The reversal of epigenetic silencing of the EBV genome is regulated by viral bZIP protein

2008 ◽  
Vol 36 (4) ◽  
pp. 637-639 ◽  
Author(s):  
Questa H. Karlsson ◽  
Celine Schelcher ◽  
Elizabeth Verrall ◽  
Carlo Petosa ◽  
Alison J. Sinclair
Keyword(s):  
Single Point ◽  
Cysteine Residue ◽  
Lytic Replication ◽  
Epigenetic Silencing ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Cpg Motifs ◽  
Epstein Barr

EBV (Epstein–Barr virus) alternates between latency and lytic replication. During latency, the viral genome is largely silenced by host-driven methylation of CpG motifs and in the switch to the lytic cycle this epigenetic silencing is overturned. A key event is the activation of the viral protein Zta with three ZREs (Zta-response elements) from the BRLF1 promoter (referred to as Rp). Two of these ZREs contain CpG motifs and are methylated in the latent genome. Biochemical analyses and molecular modelling of Zta bound to methylated RpZRE3 indicate the precise contacts made between a serine and a cysteine residue of Zta with methyl cytosines. A single point mutant of Zta, C189S, is defective in binding to the methylated ZREs both in vitro and in vivo. This was used to probe the functional relevance of the interaction. ZtaC189S was not able to activate Rp in a B-cell line, demonstrating the relevance of the interaction with methylated ZREs. This demonstrates that Zta plays a role in overturning the epigenetic control of viral latency.

scholarly journals Molecular virology of Epstein–Barr virus

2001 ◽  
Vol 356 (1408) ◽  
pp. 437-459 ◽  
Author(s):  
Georg W. Bornkamm ◽  
Wolfgang Hammerschmidt
Keyword(s):  
B Cell ◽  
Epstein Barr Virus ◽  
Descriptive Analysis ◽  
Genetic System ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Cell Immortalization ◽  
Epstein Barr

Epstein–Barr virus (EBV) interacts with its host in three distinct ways in a highly regulated fashion: (i) EBV infects human B lymphocytes and induces proliferation of the infected cells, (ii) it enters into a latent phase in vivo that follows the proliferative phase, and (iii) it can be reactivated giving rise to the production of infectious progeny for reinfection of cells of the same type or transmission of the virus to another individual. In healthy people, these processes take place simultaneously in different anatomical and functional compartments and are linked to each other in a highly dynamic steady–state equilibrium. The development of a genetic system has paved the way for the dissection of those processes at a molecular level that can be studied in vitro , i.e. B–cell immortalization and the lytic cycle leading to production of infectious progeny. Polymerase chain reaction analyses coupled to fluorescent–activated cell sorting has on the other hand allowed a descriptive analysis of the virus–host interaction in peripheral blood cells as well as in tonsillar B cells in vivo . This paper is aimed at compiling our present knowledge on the process of B–cell immortalization in vitro as well as in vivo latency, and attempts to integrate this knowledge into the framework of the viral life cycle in vivo .

scholarly journals Epstein-Barr Virus WZhet DNA Can Induce Lytic Replication in Epithelial Cells in vitro, although WZhet Is Not Detectable in Many Human Tissues in vivo

Intervirology ◽  
2009 ◽  
Vol 52 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Julie L. Ryan ◽  
Richard J. Jones ◽  
Sandra H. Elmore ◽  
Shannon C. Kenney ◽  
George Miller ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Epstein Barr Virus ◽  
Lytic Replication ◽  
Human Tissues ◽  
Barr Virus ◽  
Epstein Barr

scholarly journals Terminal Differentiation into Plasma Cells Initiates the Replicative Cycle of Epstein-Barr Virus In Vivo

