Project description:Epstein-Barr virus (EBV) is a ubiquitous human ɣ-herpesvirus implicated in various malignancies, including Burkitt’s lymphoma and gastric carcinomas. In most EBV-associated cancers, the viral genome is maintained as an extrachromosomal episome by the EBV nuclear antigen-1 (EBNA1). EBNA1 is considered to be a highly stable protein that interacts with the ubiquitin-specific protease 7 (USP7), but the precise role of USP7 in controlling EBNA1 stability and function is not fully understood. Here, we show that pharmacological inhibitors and small interfering RNA (siRNA) targeting USP7 reduce EBNA1 protein levels. The USP7 inhibitor GNE6776 altered EBNA1 protein interactions, including disrupting its ability to bind to USP7. GNE6776 also inhibited EBNA1 binding to EBV oriP DNA and reduced viral episome copy number. GNE6776 selectively inhibited EBV+ gastric and lymphoid cell proliferation in cell culture and slowed EBV+ tumor growth in mouse xenograft models. Transcriptomic studies revealed that USP7 inhibition differentially affected EBV+ cancer cells compared to EBV- cells with a significant effect on chromosome segregation and mitotic cell division pathways. Our findings indicate that USP7 inhibition perturbs EBNA1 stability and function and can be exploited to target EBV+ cancer cells selectively.
Project description:EBNA1 is the EBV-encoded nuclear antigen required for viral episome maintenance during latency. EBNA1 is a sequence specific DNA binding protein with high affinity binding sites for the viral genome, especially OriP. EBNA1 can also bind sequence specifically to a large number of sites in the host cellular genome, but the function of these binding sites has remained elusive. EBNA1 is also known to provide a host cell survival function, but the molecular mechanisms accounting for this function are not completely understood. Here, we show by integrating ChIP-Seq and RNA-Seq with experimental validation that MEF2B, IL6R, and EBF1 are high confidence target genes of EBNA1 that are essential for viability of B-lymphocytes latently infected with EBV. We show that EBNA1 binds to ~1000 sites with many, but not all, universally bound in different cell types, including Burkitt lymphoma (BL) and nasopharyngeal carcinoma (NPC). We find that a large subset of EBNA1 binding sites are located proximal to transcription start sites and correlate genome-wide with transcription activity. EBNA1 bound to genes of high significance for B-cell growth and function, including MEF2B, IL6R, EBF1, RNF145, POU2F1, KDM4C, FGR, EGFR, LAIR, CDC7, CD44, and IL17A. EBNA1 depletion from latently infected LCLs results in the loss of cell proliferation, and the loss of gene expression for some EBNA1-bound genes, including MEF2B, EBF1, and IL6R. Depletion of MEF2B, EBF1, or IL6R partially phenocopies EBNA1-depletion by decreasing EBV-positive cell growth and viability. These findings indicate that EBNA1 binds to a large cohort of cellular genes important for cell viability, and implicates EBNA1 as a master coordinator of host cell gene expression important for enhanced survival of latently infected cells. Examination of EBNA1 binding in Raji, MutuI, LCL and C666-1 cells and EBNA1 knockdown effect on mRNA gene expression in LCL
Project description:Epstein-Barr virus (EBV) genomes persist in latently infected cells as extrachromosomal plasmids that attach to host chromosomes through the tethering functions of EBNA1, a viral encoded sequence-specific DNA binding protein. Here we employed circular chromosome conformation capture (4C) analysis to identify genomewide associations between EBV episomes and host chromosomes. We found that EBV episomes in Burkitt lymphoma (BL) cells preferentially associate with EBNA1 sequence-specific DNA binding sites in the cellular genome that are also enriched for B-cell factors EBF1 and RBP-jK, the repressive histone mark H3K9me3, and surrounded by AT-rich sequence. These attachment sites corresponded to transcriptionally silenced genes with enrichment in neuronal function. Depletion of EBNA1 from EBV latently infected BL cells led to a transcriptional de-repression of these silenced genes. EBV attachment sites in lymphoblastoid cells (LCLs) showed different correlations, suggesting that latency types are functionally linked to the epigenetic environment of host chromosome attachment sites.
