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和如何治疗癌症提供宝贵的见解。ATM（共济失调毛细血管扩张突变）蛋白是一个主要的参与者。所有细胞对红外线的反应我们一直在研究ATM在DNA损伤修复、端粒染色质结构和致癌转化中的作用。缺乏ATM的细胞具有DNA修复缺陷，显示端粒染色质结构改变，并且具有更高频率的自发和红外诱导的致癌转化。最近，我们发现了一个与ATM相互作用的染色质修饰因子“hMOF”，它是果蝇MOF基因（male absent On the First）的人类同源基因。hMOF具有组蛋白乙酰转移酶（HAT）活性。细胞暴露于IR增强了hmof依赖的目标底物乙酰化，组蛋白H4的赖氨酸16 (H4- K16)，独立于ATM功能。hMOF的失活导致ATM功能的丧失。基于hMOF参与了ATM功能，MOF片段的表达增强了体外的癌性转化，以及肿瘤表现出H4-K16乙酰化（H4-K16Ac）的缺失，我们假设hMOF参与了肿瘤的发生。在这项工作中，我们将通过小鼠细胞系统中MOF （mMof）的功能表征以及mMof单倍不足和mMof条件敲除小鼠的病理生物学来确定MOF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在响应IR的细胞杀伤、DNA损伤修复和致癌转化方面的功能。H4-K16Ac缺失对小鼠肿瘤发展易感性的影响将在mMof单倍不全或mMof条件敲除小鼠中确定。本实验将探讨mMof、H4-K16Ac与自发和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之间染色质结构的生化差异的基础可以为改变对IR的反应提供策略，这在临床放射治疗中可能是有用的。

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.