruses. LANA binds cooperatively to the terminal repeat (TR) region of the viral episome via adjacent LANA binding sites (LBS), but the molecular mechanism by which LANA assembles on the TR remains elusive. We show that KSHV LANA and MHV-68 LANA proteins bind LBS DNA using strikingly different modes. Solution structure of LANA complexes revealed that while kLANA tetramer is intrinsically bent both in the free and bound state to LBS1-2 DNA, mLANA oligomers instead adopt a rigid linear conformation. In addition, we report a novel non-ring kLANA structure that displays more flexibility at its assembly interface than previously demonstrated. We identified a hydrophobic pivot point located at the dimer-dimer assembly interface, which gives rotational freedom for kLANA to adopt variable conformations to accommodate both LBS1-2 and LBS2-1-3 DNA. Alterations in the arrangement of LBS within TR or at the tetramer assembly interface have a drastic effect on the ability of kLANA binding. We also show kLANA and mLANA DNA binding functions can be reciprocated. Although KSHV and MHV-68 are closely related, the findings provide new insights into how the structure, oligomerization, and DNA binding of LANA have evolved differently to assemble on the TR DNA.
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Affiliation(s)
- Rajesh Ponnusamy
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras 2700-157, Portugal
| | - Maxim V Petoukhov
- European Molecular Biology Laboratory, Hamburg Unit, EMBL c/o DESY, Hamburg 22607, Germany
| | - Bruno Correia
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras 2700-157, Portugal
| | - Tania F Custodio
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras 2700-157, Portugal
| | - Franceline Juillard
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Min Tan
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Marta Pires de Miranda
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Maria A Carrondo
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras 2700-157, Portugal
| | - J Pedro Simas
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Kenneth M Kaye
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Dmitri I Svergun
- European Molecular Biology Laboratory, Hamburg Unit, EMBL c/o DESY, Hamburg 22607, Germany
| | - Colin E McVey
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras 2700-157, Portugal
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19
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Li S, Tan M, Juillard F, Ponnusamy R, Correia B, Simas JP, Carrondo MA, McVey CE, Kaye KM. The Kaposi Sarcoma Herpesvirus Latency-associated Nuclear Antigen DNA Binding Domain Dorsal Positive Electrostatic Patch Facilitates DNA Replication and Episome Persistence. J Biol Chem 2015; 290:28084-28096. [PMID: 26420481 DOI: 10.1074/jbc.m115.674622] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Indexed: 12/15/2022] Open
Abstract
Kaposi sarcoma-associated herpesvirus (KSHV) has a causative role in several human malignancies. KSHV latency-associated nuclear antigen (LANA) mediates persistence of viral episomes in latently infected cells. LANA mediates KSHV DNA replication and segregates episomes to progeny nuclei. The structure of the LANA DNA binding domain was recently solved, revealing a positive electrostatic patch opposite the DNA binding surface, which is the site of BET protein binding. Here we investigate the functional role of the positive patch in LANA-mediated episome persistence. As expected, LANA mutants with alanine or glutamate substitutions in the central, peripheral, or lateral portions of the positive patch maintained the ability to bind DNA by EMSA. However, all of the substitution mutants were deficient for LANA DNA replication and episome maintenance. Mutation of the peripheral region generated the largest deficiencies. Despite these deficiencies, all positive patch mutants concentrated to dots along mitotic chromosomes in cells containing episomes, similar to LANA. The central and peripheral mutants, but not the lateral mutants, were reduced for BET protein interaction as assessed by co-immunoprecipitation. However, defects in BET protein binding were independent of episome maintenance function. Overall, the reductions in episome maintenance closely correlated with DNA replication deficiencies, suggesting that the replication defects account for the reduced episome persistence. Therefore, the electrostatic patch exerts a key role in LANA-mediated DNA replication and episome persistence and may act through a host cell partner(s) other than a BET protein or by inducing specific structures or complexes.
