Mechanism of Nuclear Defects in Hutchinson-Gilford Progeria Syndrome

描述（由申请人提供）：DNA双链断裂（DSB）的细胞积累已被广泛认为是导致过早衰老、细胞衰老和衰老的标志性步骤。然而，DSB如何在具有完整DSB修复基因的细胞中积累仍然未知。我们最近意外的新发现可能涉及着色性干皮病A组（XPA）在核纤层蛋白病为基础的过早衰老，典型的哈钦森-吉尔福德早衰综合征（HGPS），打开了一个机会，以解决这个具有挑战性的问题。有趣的是，同样的核纤层蛋白A相关的分子机制负责HGPS最近被发现在人类衰老中是活跃的。虽然XPA，一种专门参与核苷酸切除修复（NER）的蛋白质，在DSB修复中没有作用，但我们的初步数据显示，XPA功能失调地定位于基于核纤层蛋白病的早衰细胞中的DSB位点，这意味着DSB修复蛋白招募到损伤位点进行修复的可能性被阻断。引人注目的是，siRNA敲除早衰样细胞中的XPA部分恢复了DSB修复。该项目的目标是描述DSB积累的分子基础和XPA在核纤层蛋白病相关的早衰，特别是HGPS和衰老中的作用，并在了解早衰和衰老的基本机制方面取得潜在的重大进展。我们将检验XPA在加速老化发展中起重要作用的主要假设。本研究主要有五个目的：（1）阐明XPA-DSB在早衰细胞中错误定位的分子基础;（2）确定XPA-DSB错误定位对细胞DNA损伤反应的影响。由于其新奇和潜在的影响，该项目可能涉及相当大的风险，但代表了高度创新的努力，有可能导致在理解过早衰老和衰老机制方面取得突破，这非常适合小额赠款计划的试点或可行性研究的主题。 公共卫生相关性：衰老是一个正常但令人困惑的生物学过程，它不仅支配着人类的寿命，而且由于老年疾病的发展而显着降低了生活质量。另一方面，异常衰老如过早衰老是毁灭性早衰症疾病的典型表型。虽然人们认为，过早衰老和衰老的主要原因之一是细胞中DNA损伤的积累，但潜在的分子机制仍然难以捉摸。该项目是一项初步或试点工作，其长期目标是阐明人类早衰和衰老的机制，并为未来开发更好地治疗早衰症和老年病的新策略提供分子基础。

DESCRIPTION (provided by applicant): Cellular accumulation of DNA double strand breaks (DSBs) has been widely suggested to be a hallmark step leading to premature aging, cellular senescence, and aging. However, how DSB can accumulate in the cells that have intact DSB repair genes remains unknown. Our recent unexpected novel findings on the possible involvement of xeroderma pigmentosum group A (XPA) in the laminopathy-based premature aging, typically Hutchinson-Gilford progeria syndrome (HGPS), open an opportunity to address this challenging question. Interestingly, the same lamin A-related molecular mechanism responsible for HGPS was recently found to be active in human aging. Although XPA, a protein exclusively involved in nucleotide excision repair (NER), has no role in DSB repair, our preliminary data showed that XPA dysfunctionally localizes to DSB sites in laminopathy-based premature aging cells, implying the possible blockage of the recruitment of DSB repair proteins to the damage sites for repair. Strikingly, siRNA knockdown of XPA in the progeroid cells partially restored DSB repair. The goal of this project is to delineate the molecular basis of DSB accumulation and the role of XPA in laminopathy-related premature aging, particularly HGPS, and aging, and to gain a potential major advance in understanding the basic mechanisms of premature aging and aging. We will test the main hypothesis that XPA plays an important role in development of accelerated aging. The investigation will be carried out in five Specific Aims: (1) To elucidate the molecular basis of XPA-DSB mislocalization in progeria cells; and (2) To determine the effects of XPA-DSB mislocalization on cellular DNA damage responses. Due to its novelty and potential impact, this project may involve considerable risk but represents a highly innovative effort with the potential to lead to a breakthrough in understanding the mechanism of premature aging and aging, which fits well into the theme of pilot or feasibility studies of the Small Grant Program. Public Health Relevance: Aging which is a normal, but puzzling biological process, not only governs human lifespan, but also significantly reduces the quality of life due to the development of gerontological diseases. On the other hand, abnormal aging such as premature aging is a typical phenotype of devastating progeria diseases. While it is believed that one of the major causes to premature aging and aging is the accumulation of DNA damage in cells, the underlying molecular mechanism remains elusive. This project represents an initial or pilot effort with a long-term goal aiming to delineate the mechanisms of human premature aging and aging, and to provide a molecular basis for future development of novel strategies for better treatment of progeria and gerontological diseases.