The high-risk (HR) human papillomaviruses (HPV) are causative agents of anogenital tract dysplasia and cancers and a fraction of head and neck cancers. The HR HPV E6 oncoprotein possesses canonical oncogenic functions, such as p53 degradation and telomerase activation. It is also capable of stimulating expression of several oncogenes, but the molecular mechanism underlying these events is poorly understood. Here, we provide evidence that HPV16 E6 physically interacts with histone H3K4 demethylase KDM5C, resulting in its degradation in an E3 ligase E6AP- and proteasome-dependent manner. Moreover, we found that HPV16-positive cancer cell lines exhibited lower KDM5C protein levels than HPV-negative cancer cell lines. Restoration of KDM5C significantly suppressed the tumorigenicity of CaSki cells, an HPV16-positive cervical cancer cell line. Whole genome ChIP-seq and RNA-seq results revealed that CaSki cells contained super-enhancers in the proto-oncogenes EGFR and c-MET. Ectopic KDM5C dampened these super-enhancers and reduced the expression of proto-oncogenes. This effect was likely mediated by modulating H3K4me3/H3K4me1 dynamics and decreasing bidirectional enhancer RNA transcription. Depletion of KDM5C or HPV16 E6 expression activated these two super-enhancers. These results illuminate a pivotal relationship between the oncogenic E6 proteins expressed by HR HPV isotypes and epigenetic activation of super-enhancers in the genome that drive expression of key oncogenes like EGFR and c-MET.

Significance: This study suggests a novel explanation for why infections with certain HPV isotypes are associated with elevated cancer risk by identifying an epigenetic mechanism through which E6 proteins expressed by those isotypes can drive expression of key oncogenes. Cancer Res; 78(6); 1418–30. ©2018 AACR.

高危（HR）人乳头瘤病毒（HPV）是生殖器生殖道发育不良和癌症以及一部分头颈癌的病因。HR HPV E6癌蛋白具有典型的致癌功能，例如p53降解和端粒酶激活。它也能够刺激几种癌基因的表达，但是对这些事件的分子机制了解甚少。在这里，我们提供的证据表明，HPV16 E6与组蛋白H3K4脱甲基酶KDM5C发生物理相互作用，导致其以E3连接酶E6AP和蛋白酶体依赖性方式降解。此外，我们发现HPV16阳性癌细胞系表现出比HPV阴性癌细胞系更低的KDM5C蛋白水平。KDM5C的恢复显着抑制了HPV16阳性宫颈癌细胞株CaSki细胞的致瘤性。EGFR和c-MET。异位KDM5C抑制了这些超级增强子并降低了原癌基因的表达。这种作用可能是通过调节H3K4me3 / H3K4me1动态和减少双向增强子RNA转录介导的。KDM5C或HPV16 E6表达的耗尽激活了这两个超级增强子。这些结果阐明了由HR HPV同种型表达的致癌E6蛋白与基因组中超增强子的表观遗传学激活之间的关键关系，该基因驱动关键致癌基因（如EGFR和c-MET）的表达。

意义：这项研究提出了一种新颖的解释，它通过确定表观遗传机制来解释为什么某些HPV同种型的感染与癌症风险升高相关联，这些同种型表达的E6蛋白可通过该机制驱动关键癌基因的表达。癌症研究；78（6）；1418–30。©2018 AACR。