Project description:EBNA1 is the EBV-encoded nuclear antigen required for viral episome maintenance during latency. EBNA1 is a sequence specific DNA binding protein with high affinity binding sites for the viral genome, especially OriP. EBNA1 can also bind sequence specifically to a large number of sites in the host cellular genome, but the function of these binding sites has remained elusive. EBNA1 is also known to provide a host cell survival function, but the molecular mechanisms accounting for this function are not completely understood. Here, we show by integrating ChIP-Seq and RNA-Seq with experimental validation that MEF2B, IL6R, and EBF1 are high confidence target genes of EBNA1 that are essential for viability of B-lymphocytes latently infected with EBV. We show that EBNA1 binds to ~1000 sites with many, but not all, universally bound in different cell types, including Burkitt lymphoma (BL) and nasopharyngeal carcinoma (NPC). We find that a large subset of EBNA1 binding sites are located proximal to transcription start sites and correlate genome-wide with transcription activity. EBNA1 bound to genes of high significance for B-cell growth and function, including MEF2B, IL6R, EBF1, RNF145, POU2F1, KDM4C, FGR, EGFR, LAIR, CDC7, CD44, and IL17A. EBNA1 depletion from latently infected LCLs results in the loss of cell proliferation, and the loss of gene expression for some EBNA1-bound genes, including MEF2B, EBF1, and IL6R. Depletion of MEF2B, EBF1, or IL6R partially phenocopies EBNA1-depletion by decreasing EBV-positive cell growth and viability. These findings indicate that EBNA1 binds to a large cohort of cellular genes important for cell viability, and implicates EBNA1 as a master coordinator of host cell gene expression important for enhanced survival of latently infected cells.
Project description:Microarry from Treg with conditional knockout of Usp7 RNA from three independent samples from FACS sorted CD4+YFP+ Treg of fl-Usp7/Foxp3cre mice, compared to Foxp3cre control (C57BL/6 background).
Project description:Background: In several types of malignancies, especially EBV-associated nasopharyngeal carcinomas, high Galectin-9 (Gal-9) expression is indicative of an aggressive tumor phenotype. The contribution of Gal-9 to the oncogenesis of B-cell lymphomas (BCLs) has not yet been investigated. Methods: The expression of Gal-9, STING, and EBNA1 was measured by immunohistochemical (IHC) staining on tumor sections from 66 BCL patients. Artificial EBV infection of normal primary B cells in vitro was used as an experimental model. The dynamic changes of the transcriptome of EBV-infected B cells undergoing transformation were investigated by bulk RNA-sequencing and bioinformatics analysis. The oncogenic role of Gal-9 was investigated in vitro by addition of recombinant Gal-9 to EBV-infected primary B-cells, and growth assays. The underlying molecular mechanisms were investigated by immunoblotting and immunofluorescent (IF) staining, CHIP and luciferase reporter assays. Results: In clinical specimens of BCLs, Gal-9 expression was significantly associated with tumor stage, latent EBV infection and abundance of the viral latent protein EBNA1. Looking at the transcriptome changes occurring in vitro during EBV-driven B-cell transformation, we could identify a series of genes undergoing long term activation and remaining highly expressed in mature LCLs. The Gal-9 gene is one of them. Its expression is enhanced during the transformation process at the mRNA level and even more at the protein level. This up-regulation results at least in part from its transactivation by EBNA1 which can bind its promoter. Reciprocally, we find that addition of extra-cellular Gal-9 promotes B-cell transformation and establishment of the latent phase of EBV-infection. Concomitantly, extra-cellular Gal-9 blocks STING signaling and enhances STAT3 phosphorylation. Inhibition of Sting signaling or STAT3 phosphorylation blocks B-cell transformation, even in the presence of Gal-9. Conclusion: our data unveil a role of amplification and acceleration for Gal-9 in the process of EBV-driven B-cell transformation. This process might be relevant to the pathogenesis of EBV-associated BCLs.
