Telomere maintainance by werner syndrome family proteins

描述(申请人提供)：细胞衰老和细胞凋亡被认为与哺乳动物的年龄相关疾病有关，可由严重缩短的端粒引起，因此端粒没有上限。在人类中，端粒缩短伴随着衰老，而且越来越多的证据表明，端粒缩短会损害组织的动态平衡。虽然端粒酶维持端粒的作用已为人们所熟知，但其他端粒维持途径的作用还不是很清楚。人类Werner程序性综合征是由WRN RecQ家族解旋酶缺乏引起的，其特征是端粒维持缺陷。几条研究路线，包括我们自己对小鼠WRN和酿酒酵母同源物SGS1的工作，表明了RecQ解旋酶通过基于同源重组(HR)和基于G-四链(G4)DNA的机制在端粒维持中的作用。在这里，我们将研究端粒维持的新方面，涉及RecQ解旋酶、G4-DNA和HR。这些研究将有三个特定的目的：1)确定SAS2编码的组蛋白乙酰转移酶的缺失以一种依赖于HR的方式延长端粒酶突变体的寿命的机制；2)研究SGS1的缺失如何使缺乏端粒酶和同源重组的细胞形成端粒丢失的幸存者；以及3)检验RecQ解旋酶可以通过调节G4-DNA的形成来调节端粒维持机制的假设。这些目标将在酿酒酵母中实现，它提供了一个实验上易于处理的模型，在其中剖析机制，然后从酵母中发现的结果将在小鼠以及培养的小鼠和人类细胞中进行测试。将通过使用已建立的遗传、生化、药理学、分子和细胞生物学方法来探索这一机制。了解RecQ解旋酶、HR、G4-DNA和组蛋白乙酰转移酶如何协同调节端粒的维持，将为衰老和癌症生物学提供新的见解，并将为未来旨在治疗年龄相关疾病和恶性肿瘤的疗法的发展提供新的靶点。与公共健康相关：端粒是染色体的末端，在衰老和癌症的发展中发挥着重要作用。我们正在研究维持端粒的新机制，包括1)RecQ亚型DNA解旋酶的作用，当不存在时，可能导致人类过早衰老和癌症疾病，2)同源重组的作用，以及3)称为G-四链的不寻常DNA结构的作用。这些研究将有助于阐明维持端粒的机制，从而有助于确定治疗包括癌症在内的衰老疾病的新靶点。

DESCRIPTION (provided by applicant): Cell senescence and apoptosis are thought to contribute to age-related diseases in mammals, and can be induced by critically shortened and thus uncapped telomeres. In humans, telomere shortening accompanies aging, and there is increasing evidence that shortening impairs tissue homeostasis. While maintenance of telomeres by telomerase is well understood, the roles of other telomere maintenance pathways are less well defined. The human Werner progeroid syndrome, caused by deficiency of the WRN RecQ-family helicase, is characterized by defects in telomere maintenance. Several lines of investigation, including our own work with mouse WRN and the S. cerevisiae homolog Sgs1, indicate roles for RecQ helicases in telomere maintenance by homologous recombination (HR)-based and G-quadruplex (G4) DNA-based mechanisms. Here we will investigate novel aspects of telomere maintenance involving RecQ helicases, G4-DNA, and HR. These will be investigated in three specific aims: 1) Determine the mechanisms by which deletion of the histone acetyltransferase encoded by SAS2 extends, in an HR- dependent fashion, the lifespan of telomerase mutants, 2) Investigate how the absence of Sgs1 enables cells lacking telomerase and homologous recombination to form survivors of telomere loss, and 3) Test the hypothesis that RecQ helicases can modulate telomere maintenance mechanisms via regulation of G4-DNA formation. These aims will be carried in S. cerevisiae, which provides an experimentally tractable model in which to dissect mechanisms, and findings from yeast will then be tested in mice and cultured murine and human cells. Mechanism will be explored through the use of established genetic, biochemical, pharmacological, molecular and cell biological approaches. Understanding how RecQ helicases, HR, G4-DNA, and histone acetyltransferases collaborate to regulate telomere maintenance will offer new insights into aging and cancer biology, and should provide new targets for the future development of therapeutics aimed at treating age- related diseases and malignancies. PUBLIC HEALTH RELEVANCE: Telomeres, the ends of chromosomes, play important roles in aging and the development of cancer. We are studying novel mechanisms by which telomeres are maintained, including 1) roles for the RecQ subtype of DNA helicase that, when absent, can lead to human premature aging and cancer diseases, 2) roles for homologous recombination and 3) roles for unusual DNA structures called G-quadruplexes. These studies will help illuminate mechanisms by which telomeres are maintained and will thus help identify new targets for treating diseases of aging, including cancer.