EBV infection is associated with histone bivalent switch modifications in squamous epithelial cells

Abstract

Epstein−Barr virus (EBV) induces histone modifications to regulate signaling pathways involved in EBV-driven tumorigenesis. To date, the regulatory mechanisms involved are poorly understood. In this study, we show that EBV infection of epithelial cells is associated with aberrant histone modification; specifically, aberrant histone bivalent switches by reducing the transcriptional activation histone mark (H3K4me3) and enhancing the suppressive mark (H3K27me3) at the promoter regions of a panel of DNA damage repair members in immortalized nasopharyngeal epithelial (NPE) cells. Sixteen DNA damage repair family members in base excision repair (BER), homologous recombination, nonhomologous end-joining, and mismatch repair (MMR) pathways showed aberrant histone bivalent switches. Among this panel of DNA repair members,MLH1, involved in MMR, was significantly down-regulated in EBV-infected NPE cells through aberrant histone bivalent switches in a promoter hypermethylation-independent manner. Functionally, expression ofMLH1correlated closely with cisplatin sensitivity both in vitro and in vivo. Moreover, seven BER members with aberrant histone bivalent switches in the EBV-positive NPE cell lines were significantly enriched in pathway analysis in a promoter hypermethylation-independent manner. This observation is further validated by their down-regulation in EBV-infected NPE cells. The in vitro comet and apurinic/apyrimidinic site assays further confirmed that EBV-infected NPE cells showed reduced DNA damage repair responsiveness. These findings suggest the importance of EBV-associated aberrant histone bivalent switch in host cells in subsequent suppression of DNA damage repair genes in a methylation-independent manner.

The Impact of Epstein-Barr Virus Infection on Epigenetic Regulation of Host Cell Gene Expression in Epithelial and Lymphocytic Malignancies

“…As AP-1 was also demonstrated to regulate DNMT1 expression for methylation of the E-cadherin promoter in the presence of LMP1, it is possible a cross-talk exists in which LMP1 enhances the expression of AP-1 through phosphorylation of H3Ser10 at the promoter of AP-1, providing sufficient AP-1 for JNK/AP-1 pathway to up-regulate DNMT1 (Figure 1). In addition, our previous ChIP-Seq study comparing two pairs of EBV-positive and -negative NPE cell lines illustrated that EBV infection dysregulated histone bivalent switches, showing reduction of H3K4me3 and gain of H3K27me3, to suppress DNA damage repair (DDR) gene expression in a methylation-independent manner (103). The same study further showed that over-expression of EBNA1 could inhibit the expression of DDR genes (103).…”

“…In addition, our previous ChIP-Seq study comparing two pairs of EBV-positive and -negative NPE cell lines illustrated that EBV infection dysregulated histone bivalent switches, showing reduction of H3K4me3 and gain of H3K27me3, to suppress DNA damage repair (DDR) gene expression in a methylation-independent manner (103). The same study further showed that over-expression of EBNA1 could inhibit the expression of DDR genes (103). It seems that EBV could dysregulate the histone modifications in the precancerous host cells to suppress the key cancer-related genes without the involvement of DNA methylation.…”

Role of Virus-Induced Host Cell Epigenetic Changes in Cancer

“…EBV infection of nasopharyngeal epithelial cells reduced the transcriptional activation mark H3K4me3 and enhanced the suppressive mark H3K27me3 at the promoter regions of several genes, including 16 DNA damage repair genes. The reduced DNA repair ability in EBV-infected nasopharyngeal epithelial cells may play an important role in nasopharyngeal carcinoma [ 222 ]. Infection of B cells with EBV resulted in a loss of H3K9me3, H3K27me3, and H4K20me3, histone markers that are associated with histone condensation.…”

“…EBV induced chromatin changes can also be mediated by microRNA. The EBV protein EBNA2 was found to induce miR-146-5p, which targets KDM2 mRNA [ 222 ].…”

Clinical Manifestations and Epigenetic Regulation of Oral Herpesvirus Infections

“…Latent viral proteins can also modify host chromatin, such as in the case of latent factors EBNA3A- and EBNA3C-dependent recruitment of PRC2 to deposit repressive H3K27me3 marks on host tumor suppressor genes [ 107 , 113 ]. In nasopharyngeal carcinoma cells, EBV infection has also been shown to be associated with loss of H3K4me3/H3K27me3 bivalency in the promoter regions of crucial DNA damage response genes, demonstrating a viral mechanism of host chromatin regulation that may drive tumorigenesis in the epithelium [ 114 ].…”