2005 ◽  
Vol 79 (2) ◽  
pp. 1296-1307 ◽  
Author(s):  
Lauri L. Laichalk ◽  
David A. Thorley-Lawson
Keyword(s):  
Viral Replication ◽  
Epstein Barr Virus ◽  
Plasma Cells ◽  
Acute Stress ◽  
Cytotoxic T Lymphocyte ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT In this paper we demonstrate that the cells which initiate replication of Epstein-Barr virus (EBV) in the tonsils of healthy carriers are plasma cells (CD38hi, CD10−, CD19+, CD20lo, surface immunoglobulin negative, and cytoplasmic immunoglobulin positive). We further conclude that differentiation into plasma cells, and not the signals that induce differentiation, initiates viral replication. This was confirmed by in vitro studies showing that the promoter for BZLF1, the gene that begins viral replication, becomes active only after memory cells differentiate into plasma cells and is also active in plasma cell lines. This differs from the reactivation of BZLF1 in vitro, which occurs acutely and is associated with apoptosis and not with differentiation. We suggest that differentiation and acute stress represent two distinct pathways of EBV reactivation in vivo. The fraction of cells replicating the virus decreases as the cells progress through the lytic cycle such that only a tiny fraction actually release infectious virus. This may reflect abortive replication or elimination of cells by the cellular immune response. Consistent with the later conclusion, the cells did not down regulate major histocompatibility complex class I molecules, suggesting that this is not an immune evasion tactic used by EBV and that the cells remain vulnerable to cytotoxic-T-lymphocyte attack.

scholarly journals Inhibition of the Epstein–Barr virus lytic cycle by Zta-targeted RNA interference

2004 ◽  
Vol 85 (6) ◽  
pp. 1371-1379 ◽  
Author(s):  
Yao Chang ◽  
Shih-Shin Chang ◽  
Heng-Huan Lee ◽  
Shin-Lian Doong ◽  
Kenzo Takada ◽  
...  
Keyword(s):  
Rna Interference ◽  
Epstein Barr Virus ◽  
Disease Risk ◽  
Lytic Replication ◽  
Lytic Cycle ◽  
Viral Gene ◽  
Barr Virus ◽  
Ebv Reactivation ◽  
Epstein Barr

Epstein–Barr virus (EBV) reactivation into the lytic cycle plays certain roles in the development of EBV-associated diseases, so an effective strategy to block the viral lytic cycle may be of value to reduce the disease risk or to improve the clinical outcome. This study examined whether the EBV lytic cycle could be inhibited using RNA interference (RNAi) directed against the essential viral gene Zta. In cases of EBV reactivation triggered by chemicals or by exogenous Rta, Zta-targeted RNAi prevented the induction of Zta and its downstream genes and further blocked the lytic replication of viral genomes. This antiviral effect of RNAi was not likely to be mediated by activation of the interferon pathway, as phosphorylation of STAT1 was not induced. In addition, novel EBV-infected epithelial cells showing constitutive activation of the lytic cycle were cloned; such established lytic infection was also suppressed by Zta-targeted RNAi. These results indicate that RNAi can be used to inhibit the EBV lytic cycle effectively in vitro and could also be of potential use to develop anti-EBV treatments.

scholarly journals A Redox-Sensitive Cysteine in Zta Is Required for Epstein-Barr Virus Lytic Cycle DNA Replication

2005 ◽  
Vol 79 (21) ◽  
pp. 13298-13309 ◽  
Author(s):  
Pu Wang ◽  
Latasha Day ◽  
Jayaraju Dheekollu ◽  
Paul M. Lieberman
Keyword(s):  
Dna Replication ◽  
Dna Binding ◽  
Redox Regulation ◽  
Binding Activity ◽  
Lytic Replication ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Dna Binding Activity ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) reactivation from latency is known to be sensitive to redox regulation. The immediate-early protein Zta is a member of the basic-leucine zipper (bZIP) family of DNA binding proteins that stimulates viral and cellular transcription and nucleates a replication complex at the viral lytic origin. Zta shares with several members of the bZIP family a conserved cysteine residue (C189) that confers redox regulation of DNA binding. In this work, we show that replacement of C189 with serine (C189S) eliminated lytic cycle DNA replication function of Zta. The mechanistic basis for this replication defect was investigated. We show that C189S was not significantly altered for DNA binding activity in vitro or in vivo. We also show that C189S was not defective for transcription activation of EBV early gene promoters. C189S was deficient for transcription activation of several viral late genes that depend on lytic replication and therefore was consistent with a primary defect of C189S in activating lytic replication. C189S was not defective in binding methylated DNA binding sites and was capable of activating Rta from endogenous latent viral genomes, in contrast to the previously characterized S186A mutation. C189S was slightly impaired for its ability to form a stable complex with Rta, although this did not prevent Rta recruitment to OriLyt. C189S did provide some resistance to oxidation and nitrosylation, which potently inhibit Zta DNA binding activity in vitro. Interestingly, this redox sensitivity was not strictly dependent on C189S but involved additional cysteine residues in Zta. These results provide evidence that the conserved cysteine in the bZIP domain of Zta plays a primary role in EBV lytic cycle DNA replication.

