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是未知的。我们最近出人意料的新发现，着色性干皮病A组(XPA)可能参与了椎板病所致的早衰，典型的Hutchinson-Gilford早衰症(HGPS)，为解决这一具有挑战性的问题打开了机会。有趣的是，最近发现与层蛋白A相关的导致HGPS的分子机制在人类衰老过程中也很活跃。虽然XPA是一种专门参与核苷酸切除修复(NER)的蛋白质，但我们的初步数据显示，XPA功能障碍地定位于椎板病早衰细胞中的DSB位点，这意味着可能阻止DSB修复蛋白募集到损伤部位进行修复。引人注目的是，siRNA敲除了黄体细胞中的XPA，部分恢复了DSB修复。本项目的目标是阐明DSB积累的分子基础和XPA在椎板病相关的过早衰老，特别是HGPS和衰老中的作用，并在了解过早衰老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在加速衰老的发展中起重要作用的主要假设。本研究将在五个特定目标下进行：(1)阐明XPA-DSB在早衰细胞中错位的分子基础；(2)确定XPA-DSB错位对细胞DNA损伤反应的影响。由于其新颖性和潜在影响，该项目可能会涉及相当大的风险，但代表着一项高度创新的努力，有可能导致在理解过早衰老和衰老的机制方面取得突破，这非常符合小额赠款计划试点或可行性研究的主题。公共卫生相关性：老龄化是一种正常但令人困惑的生物过程，它不仅支配着人类的寿命，而且由于老年病的发展而显著降低了生活质量。另一方面，早衰等异常衰老是破坏性早衰病的典型表型。虽然人们认为导致过早衰老和衰老的主要原因之一是细胞内DNA损伤的积累，但其潜在的分子机制仍不清楚。该项目是一项具有长期目标的初步或试点工作，旨在阐明人类过早衰老和衰老的机制，并为未来更好地治疗早衰症和老年病的新战略的开发提供分子基础。

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.