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Affiliation(s)
- Shijun Li
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, 02115
| | - Min Tan
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, 02115
| | - Franceline Juillard
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, 02115
| | - Rajesh Ponnusamy
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal
| | - Bruno Correia
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal
| | - J Pedro Simas
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Maria A Carrondo
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal
| | - Colin E McVey
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal
| | - Kenneth M Kaye
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, 02115.
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20
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Frederico B, Chao B, Lawler C, May JS, Stevenson PG. Subcapsular sinus macrophages limit acute gammaherpesvirus dissemination. J Gen Virol 2015; 96:2314-2327. [PMID: 25872742 PMCID: PMC4681069 DOI: 10.1099/vir.0.000140] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lymphocyte proliferation, mobility and longevity make them prime targets for virus infection. Myeloid cells that process and present environmental antigens to lymphocytes are consequently an important line of defence. Subcapsular sinus macrophages (SSMs) filter the afferent lymph and communicate with B-cells. How they interact with B-cell-tropic viruses is unknown. We analysed their encounter with murid herpesvirus-4 (MuHV-4), an experimentally accessible gammaherpesvirus related to Kaposi's sarcoma-associated herpesvirus. MuHV-4 disseminated via lymph nodes, and intranasally or subcutaneously inoculated virions readily infected SSMs. However, this infection was poorly productive. SSM depletion with clodronate-loaded liposomes or with diphtheria toxin in CD169–diphtheria toxin receptor transgenic mice increased B-cell infection and hastened virus spread to the spleen. Dendritic cells provided the main route to B-cells, and SSMs slowed host colonization, apparently by absorbing virions non-productively from the afferent lymph.
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Affiliation(s)
- Bruno Frederico
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Brittany Chao
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Clara Lawler
- Sir Albert Sakzewski Virus Research Centre, Clinical Medical Virology Centre, School of Chemistry and Molecular Biosciences, Royal Children's Hospital and University of Queensland, Brisbane, Australia
| | - Janet S May
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK.,Sir Albert Sakzewski Virus Research Centre, Clinical Medical Virology Centre, School of Chemistry and Molecular Biosciences, Royal Children's Hospital and University of Queensland, Brisbane, Australia
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Abstract
UNLABELLED Lymphocyte colonization by gammaherpesviruses (γHVs) is an important target for cancer prevention. However, how it works is not clear. Epstein-Barr virus drives autonomous B cell proliferation in vitro but in vivo may more subtly exploit the proliferative pathways provided by lymphoid germinal centers (GCs). Murid herpesvirus 4 (MuHV-4), which realistically infects inbred mice, provides a useful tool with which to understand further how a γHV colonizes B cells in vivo. Not all γHVs necessarily behave the same, but common events can with MuHV-4 be assigned an importance for host colonization and so a potential as therapeutic targets. MuHV-4-driven B cell proliferation depends quantitatively on CD4(+) T cell help. Here we show that it also depends on T cell-independent survival signals provided by the B cell-activating factor (BAFF) receptor (BAFF-R). B cells could be infected in BAFF-R(-/-) mice, but virus loads remained low. This corresponded to a BAFF-R-dependent defect in GC colonization. The close parallels between normal, antigen-driven B cell responses and virus-infected B cell proliferation argue that in vivo, γHVs mostly induce infected B cells into normal GC reactions rather than generating large numbers of autonomously proliferating blasts. IMPORTANCE γHVs cause cancers by driving the proliferation of infected cells. B cells are a particular target. Thus, we need to know how virus-driven B cell proliferation works. Controversy exists as to whether viral genes drive it directly or less directly orchestrate the engagement of normal, host-driven pathways. Here we show that the B cell proliferation driven by a murid γHV requires BAFF-R. This supports the idea that γHVs exploit host proliferation pathways and suggests that interfering with BAFF-R could more generally reduce γHV-associated B cell proliferation.
