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Repression of DERL3 via DNA methylation by Epstein-Barr virus latent membrane protein 1 in nasopharyngeal carcinoma [ChIP-seq]

ABSTRACT: We analysed active histone marks with EBV-LMP1 inducible methylation genes by performing ChIP-seq on H3K4me3 and H3K27ac.

ORGANISM(S): Homo sapiens

PROVIDER: GSE198334 | GEO | 2023/02/26

REPOSITORIES: GEO

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Project description:The Epstein Barr virus (EBV) encoded latent membrane protein-1 (LMP1) is a functional homologue of the tumor necrosis factor receptor family and contributes substantially to the oncogenic potential of EBV through activation of Nuclear Factor-kappaB (NF-kappaB). MicroRNAs (miRNAs) are a class of small RNA molecules that are involved in the regulation of cellular processes such as growth, development, and apoptosis, and have recently been linked to cancer phenotypes. Through miRNA microarray analysis, we demonstrate that LMP1 dysregulates the expression of several cellular miRNAs, including the most highly regulated of these, miR-146a. Quantitative RT-PCR analysis confirmed induced expression of miR-146a by LMP1. Analysis of miR-146a expression in EBV latency type III and type I cell lines revealed substantial expression of miR-146a in type III (which express LMP1) but not in type I cell lines. Reporter studies demonstrated that LMP1 induces miR-146a predominantly through two NF-kappaB binding sites in the miR-146a promoter and identified a role for an OCT-1 site in conferring basal and induced expression. Array analysis of cellular mRNAs expressed in Akata cells transduced with an miR-146a expressing retrovirus identified genes that are directly or indirectly regulated by miR-146a, including a group of interferon responsive genes that are inhibited by miR-146a. Since miR-146a is known to be induced by agents that activate the interferon response pathway (including LMP1), these results suggest that miR-146a functions in a negative feedback loop to modulate the intensity and/or duration of the interferon response. Keywords: Analysis of gene expression changes altered by the microRNA, miR-146a EBV positive Burkitt's lymphoma cell line, Akata, was infected with the control retrovirus, pEhyg, or the miR-146a expressing retrovirus, pEhyg-miR-146a. Two infections were carried out for control retrovirus and two infections were carried out with the pEhyg-miR-146a retrovirus. Total RNA was prepared from each of the 4 infections. Control and miR-146a infection set 1 was subjected to dual color array analysis on chip 1. Control and miR-146a infection set 2 was subjected to dual color array analysis on second array of chip 1. Dye swaps of each of these were carried out on two arrays from a second chip (chip 2).

Project description:Epstein-Barr Virus (EBV) Latent Membrane Protein 1 (LMP1) transforms rodent fibroblasts and is expressed in most EBV-associated malignancies. LMP1 Transformation Effector Site 2 (TES2)/C-Terminal Activation Region 2 (CTAR2) activates NF-kappaB, p38, JNK, ERK and IRF7 pathways. We have investigated LMP1 TES2 genome-wide RNA effects at 4 time points after LMP1 TES2 expression in HEK 293 cells. Using a False Discovery Rate (FDR) of < 0.001 after correction for multiple hypotheses, LMP1 TES2 caused > 2-fold changes in 1916 mRNAs; 1479 RNAs were up-regulated and 437 down-regulated. In contrast to TNFalpha stimulation, which transiently up-regulates many target genes, LMP1 TES2 maintained most RNA effects through the time course, despite robust and sustained induction of negative feedback regulators, such as IkappaBalpha and A20. LMP1 TES2 regulated RNAs encode many NF-kappaB signaling proteins and secondary interacting proteins. Consequently, many LMP1 TES2-regulated RNAs encode proteins that form an extensive interactome. Gene Set Enrichment Analyses found LMP1 TES2 up-regulated genes to be significantly enriched for Pathways in Cancer, B-and T-cell receptor signaling, and Toll-like receptor signaling. Surprisingly, LMP1 TES2 and IkappaBalpha super-repressor co-expression decreased LMP1 TES2 RNA effects to only 5 RNAs with FDR<0.001 and >2 fold change. Thus, canonical NF-kappaB activation is critical for almost all LMP1 TES2 RNA effects in HEK-293 cells and a more significant therapeutic target than previously appreciated. An LMP1 double point mutant (P204A, Q206A) was used to construct a HEK-293 TET-On LMP1 TES2 cell line. Stable cell clones were selected that carry an inducible system for LMP1 TES2 expression. The Tet-system is composed of three parts: 1) the LMP1 TES2 cDNA cloned into the tetracycline-regulated pJEF vector; 2) a tetracycline suppressor (tTS) that binds Tet-operator sites in the absence of tetracyclines and silences expression; 3) a reverse-tetracycline transactivator fused to the 4-hydroxy tamoxifen (4HT) ligand binding domain (rTTA M2). LMP1 expression was induced by addition of doxycycline (1 ug/ml) and 4HT (100 nM). For simultaneous inducible expression of LMP1 TES2 and an IkBa super-repressor, a stable cell line was derived. A pJEF vector encoding IkBa residues 37-317 was introduced into the inducible LMP1 TES2 cell line. Cell lines were cultured with DMEM (GIBCO) supplemented with 10% tetracycline-free serum (Clontech). LMP1 expression was induced by addition of tetracycline (1 ug/ml). RNA samples were collected from triplicate samples using RNABee (Qiagen) according to the manufacturer’s instructions from 293 cells induced for LMP1 TES2 (and IkBa super-repressor, where indicated) expression at 0, 6, 9, 12 and 24 hours of induction. Cells were in the log-phase of growth. Gene expression profiles were assayed using the Affymetrix HU-133 plus2 GeneChip according to the manufacturer's instructions. Real-time RT-PCR was performed with the Power SYBR Green RNA-to-CT™ 1-Step Kit (Applied Biosystems, Foster City, CA). Fold changes were determined using delta delta Ct method and normalized by GAPDH expression levels. RNA expression data were normalized using RMA and array quality assessed by NUSE and RLE scores. The data was collected according to methods that fall under the MIAME standards.