RESUMEN
Epstein-Barr virus (EBV) is associated with approximately 10% of gastric cancers (GCs). We previously showed that EBV infection of gastric epithelial cells induces aberrant DNA methylation in promoter regions, which causes silencing of critical tumor suppressor genes. Here, we analyzed gene expressions and active histone modifications (H3K4me3, H3K4me1, and H3K27ac) genome-widely in EBV-positive GC cell lines and in vitro EBV-infected GC cell lines to elucidate the transcription factors contributing to tumorigenesis through enhancer activation. Genes associated with "signaling of WNT in cancer" were significantly enriched in EBV-positive GC, showing increased active ß-catenin staining. Genes neighboring activated enhancers were significantly upregulated, and EHF motif was significantly enriched in these active enhancers. Higher expression of EHF in clinical EBV-positive GC compared with normal tissue and EBV-negative GC was confirmed by RNA-seq using The Cancer Genome Atlas cohort, and by immunostaining using our cohort. EHF knockdown markedly inhibited cell proliferation. Moreover, there was significant enrichment of critical cancer pathway-related genes (eg, FZD5) in the downstream of EHF. EBV protein LMP2A caused upregulation of EHF via phosphorylation of STAT3. STAT3 knockdown was shown to inhibit cellular growth of EBV-positive GC cells, and the inhibition was rescued by EHF overexpression. Our data highlighted the important role of EBV infection in gastric tumorigenesis via enhancer activation.
Asunto(s)
Infecciones por Virus de Epstein-Barr/genética , Herpesvirus Humano 4/metabolismo , Factor de Transcripción STAT3/metabolismo , Neoplasias Gástricas/virología , Factores de Transcripción/genética , Proteínas de la Matriz Viral/metabolismo , Línea Celular Tumoral , Metilación de ADN , Infecciones por Virus de Epstein-Barr/metabolismo , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Regulación Viral de la Expresión Génica , Código de Histonas , Humanos , Fosforilación , Análisis de Secuencia de ARN , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Factores de Transcripción/metabolismo , Regulación hacia ArribaRESUMEN
Polycomb repressive complex (PRC) 2 represses transcription through histone H3K27 trimethylation (H3K27me3). We previously reported that the hematopoietic-cell-specific deletion of Ezh2, encoding a PRC2 enzyme, induced myelodysplastic syndrome (MDS) in mice, whereas the concurrent Ezh1 deletion depleted hematopoietic stem and progenitor cells (HSPCs). We herein demonstrated that mice with only one Ezh1 allele (Ezh1+/-Ezh2Δ/Δ) maintained HSPCs. A chromatin immunopreciptation sequence analysis revealed that residual PRC2 preferentially targeted genes with high levels of H3K27me3 and H2AK119 monoubiquitination (H2AK119ub1) in HSPCs (designated as Ezh1 core target genes), which were mostly developmental regulators, and maintained H3K27me3 levels in Ezh1+/-Ezh2Δ/Δ HSPCs. Even upon the complete depletion of Ezh1 and Ezh2, H2AK119ub1 levels were largely retained, and only a minimal number of Ezh1 core targets were de-repressed. These results indicate that genes marked with high levels of H3K27me3 and H2AK119ub1 are the core targets of polycomb complexes in HSPCs as well as MDS stem cells.