Rta,爱泼斯坦-巴尔病毒(EBV)立即早期蛋白,重新激活与肿瘤发生密切相关的病毒裂解复制。在以往的研究中,我们证明,在上皮细胞中,Rta有效地诱导细胞衰老,这是一种不可逆的G1期阻滞,可能为EBV和卡波西肉瘤相关疱疹病毒(KSHV)的生产性复制提供有利的环境。为了限制细胞周期的进展,Rta同时上调CDK抑制剂并下调MYC,CCND1和JUN,在其他人中。Rta长期以来被认为是一种有效的转录激活因子,因此,它在基因抑制中的作用是出乎意料的。计算机模拟分析表明,MYC的启动子区域,CCND1和JUN在(i)CpG岛的存在中很常见,(ii)CCCTC结合因子(CTCF)的强染色质免疫沉淀(ChIP)信号,和(iii)具有至少一个Rta结合位点。通过结合ChIP分析和DNA甲基化分析,在这里,我们提供的证据表明,Rta结合积累了CpG甲基化和减少CTCF占据MYC的调控区,CCND1和JUN,与基因表达下调有关。CTCF在病毒潜伏期和再激活控制区中的稳定驻留是病毒潜伏期的标志。这里,我们观察到Rta介导的CTCF在病毒基因组中的结合减少与病毒再激活同时发生.通过干扰CTCF结合,在宿主基因组中,Rta可以作为基因沉默的转录抑制因子,而在病毒基因组中,Rta通过消除CTCF建立的拓扑约束而充当裂解基因位点的激活剂。IMPORTANCECTCF是一种多功能蛋白,以各种方式参与细胞和病毒基因组的基因表达和高级染色质结构。在基因组的某些基因座中,CTCF占有率和DNA甲基化是相互排斥的。这里,我们证明爱泼斯坦-巴尔病毒(EBV)立即早期蛋白,Rta,已知是转录激活因子,也可以作为转录抑制因子。通过富集CpG甲基化和减少CTCF重新加载,Rta结合有效地关闭了MYC的表达,CCND1和JUN,从而阻碍细胞周期进程。在EBV基因组的潜伏期/再激活控制区也检测到Rta介导的CTCF结合的破坏,这反过来导致病毒裂解周期进展。随着新的证据表明,甲基化的EBV基因组是EBVZta的优选底物,另一种早期蛋白质,我们的研究结果提示在理解病毒潜伏-裂解转换的分子过程中存在机械联系.
Rta, an Epstein-Barr virus (EBV) immediate-early protein, reactivates viral lytic replication that is closely associated with tumorigenesis. In previous studies, we demonstrated that in epithelial cells Rta efficiently induced cellular senescence, which is an irreversible G1 arrest likely to provide a favorable environment for productive replications of EBV and Kaposi\'s sarcoma-associated herpesvirus (KSHV). To restrict progression of the cell cycle, Rta simultaneously upregulates CDK inhibitors and downregulates MYC, CCND1, and JUN, among others. Rta has long been known as a potent transcriptional activator, thus its role in gene repression is unexpected. In silico analysis revealed that the promoter regions of MYC, CCND1, and JUN are common in (i) the presence of CpG islands, (ii) strong chromatin immunoprecipitation (ChIP) signals of CCCTC-binding factor (CTCF), and (iii) having at least one Rta binding site. By combining ChIP assays and DNA methylation analysis, here we provide evidence showing that Rta binding accumulated CpG methylation and decreased CTCF occupancy in the regulatory regions of MYC, CCND1, and JUN, which were associated with downregulated gene expression. Stable residence of CTCF in the viral latency and reactivation control regions is a hallmark of viral latency. Here, we observed that Rta-mediated decreased binding of CTCF in the viral genome is concurrent with virus reactivation. Via interfering with CTCF binding, in the host genome Rta can function as a transcriptional repressor for gene silencing, while in the viral genome Rta acts as an activator for lytic gene loci by removing a topological constraint established by CTCF.IMPORTANCE CTCF is a multifunctional protein that variously participates in gene expression and higher-order chromatin structure of the cellular and viral genomes. In certain loci of the genome, CTCF occupancy and DNA methylation are mutually exclusive. Here, we demonstrate that the Epstein-Barr virus (EBV) immediate-early protein, Rta, known to be a transcriptional activator, can also function as a transcriptional repressor. Via enriching CpG methylation and decreasing CTCF reloading, Rta binding efficiently shut down the expression of MYC, CCND1, and JUN, thus impeding cell cycle progression. Rta-mediated disruption of CTCF binding was also detected in the latency/reactivation control regions of the EBV genome, and this in turn led to viral lytic cycle progression. As emerging evidence indicates that a methylated EBV genome is a preferable substrate for EBV Zta, the other immediate-early protein, our results suggest a mechanistic link in understanding the molecular processes of viral latent-lytic switch.