scholarly journals Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Promotes EBV Reactivation through Activation of the p38 Mitogen-Activated Protein Kinase

2015 ◽  
Vol 90 (2) ◽  
pp. 1129-1138 ◽  
Author(s):  
XueQiao Liu ◽  
Jeffrey I. Cohen
Keyword(s):  
Protein Kinase ◽  
Signaling Pathways ◽  
Epstein Barr Virus ◽  
Virus Production ◽  
Mitogen Activated Protein Kinase ◽  
Tegument Protein ◽  
Barr Virus ◽  
Ebv Reactivation ◽  
Mitogen Activated Protein ◽  
Epstein Barr

ABSTRACTEpstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus associated with both B cell and epithelial cell malignancies. EBV infection of B cells triggers activation of several signaling pathways that are critical for cell survival, virus latency, and growth transformation. To identify EBV proteins important for regulating cell signaling, we used a proteomic approach to screen viral proteins for AP-1 and NF-κB promoter activity in AP-1– and NF-κB–luciferase reporter assays. We found that EBV BGLF2 activated AP-1 but not NF-κB reporter activity. Expression of EBV BGLF2 in cells activated p38 and c-Jun N-terminal kinase (JNK), both of which are important for mitogen-activated protein kinase (MAPK) signaling. Deletion of the carboxyl-terminal 66 amino acids of BGLF2 reduced the ability of BGLF2 to activate JNK and p38. Expression of BGLF2 enhanced BZLF1 expression in latently EBV-infected lymphoblastoid cell lines, and knockdown of BGLF2 reduced EBV reactivation induced by IgG cross-linking. Expression of BGLF2 induced BZLF1 expression and virus production in EBV-infected gastric carcinoma cells. BGLF2 enhanced BZLF1 expression and EBV production by activating p38; chemical inhibition of p38 and MAPK/ERK kinases 1 and 2 (MEK1/2) reduced expression of BZLF1 and virus production induced by BGLF2. In summary, the EBV tegument protein BGLF2, which is delivered to the cell at the onset of virus infection, activates the AP-1 pathway and enhances EBV reactivation and virus production.IMPORTANCEEpstein-Barr virus (EBV) is associated with both B cell and epithelial cell malignancies, and the virus activates multiple signaling pathways important for its persistence in latently infected cells. We identified a viral tegument protein, BGLF2, which activates members of the mitogen-activated protein kinase signaling pathway. Expression of BGLF2 increased expression of EBV BZLF1, which activates a switch from latent to lytic virus infection, and increased production of EBV. Inhibition of BGFL2 expression or inhibition of p38/MAPK, which is activated by BGLF2, reduced virus reactivation from latency. These results indicate that a viral tegument protein which is delivered to cells upon infection activates signaling pathways to enhance virus production and facilitate virus reactivation from latency.

scholarly journals Inhibition of Epstein-Barr Virus (EBV) Reactivation by Short Interfering RNAs Targeting p38 Mitogen-Activated Protein Kinase or c-myc in EBV-Positive Epithelial Cells

2004 ◽  
Vol 78 (21) ◽  
pp. 11798-11806 ◽  
Author(s):  
Xiangrong Gao ◽  
Haoran Wang ◽  
Takeshi Sairenji
Keyword(s):  
Protein Kinase ◽  
Epstein Barr Virus ◽  
Antiviral Effect ◽  
Mitogen Activated Protein Kinase ◽  
Early Gene ◽  
No Donor ◽  
Barr Virus ◽  
Ebv Reactivation ◽  
Mitogen Activated Protein ◽  
Epstein Barr

