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) 反应中的作用将为了解癌症如何发生以及如何治愈癌症的问题提供宝贵的见解。 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。缺乏 ATM 的细胞在 DNA 修复方面存在缺陷，显示端粒染色质结构改变，并且具有更高频率的自发以及 IR 诱导的致癌转化。最近，我们鉴定了一种染色质修饰因子“hMOF”，它是果蝇 MOF 基因（雄性先缺失）的人类直系同源物，与 ATM 相互作用。 hMOF 具有组蛋白乙酰转移酶 (HAT) 活性。细胞暴露于 IR 会增强其靶底物、组蛋白 H4 (H4-K16) 赖氨酸 16 的 hMOF 依赖性乙酰化，与 ATM 功能无关。 hMOF 失活导致 ATM 功能失效。基于hMOF参与ATM功能、MOF片段的表达增强体外致癌转化以及肿瘤显示H4-K16乙酰化(H4-K16Ac)丧失的事实，我们假设hMOF参与肿瘤发生。在拟议的工作中，我们将通过小鼠细胞系统中小鼠 Mof (mMof) 的功能表征以及 mMof 单倍体不足和 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 功能，以响应 IR 的细胞杀伤、DNA 损伤修复和致癌转化。 H4-K16Ac 缺失对小鼠肿瘤发展倾向的影响将在 mMof 单倍剂量不足或 mMof 条件敲除小鼠中确定。该提案中描述的实验将研究 mMof、H4-K16Ac 与自发以及 IR 诱导的肿瘤形成之间的功能联系。这些研究将增进我们对 mMof 在 IR 反应和肿瘤发生中作用的理解。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提供改变对 IR 反应的策略，这在临床放射治疗中可能有用。

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.