Study the Role of Chfr in Tumorigenesis

描述（由申请人提供）：染色体不稳定性是人类癌症的常见特征。染色体的不稳定性允许多种遗传改变的积累，最终导致癌症的发展。在过去的十年中，越来越多的证据表明，有丝分裂检查点控制是必不可少的染色体稳定性的维护。Chfr（checkpoint with FHA and ring finger domains）是一种新发现的参与有丝分裂转换的检查点蛋白。对人类原发性肿瘤和肿瘤细胞系的研究表明，Chfr下调与人类癌症的发展有关。然而，它仍然有待确定是否Chfr下调直接有助于肿瘤的发生。我们最近产生了Chfr敲除小鼠。使用这些小鼠，我们已经证明，Chfr-缺陷小鼠有自发性和致癌物质诱导的肿瘤的发病率增加，这表明Chfr表达的损失或下调有助于肿瘤的发生。在这里，我们建议研究机制如何Chfr控制有丝分裂的进展和抑制肿瘤的形成。Chfr含有一个RING结构域，在体外具有E3泛素连接酶活性。我们已经表明，Chfr的生理底物之一是一个关键的有丝分裂激酶Aurora-A。在具体目标1中，我们将确定Chfr/Aurora A复合物的结构，并在分子水平上研究Chfr如何与Aurora A相互作用并调节Aurora A。在特定目标2中，我们将探讨在缺乏Chfr的情况下，Aurora A过表达和/或p53突变是否对肿瘤发展至关重要。这些研究将揭示Chfr缺陷促进肿瘤发生的机制。我们和其他人已经表明，Chfr在结直肠癌中经常下调，这表明Chfr缺乏可能有助于人类结直肠癌的发展。具体目标3将探讨这种可能性。总之，本文概述的研究将阐明Chfr在控制有丝分裂转变中的精确分子作用，并提供对这种新定义的早期有丝分裂检查点在维持基因组稳定性和癌症预防中的功能的见解。

DESCRIPTION (provided by applicant): Chromosomal instability is a common feature of human cancers. Chromosomal instability allows the accumulation of multiple genetic alterations that ultimately leads to the development of cancer. Increasing evidence in the last decade suggest that mitotic checkpoint controls are essential for the maintenance of chromosomal stability. Chfr (checkpoint with FHA and ring finger domains) is a newly identified checkpoint protein involved in mitotic transitions. Studies of human primary tumors and tumor cell lines suggest that Chfr downregulation is associated with human cancer development. However, it remains to be determined whether Chfr downregulation directly contributes to tumorigenesis. We recently generated Chfr knockout mice. Using these mice, we have demonstrated that Chfr-deficient mice have an increased incidence of spontaneous and carcinogen-induced tumors, suggesting that loss or downregulation of Chfr expression contributes to tumorigenesis. Here, we propose to study mechanistically how Chfr controls mitotic progression and suppress tumor formation. Chfr contains a RING domain and has E3 ubiquitin ligase activity in vitro. We have shown that one of the physiological substrates of Chfr is a key mitotic kinase Aurora-A. In Specific Aim 1, we will determine the structure of Chfr/Aurora A complex and study at molecular level how Chfr interacts with and regulates Aurora A. In Specific Aim 2, we will explore whether Aurora A overexpression and/or p53 mutation are critical for tumor development in the absence of Chfr. These studies will reveal the mechanisms by which Chfr deficiency promotes tumorigenesis. We and others have shown that Chfr is frequently downregulated in colorectal cancers, suggesting that Chfr deficiency may contribute to colorectal cancer development in humans. This possibility will be explored in Specific Aim 3. In conclusion, studies outlined here will elucidate the precise molecular role of Chfr in the control of mitotic transition, and provide insights into the function of this newly defined early mitotic checkpoint in the maintenance of genomic stability and cancer prevention.