Epstein-Barr virus nuclear antigen 3C (EBNA3C) interacts with the metabolism sensing C-terminal binding protein (CtBP) repressor to upregulate host genes

Latent Epstein-Barr virus infection collaborates with Myc over-expression in normal human B cells to induce Burkitt-like Lymphomas in mice

Epstein-Barr virus (EBV) is an important cause of human lymphomas, including Burkitt lymphoma (BL). EBV+ BLs are driven by Myc translocation and have stringent forms of viral latency that do not express either of the two major EBV oncoproteins, EBNA2 (which mimics Notch signaling) and LMP1 (which activates NF-κB signaling). Suppression of Myc-induced apoptosis, often through mutation of the TP53 (p53) gene or inhibition of pro-apoptotic BCL2L11 (BIM) gene expression, is required for development of Myc-driven BLs. EBV+ BLs contain fewer cellular mutations in apoptotic pathways compared to EBV-negative BLs, suggesting that latent EBV infection inhibits Myc-induced apoptosis. Here we use an EBNA2-deleted EBV virus (ΔEBNA2 EBV) to create the first in vivo model for EBV+ BL-like lymphomas derived from primary human B cells. We show that cord blood B cells infected with both ΔEBNA2 EBV and a Myc-expressing vector proliferate indefinitely on a CD40L/IL21 expressing feeder layer in vitro and cause rapid onset EBV+ BL-like tumors in NSG mice. These LMP1/EBNA2-negative Myc-driven lymphomas have wild type p53 and very low BIM, and express numerous germinal center B cell proteins (including TCF3, BACH2, Myb, CD10, CCDN3, and GCSAM) in the absence of BCL6 expression. Myc-induced activation of Myb mediates expression of many of these BL-associated proteins. We demonstrate that Myc blocks LMP1 expression both by inhibiting expression of cellular factors (STAT3 and Src) that activate LMP1 transcription and by increasing expression of proteins (DNMT3B and UHRF1) known to enhance DNA methylation of the LMP1 promoters in human BLs. These results show that latent EBV infection collaborates with Myc over-expression to induce BL-like human B-cell lymphomas in mice. As NF-κB signaling retards the growth of EBV-negative BLs, Myc-mediated repression of LMP1 may be essential for latent EBV infection and Myc translocation to collaboratively induce human BLs.

LMP1 and EBNA2 constitute a minimal set of EBV genes for transformation of human B cells

Introduction

Epstein-Barr virus (EBV) infection in humans is associated with a wide range of diseases including malignancies of different origins, most prominently B cells. Several EBV latent genes are thought to act together in B cell immortalization, but a minimal set of EBV genes sufficient for transformation remains to be identified.

Methods

Here, we addressed this question by transducing human peripheral B cells from EBV-negative donors with retrovirus expressing the latent EBV genes encoding Latent Membrane Protein (LMP) 1 and 2A and Epstein-Barr Nuclear Antigen (EBNA) 2.

Results

LMP1 together with EBNA2, but not LMP1 alone or in combination with LMP2A was able to transform human primary B cells. LMP1/EBNA2-immortalized cell lines shared surface markers with EBV-transformed lymphoblastoid cell lines (LCLs). They showed sustained growth for more than 60 days, albeit at a lower growth rate than EBV-transformed LCLs. LMP1/EBNA2-immortalized cell lines generated tumors when transplanted subcutaneously into severely immunodeficient NOG mice.

Conclusion

Our results identify a minimal set of EBV proteins sufficient for B cell transformation.

Genotype characterization of Epstein-Barr virus among adults living with human immunodeficiency virus in Ethiopia

Background

Epstein-Barr virus (EBV) is a human lymphotropic herpesvirus with a causative agent in cancer. There are two genotypes of EBV (EBV genotype 1 and EBV genotype 2) that have been shown to infect humans. This study aimed to characterize the EBV genotype among people with human immunodeficiency virus (PWH) and HIV-negative individuals in Ethiopia.

