scholarly journals Combination of Bortezomib and Venetoclax Induces Synergistic Killing of Epstein-Barr Virus-Driven Lymphoproliferative Diseases By Targeting the Pro-Survival Function of Latent Membrane Protein-1 and Epstein-Barr Nuclear Antigen-3C

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 12-13
Author(s):  
Alan Kwok Shing Chiang ◽  
Kam Pui Tam ◽  
Rex Kwok Him Au-Yeung
Keyword(s):  
Drug Combination ◽  
Epstein Barr Virus ◽  
Survival Function ◽  
Latent Membrane Protein ◽  
Nuclear Antigen ◽  
Latent Membrane Protein 1 ◽  
Lymphoproliferative Diseases ◽  
Barr Virus ◽  
Epstein Barr ◽  
Epstein Barr Nuclear Antigen

Epstein-Barr virus (EBV) is strongly associated with lymphoproliferative diseases (LPDs), in particular B cell, in both immunocompetent and immunocompromised hosts. The virus is able to manipulate host cell machineries such as the ubiquitin-proteasome system and regulators of Bcl-2 family to enable the persistence of the virus and the survival of the host cells through expression of various viral proteins in distinct latency patterns. Latent membrane protein-1 (LMP-1) is a constitutively active CD40 receptor homolog and activates NF-κB signaling pathways to induce Bcl-2 expression whilst Epstein-Barr nuclear antigen-3C (EBNA-3C) interacts with and mediates proteasomal degradation of Bcl-6 protein which, in turn, increases Bcl-2 expression. We hypothesize that combining a proteasome inhibitor, bortezomib, with a Bcl-2 inhibitor, venetoclax, will induce synergistic killing of EBV-driven LPDs expressing both LMP-1 and EBNA-3C in the latency III pattern. Isobologram showed that combination of bortezomib and venetoclax could synergistically induce potent apoptosis of spontaneous lymphoblastoid cell lines (sLCL), derived from patients with post-transplant lymphoproliferative disorder (PTLD), expressing LMP-1 and EBNA-3C proteins. The mechanism of killing was related to the suppression of NF-κB signaling pathway induced by LMP-1. The phosphorylation of serine 70 of Bcl-2, which enhances the anti-apoptotic activity of Bcl-2 through stabilization of its interaction with other pro-apoptotic proteins such as Bak and Bim, was decreased in the sLCL, but not in the LMP-1 or EBNA-3C knockdown LCL, upon treatment with the drug combination. Activation of DNA damage response and production of reactive oxygen species were observed in the sLCL, contributing to the synergistic cell death. Bortezomib induced the expression of pro-apoptotic initiator, NOXA, to enhance the susceptibility of the sLCL to apoptosis upon treatment with venetoclax whilst knockdown of NOXA in the sLCL led to the resistance of the cells to apoptosis induced by the drug combination. In-vivo study demonstrated that the drug combination significantly inhibited the growth of xenograft of sLCL in SCID mice (p<0.001). Taken together, we conclude that the combination of bortezomib and venetoclax induces synergistic killing of EBV-driven LPDs such as PTLD by targeting the pro-survival function of LMP-1 and EBNA-3C. Disclosures No relevant conflicts of interest to declare.

scholarly journals Epstein-Barr Virus Nuclear Antigen 3C Activates the Latent Membrane Protein 1 Promoter in the Presence of Epstein-Barr Virus Nuclear Antigen 2 through Sequences Encompassing an Spi-1/Spi-B Binding Site

2000 ◽  
Vol 74 (11) ◽  
pp. 5151-5160 ◽  
Author(s):  
Bo Zhao ◽  
Clare E. Sample
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Binding Sites ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Nuclear Antigen ◽  
Latent Membrane Protein 1 ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) protein is a transcriptional regulator of viral and cellular genes that is essential for EBV-mediated immortalization of B lymphocytes in vitro. EBNA-3C can inhibit transcription through an association with the cellular DNA-binding protein Jκ, a function shared by EBNA-3A and EBNA-3B. Here, we report a mechanism by which EBNA-3C can activate transcription from the EBV latent membrane protein 1 (LMP-1) promoter in conjunction with EBNA-2. Jκ DNA-binding sites were not required for this activation, and a mutant EBNA-3C protein unable to bind Jκ activated transcription as efficiently as wild-type EBNA-3C, indicating that EBNA-3C can regulate transcription through a mechanism that is independent of Jκ. Furthermore, activation of the LMP-1 promoter is a unique function of EBNA-3C, not shared by EBNA-3A and EBNA-3B. The DNA element through which EBNA-3C activates the LMP-1 promoter includes a Spi-1/Spi-B binding site, previously characterized as an important EBNA-2 response element. Although this element has considerable homology to mouse immunoglobulin light chain promoter sequences to which the mouse homologue of Spi-1 binds with its dimerization partner IRF4, we demonstrate that the IRF4-like binding sites in the LMP-1 promoter do not play a role in EBNA-3C-mediated activation. Both EBNA-2 and EBNA-3C were required for transcription mediated through a 41-bp region of the LMP-1 promoter encompassing the Spi binding site. However, EBNA-3C had no effect on transcription mediated in conjunction with the EBNA-2 activation domain fused to the GAL4 DNA-binding domain, suggesting that it does not function as an adapter between EBNA-2 and the cellular transcriptional machinery. Like EBNA-2, EBNA-3C bound directly to both Spi-1 and Spi-B in vitro. This interaction was mediated by a region of EBNA-3C encompassing a likely basic leucine zipper (bZIP) domain and the ets domain of Spi-1 or Spi-B, reminiscent of interactions between bZIP and ets domains of other transcription factors that result in their targeting to DNA. There are many examples of regulation of the hematopoietic-specific Spi transcription factors through protein-protein interactions, and a similar regulation by EBNA-3C, in conjunction with EBNA-2, is likely to be an important and unique contribution of EBNA-3C to EBV-mediated immortalization.