ABSTRACT Latent Epstein-Barr virus (EBV) is reactivated by 12-O-tetradecanoylphorbol-13-acetate (TPA) in EBV-infected cells. In this study, we found that TPA up-regulated phosphorylation of p38, a mitogen-activated protein kinase, and activated c-myc mRNA in EBV-positive epithelial GT38 cells. The EBV immediate-early gene BZLF1 mRNA and its product ZEBRA protein were induced following TPA treatment. Protein kinase C inhibitors, 1-(5-isoquinolinesulphonyl)-2, 5-dimethylpiperazine (H7) and staurosporine, inhibited the induction of p38 phosphorylation and the activation of c-Myc by TPA. The p38 inhibitor SB203580 blocked both p38 phosphorylation and ZEBRA expression by TPA. Pretreatment of GT38 cells with the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine inhibited p38 phosphorylation and c-Myc activation by TPA, suggesting that NO may inhibit EBV reactivation via both p38 and c-Myc. By using short interfering RNA (siRNA) targeting either p38 or c-myc, we found that p38 or c-myc siRNA specifically inhibited expression of the respective gene and also suppressed the induction of ZEBRA and EBV early antigen. The interferon (IFN)-responsive gene expression tests ruled out the possibility that the antiviral effect of siRNA is dependent on IFN. Our present study demonstrates for the first time that either p38 or c-myc siRNA can efficiently inhibit TPA-induced EBV reactivation in GT38 cells, indicating that p38- and/or c-myc-associated signaling pathways may play critical roles in the disruption of EBV latency by TPA.

scholarly journals The Epstein-Barr Virus-Encoded LMP2A and LMP2B Proteins Promote Epithelial Cell Spreading and Motility

2005 ◽  
Vol 79 (3) ◽  
pp. 1789-1802 ◽  
Author(s):  
Michael D. Allen ◽  
Lawrence S. Young ◽  
Christopher W. Dawson
Keyword(s):  
Protein Kinase ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Tyrosine Kinases ◽  
Epstein Barr Virus ◽  
Cell Spreading ◽  
Mitogen Activated Protein Kinase ◽  
Barr Virus ◽  
Mitogen Activated Protein ◽  
Epstein Barr

ABSTRACT The frequent expression of latent membrane proteins LMP2A and LMP2B in Epstein Barr virus (EBV)-associated tumors suggests that these proteins play a role in EBV-induced epithelial cell growth transformation. Expression of LMP2A and LMP2B had no effect on the morphology of squamous epithelial cells in monolayer culture, but their expression was associated with an increased capacity to spread and migrate on extracellular matrix. Although the mechanisms by which LMP2A and LMP2B promote cell spreading and motility are unclear, the use of selective pharmacological inhibitors has established a role for tyrosine kinases in this phenotype but ruled out contributions of phosphatidylinositol 3-kinase, extracellular signal-regulated kinase/mitogen-activated protein kinase, and protein kinase C. The ability of LMP2B to induce a phenotype that is virtually indistinguishable from that of LMP2A suggests that regions of the LMP2 protein in addition to the cytosolic amino terminus are capable of inducing phenotypic effects in epithelial cells. Thus, rather than serving to modulate the activity of LMP2A, LMP2B may directly engage signaling pathways to influence epithelial cell behavior such as cell adhesion and motility.

scholarly journals Retrograde Regulation by the Viral Protein Kinase Epigenetically Sustains the Epstein-Barr Virus Latency-to-Lytic Switch To Augment Virus Production

2019 ◽  
Vol 93 (17) ◽  
Author(s):  
Xiaofan Li ◽  
Sergei V. Kozlov ◽  
Ayman El-Guindy ◽  
Sumita Bhaduri-McIntosh
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Epstein Barr Virus ◽  
Infectious Virus ◽  
Virus Production ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Viral Protein Kinase ◽  
Epstein Barr ◽  
Productive Phase