Methods

DNA was extracted from peripheral blood mononuclear cells (PBMCs). Conventional polymerase chain reaction (cPCR) targeting EBNA3C genes was performed for genotyping. A quantitative real-time PCR (q-PCR) assay for EBV DNA (EBNA1 ORF) detection and viral load quantification was performed. Statistical significance was determined at a value of p < 0.05.

Result

In this study, 155 EBV-seropositive individuals were enrolled, including 128 PWH and 27 HIV-negative individuals. Among PWH, EBV genotype 1 was the most prevalent (105/128, 82.0%) genotype, followed by EBV genotype 2 (17/128, 13.3%), and mixed infection (6/128, 4.7%). In PWH, the median log10 of EBV viral load was 4.23 copies/ml [interquartile range (IQR): 3.76-4.46], whereas it was 3.84 copies/ml (IQR: 3.74-4.02) in the HIV-negative group. The EBV viral load in PWH was significantly higher than that in HIV-negative individuals (value of p = 0.004). In PWH, the median log10 of EBV viral load was 4.25 copies/ml (IQR: 3.83-4.47) in EBV genotype 1 and higher than EBV genotype 2 and mixed infection (p = 0.032).

Conclusion

In Ethiopia, EBV genotype 1 was found to be the most predominant genotype, followed by EBV genotype 2. Understanding the genotype characterization of EBV in PWH is essential for developing new and innovative strategies for preventing and treating EBV-related complications in this population.

Epstein-Barr Virus B Cell Growth Transformation: The Nuclear Events

Epstein-Barr virus (EBV) is the first human DNA tumor virus identified from African Burkitt's lymphoma cells. EBV causes ~200,000 various cancers world-wide each year. EBV-associated cancers express latent EBV proteins, EBV nuclear antigens (EBNAs), and latent membrane proteins (LMPs). EBNA1 tethers EBV episomes to the chromosome during mitosis to ensure episomes are divided evenly between daughter cells. EBNA2 is the major EBV latency transcription activator. It activates the expression of other EBNAs and LMPs. It also activates MYC through enhancers 400-500 kb upstream to provide proliferation signals. EBNALP co-activates with EBNA2. EBNA3A/C represses CDKN2A to prevent senescence. LMP1 activates NF-κB to prevent apoptosis. The coordinated activity of EBV proteins in the nucleus allows efficient transformation of primary resting B lymphocytes into immortalized lymphoblastoid cell lines in vitro.

Galectin-9 Facilitates Epstein-Barr Virus Latent Infection and Lymphomagenesis in Human B Cells

The immune regulator galectin-9 (Gal-9) is commonly involved in the regulation of cell proliferation, but with various impacts depending on the cell type. Here, we revealed that Gal-9 expression was persistently increased in Epstein-Barr virus (EBV)-infected primary B cells from the stage of early infection to the stage of mature lymphoblastoid cell lines (LCLs). This sustained upregulation paralleled that of gene sets related to cell proliferation, such as oxidative phosphorylation, cell cycle activation, and DNA replication. Knocking down or blocking Gal-9 expression obstructed the establishment of latent infection and outgrowth of EBV-infected B cells, while exogenous Gal-9 protein promoted EBV acute and latent infection and outgrowth of EBV-infected B cells at the early infection stage. Mechanically, stimulator of interferon gene (STING) activation or signal transducer and activator of transcription 3 (STAT3) inhibition impeded the outgrowth of EBV-infected B cells and promotion of Gal-9-induced lymphoblastoid cell line (LCL) transformation. Accordingly, Gal-9 expression was upregulated by forced EBV nuclear antigen 1 (EBNA1) expression in 293T cells in vitro. Clinical data showed that Gal-9 expression in B-cell lymphomas (BCLs) correlated positively with EBNA1 and disease stage. Targeting Gal-9 slowed LCL tumor growth and metastasis in xenografted immunodeficient mice. These findings highlight an oncogenic role of Gal-9 in EBV-associated BCLs, indicating that Gal-9 boosts the transformation of EBV-infected B cells. IMPORTANCE The cross talk between Epstein-Barr virus (EBV) and the host cell transcriptome assumes important roles in the oncogenesis of EBV-associated malignancies. Here, we first observed that endogenous Gal-9 expression was persistently increased along with an overturned V-type change in antivirus signaling during the immortalization of EBV-transformed B cells. Upregulation of Gal-9 promoted the outgrowth and latent infection of EBV-infected B cells, which was linked to B-cell-origin tumors by suppressing STING signaling and subsequently promoting STAT3 phosphorylation. EBV nuclear antigen EBNA1 induced Gal-9 expression and formed a positive feedback loop with Gal-9 in EBV-infected B cells. Tumor Gal-9 levels were positively correlated with disease stage and EBNA1 expression in patients with B-cell lymphomas (BCLs). Targeting Gal-9 slowed the growth and metastases of LCL tumors in immunodeficient mice. Altogether, our findings indicate that Gal-9 is involved in the lymphomagenesis of EBV-positive BCLs through cross talk with EBNA1 and STING signals.

