Language：Japanese   Publishing type：Research paper (scientific journal)  

N6-methyladenosine (m6A) mediates various biological processes by affecting RNA stability, splicing, and translational efficiency. The roles of m6A modification in Epstein-Barr virus (EBV) infection in the lytic phase are unclear. Here, knockout of the m6A methyltransferase, N6-methyladenosine methyltransferase-like 3 (METTL3), or inhibition of methylation by DAA or UZH1a decreased the expression of viral lytic proteins and reduced progeny virion production. Interestingly, cell growth and viability were decreased by induction of the lytic cycle in METTL3-knockout or inhibitor-treated cells. Apoptosis was induced in those conditions possibly because of a decreased level of the anti-apoptotic viral protein, BHRF1. Therefore, m6A shows potential as a target of lytic induction therapy for EBV-associated cancers, including Burkitt lymphoma.

DOI： 10.3389/fmicb.2022.870816

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Language：English   Publisher：Virology  

Epstein-Barr virus (EBV) is an etiologic agent of infectious mononucleosis and several malignancies. Here, we found that reactivation of EBV resulted in increased programmed cell death-ligand 1 (PD-L1) expression in a cell type-dependent manner. Lytic induction in EBV-positive Akata, AGS, MutuI, and Jijoye cell lines increased PD-L1 levels, but cells such as EBV-negative Akata, MutuIII, and P3HR1 did not have increased PD-L1. EBV in the P3HR1 cell line has a deletion in the EBNA2 gene, while EBV in its parental cell line, Jijoye, has the complete EBNA2 gene. PD-L1 expression by lytic induction was reduced when EBNA2 was knocked down. In addition, pharmacological inhibition indicated involvement of nuclear factor kappa B, mitogen-activated protein kinase, and AKT signaling. These results suggest that EBV likely evades immunity by inducing PD-L1 upon reactivation, through the increased expression of EBNA2 and activation of signaling pathways.

DOI： 10.1016/j.virol.2022.01.006

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Epstein-Barr virus (EBV) is a causative agent of infectious mononucleosis and several types of cancer. Like other herpesviruses, it establishes an asymptomatic, life-long latent infection, with occasional reactivation and shedding of progeny viruses. During latency, EBV expresses a small number of viral genes, and exists as an episome in the host-cell nucleus. Expression patterns of latency genes are dependent on the cell type, time after infection, and milieu of the cell (e.g., germinal center or peripheral blood). Upon lytic induction, expression of the viral immediate-early genes, BZLF1 and BRLF1, are induced, followed by early gene expression, viral DNA replication, late gene expression, and maturation and egress of progeny virions. Furthermore, EBV reactivation involves more than just progeny production. The EBV life cycle is regulated by signal transduction, transcription factors, promoter sequences, epigenetics, and the 3D structure of the genome. In this article, the molecular basis of EBV latency establishment and reactivation is summarized.

DOI： 10.3390/v13122344

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Epstein-Barr virus-associated lymphoproliferative disease (EBV-LPD) is frequently fatal. Innate immunity plays a key role in protecting against pathogens and cancers. The stimulator of interferon genes (STING) is regarded as a key adaptor protein allowing DNA sensors recognizing exogenous cytosolic DNA to activate the type I interferon signaling cascade. In terms of EBV tumorigenicity, the role of STING remains elusive. Herein we showed that treatment with the STING inhibitor, C-176, suppressed EBV-induced transformation in peripheral blood mononuclear cells. In an EBV-LPD mouse model, C-176 treatment also inhibited tumor formation and prolonged survival. Treatment with B cells alone did not affect EBV transformation, but suppression of EBV-induced transformation was observed in the presence of T cells. Even without direct B cell-T cell contact in a Transwell system, the inhibitor reduced the transformation activity, indicating that intercellular communication by humoral factors was critical to prevent EBV-induced transformation. These findings suggest that inhibition of STING signaling pathway with C-176 could be a new therapeutic target of EBV-LPD.

