DNA Double Strand Break Chromatin Alterations and Genome Integrity

描述(申请人提供)：在人类癌症中，染色体大体重排是突出的，特殊的细胞遗传学异常导致血液系统、甲状腺、前列腺癌和肺癌。虽然这种染色体异常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，就会出现一种特别危险的情况。这些发现表明，维持基因组的完整性需要DNA修复和局部转录事件之间的协调。我们已经报道，双链断裂抑制了DNA损伤部位染色质连续伸展上的转录。沉默需要ATM激酶活性和组蛋白H_2A泛素化。我们通过发现DSB相关的SUMO化对DSB沉默是必不可少的，从而扩展了这些发现。这些研究中一个有趣的观察是，ATM依赖的DSB沉默阻止了转录依赖的染色质移动，这一功能可能与基因组完整性控制有关。这一建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依赖的染色质改变如何促进顺式到DSB的转录基因沉默？(Ii)DSB染色质改变是否通过反对RNAPII驱动的染色质运动来促进准确的DNA修复机制？总的来说，这些问题将解决基因组完整性和辐射生物学中的基本问题，这些问题与DSB染色质反应和转录之间的通信有关。

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.