scholarly journals c-Myc Represses Transcription of Epstein-Barr Virus Latent Membrane Protein 1 Early after Primary B Cell Infection

2017 ◽  
Vol 92 (2) ◽  
Author(s):  
Alexander M. Price ◽  
Joshua E. Messinger ◽  
Micah A. Luftig
Keyword(s):  
Transcription Factor ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cell Infection ◽  
Barr Virus ◽  
Epstein Barr ◽  
Factor C

ABSTRACTRecent evidence has shown that the Epstein-Barr virus (EBV) oncogene LMP1 is not expressed at high levels early after EBV infection of primary B cells, despite its being essential for the long-term outgrowth of immortalized lymphoblastoid cell lines (LCLs). In this study, we found that expression of LMP1 increased 50-fold between 7 days postinfection and the LCL state. Metabolic labeling of nascent transcribed mRNA indicated that this was primarily a transcription-mediated event. EBNA2, the key viral transcription factor regulating LMP1, and CTCF, an important chromatin insulator, were recruited to the LMP1 locus similarly early and late after infection. However, the activating histone H3K9Ac mark was enriched at the LMP1 promoter in LCLs relative to that in infected B cells early after infection. We found that high c-Myc activity in EBV-infected lymphoma cells as well as overexpression of c-Myc in an LCL model system repressed LMP1 transcription. Finally, we found that chemical inhibition of c-Myc both in LCLs and early after primary B cell infection increased LMP1 expression. These data support a model in which high levels of endogenous c-Myc activity induced early after primary B cell infection directly repress LMP1 transcription.IMPORTANCEEBV is a highly successful pathogen that latently infects more than 90% of adults worldwide and is also causally associated with a number of B cell malignancies. During the latent life cycle, EBV expresses a set of viral oncoproteins and noncoding RNAs with the potential to promote cancer. Critical among these is the viral latent membrane protein LMP1. Prior work suggests that LMP1 is essential for EBV to immortalize B cells, but our recent work indicates that LMP1 is not produced at high levels during the first few weeks after infection. Here we show that transcription of the LMP1 gene can be negatively regulated by a host transcription factor, c-Myc. Ultimately, understanding the regulation of EBV oncogenes will allow us to better treat cancers that rely on these viral products for survival.

scholarly journals c-Myc Represses Transcription of the Epstein-Barr Virus Latent Membrane Protein 1 Early After Primary B Cell Infection

2017 ◽  
Author(s):  
Alexander M. Price ◽  
Joshua E. Messinger ◽  
Micah A. Luftig
Keyword(s):  
Transcription Factor ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Latent Membrane Protein ◽  
Metabolic Labeling ◽  
Cell Infection ◽  
Barr Virus ◽  
Virus Latent Membrane Protein ◽  
Factor C

ABSTRACTRecent evidence has shown that the EBV oncogene LMP1 is not expressed at high levels early after EBV-infection of primary B cells, despite its being essential for the long-term outgrowth of immortalized lymphoblastoid cell lines (LCLs). In this study, we found that expression of LMP1 increased fifty-fold between seven days post infection and the LCL state. Metabolic labeling of nascently transcribed mRNA indicated this was primarily a transcription-mediated event. EBNA2, the key viral transcription factor regulating LMP1, and CTCF, an important chromatin insulator, were recruited to the LMP1 locus similarly early and late after infection. However, the activating histone H3K9Ac mark was enriched at the LMP1 promoter in LCLs relative to early-infected B cells. We found that high c-Myc activity in EBV-infected lymphoma cells as well as overexpression of c-Myc in an LCL model system repressed LMP1 transcription. Finally, we found that chemical inhibition of c-Myc expression both in LCLs and early after primary B-cell infection increased LMP1 expression. These data support a model in which high levels of endogenous c-Myc activity induced early after primary B-cell infection directly represses LMP1 transcription.IMPORTANCEEBV is a highly successful pathogen that latently infects greater than 90% of adults worldwide and is also causally associated with a number of B-cell malignancies. EBV expresses a set of viral oncoproteins and non-coding RNAs during the latent life cycle with the potential to promote cancer. Critical among these is the viral latent membrane protein, LMP1. Prior work suggests that LMP1 is essential for EBV to immortalize B cells, but our recent work indicates that LMP1 is not produced at high levels during the first few weeks after infection. Here, we show that the transcription of LMP1 can be negatively regulated by a host transcription factor, c-Myc. Ultimately, understanding the regulation of EBV-encoded oncogenes will allow us to better treat cancers that rely on these viral products for survival.

