| Summary: | 碩士 === 國立陽明大學 === 微生物及免疫學研究所 === 100 === Epstein-Barr virus (EBV) is human herpesvirus, it establishes life-long latent infection in B cells. The latent EBV genome is associated with cellular histone proteins to form chromatin-like structure. During latency, the two immediate-early promoters, BZLF1 promoter (Zp) and BRLF1 promoter (Rp), are repressed. However, these two promoters can be activated upon viral reactivation. Regulation of EBV immediate-early gene expression by cellular DNA binding factors is widely studied, but epigenetic control of EBV reactivation is poorly understood. Our pervious study showed that histone modifications at viral genome were dynamically changed upon reactivation. To confirm these results, we performed chromatin immunoprecipitation (ChIP) assay with two EBV positive cell lines, Akata(+) and Raji. We found that H3K4me3, H3K9ac and H3K14ac were increased at both latent and lytic promoters in Raji cells, suggesting that the latent viral genome was activated upon reactivation. In Akata(+) cells, H3K9ac was increased at both latent and lytic promoters, whereas increase of H3K4me3 and H3K14ac levels were specifically associated with Zp and lytic replication origin (OriLyt), respectively. These results indicated that increase of H3K4me3 and H3K14ac at viral genome in Raji cells might be interfered by histone deacetylase inhibitor, sodium butyrate. Furthermore, the repressive H3K9me3 mark was detected at latent viral genome, but its dynamic alteration was undefined in two cell lines. Although dynamic alteration of H3K9me3 upon viral reactivation was not observed, presence of this repressive mark might be required for maintaining latent viral genome. On the other hand, we used 293/maxi-EBV cells as a model to screen four H3K9me3- and one H3K9me1/2 demethylases. We found that knockdown of KDM4A suppressed immediate-early and early genes expression, suggesting that KDM4A may be involved in EBV reactivation. Surprisingly, knockdown of either KDM4C or KDM3A spontaneously induced immediate-early and early genes expression. In this study, we propose that an unknown mechanism may be involved in suppression of EBV reactivation, which is mediated by KDM4C and KDM3A.
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