scholarly journals Identification of Major Phosphorylation Sites of Epstein-Barr Virus Nuclear Antigen Leader Protein (EBNA-LP): Ability of EBNA-LP To Induce Latent Membrane Protein 1 Cooperatively with EBNA-2 Is Regulated by Phosphorylation

2001 ◽  
Vol 75 (11) ◽  
pp. 5119-5128 ◽  
Author(s):  
Akihiko Yokoyama ◽  
Michiko Tanaka ◽  
Go Matsuda ◽  
Kentaro Kato ◽  
Mikiko Kanamori ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Nuclear Antigen ◽  
Latent Membrane Protein 1 ◽  
Phosphorylation Sites ◽  
Barr Virus ◽  
Leader Protein ◽  
Repeat Domain ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization of B cells. One of the potential functions of EBNA-LP is a cooperative induction with EBNA-2 of viral and cellular gene expression, including that of the genes for viral latent membrane protein 1 (LMP-1) and cellular cyclin D2. We report here that the phosphorylation of EBNA-LP by cellular kinase(s) is critical to its ability to cooperate with EBNA-2 in up-regulating the expression of LMP-1 in a B-lymphoma cell line. Our conclusion is based on the following observations. (i) Mass-spectrometric analysis of purified EBNA-LP and mutational analyses of EBNA-LP revealed that the serine residue at position 35 in the W2 repeat domain is the major phosphorylation site of EBNA-LP in vivo. (ii) Substitutions of this site in each W2 repeat domain with alanine markedly reduced the ability of the protein to induce LMP-1 expression in combination with EBNA-2 in Akata cells. (iii) Replacement at the major phosphorylation sites with glutamic acids restored the wild-type phenotype. It is well established that this substitution mimics constitutive phosphorylation. These results indicated that the coactivator function of EBNA-LP is regulated by phosphorylation.

scholarly journals Modulation of MicroRNA Cluster miR-183-96-182 Expression by Epstein-Barr Virus Latent Membrane Protein 1

2015 ◽  
Vol 89 (23) ◽  
pp. 12178-12188 ◽  
Author(s):  
Lassad Oussaief ◽  
Ali Fendri ◽  
Béatrice Chane-Woon-Ming ◽  
Remy Poirey ◽  
Henri-Jacques Delecluse ◽  
...  
Keyword(s):  
Cell Death ◽  
Membrane Protein ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Nuclear Antigen ◽  
Latent Membrane Protein 1 ◽  
Type I ◽  
Cellular Mirnas ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACTEpstein-Barr virus (EBV) is an oncogenic human herpesvirus involved in the pathogenesis of Burkitt's lymphoma (BL) and various other lymphoproliferative disorders. In BL, EBV protein expression is restricted to EBV nuclear antigen 1 (EBNA1), but small noncoding RNAs such as EBV-encoded small RNAs (EBERs) and microRNAs (miRNAs) can also be detected. miRNAs play major roles in crucial processes such as proliferation, differentiation, and cell death. It has recently become clear that alterations in the expression profile of miRNAs contribute to the pathogenesis of a number of malignancies. During latent infection, EBV expresses 25 viral pre-miRNAs and modulates the expression of specific cellular miRNAs, such as miR-155 and miR-146, which potentially play a role in oncogenesis. Here, we established the small-RNA expression profiles of three BL cell lines. Using large-scale sequencing coupled to Northern blotting and real-time reverse transcription-PCR (RT-PCR) analysis validation, we demonstrated the differential expression of some cellular and viral miRNAs. High-level expression of the miR-183-96-182 cluster and EBV miR-BamHI A rightward transcript (miR-BART) cluster was significantly associated with EBV type I latency. This expression was not affected by viral reactivation since transforming growth factor β1 (TGF-β1) stimulation did not significantly change the miRNA profiles. However, using several approaches, includingde novoinfection with a mutant virus, we present evidence that the expression of latent membrane protein 1 (LMP-1) triggered downregulation of the expression of the miR-183-96-182 cluster. We further show that this effect involves the Akt signaling pathway.IMPORTANCEIn addition to expressing their own miRNAs, herpesviruses also impact the expression levels of cellular miRNAs. This regulation can be either positive or negative and usually results in the perturbation of pathways to create a cellular environment that is more “virus-friendly.” For example, EBV induces the expression of miR-155, a well-characterized oncomiR, which leads to increased cell proliferation and decreased cell death. Here, we show that EBV-encoded LMP-1 is also involved in the downregulation of a cluster of three miRNAs, miR-183, -96, and -182, which are known to be also repressed in several cancers. We therefore identify yet another potential player in EBV-induced oncogenesis.

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