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2B (LMP2B) Modulates LMP2A Activity

2006 ◽  
Vol 81 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
Signal Transduction ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cross Linking ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) and LMP2B are viral proteins expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor (BCR) signal transduction by associating with the cellular tyrosine kinases Lyn and Syk via specific phosphotyrosine motifs found within the LMP2A N-terminal tail domain. LMP2A has been shown to alter normal BCR signal transduction in B cells by reducing levels of Lyn and by blocking tyrosine phosphorylation and calcium mobilization following BCR cross-linking. Although little is currently known about the function of LMP2B in B cells, the similarity in structure between LMP2A and LMP2B suggests that they may localize to the same cellular compartments. To investigate the function of LMP2B, B-cell lines expressing LMP2A, LMP2B, LMP2A/LMP2B, and the relevant vector controls were analyzed. As was previously shown, cells expressing LMP2A had a dramatic block in normal BCR signal transduction as measured by calcium mobilization and tyrosine phosphorylation. There was no effect on BCR signal transduction in cells expressing LMP2B. Interestingly, when LMP2B was expressed in conjunction with LMP2A, there was a restoration of normal BCR signal transduction upon BCR cross-linking. The expression of LMP2B did not alter the cellular localization of LMP2A but did bind to and prevent the phosphorylation of LMP2A. A restoration of Lyn levels, but not a change in LMP2A levels, was also observed in cells coexpressing LMP2B with LMP2A. From these results, we conclude that LMP2B modulates LMP2A activity.

scholarly journals Epstein-Barr Virus Represses the FoxO1 Transcription Factor through Latent Membrane Protein 1 and Latent Membrane Protein 2A

2006 ◽  
Vol 80 (22) ◽  
pp. 11191-11199 ◽  
Author(s):  
Angharad M. Shore ◽  
Paul C. White ◽  
Rosaline C.-Y. Hui ◽  
Abdelkader Essafi ◽  
Eric W.-F. Lam ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 1 ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Ebv Infection ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) infection is associated with the development of many B-cell lymphomas, including Burkitt's lymphoma, Hodgkin's lymphoma, and posttransplant lymphoproliferative disease. The virus alters a diverse range of cellular molecules, which leads to B-cell growth and immortalization. This study was initiated to investigate the interplay between EBV and a proapoptotic transcription factor target, FoxO1. In this report, we show that EBV infection of B cells leads to the downregulation of FoxO1 expression by phosphatidylinositol 3-kinase-mediated nuclear export, by inhibition of FoxO1 mRNA expression, and by alteration of posttranslational modifications. This repression directly correlates with the expression of the FoxO1 target gene Bcl-6 and inversely correlates with the FoxO1-regulated gene Cyclin D2. Expression of the EBV genes for latent membrane protein 1 and latent membrane protein 2A decreases FoxO1 expression. Thus, our data elucidate distinct mechanisms for the regulation of the proapoptotic transcription factor FoxO1 by EBV.

scholarly journals Epstein-Barr virus latent membrane protein 2A is a B-cell receptor mimic and essential for B-cell survival

Blood ◽  
2007 ◽  
Vol 110 (10) ◽  
pp. 3715-3721 ◽  
Author(s):  
Christoph Mancao ◽  
Wolfgang Hammerschmidt
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
Latent Membrane Protein ◽  
B Cell Receptor ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

AbstractMany cells latently infected with Epstein-Barr virus (EBV), including certain virus-associated tumors, express latent membrane protein 2A (LMP2A), suggesting an important role for this protein in viral latency and oncogenesis. LMP2A mimics B-cell receptor signaling but can also act as a decoy receptor blocking B-cell receptor (BCR) activation. Studies of peripheral B cells have not resolved this apparent contradiction because LMP2A seems to be dispensable for EBV-induced transformation of these B cells in vitro. We show here that LMP2A is essential for growth transformation of germinal center B cells, which do not express the genuine BCR because of deleterious somatic hypermutations in their immunoglobulin genes. BCR-positive (BCR+) and BCR-negative (BCR−) B cells are readily transformed with a recombinant EBV encoding a conditional, floxed LMP2A allele, but the survival and continued proliferation of both BCR+ and BCR− B cells is strictly dependent on LMP2A. These findings indicate that LMP2A has potent, distinct antiapoptotic and/or transforming characteristics and point to its role as an indispensable BCR mimic in certain B cells from which human B-cell tumors such as Hodgkin lymphoma originate.

scholarly journals Latent Membrane Protein 2B Regulates Susceptibility to Induction of Lytic Epstein-Barr Virus Infection