Project description:Epstein-Barr Virus (EBV) immortalizes resting B-lymphocytes through a highly orchestrated process involving extensive reprogramming of host transcription and metabolism. Here, we use multiple omics-based approaches concurrently across the time course of B-cell infection to investigate the underlying mechanisms that control EBV-induced B-cell immortalization. ATAC-seq revealed that over a third of accessible chromatin is altered with the most perturbed sites overlapping Ets-family, including PU.1 and RUNX1 transcription factors. EBV nuclear antigens (EBNAs) clustered with different gene categories and RNA-seq identified the transcriptional response of these gene. Focusing on EBNA1 revealed a selection of gene targets involved in nucleotide metabolism. Metabolomics indicated that adenosine and purine metabolism are significantly altered by EBV immortalization, and we validated that adenosine deaminase (ADA) is a direct and critical target of EBNA1 and the EBV-directed immortalization process. These findings reveal that purine metabolism and ADA inhibitors may be a useful therapeutic for EBV-driven lymphoid cancers
Project description:USP7, a dominant DUB activity in 3T3-L1 adipocytes and in mouse adipose tissue, increases Tip60 protein levels, and deubiquitinates Tip60 both in intact cells and in vitro. Treatment with a pan deubiquitinase (DUB) inhibitor, or knockdown of USP7, decreases adipogenesis. Transcriptome analysis reveals a common set of cell cycle genes to be co-regulated by both Tip60 and USP7. Knock down of either factor results in impaired mitotic clonal expansion, an early step in adipogenesis. These results therefore reveal deubiquitination of a transcriptional coregulator to be a key mechanism in the regulation of early adipogenesis Mature 3T3-L1 adipocytes were subjected to RNAi-mediated knock down with control(C), USP7(U)- or Tip60(T)-specific oligonucleotides. For this, 4 replicates of differentiated 3T3-L1 cells were transfected with Amaxa technology. Two days after transfection cells were washed twice with PBS twice and lysed in 0.5ml Trizol (Invitrogen). mRNA expression of Tip60 and USP7 was assessed by qRT-PCR. Amplified cRNA samples were labeled with either cy3 or cy5 and put on microarray together with and oppositely labeled common reference sample consisting of cRNA derived from undifferentiated 3T3-L1 cells.
Project description:Subpopulations of B-lymphocytes traffic to different sites and organs to provide diverse and tissue-specific functions. Here, we provide evidence that epigenetic differences confer a neuroinvasive phenotype. An EBV+ B cell lymphoma cell line (M14) with low frequency trafficking to the CNS was neuroadapted to generate a highly neuroinvasive B-cell population (MUN14). MUN14 B cells efficiently infiltrated the CNS within one week and produced neurological pathologies. We compared the gene expression profiles of viral and cellular genes using RNA-Seq and identified one viral (EBNA1) and several cellular gene candidates, including secreted phosphoprotein 1/osteopontin (SPP1/OPN), neuron navigator 3 (NAV3), CXCR4, and germinal center-associated signaling and motility protein (GCSAM)) that were selectively upregulated in MUN14. ATAC-Seq and ChIP-qPCR revealed that these gene expression changes correlated with epigenetic changes at gene regulatory elements. The neuroinvasive phenotype could be attenuated with a neutralizing antibody to OPN, confirming the functional role of this protein in trafficking EBV+ B cells to the CNS. These studies indicate that B-cell trafficking to the CNS can be acquired by epigenetic adaptations and provide a new model to study B-cell neuroinvasion associated CNS lymphoma and autoimmune disease of the CNS, including multiple sclerosis (MS).cell infection to investigate the underlying mechanisms that control EBV-induced B-cell immortalization. ATAC-seq revealed that over a third of accessible chromatin is altered with the most perturbed sites overlapping Ets-family, including PU.1 and RUNX1 transcription factors. EBV nuclear antigens (EBNAs) clustered with different gene categories and RNA-seq identified the transcriptional response of these gene. Focusing on EBNA1 revealed a selection of gene targets involved in nucleotide metabolism. Metabolomics indicated that adenosine and purine metabolism are significantly altered by EBV immortalization, and we validated that adenosine deaminase (ADA) is a direct and critical target of EBNA1 and the EBV-directed immortalization process. These findings reveal that purine metabolism and ADA inhibitors may be a useful therapeutic for EBV-driven lymphoid cancers