Role of nuclear architecture in the spatial and temporal dynamics of heterochromatin repair

总结 提高我们对着丝粒周围异染色质修复的认识是一项高影响力的投资， 人类健康：异染色质是一个特征性很差的区域，占人类染色体的近三分之一。 基因组;该区域的双链断裂（DSB）修复失败不仅影响特定基因， 全基因组的稳定性;失败的风险很高，因为有大量的重复序列， 描述了该领域的特征。尽管描述这些过程的基本重要性，DSB 异染色质中的修复机制大多是未知的。我们最近发现了一种特殊的途径 促进异染色质中的忠实同源重组（HR）修复，同时防止大规模的 基因组不稳定性我们发现Smc 5/6复合体在这一通路中起着关键作用，但这种复合体如何在细胞内发挥作用呢？ 参与异染色质修复是未知的。异染色质修复的失调可能是 最被低估和强大的肿瘤发生的来源，并确定所涉及的成分是 对于了解癌症病因和开发更有效的治疗策略至关重要 干预为了深入了解Smc 5/6在异染色质修复中的作用，我们使用质谱法， 确定这一综合体的新的相互作用者，这将在本提案中进一步研究。我们的中央 假设修复分三步进行：初始阶段，HR异常进展， 在异染色质结构域内受到抑制;第二阶段，修复位点重新定位到细胞核 第三阶段，其特征在于去除了在核上对HR进展的阻滞。 外围我们将在果蝇细胞中结合联合收割机大量的成像、遗传和生物化学方法， 生物体，以确定参与这些步骤的分子靶点，并确定它们在空间和 异染色质修复的时间调节。这项研究的预期积极成果包括： 保护异染色质免受大规模基因组伤害的分子机制的系统鉴定 重新安排，使成功完成人力资源修复。这些研究也有望阐明 核结构和动力学、修复进展、RNAi沉默途径之间缺少联系， 重复DNA序列的稳定性。这些结果将产生重要的积极影响， 正常细胞用来保护基因组免受环境威胁的重要保护机制。 这些途径中的突变导致基因组不稳定、肿瘤发生和寿命缩短。因此我们 预计拟议的研究和未来的研究将引发令人兴奋的进展，在预防，早期 检测和治疗癌症和其他与基因组不稳定性和衰老相关的人类疾病- 相关疾病。

SUMMARY Advancing our knowledge of pericentromeric heterochromatin repair is a high impact investment for improving human health: heterochromatin is a poorly characterized region that comprises nearly a third of the human genome; double-strand break (DSB) repair failures in this region affect not just specific genes but also genome-wide stability; and failures here are a high risk because of the abundance of repeated sequences that characterizes this domain. In spite of the foundational importance of characterizing these processes, DSB repair mechanisms in heterochromatin are mostly unknown. We recently discovered a specialized pathway that promotes faithful homologous recombination (HR) repair in heterochromatin while preventing massive genome instability. We discovered a critical role of the Smc5/6 complex in this pathway, but how this complex participates in heterochromatin repair is unknown. Deregulation of heterochromatin repair is likely one of the most underestimated and powerful sources of tumorigenesis, and identifying the components involved is essential for understanding cancer etiology and developing more effective strategies for therapeutic intervention. To gain insight into the role of Smc5/6 in heterochromatin repair, we used mass spectroscopy to identify new interactors of this complex, which will be further investigated in this proposal. Our central hypothesis is that repair occurs in three steps: an initial phase when abnormal progression of HR is suppressed inside the heterochromatin domain; a second phase when repair sites relocalize to the nuclear periphery; and a third phase characterized by the removal of the block to HR progression at the nuclear periphery. We will combine a wealth of imaging, genetic and biochemical approaches in Drosophila cells and organisms to identify the molecular targets involved in these steps, and determine their role in the spatial and temporal regulation of heterochromatin repair. Expected positive outcomes of this research include the first systematic identification of the molecular machinery that protects heterochromatin from massive genome rearrangements, enabling successful completion of HR repair. These studies are also expected to illuminate missing links between nuclear architecture and dynamics, repair progression, RNAi silencing pathways, and the stability of repeated DNA sequences. These results will have an important positive impact by identifying crucial safeguard mechanisms used by normal cells to protect the genome from environmental threats. Mutations in these pathways result in genome instability, tumorigenesis, and reduced life span. Thus, we expect that the proposed studies and future research will trigger exciting advancements in the prevention, early detection, and treatment of cancer and other human diseases associated with genome instability and aging- related disorders.