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The three-dimensional structure of the EBV genome plays a crucial role in regulating viral gene expression in EBVaGC [HiChIP]

ABSTRACT: Epstein-Barr virus (EBV) establishes lifelong asymptomatic infection by replication of its chromatinized episomes with the host genome. EBV exhibits different latency-associated transcriptional repertoires, each with distinct three-dimensional structures. CTCF, Cohesin and PARP1 are involved in maintaining viral latency and establishing episome architecture. Epstein-Barr virus-associated gastric cancer (EBVaGC) represents 1.3% to 30.9% of all gastric cancers globally. EBV-positive gastric cancers exhibit an intermediate viral transcription profile known as "Latency II", expressing specific viral genes and noncoding RNAs. In this study, we investigated the impact of PARP1 inhibition on CTCF/Cohesin binding in Type II latency. We observed destabilization of the binding of both factors, leading to a disrupted three-dimensional architecture of the episomes and an altered viral gene expression. Despite sharing the same CTCF binding profile, Type I, II, and III latencies exhibit different 3D structures that correlate with variations in viral gene expression. Additionally, our analysis of H3K27ac-enriched interactions revealed differences between Type II latency episomes and a link to cellular transformation through docking of the EBV genome at specific sites of the Human genome, thus promoting oncogene expression. Overall, this work provides insights into the role of PARP1 in maintaining active latency and novel mechanisms of EBV-induced cellular transformation.

ORGANISM(S): human gammaherpesvirus 4 Homo sapiens

PROVIDER: GSE239992 | GEO | 2023/10/11

REPOSITORIES: GEO

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Project description:Epstein-Barr virus (EBV) establishes life-long latency in human B-cells by maintaining its chromatinized episomes within the nucleus. These circularized mini-chromosomes do not integrate into the host genome. Therefore, it is essential for EBV to organize its chromatin in a manner suitable for genomic stability, DNA replication, and efficient gene expression. Poly [ADP-ribose] polymerase 1 (PARP1) activity is significantly higher in B-cells infected with EBV than those without, and considerably higher in the transcriptionally active type III latency compared to the immunoevasive type I. In addition to its role in DNA damage response, PARP1 has been implicated in transcriptional regulation and structural maintenance of both the human and EBV genome at specific regions. To better understand PARP1's role in the regulation of the EBV episome, we have functionally characterized the effect of PARP enzymatic inhibition on total episomal structure through in situ Hi-C mapping, generating the first complete 3D structure of the EBV genome. We have also mapped intragenomic contact changes after PARP inhibition to global binding of the chromatin looping factors CTCF and cohesin across the EBV genome. Additionally, PARP inhibition was shown to alter gene expression at the regions where chromatin looping was most effected. Finally, we have identified a novel function of PARP, which regulates cohesin complex chromatin binding. In conclusion, PARP1 inhibition does not alter the location of cohesin binding but does increase its frequency of binding at these regions. Despite this, there are fewer overall unique intragenomic interactions after PARP inhibition, while some areas have new chromatin loops not seen in the untreated EBV episome, leading us to conclude that PARP does have an essential role in the regulation of global EBV chromatin structure. The altered expression profile after the structural rearrangement induced by PARP inhibition also supports the idea that PARP1 helps maintain EBV latency programs.

Project description:Comprehensive Profiling of Epstein-Barr Virus-Encoded miRNAome Associated with Specific Latent Type in Tumor Cells Epstein-Barr virus (EBV) is an etiological cause of many human lymphocytic and epithelial malignancies. EBV expressed different genes associated with three latent types. So far as many as 44 EBV-encoded miRNA species have been found but their comprehensive and comparative profiling is not well documented in three latent infection states linked to various tumor cells. In this study, we utilized the polyA-tailed quantitative real time RT-PCR procedure to measure the relative abundance of viral miRNA species that linked to individual viral genome locations in combination with microarray evaluation in a subset of representative lymphoid and epithelial tumor cells undergoing various types of EBV latent infection. The results showed that miR-BHRF1 family and miR-BART family are expressed differentially in a tissue-dependent and latency-dependent manner. In particular, in NPC tissue and the only EBV consistently harboring cell line C666-1 with latency type II, there were highly abundant miR-BART family but not miR-BHRF1 family members that accounted for more than 10% of the whole known human miRNA library, implicating their important roles in maintaining EBV latent infection and driving NPC tumorigenesis. In addition, EBV miRNAome-based clustering analysis could classify three distinct EBV latency types, meanwhile, for the first time, we found and subsequently evaluated a novel secret latent switch in BL cell line Daudi from type I to III, which was unable to be identified by traditional latent biomarkers. Together, our data provided an in-depth and comparative profiling of EBV miRNA transcriptome in correspondence with three EBV latent infections, suggesting that different viral miRNA species were involved in divergent host cell carcinogenesis. Finally, EBV miRNAome, as a cluster of novel latency biomarkers expressed variedly in tumor cells, greatly complements and improves the classical typing criteria in conjunction with other latently expressed marker genes. 2 NPC tissue samples and 2 NPC cell lines and 5 lymphocytic cell lines

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The three-dimensional structure of the EBV genome plays a crucial role in regulating viral gene expression in EBVaGC [HiChIP]

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