CHROMATIN MODIFYING FACTORS CONTROL RADIATION RESPONSE AND GENOMIC STABILITY

描述（由申请人提供）：在真核细胞中，电离辐射（IR）诱导的DNA损伤激活信号转导途径，迅速影响下游过程，如基因转录、细胞周期进程和DNA复制。所有这些过程都需要染色质改变以允许DNA进入。几年来，我们一直在研究ATM（共济失调毛细血管扩张症突变）在DNA损伤修复和端粒染色质结构维持中的作用。缺乏ATM的细胞在DNA修复方面有缺陷，并显示端粒染色质结构改变。最近，我们已经确定了一个染色质修饰因子“hMOF”的人类直系同源的果蝇MOF基因（男性缺席的第一），这是必不可少的早期胚胎存活在小鼠。hMOF具有与ATM相互作用的染色体结构域和组蛋白乙酰转移酶（HAT）活性。细胞暴露于IR增强其靶底物，组蛋白H4的赖氨酸16（K16）的hMOF依赖性乙酰化，独立于ATM功能。然而，hMOF的失活导致ATM自磷酸化、ATM激酶活性和DNA修复的消除，同时增加IR暴露后的细胞杀伤。基于这些初步的研究，hMOF参与IR依赖的ATM激活，我们推测，hMOF有多种作用，除了参与DNA损伤诱导的ATM激活的调节。在这项工作中，我们将确定ATM独立的hMOF在细胞存活，DNA DSB修复和端粒代谢的IR反应中的作用。本提案中描述的实验将研究hMOF和IR响应之间的功能联系。我们将研究hMOF影响基因组不稳定性的机制。这些研究将提高我们对hMOF在端粒染色质结构、DNA DSB修复中的作用以及MOF在IR反应中的ATM独立作用的理解。最终，了解hMOF和ATM之间的联系可以提供修改对IR的反应的策略，这可能在临床放射治疗中有用，因为肿瘤细胞和正常细胞在染色质结构和端粒代谢方面存在显着差异。公共卫生相关性：该项目将定义hMOF在细胞对电离辐射的反应、端粒代谢和DNA修复中的作用。这些研究结果将进一步加深我们对hMOF如何参与识别、信号传导和修复双链断裂的理解。此外，这项研究将提供机制的基础，了解如何染色质屏障DNA访问的hMOF活性调节，以确保端粒的维护和修复的DNA双链断裂。因此，理解这些机制对于癌症预防以及发展策略以优化关于共济失调-毛细血管扩张症疾病的靶向和组合治疗方案都是至关重要的。

DESCRIPTION (provided by applicant): In eukaryotic cells, ionizing radiation (IR) induced DNA damage activates signal transduction pathways that rapidly affect downstream processes such as gene transcription, cell-cycle progression and DNA replication. All of these processes require chromatin alterations to allow for DNA access. For several years we have been studying the role of the ATM (mutated in ataxia-telangiectasia) in DNA damage repair and maintenance of telomere chromatin structure. Cells deficient in ATM have defects in DNA repair and display altered telomere chromatin structure. Recently, we have identified a chromatin-modifying factor "hMOF" the human ortholog of Drosophila MOF gene (males absent on the first) that is essential for early embryonic survival in mice. hMOF has a chromodomain and histone acetyltransferase (HAT) activity that interacts with ATM. Cellular exposure to IR enhances hMOF-dependent acetylation of its target substrate, lysine 16 (K16) of histone H4, independent of ATM function. However, inactivation of hMOF results in abrogation of ATM autophosphorylation, ATM kinase activity and DNA repair while increasing cell killing after IR exposure. Based on these preliminary studies, that hMOF participates in the IR-dependent activation of ATM, we hypothesize that hMOF has multiple roles in addition to being involved in the regulation of DNA damage-induced ATM activation. In the proposed work, we will determine ATM independent role of hMOF in IR response for cell survival, DNA DSB repair and telomere metabolism. Experiments described in this proposal will investigate the functional links between hMOF and IR response. We will investigate mechanisms by which hMOF influences genomic instability. These studies will improve our understanding of the role of hMOF in telomere chromatin structure, DNA DSB repair and, ATM independent role of the MOF in IR response. Ultimately, understanding the links between hMOF and ATM could provide strategies for modifying the response to IR that could be useful in clinical radiation therapy, since tumor cells and normal cells have significant differences in their chromatin structure and telomere metabolism. PUBLIC HEALTH RELEVANCE: This project will define the role of hMOF in the cellular response to ionizing radiation, telomere metabolism and DNA repair. The results of the proposed studies will further our understanding of how hMOF is involved in recognizing, signaling and repairing double-strand breaks. In addition this study will provide the mechanistic basis for understanding how the chromatin barrier to DNA access is regulated by hMOF activity to ensure telomere maintenance and repair of DNA DSBs. Thus understanding these mechanisms is critical to both cancer prevention as well as development of strategies to optimize targeted and combinatorial treatment regimens with regard to the disease Ataxia- Telangiectasia.