Integrated Analysis of MicroRNA and mRNA Expression Profiles in the Fat Bodies of MbMNPV-Infected Helicoverpa armigera

MicroRNAs (miRNAs), are a novel class of gene expression regulators, that have been found to participate in regulating host-virus interactions. However, the function of insect-derived miRNAs in response to virus infection is poorly understood. We analyzed miRNA expression profiles in the fat bodies of Helicoverpa armigera (H. armigera) infected with Mamestra brassicae multiple nucleopolyhedroviruses (MbMNPV). A total of 52 differentially expressed miRNAs (DEmiRNAs) were filtered out through RNA-seq analysis. The targets of 52 DEmiRNAs were predicted and 100 miRNA-mRNA interaction pairs were obtained. The predicted targets of DEmiRNAs were mainly enriched in the Wnt signaling pathway, phagosome, and mTOR signaling pathway, which are related to the virus infection. Real-time PCR was used to verify the RNA sequencing results. ame-miR-317-3p, mse-miR-34, novel1-star, and sfr-miR-6094-5p were shown to be involved in the host response to MbMNPV infection. Results suggest that sfr-miR-6094-5p can negatively regulate the expression of four host genes eIF3-S7, CG7583, CG16901, and btf314, and inhibited MbMNPV infection significantly. Further studies showed that RNAi-mediated knockdown of eIF3-S7 inhibited the MbMNPV infection. These findings suggest that sfr-miR-6094-5p inhibits MbMNPV infection by negatively regulating the expression of eIF3-S7. This study provides new insights into MbMNPV and H. armigera interaction mechanisms.

The Epstein-Barr Virus Enhancer Interaction Landscapes in Virus-Associated Cancer Cell Lines

