CHROMATIN MODIFYING FACTORS CONTROL RADIATION RESPONSE AND GENOMIC STABILITY

描述(申请人提供)：在真核细胞中，电离辐射(IR)引起的DNA损伤激活信号转导通路，迅速影响下游过程，如基因转录、细胞周期进展和DNA复制。所有这些过程都需要染色质的改变才能获得DNA。几年来，我们一直在研究ATM(在共济失调-毛细血管扩张中突变)在DNA损伤修复和端粒染色质结构维持中的作用。ATM缺乏的细胞在DNA修复方面存在缺陷，并显示端粒染色质结构改变。最近，我们已经确定了一种染色质修饰因子“hMOF”，它是人类果蝇MOF基因的同源基因(雄性果蝇第一次缺失)，对小鼠早期胚胎存活是必不可少的。HMOF具有与ATM相互作用的染色域和组蛋白乙酰转移酶(HAT)活性。细胞暴露于IR可增强其靶底物组蛋白H4的赖氨酸16(K16)依赖于hMOF的乙酰化，而不依赖于ATM功能。然而，hMOF的失活会导致ATM自磷酸化、ATM激酶活性和DNA修复的丧失，同时增加IR暴露后的细胞杀伤率。在这些初步研究的基础上，hMOF参与了ATM的IR依赖的激活，我们假设hMOF除了参与DNA损伤诱导的ATM激活的调节外，还具有多种作用。在这项拟议的工作中，我们将确定hMOF在IR反应中对细胞存活、DNA DSB修复和端粒代谢的ATM独立作用。本提案中描述的实验将研究hMOF和IR反应之间的功能联系。我们将研究hMOF影响基因组不稳定性的机制。这些研究将加深我们对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非依赖性作用的理解。最终，由于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著差异，了解hMOF和ATM之间的联系可以为改变对IR的反应提供策略，这可能有助于临床放射治疗。公共卫生相关性：该项目将确定hMOF在细胞对电离辐射的反应、端粒新陈代谢和DNA修复中的作用。这些研究的结果将进一步加深我们对hMOF如何参与识别、信号和修复双链断裂的理解。此外，这项研究将为理解hMOF活性如何调节染色质屏障以确保DNA双链断裂的端粒维持和修复提供机制基础。因此，了解这些机制对于癌症预防以及制定针对共济失调-毛细血管扩张症的靶向和联合治疗方案的策略至关重要。

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.