DOI： 10.1111/cas.15152

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Language：Japanese   Publisher：Frontiers in Microbiology  

Epstein–Barr virus (EBV), which encodes >80 genes and nearly 50 non-coding RNAs, is a double-stranded DNA virus. EBV is associated with various types of lymphomas and lymphoproliferative disorders not only of B-cell but also T/NK-cell origin. However, the oncogenic mechanism remains poorly understood, including the EBV receptors expressed on T/NK cells, relationship of EBV with host genes, and epigenetic regulation of EBV and host genes. The roles of host and viral non-coding RNAs during tumorigenesis have been elucidated. EBV encodes at least 49 mature microRNAs (miRNAs), of which 44 are located in BamHI-A rightward transcripts (BARTs) region, and the remaining five are located in BamHI-H rightward fragment 1. BART miRNAs modulate cell differentiation, proliferation, apoptosis, and the cell cycle, and they are considered positive regulators of oncogenesis. We and others have recently reported that EBV-positive lymphomas frequently possess large deletions in BART miRNA clusters, suggesting that some viral miRNAs have suppressive effects on oncogenesis, and that deletion of these miRNAs may aid lymphoma formation.

DOI： 10.3389/fmicb.2021.667968

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Epstein-Barr virus (EBV) is a causative agent of infectious mononucleosis and several types of malignancy. RNAseq of peripheral blood primary B cell samples infected with wild-type EBV revealed that expression of programmed cell death ligand-1 (PD-L1) is markedly induced by infection. This induction of PD-L1 was alleviated by knockout of the EBNA2 gene, but knockout of LMP1 had little effect. ChIPseq, ChIA-PET, and reporter assays further confirmed that EBNA2-binding sites in the promoter region and at 130 kb downstream of the PD-L1 gene played important roles in PD-L1 induction. Our results indicate that EBV mainly utilizes the EBNA2 gene for induction of PD-L1 and to evade host immunity on infection of primary B cells. Furthermore, pathway analysis revealed that genes involved in the cell cycle, metabolic processes, membrane morphogenesis, and vesicle regulation were induced by EBNA2, and that EBNA2 suppressed genes related to immune signaling.

DOI： 10.1016/j.virol.2021.02.004

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：{MDPI} {AG}  

The Epstein-Barr virus (EBV) is the cause of several malignancies, including diffuse large B cell lymphoma (DLBCL). We recently found that EBV genomes in EBV-positive cancer specimens have various deletions (Okuno et al. Nat Microbiol. 2019). Here, we focus on the deletion of C promoter (Cp), which transcribes EBV nuclear antigen (EBNA) genes in type III latency. The Cp deletion found in a DLBCL patient (332 bp) was introduced into EBV-BAC of the B95-8 strain. Interestingly, the dCp virus transformed B cells more efficiently than WT and revertant strains. Deletion of Cp also promoted tumor formation and severe pathogenicity in a mouse xenograft model. RNA sequencing and qRT-PCR analyses revealed that Cp transcription was undetectable in the dCp cells. Instead, transcription from the W promoter (Wp), an alternative promoter for EBNA, was activated in the dCp mutant. We also found that the expression of latent membrane protein 2A (LMP2A) was somehow induced in the dCp mutant. Double knockout of Cp and LMP2A indicated that LMP2A is crucial for B cell transformation, but the increased transformation induced by Cp deletion cannot be explained by LMP2A alone. We also tested the effect of an anti-apoptotic viral BCL2 homolog, BHRF1, because its expression was reportedly induced more efficiently by that of Wp. However, increased growth transformation via Cp deletion was not due to the BHRF1 gene. Taken together, the results indicated that deletion of a specific region in Cp increased in vitro transformation and the rate of progression of EBV-positive lymphoproliferative disorders in vivo. Our data suggest that genomic alteration not only of the host but also the virus promotes EBV-positive tumor generation and expansion, although the molecular mechanism underlying this phenomenon is still unclear. However, LMP2A and BHRF1 are not involved.

DOI： 10.3390/cancers13030561

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers in Microbiology  

DOI： 10.3389/fmicb.2020.575255

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Language：English   Publisher：(一社)日本癌学会  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

DOI： 10.1038/s41417-019-0129-3

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DOI： 10.1111/cas.14241

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DOI： 10.3390/microorganisms7120705

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DOI： 10.1016/j.virol.2019.02.015

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DOI： 10.3390/v11030285

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DOI： 10.1038/s41564-018-0334-0

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publisher：(一社)日本癌学会  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：(一社)日本血液学会-東京事務局  

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DOI： 10.1002/cam4.1311

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DOI： 10.1128/JVI.00975-17

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DOI： 10.1038/s41598-017-06413-7

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DOI： 10.3389/fmicb.2017.02302

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DOI： 10.3389/fmicb.2017.00125

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DOI： 10.18632/oncotarget.12529

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DOI： 10.1128/JVI.03227-15

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DOI： 10.1016/j.virol.2015.05.010

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DOI： 10.1128/JVI.01604-15

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DOI： 10.1016/j.virol.2015.04.007

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DOI： 10.1038/srep11767

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