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Correia B, Cerqueira SA, Beauchemin C, Pires de Miranda M, Li S, Ponnusamy R, Rodrigues L, Schneider TR, Carrondo MA, Kaye KM, Simas JP, McVey CE. Crystal structure of the gamma-2 herpesvirus LANA DNA binding domain identifies charged surface residues which impact viral latency. PLoS Pathog 2013; 9:e1003673. [PMID: 24146618 PMCID: PMC3798461 DOI: 10.1371/journal.ppat.1003673] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 08/16/2013] [Indexed: 01/12/2023] Open
Abstract
Latency-associated nuclear antigen (LANA) mediates γ2-herpesvirus genome persistence and regulates transcription. We describe the crystal structure of the murine gammaherpesvirus-68 LANA C-terminal domain at 2.2 Å resolution. The structure reveals an alpha-beta fold that assembles as a dimer, reminiscent of Epstein-Barr virus EBNA1. A predicted DNA binding surface is present and opposite this interface is a positive electrostatic patch. Targeted DNA recognition substitutions eliminated DNA binding, while certain charged patch mutations reduced bromodomain protein, BRD4, binding. Virus containing LANA abolished for DNA binding was incapable of viable latent infection in mice. Virus with mutations at the charged patch periphery exhibited substantial deficiency in expansion of latent infection, while central region substitutions had little effect. This deficiency was independent of BRD4. These results elucidate the LANA DNA binding domain structure and reveal a unique charged region that exerts a critical role in viral latent infection, likely acting through a host cell protein(s). Herpesviruses establish life-long latent infections. During latency, gammaherpesviruses, such as Kaposi's sarcoma-associated herpesvirus (KSHV), persist as multicopy, circularized genomes in the cell nucleus and express a small subset of viral genes. KSHV latency-associated nuclear antigen (LANA) is the predominant gene expressed during latent infection. C-terminal LANA binds KSHV terminal repeat (TR) DNA to mediate DNA replication. TR DNA binding also allows tethering of the viral genome to mitotic chromosomes to mediate DNA segregation to daughter nuclei. We describe here the crystal structure of the murine gammaherpesvirus 68 LANA DNA binding domain, which is homologous to that of KSHV LANA. The structure revealed a dimer and we identified residues involved in the interaction with viral DNA. Mutation of these residues abolished DNA binding and viable latency establishment in a mouse model of infection. We also identified a positively charged patch on the dimer surface opposite to the DNA binding region and found this patch exerts an important role in the virus's ability to expand latent infection in vivo. This work elucidates the structure of the LANA DNA binding domain and identifies a novel surface feature that is critical for viral latent infection, likely by acting through a host cell protein.
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Affiliation(s)
- Bruno Correia
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Sofia A. Cerqueira
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Chantal Beauchemin
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marta Pires de Miranda
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Shijun Li
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Rajesh Ponnusamy
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Lénia Rodrigues
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | | | - Maria A. Carrondo
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
- * E-mail: (MAC); (KMK); (JPS); (CEM)
| | - Kenneth M. Kaye
- Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (MAC); (KMK); (JPS); (CEM)
| | - J. Pedro Simas
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
- * E-mail: (MAC); (KMK); (JPS); (CEM)
| | - Colin E. McVey
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
- * E-mail: (MAC); (KMK); (JPS); (CEM)
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A structural basis for BRD2/4-mediated host chromatin interaction and oligomer assembly of Kaposi sarcoma-associated herpesvirus and murine gammaherpesvirus LANA proteins. PLoS Pathog 2013; 9:e1003640. [PMID: 24146614 PMCID: PMC3798688 DOI: 10.1371/journal.ppat.1003640] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 08/03/2013] [Indexed: 12/31/2022] Open
Abstract