scholarly journals An Ancestral Retrovirus Envelope Protein Regulates Persistent Gammaherpesvirus Lifecycles

2021 ◽  
Vol 12 ◽  
Author(s):  
Tiffany R. Frey ◽  
Ibukun A. Akinyemi ◽  
Eric M. Burton ◽  
Sumita Bhaduri-McIntosh ◽  
Michael T. McIntosh
Keyword(s):  
B Cell ◽  
Envelope Protein ◽  
Cell Cycle Progression ◽  
Lytic Replication ◽  
Epigenetic Silencing ◽  
Endogenous Retroviruses ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Immediate Early Proteins ◽  
Epstein Barr

Human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV) persist as life-long infections alternating between latency and lytic replication. Human endogenous retroviruses (HERVs), via integration into the host genome, represent genetic remnants of ancient retroviral infections. Both show similar epigenetic silencing while dormant, but can reactivate in response to cell signaling cues or triggers that, for gammaherpesviruses, result in productive lytic replication. Given their co-existence with humans and shared epigenetic silencing, we asked if HERV expression might be linked to lytic activation of human gammaherpesviruses. We found ERVW-1 mRNA, encoding the functional HERV-W envelope protein Syncytin-1, along with other repeat class elements, to be elevated upon lytic activation of EBV. Knockdown/knockout of ERVW-1 reduced lytic activation of EBV and KSHV in response to various lytic cycle triggers. In this regard, reduced expression of immediate early proteins ZEBRA and RTA for EBV and KSHV, respectively, places Syncytin-1’s influence on lytic activation mechanistically upstream of the latent-to-lytic switch. Conversely, overexpression of Syncytin-1 enhanced lytic activation of EBV and KSHV in response to lytic triggers, though this was not sufficient to induce lytic activation in the absence of such triggers. Syncytin-1 is expressed in replicating B cell blasts and lymphoma-derived B cell lines where it appears to contribute to cell cycle progression. Together, human gammaherpesviruses and B cells appear to have adapted a dependency on Syncytin-1 that facilitates the ability of EBV and KSHV to activate lytic replication from latency, while promoting viral persistence during latency by contributing to B cell proliferation.

scholarly journals CCAAT/Enhancer Binding Protein α Binds to the Epstein-Barr Virus (EBV) ZTA Protein through Oligomeric Interactions and Contributes to Cooperative Transcriptional Activation of the ZTA Promoter through Direct Binding to the ZII and ZIIIB Motifs during Induction of the EBV Lytic Cycle

2004 ◽  
Vol 78 (9) ◽  
pp. 4847-4865 ◽  
Author(s):  
Frederick Y. Wu ◽  
Shizhen Emily Wang ◽  
Honglin Chen ◽  
Ling Wang ◽  
S. Diane Hayward ◽  
...  
Keyword(s):  
Protein Expression ◽  
Epstein Barr Virus ◽  
Leucine Zipper ◽  
Binding Protein ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Enhancer Binding Protein ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV)-encoded ZTA protein interacts strongly with and stabilizes the cellular CCAAT/enhancer binding protein α (C/EBPα), leading to the induction of p21-mediated G1 cell cycle arrest. Despite the strong interaction between these two basic leucine zipper (bZIP) family proteins, the ZTA and C/EBPα subunits do not heterodimerize, as indicated by an in vitro cross-linking assay with in vitro-cotranslated 35S-labeled C/EBPα and 35S-labeled ZTA protein. Instead, they evidently form a higher-order oligomeric complex that competes with C/EBPα binding but not with ZTA binding in electrophoretic mobility shift assays (EMSAs). Glutathione S-transferase affinity assays with mutant ZTA proteins revealed that the basic DNA binding domain and the key leucine zipper residues required for homodimerization are all required for the interaction with C/EBPα. ZTA is known to bind to two ZRE sites within the ZTA promoter and to positively autoregulate its own expression in transient cotransfection assays, but there is conflicting evidence about whether it does so in vivo. Examination of the proximal ZTA upstream promoter region by in vitro EMSA analysis revealed two high-affinity C/EBP binding sites (C-2 and C-3), which overlap the ZII and ZIIIB motifs, implicated as playing a key role in lytic cycle induction. A chromatin immunoprecipitation assay confirmed the in vivo binding of both endogenous C/EBPα and ZTA protein to the ZTA promoter after lytic cycle induction but not during the latent state in EBV-infected Akata cells. Reporter assays revealed that cotransfected C/EBPα activated the ZTA promoter even more effectively than cotransfected ZTA. However, synergistic activation of the ZTA promoter was not observed when ZTA and C/EBPα were cotransfected together in either HeLa or DG75 cells. Mutagenesis of either the ZII or the ZIIIB sites in the ZTA promoter strongly reduced C/EBPα transactivation, suggesting that these sites act cooperatively. Furthermore, the introduction of exogenous C/EBPα into EBV-infected HeLa-BX1 cells induced endogenous ZTA mRNA and protein expression, as demonstrated by both reverse transcription-PCR and immunoblotting assays. Finally, double-label immunofluorescence assays suggested that EAD protein expression was activated even better than ZTA expression in latently infected C/EBPα-transfected Akata cells, perhaps because of the presence of a strong B-cell-specific repressed chromatin conformation on the ZTA promoter itself during EBV latency.

