Telomere Structure and Function in Arabidopsis

描述（由申请人提供）：端粒是高级核蛋白 这些结构覆盖在染色体末端， 基因组完整性在具有无限增殖能力的细胞中，包括95 百分之二十的人类癌症，端粒是由端粒酶维持的。相比之下， 正常索马和端粒的大多数细胞中不存在端粒酶 不可避免地缩短，直到染色体末端变得无帽且难以区分 双链断裂诱导端到端融合，最终导致 到细胞周期停滞在这里，我们建议利用阿拉伯idopsis阐明 端粒帽的结构和功能，以更好地了解该设备如何 为基因组提供稳定性，并促进细胞持续增殖。 我们的初步结果表明，拟南芥具有异常高的 对端粒功能障碍的耐受性。这一发现，加上fascile 拟南芥的遗传学，其完全测序的基因组，以及 转基因工具表明，该系统可以提供独特的机会， 用于研究端粒生物学中的必需基因。前两个目标 该提案利用了我们开发的端粒聚合酶缺陷的拟南芥模型， 探测有帽染色体和无帽染色体之间的分子过渡。在Aim中 我们将检测端粒重组的频率， 缩短但有功能的端粒我们还将确定 体细胞和减数分裂重组到端粒的维持， 端粒酶在目标2中，我们将探索端粒融合的机制， 对染色体连接处的DNA进行测序，并通过评估DNA的作用 非同源末端连接途径。遗传策略也是 建议检查携带染色体融合的细胞的繁殖。的 后两个目标集中在形成染色体帽的蛋白质上。在目标3中，我们 通过以下方法检测拟南芥中两个假定的Pot1直系同源物的功能： 阐明它们的DNA结合特性和分子伴侣， 确定过度表达和基因破坏的后果。在目标4中， 描述了生物化学和遗传学方法来发现 促进染色体加帽。因为几乎所有哺乳动物的基因 在端粒内稳态中有一个拟南芥的对应物，这些实验 应该能揭示所有多细胞生物的共同机制

DESCRIPTION (provided by applicant): Telomeres are higher order nucleoprotein structures that physically cap the chromosome terminus and help to perserve genome integrity. In cells with unlimited proliferative capacity, including 95 percent of human cancers, telomeres are maintained by telomerase. By contrast, telomerase is absent from most cells of the normal soma and telomeres inexorably shorten until chromosome ends become uncapped and indistinguishable from double strand breaks. End-to-end fusions are induced, ultimately leading to cell cycle arrest. Here we propose to exploit Arab idopsis to elucidate the structure and function of the telomere cap to better understand how this device provides stability to the genome, and facilitates continued cell proliferation. Our preliminary results indicate that Arabidopsis has an exceptionally high tolerance for telomere dysfunction. This finding, coupled with the fascile genetics of Arabidopsis, its completely sequenced genome, and arsenal of transgenic tools demonstrate that this system can offer unique opportunities for investigating essential genes in telomere biology. The first two goals of the proposal exploit the telomerase-deficient Arabidopsis model we developed to probe the molecular transition between capped and uncapped chromosomes. In Aim I, we will examine the frequency of telomere recombination in cells with shortened, but functional telomeres. We will also determine the contribution of somatic and meiotic recombination to telomere maintenance in the absence of telomerase. In Aim 2, we will explore the mechanism of telomere fusions by sequencing DNA at chromosome junctions, and by assessing the role of the non-homologous end-joining pathway in this process. A genetic strategy is also proposed to examine the propagation of cells harboring chromosome fusions. The last two aims focus on proteins that form the chromosome cap. In Aim 3, we will examine the function of two putative Pot1 orthologs in Arabidopsis by elucidating their DNA binding properties and molecular partners, and by determining the consequences of over-expression and gene disruption. In Aim 4, biochemical and genetic approaches are described to discover genes that facilitate chromosome capping. Because virtually every mammalian gene involved in telomere homeostasis has an Arabidopsis counterpart, these experiments should uncover mechanisms common to all multicellular organisms.