Chromatin's Role in Repair of Radiation-induced Damage.

描述（由申请人提供）：本研究的目的是确定染色质在辐射诱导的双链断裂（DSBs）修复过程中所起的基本作用。细胞存活和基因组完整性的维持严重依赖于dsb的修复。如果修复不正确，dsb会导致染色体重排等畸变，并可能导致癌症的形成。为了充分了解辐射诱导的dsb修复，考虑自然环境-染色质是很重要的。基因组包装成染色质可能会影响DNA修复过程，类似于基因表达的情况。因此，我们发现染色质组装因子Asf1和ca -1对于体内辐射诱导的内源性和发育程序性DNA损伤修复后的细胞存活至关重要。此外，我们最近首次表明，在DSB修复过程中，通过同源重组途径，组蛋白乙酰化会局部改变，如果在DSB修复过程中不能改变其乙酰化状态，细胞就会死亡。我们将测试组蛋白的特定翻译后修饰，染色质的重塑，拆卸和重组在修复过程中发生在DSB的假设。此外，我们将定义分子机制，为什么这些染色质动力学是必不可少的和内在的染色体修复。最后，我们将确定对DSB修复至关重要的新的染色质修饰。为了深入了解辐射诱导DNA损伤的修复，该方法将在酵母内同步诱导高度特异性的核酸内切酶来研究独特定义的DSB上的分子事件。使用这个模型系统，我们将绘制出在DSB修复之前、伴随和之后的染色质结构的变化。这些实验结果将为理解辐射诱导的dsb修复过程中染色质结构的基本作用提供基础。因此，这些研究直接适用于因辐射引起的基因组完整性丧失而导致的人类疾病，包括许多形式的癌症。

DESCRIPTION (provided by applicant): The goal of this research is to define the fundamental role that chromatin plays during the repair of radiation-induced double-strand breaks (DSBs). Cell survival and maintenance of genome integrity are critically dependent on the repair of DSBs. If repaired incorrectly, DSBs result in aberrations such as chromosomal rearrangements and can lead to formation of cancers. In order to fully understand the repair of radiation-induced DSBs, it is important to consider the natural context - chromatin. The packaging of the genome into chromatin is likely to influence DNA repair processes by analogy to the situation with gene expression. Accordingly, we have discovered that the chromatin assembly factors Asf1 and CAF-1 are essential for cell survival following the repair of radiation-induced, endogenous and developmentally-programmed DNA damage in vivo. Furthermore, we have recently shown for the first time that histone acetylation changes locally during DSB repair via the homologous recombination pathway, and that cells die if they cannot change their acetylation state during DSB repair. We will test the hypothesis that specific post- translational modifications of histones, remodeling, disassembly, and reassembly of the chromatin occur at the DSB during repair. Furthermore, we will define the molecular mechanism as to why these chromatin dynamics are essential and intrinsic to chromosomal repair. Finally, we will identify novel chromatin modifications that are critical for DSB repair. In order to gain insight into the repair of radiation-induced DNA damage, the approach will be to synchronously induce a highly specific endonuclease within yeast to study the molecular events at a unique defined DSB. Using this model system, we will map the changes to the chromatin structure that precede, accompany and follow the repair of a DSB. The findings of the proposed experiments will provide the foundation for understanding the fundamental, yet poorly understood, role of chromatin structure during the repair of radiation-induced DSBs. As such, these studies are directly applicable to human diseases that result from radiation-induced loss of genome integrity, including many forms of cancer.