scholarly journals Epstein-Barr Virus SM Protein Interacts with mRNA In Vivo and Mediates a Gene-Specific Increase in Cytoplasmic mRNA

2001 ◽  
Vol 75 (13) ◽  
pp. 6033-6041 ◽  
Author(s):  
Vivian Ruvolo ◽  
Ashish K. Gupta ◽  
Sankar Swaminathan
Keyword(s):  
Epstein Barr Virus ◽  
Rna Binding ◽  
Lytic Replication ◽  
Nuclear Accumulation ◽  
Rich Region ◽  
Rnase Protection ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT SM is an Epstein-Barr virus (EBV) gene expressed during early lytic replication of EBV. SM encodes a nuclear phosphoprotein that functions as a posttranscriptional regulator of gene expression. SM has been implicated in several aspects of gene regulation, including nuclear mRNA stabilization, posttranscriptional processing, and nuclear mRNA export. Activation by SM is promoter independent but gene specific. The mechanism by which SM selectively activates some EBV target genes or heterologous reporter genes remains to be determined. SM binds RNA in vitro, suggesting that sequence- or structure-specific mRNA interactions might mediate SM specificity. We have further analyzed RNA binding by SM and demonstrated that proteolytic cleavage of SM and consequent exposure of an arginine-rich region are necessary to allow RNA binding in vitro. However, SM mutants with deletions of this arginine-rich region localized normally in the nucleus and were fully functional in gene activation. We therefore developed an assay to study in vivo interactions of SM with target mRNAs based on immunoprecipitation of SM from cell lysates followed by RNase protection analysis. Using this assay, we demonstrated that SM forms complexes with specific mRNAs in vivo. SM binds mRNAs from both SM-responsive as well as nonresponsive intronless genes and increases the nuclear accumulation of both types of mRNAs. In addition, SM preferentially associates with newly transcribed mRNAs. These data indicate that SM forms complexes with mRNAs in the nucleus and enhances their nuclear accumulation. However, SM does not enhance cytoplasmic accumulation of all transcripts that it binds to the same degree, suggesting that additional mRNA-specific characteristics, such as nuclear retention motifs or binding sites for cellular proteins, also determine responsiveness to SM.

scholarly journals Identification and Cloning of a New Western Epstein-Barr Virus Strain That Efficiently Replicates in Primary B Cells