Kaposi sarcoma-associated herpesvirus (KSHV) establishes a lifelong latent infection and causes several malignancies in humans. Murine herpesvirus 68 (MHV-68) is a related γ2-herpesvirus frequently used as a model to study the biology of γ-herpesviruses in vivo. The KSHV latency-associated nuclear antigen (kLANA) and the MHV68 mLANA (orf73) protein are required for latent viral replication and persistence. Latent episomal KSHV genomes and kLANA form nuclear microdomains, termed ‘LANA speckles’, which also contain cellular chromatin proteins, including BRD2 and BRD4, members of the BRD/BET family of chromatin modulators. We solved the X-ray crystal structure of the C-terminal DNA binding domains (CTD) of kLANA and MHV-68 mLANA. While these structures share the overall fold with the EBNA1 protein of Epstein-Barr virus, they differ substantially in their surface characteristics. Opposite to the DNA binding site, both kLANA and mLANA CTD contain a characteristic lysine-rich positively charged surface patch, which appears to be a unique feature of γ2-herpesviral LANA proteins. Importantly, kLANA and mLANA CTD dimers undergo higher order oligomerization. Using NMR spectroscopy we identified a specific binding site for the ET domains of BRD2/4 on kLANA. Functional studies employing multiple kLANA mutants indicate that the oligomerization of native kLANA CTD dimers, the characteristic basic patch and the ET binding site on the kLANA surface are required for the formation of kLANA ‘nuclear speckles’ and latent replication. Similarly, the basic patch on mLANA contributes to the establishment of MHV-68 latency in spleen cells in vivo. In summary, our data provide a structural basis for the formation of higher order LANA oligomers, which is required for nuclear speckle formation, latent replication and viral persistence. Kaposi sarcoma-associated herpesvirus (KSHV) causes Kaposi Sarcoma, Primary Effusion lymphoma and the plasma cell variant of Multicentric Castleman's Disease. Its oncogenic effect is linked to its ability to persist in a latent form for the life time of infected individuals. During latency viral genomes are replicated and passed to daughter cells in synchrony with the infected cell without the formation of new virions. A key viral protein in this process is the latency-associated nuclear antigen, LANA. In latently infected cells, viral genomes and LANA form characteristic nuclear microdomains, termed ‘LANA speckles’, which also contain cellular chromatin components. We have solved the crystal structure of the c-terminal, DNA-binding, domain (CTD) of KSHV LANA (kLANA) and its homologue mLANA of a related murine γ2-herpesvirus, which is frequently used as a model to study latent persistence in vivo. We also identified the binding site for two chromatin proteins, BRD2/4, by NMR spectroscopy. We demonstrate the functional importance of these structural features, and their contribution to latent replication and ‘LANA speckle’ formation, in cell culture and in vivo experiments. Our results provide a structural basis for the assembly of LANA-containing nuclear structures that are required for latent viral replication and persistence.
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Rodrigues L, Popov N, Kaye KM, Simas JP. Stabilization of Myc through heterotypic poly-ubiquitination by mLANA is critical for γ-herpesvirus lymphoproliferation. PLoS Pathog 2013; 9:e1003554. [PMID: 23950719 PMCID: PMC3738482 DOI: 10.1371/journal.ppat.1003554] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 06/28/2013] [Indexed: 11/18/2022] Open
Abstract
Host colonization by lymphotropic γ-herpesviruses depends critically on expansion of viral genomes in germinal center (GC) B-cells. Myc is essential for the formation and maintenance of GCs. Yet, the role of Myc in the pathogenesis of γ-herpesviruses is still largely unknown. In this study, Myc was shown to be essential for the lymphotropic γ-herpesvirus MuHV-4 biology as infected cells exhibited increased expression of Myc signature genes and the virus was unable to expand in Myc defficient GC B-cells. We describe a novel strategy of a viral protein activating Myc through increased protein stability resulting in increased progression through the cell cycle. This is acomplished by modulating a physiological post-translational regulatory pathway of Myc. The molecular mechanism involves Myc heterotypic poly-ubiquitination mediated via the viral E3 ubiquitin-ligase mLANA protein. EC5S(mLANA) modulates cellular control of Myc turnover by antagonizing SCF(Fbw7) mediated proteasomal degradation of Myc, mimicking SCF(β-TrCP). The findings here reported reveal that modulation of Myc is essential for γ-herpesvirus persistent infection, establishing a link between virus induced lymphoproliferation and disease.
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Affiliation(s)
- Lénia Rodrigues
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Nikita Popov
- Theodor Boveri Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Kenneth M. Kaye
- Channing Laboratory and Departments of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - J. Pedro Simas
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
- * E-mail:
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