Mechanisms of Telomere Cohesion

项目总结/摘要 端粒是染色体末端的特化结构，由TTAGGG重复序列、端粒重复序列和端粒重复序列组成， 含有RNA（TERRA）和shelterin蛋白复合物。姐妹染色单体从那时起就结合在一起 在有丝分裂中被粘附素环分离。环介导的内聚是 在有丝分裂中，确保染色体准确地分配到子细胞中至关重要。姐妹篇之间的凝聚力 对于重组和修复也很重要，特别是在端粒等重复序列中， 他们是一致的。为此，需要更紧密的接触（除了粘附素环之外），因此， 是端粒对凝聚力的特定要求。端粒内聚的建立需要保护 亚基和相关蛋白质。端粒之间的凝聚力的解决需要PARP，端锚聚合酶。 端锚聚合酶在S/G2晚期通过结合TTAGGG重复序列结合的shelterin亚基TRF 1定位于端粒 解决凝聚力。在端锚聚合酶耗尽的细胞中，姐妹端粒在有丝分裂中保持凝聚，尽管正常的端粒在有丝分裂中保持凝聚。 臂和着丝粒的分辨率。这种持久的端粒凝聚力不仅仅是一种异常状态， 由于端锚聚合酶的缺失，它自然发生在某些缺乏端粒酶的人类细胞类型中， 短端粒：正常衰老细胞和癌ALT细胞。出乎意料的是，（我们的实验室在过去的几年里显示， 这种持久的凝聚力对细胞是有益的;它起到保护作用，防止过早衰老 和ALT癌细胞的生长停滞。我们未来五年的研究目标是阐明 建立和解决凝聚力所需的蛋白质和机制。我们将建立在我们以前的 在我们确定了内聚所需的子单元和相关因素的地方工作，我们将 重点放在我们最近的发现表明RNA（TERRA和TERRA R环）在端粒中的作用 凝聚力我们将确定端粒成分如何有助于建立，维持， 正常人类细胞、衰老和癌症中端粒凝聚力的解析。为了建立凝聚力，我们将 确定所需的蛋白质如何以及何时沉积在端粒上，以及进入染色体的距离 它们延伸。对于内聚解决，我们将确定端锚聚合酶的募集如何用于解决内聚。 我们将描述端锚聚合酶本身招募到端粒的蛋白质，并研究端锚聚合酶如何使用 功能划分以协调解决过程。我们将确定TERRA RNA和 TERRA R环有助于正常细胞中端粒的凝聚，并有助于细胞中端粒的持久凝聚。 衰老和ALT癌症的病理状况。最后，我们将阐明完整的蛋白质组的连贯 端粒状态最终，对端粒凝聚力的完整理解将阐明 正常人类细胞中染色体稳定性和基因组完整性的机制， 预防老化细胞的过早衰老和促进ALT癌细胞的过早死亡。

Project Summary/Abstract Telomeres, the specialized structures at chromosome ends, are comprised of TTAGGG repeats, telomere repeat containing RNA (TERRA), and the shelterin protein complex. Sister chromatids are held together from the time of their replication in S phase until their separation in mitosis by cohesin rings. Ring-mediated cohesion is essential to ensure accurate distribution of chromosomes to daughter cells in mitosis. Cohesion between sisters is also important for recombination and repair, particularly at repetitive sequences like telomeres, where it keeps them aligned. For this, more intimate contacts (in addition to the cohesin ring) are needed and as such, there are telomere-specific requirements for cohesion. Establishment of cohesion at telomeres requires shelterin subunits and associated proteins. Resolution of cohesion between telomeres requires the PARP, tankyrase. Tankyrase localizes to telomeres by binding to the TTAGGG-repeat binding shelterin subunit TRF1, in late S/G2 to resolve cohesion. In tankyrase-depleted cells sister telomeres remain cohered in mitosis despite normal resolution of arms and centromeres. This persistent telomere cohesion is not just an aberrant state induced by depletion of tankyrase, it occurs naturally in certain human cell types that lack telomerase and have critically short telomeres: normal aged cells and cancer ALT cells. Unexpectedly, (and shown by our lab in the last few years) this persistent cohesion is beneficial to cells; it serves a protective role to prevent premature senescence in aged cells and growth arrest in ALT cancer cells. The goal of our research for the next five years is to elucidate the proteins and mechanisms required for establishment and resolution of cohesion. We will build on our previous work where we identified shelterin subunits and associated factors that are required for cohesion and we will focus on our most recent discovery indicating a role for RNA (TERRA and TERRA R-Loops) in telomere cohesion. We will determine how the telomeric components contribute to the establishment, maintenance, and resolution of telomere cohesion in normal human cells, aging, and cancer. For cohesion establishment, we will determine how and when the required proteins are deposited on telomeres and how far into the chromosome they extend. For cohesion resolution, we will determine how recruitment of tankyrase serves to resolve cohesion. We will characterize the proteins that tankyrase itself recruits to telomeres and investigate how tankyrase uses functional compartmentalization to orchestrate the resolution process. We will determine how TERRA RNA and TERRA R-loops contribute to telomere cohesion in normal cells and to persistent telomere cohesion in pathological conditions of aging and ALT cancer. And finally, we will elucidate the full proteome of the cohered telomeric state. Ultimately, a complete understanding of telomere cohesion will elucidate fundamental mechanisms of chromosome stability and genome integrity in normal human cells and provide insights into prevention of premature senescence in aging cells and into promotion of premature death in ALT cancer cells.