RESUMO
Epstein-Barr Virus (EBV) conversion of B-lymphocytes to Lymphoblastoid Cell Lines (LCLs) requires four EBV nuclear antigen (EBNA) oncoproteins: EBNA2, EBNALP, EBNA3A, and EBNA3C. EBNA2 and EBNALP associate with EBV and cell enhancers, up-regulate the EBNA promoter, MYC, and EBV Latent infection Membrane Proteins (LMPs), which up-regulate BCL2 to protect EBV-infected B-cells from MYC proliferation-induced cell death. LCL proliferation induces p16(INK4A) and p14(ARF)-mediated cell senescence. EBNA3A and EBNA3C jointly suppress p16(INK4A) and p14(ARF), enabling continuous cell proliferation. Analyses of the EBNA3A human genome-wide ChIP-seq landscape revealed 37% of 10,000 EBNA3A sites to be at strong enhancers; 28% to be at weak enhancers; 4.4% to be at active promoters; and 6.9% to be at weak and poised promoters. EBNA3A colocalized with BATF-IRF4, ETS-IRF4, RUNX3, and other B-cell Transcription Factors (TFs). EBNA3A sites clustered into seven unique groups, with differing B-cell TFs and epigenetic marks. EBNA3A coincidence with BATF-IRF4 or RUNX3 was associated with stronger EBNA3A ChIP-Seq signals. EBNA3A was at MYC, CDKN2A/B, CCND2, CXCL9/10, and BCL2, together with RUNX3, BATF, IRF4, and SPI1. ChIP-re-ChIP revealed complexes of EBNA3A on DNA with BATF. These data strongly support a model in which EBNA3A is tethered to DNA through a BATF-containing protein complexes to enable continuous cell proliferation.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , DNA/genética , DNA/metabolismo , Antígenos Nucleares do Vírus Epstein-Barr/genética , Genoma Viral , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/patogenicidade , Linfócitos B/metabolismo , Linfócitos B/virologia , Sítios de Ligação/genética , Linhagem Celular , Quimiocina CXCL10/genética , Quimiocina CXCL9/genética , Subunidade alfa 3 de Fator de Ligação ao Core/metabolismo , Ciclina D2/genética , Elementos Facilitadores Genéticos , Antígenos Nucleares do Vírus Epstein-Barr/metabolismo , Genes bcl-2 , Genes myc , Genes p16 , Genoma Humano , Herpesvirus Humano 4/fisiologia , Interações Hospedeiro-Patógeno/genética , Humanos , Proteína de Ligação a Sequências Sinal de Recombinação J de Imunoglobina/metabolismo , Fatores Reguladores de Interferon/metabolismo , Regiões Promotoras Genéticas , Proteínas Virais/genética , Proteínas Virais/metabolismoRESUMO
Epstein-Barr virus (EBV) transforms B cells to continuously proliferating lymphoblastoid cell lines (LCLs), which represent an experimental model for EBV-associated cancers. EBV nuclear antigens (EBNAs) and LMP1 are EBV transcriptional regulators that are essential for LCL establishment, proliferation, and survival. Starting with the 3D genome organization map of LCL, we constructed a comprehensive EBV regulome encompassing 1,992 viral/cellular genes and enhancers. Approximately 30% of genes essential for LCL growth were linked to EBV enhancers. Deleting EBNA2 sites significantly reduced their target gene expression. Additional EBV super-enhancer (ESE) targets included MCL1, IRF4, and EBF. MYC ESE looping to the transcriptional stat site of MYC was dependent on EBNAs. Deleting MYC ESEs greatly reduced MYC expression and LCL growth. EBNA3A/3C altered CDKN2A/B spatial organization to suppress senescence. EZH2 inhibition decreased the looping at the CDKN2A/B loci and reduced LCL growth. This study provides a comprehensive view of the spatial organization of chromatin during EBV-driven cellular transformation.
Assuntos
Linfócitos B/virologia , Cromatina/virologia , Herpesvirus Humano 4/genética , Interações Hospedeiro-Patógeno , Linhagem Celular , Inibidor de Quinase Dependente de Ciclina p15/genética , Inibidor de Quinase Dependente de Ciclina p15/metabolismo , Inibidor p16 de Quinase Dependente de Ciclina , Inibidor de Quinase Dependente de Ciclina p18/genética , Inibidor de Quinase Dependente de Ciclina p18/metabolismo , Antígenos Nucleares do Vírus Epstein-Barr/genética , Antígenos Nucleares do Vírus Epstein-Barr/metabolismo , Humanos , Fatores Reguladores de Interferon/genética , Fatores Reguladores de Interferon/metabolismo , Proteína de Sequência 1 de Leucemia de Células Mieloides/genética , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Cultura Primária de Células , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Transativadores/genética , Transativadores/metabolismo , Proteínas da Matriz Viral/genética , Proteínas da Matriz Viral/metabolismoRESUMO
Super-enhancers are clusters of gene-regulatory sites bound by multiple transcription factors that govern cell transcription, development, phenotype, and oncogenesis. By examining Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs), we identified four EBV oncoproteins and five EBV-activated NF-κB subunits co-occupying â¼1,800 enhancer sites. Of these, 187 had markedly higher and broader histone H3K27ac signals, characteristic of super-enhancers, and were designated "EBV super-enhancers." EBV super-enhancer-associated genes included the MYC and BCL2 oncogenes, which enable LCL proliferation and survival. EBV super-enhancers were enriched for B cell transcription factor motifs and had high co-occupancy of STAT5 and NFAT transcription factors (TFs). EBV super-enhancer-associated genes were more highly expressed than other LCL genes. Disrupting EBV super-enhancers by the bromodomain inhibitor JQ1 or conditionally inactivating an EBV oncoprotein or NF-κB decreased MYC or BCL2 expression and arrested LCL growth. These findings provide insight into mechanisms of EBV-induced lymphoproliferation and identify potential therapeutic interventions.
Assuntos
Linfócitos B/virologia , Proliferação de Células , Regulação da Expressão Gênica , Herpesvirus Humano 4/fisiologia , Interações Hospedeiro-Patógeno , Proteínas Oncogênicas/metabolismo , Proteínas Virais/metabolismo , Linfócitos B/fisiologia , Perfilação da Expressão Gênica , Dados de Sequência Molecular , Análise de Sequência de DNA , Transcrição GênicaRESUMO
The nuclear factor κB (NF-κΒ) subunits RelA, RelB, cRel, p50, and p52 are each critical for B cell development and function. To systematically characterize their responses to canonical and noncanonical NF-κB pathway activity, we performed chromatin immunoprecipitation followed by high-throughput DNA sequencing (ChIP-seq) analysis in lymphoblastoid B cell lines (LCLs). We found a complex NF-κB-binding landscape, which did not readily reflect the two NF-κB pathway paradigms. Instead, 10 subunit-binding patterns were observed at promoters and 11 at enhancers. Nearly one-third of NF-κB-binding sites lacked κB motifs and were instead enriched for alternative motifs. The oncogenic forkhead box protein FOXM1 co-occupied nearly half of NF-κB-binding sites and was identified in protein complexes with NF-κB on DNA. FOXM1 knockdown decreased NF-κB target gene expression and ultimately induced apoptosis, highlighting FOXM1 as a synthetic lethal target in B cell malignancy. These studies provide a resource for understanding mechanisms that underlie NF-κB nuclear activity and highlight opportunities for selective NF-κB blockade.