DNA Double Strand Break Chromatin Alterations and Genome Integrity

描述（由申请方提供）：总体染色体重排在人类癌症中很突出，特定的细胞遗传学异常导致造血系统、甲状腺、前列腺和肺部恶性肿瘤。虽然这种染色体畸变的起源还不完全清楚，但现在有强有力的证据表明，当DNA双链断裂（DSB）发生在活跃转录附近时，会出现特别危险的情况。这些发现表明，基因组完整性的维护需要DNA修复和局部转录事件之间的协调。 我们已经报道了DSB沉默转录连续延伸的染色质顺式DNA损伤位点。沉默需要ATM激酶活性和组蛋白H2A泛素化。我们通过发现DSB相关的SUMO化对于DSB沉默是必不可少的来扩展这些发现。这些研究中一个有趣的观察结果是ATM依赖性DSB沉默阻止转录依赖性染色质移动，这是一种可能与基因组完整性控制相关的功能。 该提议利用几种新的方法来解决与DSB染色质改变和转录之间的相互作用相关的两个主要问题：（i）DSB依赖性染色质改变如何有助于顺式DSB的转录基因沉默？(ii)DSB染色质改变是否通过对抗RNAPII驱动的染色质移动来促进准确的DNA修复机制？总的来说，这些问题将解决与DSB染色质反应和转录之间的通信有关的基因组完整性和辐射生物学的基本问题。

DESCRIPTION (provided by applicant): Gross chromosomal rearrangements are prominent in human cancers, with specific cytogenetic abnormalities contributing to hematopoietic, thyroid, prostate, and lung malignancies. Although the genesis of such chromosomal aberrations is incompletely understood, there is now strong evidence that a particularly dangerous situation arises when DNA double strand breaks (DSBs) occur in proximity to active transcription. These findings suggest that maintenance of genome integrity necessitates coordination between DNA repair and local transcriptional events. We have reported that DSBs silence transcription on contiguous stretches of chromatin in cis to DNA damage sites. Silencing requires ATM kinase activity and histone H2A ubiquitylation. We have extended these findings by discovering that DSB associated SUMOylation is essential for DSB silencing. An interesting observation from these studies is that ATM dependent DSB silencing prevents transcription dependent chromatin movement, a function that may relate to genome integrity control. This proposal utilizes several novel approaches to address two principle questions related to the interplay between DSB chromatin alterations and transcription: (i) How do DSB dependent chromatin alterations contribute to transcriptional gene silencing in cis to DSBs? (ii) Do DSB chromatin alterations promote accurate DNA repair mechanisms by opposing RNAPII driven chromatin movement? Collectively, these questions will address fundamental issues in genome integrity and radiation biology that are related to communication between DSB chromatin responses and transcription.