2007 ◽  
Vol 82 (4) ◽  
pp. 1739-1747 ◽  
Author(s):  
Markus P. Rechsteiner ◽  
Christoph Berger ◽  
Ludwig Zauner ◽  
Jürg A. Sigrist ◽  
Matthias Weber ◽  
...  
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cross Linking ◽  
Epstein Barr Virus Infection ◽  
Barr Virus ◽  
Ebv Infection ◽  
Epstein Barr

ABSTRACT The B-lymphotropic Epstein-Barr virus (EBV) encodes two isoforms of latent membrane protein 2 (LMP2), LMP2A and LMP2B, which are expressed during latency in B cells. The function of LMP2B is largely unknown, whereas LMP2A blocks B-cell receptor (BCR) signaling transduction and induction of lytic EBV infection, thereby promoting B-cell survival. Transfection experiments on LMP2B in EBV-negative B cells and the silencing of LMP2B in EBV-harboring Burkitt's lymphoma-derived Akata cells suggest that LMP2B interferes with the function of LMP2A, but the role of LMP2B in the presence of functional EBV has not been established. Here, LMP2B, LMP2A, or both were overexpressed in EBV-harboring Akata cells to study the function of LMP2B. The overexpression of LMP2B increased the magnitude of EBV switching from its latent to its lytic form upon BCR cross-linking, as indicated by a more-enhanced upregulation and expression of EBV lytic genes and significantly increased production of transforming EBV compared to Akata vector control cells or LMP2A-overexpressing cells. Moreover, LMP2B lowered the degree of BCR cross-linking required to induce lytic EBV infection. Finally, LMP2B colocalized with LMP2A as demonstrated by immunoprecipitation and immunofluorescence and restored calcium mobilization upon BCR cross-linking, a signaling process inhibited by LMP2A. Thus, our findings suggest that LMP2B negatively regulates the function of LMP2A in preventing the switch from latent to lytic EBV replication.

scholarly journals Cd40 doesn't Complement The Function Of Epstein-barr Virus (Ebv) Latent Membrane Protein 1 In B Cells Transformation

2012 ◽  
Vol 11 (2) ◽  
pp. 112-116
Author(s):  
Mohammed Nazmul Ahsan ◽  
Anwarul A Akhand
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Medical Science ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 1 ◽  
Barr Virus ◽  
Epstein Barr

Objective: Epstein–Barr virus (EBV) latent membrane protein 1 (LMP1) is known to plays important role in B cells growth and transformation. LMP1 is considered to be a functional homologue of the CD40 receptor and they can activate many overlapping signaling pathways. In this study, we compared the function of CD40 with that of LMP1 in B cells transformation. Materials and methods: Expression of CD40L was observed in infected B cells with LMP1 mutated EBV. To observe the expression reverse transcription-PCR were performed. Results: This expression of CD40L did not support proliferation and transformation of B cell. Even in vitro proliferation and transformation of B cell infected with LMP1 deleted EBV supplemented with CD40L were also not observed. Conclusion: Despite many similarities shared between CD40 and LMP1, CD40-CD40L interaction didn’t complement on LMP1 mediated B cells transformation in vitro. DOI: http://dx.doi.org/10.3329/bjms.v11i2.8175 Bangladesh Journal of Medical Science Vol. 11 No. 02 April 2012: 112-116

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2A Preferentially Signals through the Src Family Kinase Lyn

2008 ◽  
Vol 82 (17) ◽  
pp. 8520-8528 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Sh2 Domain ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) is a viral protein expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor signal transduction and provides survival and developmental signals to B cells in vivo. Although Lyn has been shown to be important in mediating LMP2A signaling, it is still unclear if Lyn is used preferentially or if LMP2A associates promiscuously with other Src family kinase (SFK) members. To investigate the role of various SFKs in LMP2A signaling, we crossed LMP2A transgenic mice (TgE) with Lyn−/−, Fyn−/−, or Blk−/− mice. TgE Lyn−/− mice had a larger immunoglobulin M (IgM)-positive B-cell population than TgE mice, suggesting that the absence of Lyn prevents LMP2A from delivering survival and developmental signals to the B cells. Both TgE Fyn−/− and TgE Blk−/− mice have an IgM-negative population of splenic B cells, similar to the TgE mice. LMP2A was also transiently transfected into the human EBV-negative B-cell line BJAB to determine which SFK members associate with LMP2A. Lyn was detected in LMP2A immunoprecipitates, whereas Fyn was not. Both Lyn and Fyn were able to bind to an LMP2A mutant which contained a sequence shown previously to bind tightly to the SH2 domain of multiple SFK members. From these results, we conclude that LMP2A preferentially associates with and signals through Lyn compared to its association with other SFKs. This preferential association is due in part to the SH2 domain of Lyn associating with LMP2A.

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