Roles of nuclear architecture and phase separation in heterochromatin repair dynamics

摘要 提高我们对着丝粒周围异染色质修复的认识是一项对改善 人类健康：异染色质是一个特征不佳的区域，占人类的近三分之一 基因组；该区域的双链断裂(DSB)修复失败不仅影响特定基因，还影响 全基因组的稳定性；失败的可能性很高，因为许多重复的序列 描述这一领域的特征。尽管描述这些过程具有基础性的重要性，DSB修复 异染色质的机制在很大程度上还没有得到充分的研究。我们发现了一条专门的途径，可以促进 异染色质中忠实的同源重组(HR)修复，同时防止异常重组， 在链入侵之前，有效地将异染色质修复位点隔离到核外围。我们有 最近确定了这一过程所需的几种成分，包括核肌动蛋白细丝(F-肌动蛋白)和 肌球蛋白和染色质相关的核孔蛋白，但这些成分的调节和功能仍然 人们对此知之甚少。异染色质修复的失调可能是最被低估的和 肿瘤发生的强大来源，并确定所涉及的成分对于理解 癌症病因学和开发更有效的治疗干预策略。我们的中心假设是 F-肌动蛋白、肌球蛋白、核质核孔蛋白和相分离是 异染色质修复动力学，SUMO化参与协调它们在修复中的功能 进步。我们将结合大量的超分辨率成像、遗传和生化方法来 研究这些过程中涉及的分子机制。预计这将产生积极的结果 研究包括系统地鉴定保护异染色质免受 大规模基因组重排，成功完成HR修复。这些研究也是 预计将阐明核结构和动力学、相分离、修复之间缺失的环节 进行性和重复DNA序列的稳定性。这些结果将产生重要的积极影响 通过识别正常细胞用来保护基因组免受环境影响的关键保障机制 威胁。这些途径的突变会导致基因组不稳定、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在预防方面引发令人兴奋的进展， 早期发现和治疗癌症和其他与基因组不稳定和 与衰老相关的疾病。

SUMMARY Advancing our knowledge of pericentromeric heterochromatin repair is a high impact investment for improving human health: heterochromatin is a poorly characterized region comprising 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 the likelihood of failures is high because of the many repeated sequences that characterize this domain. Despite the foundational importance of characterizing these processes, DSB repair mechanisms in heterochromatin are largely understudied. We discovered a specialized pathway that promotes faithful homologous recombination (HR) repair in heterochromatin while preventing aberrant recombination, effectively isolating heterochromatic repair sites to the nuclear periphery before strand invasion. We have recently identified several components required for this process, including nuclear actin filaments (F-actin) and myosins, and chromatin-associated nucleoporins, but the regulation and function of these components remain poorly understood. Dysregulation 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. Our central hypothesis is that F-actin, myosins, nucleoplasmic nucleoporins, and phase separation are essential regulators of heterochromatin repair dynamics, and that SUMOylation participates in coordinating their function in repair progression. We will combine a wealth of super resolution imaging, genetic and biochemical approaches to investigate the molecular mechanisms involved in these processes. Expected positive outcomes of this research include the 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, phase separation, repair progression, 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.