ABSTRACTHerpesviruses are ubiquitous, and infection by some, like Epstein-Barr virus (EBV), is nearly universal. To persist, EBV must periodically switch from a latent to a replicative/lytic phase. This productive phase is responsible for most herpesvirus-associated diseases. EBV encodes a latency-to-lytic switch protein which, upon activation, sets off a vectorially constrained cascade of gene expression that results in production of infectious virus. While triggering expression of the switch protein ZEBRA is essential to lytic cycle entry, sustaining its expression is equally important to avoid premature termination of the lytic cascade. We report that the viral protein kinase (vPK), encoded by a gene that is kinetically downstream of the lytic switch, sustains expression of ZEBRA, amplifies the lytic cascade, increasing virus production, and, importantly, prevents the abortive lytic cycle. We find that vPK, through a noncanonical site phosphorylation, activates the cellular phosphatidylinositol 3-kinase-related kinase ATM to cause phosphorylation of the heterochromatin enforcer KAP1/TRIM28 even in the absence of EBV genomes or other EBV proteins. Phosphorylation of KAP1 renders it unable to restrain ZEBRA, thereby further derepressing and sustaining its expression to culminate in virus production. This partnership with a host kinase and a transcriptional corepressor enables retrograde regulation by vPK of ZEBRA, an observation that is counter to the unidirectional regulation of gene expression reminiscent of most DNA viruses.IMPORTANCEHerpesviruses infect nearly all humans and persist quiescently for the life of the host. These viruses intermittently activate into the lytic phase to produce infectious virus, thereby causing disease. To ensure that lytic activation is not prematurely terminated, expression of the virally encoded lytic switch protein needs to be sustained. In studying Epstein-Barr virus, one of the most prevalent human herpesviruses that also causes cancer, we have discovered that a viral kinase activated by the viral lytic switch protein partners with a cellular kinase to deactivate a silencer of the lytic switch protein, thereby providing a positive feedback loop to ensure successful completion of the viral productive phase. Our findings highlight key nodes of interaction between the host and virus that could be exploited to treat lytic phase-associated diseases by terminating the lytic phase or kill cancer cells harboring herpesviruses by accelerating the completion of the lytic cascade.

scholarly journals Epstein-Barr Virus Protein Kinase BGLF4 Is a Virion Tegument Protein That Dissociates from Virions in a Phosphorylation-Dependent Process and Phosphorylates the Viral Immediate-Early Protein BZLF1

2006 ◽  
Vol 80 (11) ◽  
pp. 5125-5134 ◽  
Author(s):  
Risa Asai ◽  
Ai Kato ◽  
Kentaro Kato ◽  
Mikiko Kanamori-Koyama ◽  
Ken Sugimoto ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Epstein Barr Virus ◽  
Tegument Protein ◽  
Virus Protein ◽  
Barr Virus ◽  
Early Protein ◽  
Dependent Process ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) BGLF4 is a viral protein kinase that is expressed in the lytic phase of infection and is packaged in virions. We report here that BGLF4 is a tegument protein that dissociates from the virion in a phosphorylation-dependent process. We also present evidence that BGLF4 interacts with and phosphorylates BZLF1, a key viral regulator of lytic infection. These conclusions are based on the following observations. (i) In in vitro tegument release assays, a significant fraction of BGLF4 was released from virions in the presence of physiological NaCl concentrations. (ii) Addition of physiological concentrations of ATP and MgCl2 to virions enhanced BGLF4 release, but phosphatase treatment of virions significantly reduced BGLF4 release. (iii) A recombinant protein containing a domain of BZLF1 was specifically phosphorylated by purified recombinant BGLF4 in vitro, and BGLF4 altered BZLF1 posttranslational modification in vivo. (iv) BZLF1 was specifically coimmunoprecipitated with BGLF4 in 12-O-tetradecanoylphorbol-13-acetate-treated B95-8 cells and in COS-1 cells transiently expressing both of these viral proteins. (v) BGLF4 and BZLF1 were colocalized in intranuclear globular structures, resembling the viral replication compartment, in Akata cells treated with anti-human immunoglobulin G. Our results suggest that BGLF4 functions not only in lytically infected cells by phosphorylating viral and cellular targets but also immediately after viral penetration like other herpesvirus tegument proteins.

scholarly journals Virus and Cell RNAs Expressed during Epstein-Barr Virus Replication

2006 ◽  
Vol 80 (5) ◽  
pp. 2548-2565 ◽  
Author(s):  
Jing Yuan ◽  
Ellen Cahir-McFarland ◽  
Bo Zhao ◽  
Elliott Kieff
Keyword(s):  
Epstein Barr Virus ◽  
Cell Function ◽  
Mitogen Activated Protein Kinase ◽  
Cross Linking ◽  
Specific Cell ◽  
Barr Virus ◽  
Intergenic Sequences ◽  
Mitogen Activated Protein ◽  
Epstein Barr ◽  
Rna Levels

