Study the Role of Chfr in Tumorigenesis

描述(申请人提供)：染色体不稳定是人类癌症的常见特征。染色体的不稳定性允许多种基因改变的积累，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对于维持染色体稳定是必不可少的。Chfr(具有FHA和RING指域的检查点)是一种新发现的参与有丝分裂转换的检查点蛋白。对人类原发肿瘤和肿瘤细胞系的研究表明，CHFR下调与人类癌症的发生有关。然而，Chfr的下调是否直接导致肿瘤的发生仍有待确定。我们最近培育出了Chfr基因敲除小鼠。利用这些小鼠，我们已经证明了Chfr缺陷小鼠的自发性和致癌物诱导的肿瘤发生率增加，这表明Chfr表达的缺失或下调有助于肿瘤的发生。在这里，我们建议从机制上研究CHFR如何控制有丝分裂进程和抑制肿瘤形成。CHFR含有一个环状结构域，在体外具有E3泛素连接酶活性。我们已经证明，CHFR的一个生理底物是一个关键的有丝分裂酶Aurora-A。在特定目标1中，我们将确定Chfr/Aurora A复合体的结构，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，我们将探索在没有Chfr的情况下，Aurora A过表达和/或p53突变是否对肿瘤的发生起关键作用。这些研究将揭示CHFR缺陷促进肿瘤发生的机制。我们和其他人已经证明，CHFR在结直肠癌中经常下调，这表明CHFR缺乏可能与人类结直肠癌的发生有关。这一可能性将在特定的目标3中进行探索。总而言之，本文概述的研究将阐明Chfr在控制有丝分裂转变中的确切分子作用，并为这一新定义的早期有丝分裂检查点在维持基因组稳定和癌症预防中的功能提供见解。

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.