Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, United Kingdom.
J Virol. 2011 Nov;85(21):10999-1006. doi: 10.1128/JVI.00160-11. Epub 2011 Aug 24.
A number of epigenetic alterations occur in both the virus and host cellular genomes during human papillomavirus (HPV)-associated carcinogenesis, and investigations of such alterations, including changes in chromatin proteins and histone modifications, have the potential to lead to therapeutic epigenetic reversion. We report here that transformed HPV16 E6/E7-expressing primary human foreskin keratinocytes (HFKs) (E6/E7 cells) demonstrate increased expression of the PRC2 methyltransferase EZH2 at both the mRNA and protein levels but do not exhibit the expected increase in trimethylated H3K27 (H3K27me3) compared to normal keratinocytes. In contrast, these cells show a reduction in global H3K27me3 levels in vitro, as well as upregulation of the KDM6A demethylase. We further show for the first time that transformation with the HPV16 E6 and E7 oncogenes also results in an increase in phosphorylated EZH2 serine 21 (P-EZH2-Ser21), mediated by active Akt, and in a downregulation of the PRC1 protein BMI1 in these cells. High-grade squamous cervical intraepithelial lesions also showed a loss of H3K27me3 in the presence of increased expression of EZH2. Correlating with the loss of H3K27me3, E6/E7 cells exhibited derepression of specific EZH2-, KMD6A-, and BMI1-targeted HOX genes. These results suggest that the observed reduction in H3K27me3 may be due to a combination of reduced activities/levels of specific polycomb proteins and increases in demethylases. The dysregulation of multiple chromatin proteins resulting in the loss of global H3K27me3 and the transcriptional reprogramming in HPV16 E6/E7-infected cells could provide an epigenetic signature associated with risk and/or progression of HPV16-associated cancers, as well as the potential for epigenetic reversion in the future.
在人乳头瘤病毒（HPV）相关致癌过程中，病毒和宿主细胞基因组中都会发生许多表观遗传改变，包括染色质蛋白和组蛋白修饰的改变，这些改变的研究有可能导致治疗性表观遗传逆转。我们在此报告，转化的 HPV16 E6/E7 表达的原代人包皮角质形成细胞（HFK）（E6/E7 细胞）在 mRNA 和蛋白质水平上均表现出 PRC2 甲基转移酶 EZH2 的表达增加，但与正常角质形成细胞相比，并未表现出预期的 H3K27 三甲基化（H3K27me3）增加。相比之下，这些细胞在体外显示出全局 H3K27me3 水平降低，以及 KDM6A 去甲基酶的上调。我们进一步首次表明，HPV16 的 E6 和 E7 癌基因的转化也导致磷酸化 EZH2 丝氨酸 21 （P-EZH2-Ser21）的增加，这是由活跃的 Akt 介导的，并且这些细胞中的 PRC1 蛋白 BMI1 下调。在这些细胞中，高级别鳞状宫颈上皮内病变也显示出 H3K27me3 的丢失，同时 EZH2 的表达增加。与 H3K27me3 的丢失相关，E6/E7 细胞表现出特定 EZH2、KMD6A 和 BMI1 靶向 HOX 基因的去抑制。这些结果表明，观察到的 H3K27me3 减少可能是由于特定多梳蛋白的活性/水平降低和去甲基酶增加的组合所致。多个染色质蛋白的失调导致全局 H3K27me3 的丢失和 HPV16 E6/E7 感染细胞中的转录重编程，可能提供与 HPV16 相关癌症的风险和/或进展相关的表观遗传特征，以及未来进行表观遗传逆转的潜力。