ABSTRACT Changes in Epstein-Barr virus (EBV) and cell RNA levels were assayed following immunoglobulin G (IgG) cross-linking-induced replication in latency 1-infected Akata Burkitt B lymphoblasts. EBV replication as assayed by membrane gp350 expression was ∼5% before IgG cross-linking and increased to more than 50% 48 h after induction. Seventy-two hours after IgG cross-linking, gp350-positive cells excluded propidium iodide as well as gp350-negative cells. EBV RNA levels changed temporally in parallel with previously defined sensitivity to inhibitors of protein or viral DNA synthesis. BZLF1 immediate-early RNA levels doubled by 2 h and reached a peak at 4 h, whereas BMLF1 doubled by 4 h with a peak at 8 h, and BRLF1 doubled by 8 h with peak at 12 h. Early RNAs peaked at 8 to 12 h, and late RNAs peaked at 24 h. Hybridization to intergenic sequences resulted in evidence for new EBV RNAs. Surprisingly, latency III (LTIII) RNAs for LMP1, LMP2, EBNALP, EBNA2, EBNA3A, EBNA3C, and BARTs were detected at 8 to 12 h and reached maxima at 24 to 48 h. EBNA2 and LMP1 were at full LTIII levels by 48 h and localized to gp350-positive cells. Thus, LTIII expression is a characteristic of late EBV replication in both B lymphoblasts and epithelial cells in immune-comprised people (J. Webster-Cyriaque, J. Middeldorp, and N. Raab-Traub, J. Virol. 74:7610-7618, 2000). EBV replication significantly altered levels of 401 Akata cell RNAs, of which 122 RNAs changed twofold or more relative to uninfected Akata cells. Mitogen-activated protein kinase levels were significantly affected. Late expression of LTIII was associated with induction of NF-κB responsive genes including IκBα and A20. The exclusion of propidium, expression of EBV LTIII RNAs and proteins, and up-regulation of specific cell RNAs are indicative of vital cell function late in EBV replication.

scholarly journals Unique Signaling Properties of CTAR1 in LMP1-Mediated Transformation

2007 ◽  
Vol 81 (18) ◽  
pp. 9680-9692 ◽  
Author(s):  
Bernardo A. Mainou ◽  
David N. Everly ◽  
Nancy Raab-Traub
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Signaling Pathway ◽  
Tumor Necrosis Factor Receptor ◽  
Binding Domain ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Barr Virus ◽  
Mitogen Activated Protein ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) gene is considered the EBV oncogene as it is necessary for EBV-mediated transformation of B lymphocytes and itself transforms rodent fibroblasts. LMP1 activates the NF-κB, phosphatidylinositol 3-kinase (PI3K)-Akt, mitogen-activated protein kinase, and Jun N-terminal protein kinase signaling pathways through its two signaling domains, carboxyl-terminal activating regions 1 and 2 (CTAR1 and CTAR2). CTAR1 and CTAR2 induce signal transduction pathways through their direct (CTAR1) or indirect (CTAR2) recruitment of tumor necrosis factor receptor-associated factors (TRAFs). CTAR1 is necessary for LMP1-mediated transformation as well as activation of PI3K signaling and induction of cell cycle markers associated with G1/S transition. In this study, activation of PI3K-Akt signaling and deregulation of cell cycle markers were mapped to the TRAF-binding domain within CTAR1 and to the residues between CTAR1 and CTAR2. LMP1 CTAR1 also activated the MEK1/2-extracellular signal-regulated kinase 1/2 signaling pathway, and this activation was necessary for LMP1-induced transformation of Rat-1 fibroblasts. Dominant-negative forms of TRAF2 and TRAF3 inhibited but did not fully block LMP1-mediated transformation. These findings identify a new signaling pathway that is uniquely activated by the TRAF-binding domain of LMP1 and is required for transformation.

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