Epstein-Barr virus (EBV) persists in human cells as episomes. EBV episomes are chromatinized and their 3D conformation varies greatly in cells expressing different latency genes. We used HiChIP, an assay which combines genome-wide chromatin conformation capture followed by deep sequencing (Hi-C) and chromatin immunoprecipitation (ChIP), to interrogate the EBV episome 3D conformation in different cancer cell lines. In an EBV-transformed lymphoblastoid cell line (LCL) GM12878 expressing type III EBV latency genes, abundant genomic interactions were identified by H3K27ac HiChIP. A strong enhancer was located near the BILF2 gene and looped to multiple genes around BALFs loci. Perturbation of the BILF2 enhancer by CRISPR interference (CRISPRi) and CRISPR activation (CRISPRa) altered the expression of BILF2 enhancer-linked genes, including BARF0 and BALF2, suggesting that this enhancer regulates the expression of linked genes. H3K27ac ChIP followed by deep sequencing (ChIP-seq) identified several strong EBV enhancers in T/NK (natural killer) lymphoma cells that express type II EBV latency genes. Extensive intragenomic interactions were also found which linked enhancers to target genes. A strong enhancer at BILF2 also looped to the BALF loci. CRISPRi also validated the functional connection between BILF2 enhancer and BARF1 gene. In contrast, H3K27ac HiChIP found significantly fewer intragenomic interactions in type I EBV latency gene-expressing primary effusion lymphoma (PEL) cell lines. These data provided new insight into the regulation of EBV latency gene expression in different EBV-associated tumors. IMPORTANCE EBV is the first human DNA tumor virus identified, discovered over 50 years ago. EBV causes ~200,000 cases of various cancers each year. EBV-encoded oncogenes, noncoding RNAs, and microRNAs (miRNAs) can promote cell growth and survival and suppress senescence. Regulation of EBV gene expression is very complex. The viral C promoter regulates the expression of all EBV nuclear antigens (EBNAs), some of which are very far away from the C promoter. Another way by which the virus activates remote gene expression is through DNA looping. In this study, we describe the viral genome looping patterns in various EBV-associated cancer cell lines and identify important EBV enhancers in these cells. This study also identified novel opportunities to perturb and eventually control EBV gene expression in these cancer cells.

Epigenetic control of the Epstein-Barr lifecycle

Epstein-Barr virus (EBV) infects 95% of adults worldwide, causes infectious mononucleosis, is etiologically linked to multiple sclerosis and is associated with 200 000 cases of cancer each year. EBV manipulates host epigenetic pathways to switch between a series of latency programs and to reactivate from latency in order to colonize the memory B-cell compartment for lifelong infection and to ultimately spread to new hosts. Here, we review recent advances in the understanding of epigenetic mechanisms that control EBV latency and lytic gene expression in EBV-transformed B and epithelial cells. We highlight newly appreciated roles of DNA methylation epigenetic machinery, host histone chaperones, the Hippo pathway, m6A RNA modification and nonsense mediated decay in control of the EBV lifecycle.

ΔNp63α promotes Epstein-Barr virus latency in undifferentiated epithelial cells

Epstein-Barr virus (EBV) is a human herpesvirus that causes infectious mononucleosis and contributes to both B-cell and epithelial-cell malignancies. EBV-infected epithelial cell tumors, including nasopharyngeal carcinoma (NPC), are largely composed of latently infected cells, but the mechanism(s) maintaining viral latency are poorly understood. Expression of the EBV BZLF1 (Z) and BRLF1 (R) encoded immediate-early (IE) proteins induces lytic infection, and these IE proteins activate each other's promoters. ΔNp63α (a p53 family member) is required for proliferation and survival of basal epithelial cells and is over-expressed in NPC tumors. Here we show that ΔNp63α promotes EBV latency by inhibiting activation of the BZLF1 IE promoter (Zp). Furthermore, we find that another p63 gene splice variant, TAp63α, which is expressed in some Burkitt and diffuse large B cell lymphomas, also represses EBV lytic reactivation. We demonstrate that ΔNp63α inhibits the Z promoter indirectly by preventing the ability of other transcription factors, including the viral IE R protein and the cellular KLF4 protein, to activate Zp. Mechanistically, we show that ΔNp63α promotes viral latency in undifferentiated epithelial cells both by enhancing expression of a known Zp repressor protein, c-myc, and by decreasing cellular p38 kinase activity. Furthermore, we find that the ability of cis-platinum chemotherapy to degrade ΔNp63α contributes to the lytic-inducing effect of this agent in EBV-infected epithelial cells. Together these findings demonstrate that the loss of ΔNp63α expression, in conjunction with enhanced expression of differentiation-dependent transcription factors such as BLIMP1 and KLF4, induces lytic EBV reactivation during normal epithelial cell differentiation. Conversely, expression of ΔNp63α in undifferentiated nasopharyngeal carcinoma cells and TAp63α in Burkitt lymphoma promotes EBV latency in these malignancies.