细胞分裂周期蛋白Cdc6在HPV癌蛋白E7表达细胞中的功能与调控

Infection with specific types (high-risk) of human papillomavirus (HPV) is important for the development of cervical cancer. Although the prophylactic HPV vaccines have become available, they are type-restricted and will not be effective for those who are already infected or immunosuppressed. Therefore, understanding the molecular basis for HPV-induced cancers is still of high clinical significance. Our long-term goal is to identify molecular pathways that may be intercepted for treatment of HPV-induced diseases. E7s from the high-risk HPV types abrogate the G1 checkpoint upon DNA damage and induce DNA re-replication that contributes to carcinogenesis but the mechanism is not fully understood. Our preliminary studies show that the DNA replication initiation factor Cdc6, an oncogene whose overexpression induces re-replication, is up-regulated in E7 expressing cells. Down-regulation of Cdc6 impairs the ability of E7 to abrogate DNA damage-induced G1 arrest. We hypothesize that up-regulation of Cdc6 is important for E7 to induce re-replication; Cdc6 plays an important role for abrogation of the G1 checkpoint by E7. To test these possibilities, we propose the following specific aims: (1) To establish the role of Cdc6 in E7-induced re-replication and understand how it is regulated; (2) To explore the mechanism by which Cdc6 contributes to G1 checkpoint abrogation by E7. These studies are expected to establish the role for Cdc6 in HPV-induced re-replication and checkpoint regulation. The results will shed light on mechanisms by which HPV induces genomic instability, which could help to identify potential targets for drug development.

高危型人乳头瘤病毒（HPV）感染是诱导宫颈癌发生的主要原因。目前预防性的HPV疫苗仅针对少数型别，且对已经感染的病人无效,因此进一步阐明HPV诱导癌症发生的分子机制仍具有重要的临床意义。HPV早期基因E7能使细胞周期G1检验点失活，促进DNA重复复制，从而诱导基因组不稳定及癌症的发生，但机制不清。DNA复制起始因子Cdc6的高表达可引起癌细胞重复复制。我们的研究表明Cdc6在E7表达细胞中升高，下调Cdc6会影响E7细胞绕过DNA损伤所导致的G1期停滞。我们推断上调Cdc6对E7诱导DNA重复复制及逃避G1检验点至关重要。我们提出下列特定的研究目标：（1）研究Cdc6在E7诱导的重复复制中的作用及调控机理；（2）阐明Cdc6帮助E7逃避G1检验点的机制。以上研究将建立Cdc6在HPV诱导的重复复制及检验点调控中的重要作用，阐明HPV诱导基因组不稳定的新机制，有利于鉴定药物治疗的新靶点。

高危型人乳头瘤病毒感染是诱导宫颈癌发生的主要原因。尽管预防性的HPV疫苗已经问世，但这些疫苗仅对少数型别有效，且对已经感染及免疫抑制病人无效。因此进一步阐明HPV诱导癌症发生的分子机制仍具有重要的临床意义。HPV早期基因E7能使细胞周期G1检查点失活，促进重复复制，从而诱导基因组不稳定及癌症的发生，但机制尚不完全清楚。在癌细胞中过表达细胞分裂周期蛋白Cdc6可导致重复复制，下调Cdc6可引起细胞阻滞在G1期。我们前期的研究表明Cdc6在E7表达细胞升高，下调Cdc6影响E7细胞逃避DNA损伤导致的G1停滞的能力。我们推断上调Cdc6对E7诱导重复复制至关重要，对E7逃避G1检查点必不可少。为了验证这些假设，我们提出下列特定的研究目标：（1）研究Cdc6在E7诱导的重复复制中的作用及调控机理；（2）阐明Cdc6帮助E7逃避G1检查点的机制。以上研究将建立Cdc6在HPV诱导的重复复制及检查点调控中的作用。这些结果将阐明HPV诱导基因组不稳定的新机制，将有利于鉴定药物治疗的新靶位。