Role of the Werner syndrome protein complex in the metabolism of chromosome ends

描述（由申请人提供）：本研究的目的是获得关于Werner综合征蛋白（WRN）复合物在维持端粒完整性和防止染色体外端粒环形成过程中功能的机制见解。WRN是一种具有解旋酶和核酸外切酶活性的核蛋白，其功能丧失突变与过早衰老和癌症易感性疾病Werner综合征（WS）相关。遗传和生化证据牵连WRN在端粒代谢，并建议异常的端粒长度稳态的病理WS。我们的生化研究表明，WRN作为一个功能单位与Ku 70/80异二聚体，并进一步证明，WRN功能的损失导致生产的端粒环在成纤维细胞表达端粒酶。为了确定WRN复合物调节端粒稳态的机制，我们建议机械地表征WRN，Ku和染色体末端发现的端粒特异性因子之间的功能相互作用，并定义由负责端粒环形成的WRN功能丧失激活的过程。为了实现这些目标，我们提出以下三个目标。在目的1中，我们将描述WRN及其相互作用伙伴Ku 70/80在人类细胞端粒末端调控中的作用。在目标2中，我们将剖析由于WRN功能丧失导致染色体外t环形成的分子机制。在目标3中，我们将在体外模型端粒底物的背景下表征WRN的生化特性。本申请中提出的研究将阐明WRN在端粒中的作用，并为理解WRN功能的丧失如何促进基因组不稳定性、过早衰老以及癌症和心血管疾病等疾病的早期发作提供有价值的信息。人们认识到，这些疾病的发病率随着年龄的增长而逐渐增加。因此，在衰老过程中发生的分子、细胞和生理水平的变化深刻地影响这些疾病的发生和发展。WRN的功能分析将提供对这些变化的更清晰的理解，并将有助于开发旨在预防年龄相关疾病早期发作的治疗药物。

DESCRIPTION (provided by applicant): The goal of this study is to gain mechanistic insights on the function of the Werner syndrome protein (WRN) complex in the processes that maintain telomere integrity and prevent the formation of extrachromosomal telomeric circles. WRN is a nuclear protein with helicase and exonuclease activities, whose loss-of-function mutations are associated with the premature aging and cancer prone disease Werner syndrome (WS). Genetic and biochemical evidence implicate WRN in telomere metabolism and suggest that abnormal telomere length homeostasis contributes to the pathology of WS. Our biochemical studies have shown that WRN operates as a functional unit with the Ku70/80 heterodimer and have further demonstrated that loss of WRN function causes the production of telomeric circles in fibroblasts expressing telomerase. To determine the mechanism whereby the WRN complex regulates telomere homeostasis, we propose to mechanistically characterize the functional interplay between WRN, Ku and telomere-specific factors found at chromosome ends and define the process activated by loss of WRN function responsible for the formation of telomeric circles. To accomplish these objectives we propose the following three aims. In Aim 1, we will characterize the role of WRN and its interacting partner Ku70/80 in the regulation of telomeric termini in human cells. In Aim 2, we will dissect the molecular mechanisms leading to the formation of extrachromosomal t- circles resulting from loss of WRN function. In Aim 3, we will characterize the biochemical properties of WRN in the context of model telomeric substrates in vitro. The studies proposed in this application will elucidate the role of WRN at telomeres and provide valuable information for understanding how loss of WRN function promotes genome instability, premature aging and the early onset of diseases such as cancer and cardiovascular disease. It is recognized that the incidence of these diseases increases progressively with age. Therefore, the changes at the molecular, cellular and physiologic levels that occur during aging profoundly influence the development and progression of these diseases. Functional analysis of WRN will provide a clearer understanding of these changes and will help in the development of therapeutic agents aimed at preventing the early onset of age-associated diseases.