2020 ◽  
Vol 94 (10) ◽  
Author(s):  
Susanne Delecluse ◽  
Remy Poirey ◽  
Martin Zeier ◽  
Paul Schnitzler ◽  
Uta Behrends ◽  
...  
Keyword(s):  
B Cells ◽  
Epstein Barr Virus ◽  
Lytic Replication ◽  
Sequence Information ◽  
World Population ◽  
Barr Virus ◽  
The World ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) causes human cancers, and epidemiological studies have shown that lytic replication is a risk factor for some of these tumors. This fits with the observation that EBV M81, which was isolated from a Chinese patient with nasopharyngeal carcinoma, induces potent virus production and increases the risk of genetic instability in infected B cells. To find out whether this property extends to viruses found in other parts of the world, we investigated 22 viruses isolated from Western patients. While one-third of the viruses hardly replicated, the remaining viruses showed variable levels of replication, with three isolates replicating at levels close to that of M81 in B cells. We cloned one strongly replicating virus into a bacterial artificial chromosome (BAC); the resulting recombinant virus (MSHJ) retained the properties of its nonrecombinant counterpart and showed similarities to M81, undergoing lytic replication in vitro and in vivo after 3 weeks of latency. In contrast, B cells infected with the nonreplicating Western B95-8 virus showed early but abortive replication accompanied by cytoplasmic BZLF1 expression. Sequencing confirmed that rMSHJ is a Western virus, being genetically much closer to B95-8 than to M81. Spontaneous replication in rM81- and rMSHJ-infected B cells was dependent on phosphorylated Btk and was inhibited by exposure to ibrutinib, opening the way to clinical intervention in patients with abnormal EBV replication. As rMSHJ contains the complete EBV genome and induces lytic replication in infected B cells, it is ideal to perform genetic analyses of all viral functions in Western strains and their associated diseases. IMPORTANCE The Epstein-Barr virus (EBV) infects the majority of the world population but causes different diseases in different countries. Evidence that lytic replication, the process that leads to new virus progeny, is linked to cancer development is accumulating. Indeed, viruses such as M81 that were isolated from Far Eastern nasopharyngeal carcinomas replicate strongly in B cells. We show here that some viruses isolated from Western patients, including the MSHJ strain, share this property. Moreover, replication of both M81 and of MSHJ was sensitive to ibrutinib, a commonly used drug, thereby opening an opportunity for therapeutic intervention. Sequencing of MSHJ showed that this virus is quite distant from M81 and is much closer to nonreplicating Western viruses. We conclude that Western EBV strains are heterogeneous, with some viruses being able to replicate more strongly and therefore being potentially more pathogenic than others, and that the virus sequence information alone cannot predict this property.

scholarly journals Disruption of Epstein-Barr Virus Latency in the Absence of Phosphorylation of ZEBRA by Protein Kinase C

2002 ◽  
Vol 76 (22) ◽  
pp. 11199-11208 ◽  
Author(s):  
Ayman S. El-Guindy ◽  
Lee Heston ◽  
Yoshimi Endo ◽  
Myung-Sam Cho ◽  
George Miller
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Viral Gene ◽  
Barr Virus ◽  
Kinase C ◽  
Epstein Barr

ABSTRACT ZEBRA protein converts Epstein-Barr virus (EBV) infection from the latent to the lytic state. The ability of ZEBRA to activate this switch is strictly dependent on the presence of serine or threonine at residue 186 of the protein (A. Francis, T. Ragoczy, L. Gradoville, A. El-Guindy, and G. Miller, J. Virol. 72:4543-4551, 1999). We investigated whether phosphorylation of ZEBRA protein at this site by a serine-threonine protein kinase was required for activation of an early lytic cycle viral gene, BMRF1, as a marker of disruption of latency. Previous studies suggested that phosphorylation of ZEBRA at S186 by protein kinase C (PKC) activated the protein (M. Baumann, H. Mischak, S. Dammeier, W. Kolch, O. Gires, D. Pich, R. Zeidler, H. J. Delecluse, and W. Hammerschmidt, J. Virol 72:8105-8114, 1998). Two residues of ZEBRA, T159 and S186, which fit the consensus for phosphorylation by PKC, were phosphorylated in vitro by this enzyme. Several isoforms of PKC (α, β1, β2, γ, δ, and ε) phosphorylated ZEBRA. All isoforms that phosphorylated ZEBRA in vitro were blocked by bisindolylmaleimide I, a specific inhibitor of PKC. Studies in cell culture showed that phosphorylation of T159 was not required for disruption of latency in vivo, since the T159A mutant was fully functional. Moreover, the PKC inhibitor did not block the ability of ZEBRA expressed from a transfected plasmid to activate the BMRF1 downstream gene. Of greatest importance, in vivo labeling with [32P]orthophosphate showed that the tryptic phosphopeptide maps of wild-type ZEBRA, Z(S186A), and the double mutant Z(T159A/S186A) were identical. Although ZEBRA is a potential target for PKC, in the absence of PKC agonists, ZEBRA is not constitutively phosphorylated in vivo by PKC at T159 or S186. Phosphorylation of ZEBRA by PKC is not essential for the protein to disrupt EBV latency.

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