Modulation of a novel cell cycle checkpoint by the HPV oncogene E6

描述（由申请人提供）：感染人乳头瘤病毒（HPV）是必要的，但不是发展为宫颈癌的充分条件。由HPV引起的基因组不稳定可能使细胞积累致癌所必需的额外遗传异常。多倍体形式的基因组不稳定性与致癌的因果作用有关。在人角化细胞中单独表达HPV E6和E7癌基因也会导致多倍体，这种多倍体会因纺锤体破坏和DNA损伤而增强。以前，人们认为E6和E7通过废除纺锤体检查点诱导多倍体，但没有直接证明E6对肿瘤抑制因子p53的降解对其诱导多倍体的能力很重要。然而，我们最近的研究表明，E6和E7对原代人角质形成细胞（phk）的纺锤体检查点没有显著影响。相反，我们的研究结果表明E6和E7在微管破坏后废除了分裂后检查点诱导多倍体。此外，E7和E6在较小程度上通过再复制诱导多倍体，以应对DNA损伤，这是一个连续的DNA复制过程，没有中间的有丝分裂。有趣的是，p53降解缺陷的E6突变体也会诱导多倍体。为了进一步探讨E6和E7诱导多倍体的机制，我们提出以下具体目标：1)。探讨E6在消除有丝分裂后检查点中与p53无关的功能。2）. 阐明e7诱导再复制的分子基础。这个应用程序调查研究不足的细胞周期过程和挑战现有的教条。这些研究将阐明HPV诱导基因组不稳定的机制，并有望开发针对癌前病变这一过程的药物。人乳头瘤病毒（HPV）感染会诱发疣，并与宫颈癌的发展密切相关。HPV癌基因E6和E7对细胞周期检查点的调节有助于HPV诱导的基因组不稳定性。这些研究将揭示HPV诱发癌症的机制，并为开发针对这一过程的药物带来希望。

DESCRIPTION (provided by applicant): Infection with human papillomavirus (HPV) is necessary but not sufficient for the development of cervical cancer. Genomic instability caused by HPV may enable cells to accumulate additional genetic abnormalities necessary for carcinogenesis. Genomic instability in the form of polyploidy has been implicated in a causal role in carcinogenesis. Expression of the HPV E6 and E7 oncogenes alone in human keratinocytes also leads to polyploidy, which is enhanced by spindle disruption and DNA damage. Previously, it was thought but not directly shown that E6 and E7 induce polyploidy by abrogating the spindle checkpoint and that degradation of the tumor suppressor p53 by E6 is important for its ability to induce polyploidy. However, our recent studies demonstrate that E6 and E7 do not have a significant effect on the spindle checkpoint in primary human keratinocytes (PHKs). Instead, our results suggest that E6 and E7 abrogate the postmitotic checkpoint to induce polyploidy after microtubule disruption. In addition, E7, and to a lesser extent E6, induce polyploidy in response to DNA damage through re-replication, a process of successive rounds of DNA replication without an intervening mitosis. Interestingly, E6 mutants defective in p53 degradation also induced polyploidy. To further explore the mechanisms by which E6 and E7 induce polyploidy, we propose the following specific aims: 1). To explore the p53-independent functions of E6 in abrogating the postmitotic checkpoint. 2). To elucidate the molecular basis underlying E7-induced re-replication. This application investigates under-studied cell cycle processes and challenges existing dogmas. These studies will shed light on mechanisms by which HPV induces genomic instability and hold promise for the development of drugs that target this process in pre- cancer lesions. Infection with human papillomaviruses (HPV) induces warts and is strongly associated with the development of cervical cancer. Modulation of cell cycle checkpoints by the HPV oncogenes E6 and E7 contributes to HPV- induced genomic instability. These studies will shed light on mechanisms by which HPV induces cancer and hold promise for the development of drugs that target this process.