Induction of genomic instability by HPV E6 and E7

描述（由申请人提供）：人乳头瘤病毒（HPV）感染是必要的，但不足以发展为宫颈癌。由HPV引起的基因组不稳定性可能使细胞积累额外的遗传异常，这些遗传异常是致癌所必需的，并且与致癌的因果关系有关。HPV E6和E7癌基因在原代人角质形成细胞（PHK）中的表达导致多倍体，其通过纺锤体破坏和DNA损伤而增强。以前，假设E6和E7通过废除有丝分裂纺锤体检查点诱导多倍体，并且E6降解肿瘤抑制因子p53以诱导多倍体。我们最近的研究表明E6和E7对纺锤体检查点没有显著影响。相反，它们废除了有丝分裂后的检查点，以诱导微管破坏后的多倍性。有趣的是，p53降解缺陷的E6突变体也诱导多倍体。此外，我们的研究表明Cdk 4和Cdk 1在E6诱导的多倍体中起重要作用。此外，E7通过再复制诱导多倍体以响应DNA损伤，再复制是一个连续轮的DNA复制过程，而没有居间的有丝分裂。此外，我们发现，DNA复制起始因子Cdt 1，其不受控制的表达诱导在人类癌细胞中的再复制，在E7诱导的再复制过程中被后修饰。我们推测cdk 4和cdk 1的激活在E6诱导的非p53依赖性多倍体中起重要作用，Cdt 1的修饰是E7诱导再复制所必需的，并且E6/E7诱导的多倍体将促进向非整倍体和癌症的进展。该提案的具体目标旨在测试这些可能性。这些研究将揭示HPV诱导基因组不稳定性的机制，并有望为药物开发确定靶点。 公共卫生相关性：人乳头瘤病毒（HPV）感染会诱发疣，并与宫颈癌的发生密切相关。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诱导癌症的机制，并有望确定药物开发的靶点。

DESCRIPTION (provided by applicant): Human papillomavirus (HPV) infection 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 and has been implicated in a causal role in carcinogenesis. Expression of the HPV E6 and E7 oncogenes in primary human keratinocytes (PHKs) leads to polyploidy, which is enhanced by spindle disruption and DNA damage. Previously, it was hypothesized that E6 and E7 induce polyploidy by abrogating the mitotic spindle checkpoint and that E6 degrades the tumor suppressor p53 to induce polyploidy. Our recent studies demonstrate that E6 and E7 do not have a significant effect on the spindle checkpoint. Instead, they abrogate the postmitotic checkpoint to induce polyploidy after microtubule disruption. Interestingly, E6 mutants defective in p53 degradation also induce polyploidy. Moreover, our studies suggest an important role for Cdk4 and Cdk1 in E6-induced polyploidy. In addition, E7 induces polyploidy in response to DNA damage through re-replication, a process of successive rounds of DNA replication without an intervening mitosis. Furthermore, we find that the DNA replication initiation factor Cdt1, whose uncontrolled expression induces re-replication in human cancer cells, is post-translationally modified during E7-induced re-replication. We hypothesize that activation of cdk4 and cdk1 plays an important role in p53-independent induction of polyploidy by E6, modification of Cdt1 is required for E7 to induce re-replication, and E6/E7-induced polyploidy will enhance the progression into aneuploidy and cancer. The specific aims of the proposal are designed to test these possibilities. These studies will shed light on mechanisms by which HPV induces genomic instability and hold promise for the identification of targets for drug development. PUBLIC HEALTH RELEVANCE: 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 identification of targets for drug development.