Functional Characterization of the Mammalian MOF Gene Product

描述(由申请人提供)：了解染色质修饰因子在电离辐射(IR)反应中的作用，将为癌症如何开始以及如何治愈癌症提供宝贵的见解。ATM(共济失调-毛细血管扩张突变)蛋白是所有细胞对IR反应的主要参与者。我们一直在研究ATM在DNA损伤修复、端粒染色质结构和致癌转化中的作用。ATM缺陷细胞具有DNA修复缺陷，表现为端粒染色质结构改变，自发和IR诱导的致癌转化频率较高。最近，我们发现了一种染色质修饰因子“hMOF”，这是与ATM相互作用的果蝇MOF基因的人类同源基因(第一个是雄性缺失的)。HMOF具有组蛋白乙酰转移酶(HAT)活性。细胞暴露于IR可增强其靶底物HMOF依赖的组蛋白H4(H4-K16)赖氨酸16的乙酰化，而不依赖于ATM功能。HMOF失活会导致自动取款机功能的取消。根据hMOF参与ATM功能的事实，MOF片段的表达促进了体外的致癌转化，肿瘤显示H4-K16乙酰化(H4-K16Ac)缺失，我们推测hMOF参与了肿瘤的发生。在拟议的工作中，我们将通过小鼠多器官功能因子(MMof)在小鼠细胞系统中的功能特征以及mMof单倍体缺陷和条件基因敲除小鼠的病理生物学来确定多器官功能衰竭与肿瘤发生之间的联系。体外研究将确定ATM依赖和独立的mMof功能，以响应IR对细胞杀伤、DNA损伤修复和致癌转化的反应。H4-K16Ac缺失对小鼠肿瘤发展易感性的影响将在mMof单倍体不足或mMof条件性基因敲除小鼠中确定。这项建议中描述的实验将研究mMof、H4-K16Ac和自发以及IR诱导的肿瘤形成之间的功能联系。这些研究将提高我们对mMof在IR反应和肿瘤发生中的作用的理解。最终，了解正常组织和肿瘤组织染色质结构的生化差异的基础可以提供调整对IR的反应的策略，这可能在临床放射治疗中有用。

DESCRIPTION (provided by applicant): Understanding the role of chromatin modifying factors in response to ionizing radiation (IR) will provide invaluable insights into questions of both how cancers start and how to cure cancers. The ATM (ataxia-telangiectasia mutated) protein is a major participant in .all cellular responses to IR. We have been studying the role of ATM in DNA damage repair, telomere chromatin structure and oncogenic transformation. Cells deficient in ATM have defects in DNA repair, display altered telomere chromatin structure and have a higher frequency of spontaneous as well as IR-induced oncogenic transformation. Recently, we identified a chromatin-modifying factor "hMOF", the human ortholog of the Drosophila MOF gene (Males absent On the First) which interacts with ATM. hMOF has histone acetyltransferase (HAT) activity. Cellular exposure to IR enhances hMOF-dependent acetylation of its target substrate, lysine 16 of histone H4 (H4- K16), independent of ATM function. Inactivation of hMOF results in abrogation of ATM function. Based on the facts that hMOF is involved in ATM function, expression of MOF fragment enhances oncogenic transformation in vitro and that tumors show loss of H4-K16 acetylation (H4-K16Ac), we hypothesize that hMOF is involved in tumorigenesis. In the proposed work, we will determine the link between MOF and tumorigenesis by the functional characterization of mouse Mof (mMof) in a murine cell system and pathobiology of mMof haploinsufficient and mMof conditional knockout mice. The in vitro studies will determine Atm dependent and independent mMof functions in response to IR for cell killing, DNA damage repair and oncogenic transformation. The impact of the loss of H4-K16Ac on the predisposition of mouse tumor development will be determined in mMof haploinsufficiency or mMof conditional knockout mice. Experiments described in this proposal will investigate the functional links among mMof, H4-K16Ac and spontaneous as well as IR-induced tumor formation. These studies will improve our understanding of the role of mMof in the IR response and tumorigenesis. Ultimately, understanding the basis for biochemical differences in chromatin structure between normal and tumor tissue could provide strategies for modifying the response to IR that could be useful in clinical radiation therapy.