Deciphering the role of heterochromatin in telomere function and maintenance mechanisms

破译异染色质在端粒功能和维持机制中的作用

• 批准号: 10618906
• 负责人: Nausica C. Arnoult
• 金额: $ 38.5万
• 依托单位: UNIVERSITY OF COLORADO
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10618906
• 关键词: Aging; Binding; Biology; Buffers; Cancerous; Cell Aging; Cell Cycle Arrest; Cells; Chromatin; Chromosomes; Code; Complex; Consensus; DNA; DNA Damage; Data; Defect; Development; Enzymes; Genetic Recombination; Genetic Transcription; Genome Stability; Heterochromatin; Histones; Maintenance; Methylation; Mitotic; Nucleoproteins; Nucleosomes; Pathway interactions; Play; Property; Proteins; Regulation; Role; Signal Transduction; Structure; Telomerase; Telomere Maintenance; Telomeric Repeat Binding Protein 1; derepression; histone methylation; histone modification; neglect; non-histone protein; novel strategies; prevent; repaired; senescence; telomere; tumor

PROJECT SUMMARY Telomeres are nucleoprotein structures that protect the ends of linear chromosomes and thereby maintain genome stability. Telomeres solve both the end-protection and the end-replication problems: 1) They inhibit DNA damage at chromosome ends, which would otherwise resemble broken DNA, 2) Since chromosome ends shorten during replication, telomeres act as buffer sequences to prevent loss of coding regions, 3) Once telomeres become too short, they can no longer inhibit DNA damage, leading to permanent cell cycle arrest (senescence). This “mitotic clock” is a critical tumor-suppressive barrier that forces aging cells to stop dividing. To become cancerous, cells must acquire unlimited division potential by activating a telomere maintenance mechanism, either reactivation of telomerase, the enzyme that elongates telomeres during development, or through the alternative lengthening of telomeres (ALT) mechanism, which is based on recombination. Telomeres consist of 5-15kb of (TTAGGG)n repeats organized into tightly packed nucleosomes and bound by the shelterin, a complex of six non-histone proteins. Telomeres are considered as heterochromatin and are enriched in the repressive H3K9me3 “histone mark”. Intense focus has been placed on trying to decipher the exact chromatin status of telomeres, but the much more important question has been neglected and remains unanswered: What is the role and function of heterochromatin at telomeres? While the roles of shelterin proteins have been extensively studied, the function of heterochromatin at telomeres remains largely unexplored. Using a novel approach to locally and specifically modulate histone methylation at telomeres, we will thoroughly dissect the function of H3K9me3 in telomere protection and maintenance. By fusing histone modifying enzymes to the shelterin protein TRF1, we can locally enrich or deplete H3K9me3 at telomeres. Our preliminary data revealed that loss of H3K9me3 leads to severe replication defects and de-repression of telomere transcription. These data suggest that heterochromatin could play unanticipated roles in the regulation of replicative aging and the onset of senescence. Moreover, while the general consensus is that ALT is associated with less condensed chromatin at telomeres, we found that H3K9me3 is a driver of ALT activity. Using this unique approach to manipulate H3K9 trimethylation at telomeres, we will methodically determine the function of this heterochromatin mark on the protective properties of telomeres (end- protection, end-replication, entry into senescence) as well as on the ALT mechanism of telomere maintenance.

项目摘要 端粒是保护线性染色体末端的核蛋白结构，从而 保持基因组稳定性。端粒解决终端保护和最终复制问题：1） 它们抑制染色体末端的DNA损伤，否则它类似于破裂的DNA，2），因为 染色体在复制过程中缩短缩短，端粒充当缓冲序列，以防止编码丢失 区域，3）一旦端粒变得太短，它们就无法抑制DNA损伤，导致 永久性细胞周期停滞（传感）。这个“有丝分裂时钟”是一个关键的肿瘤抑制屏障 迫使衰老细胞停止分裂。要取消，细胞必须获得无限的分裂潜力 通过激活端粒维护机制，要么重新激活端粒酶，即酶 在开发过程中或通过端粒的替代延长（ALT）拉长端粒（ALT） 机制，基于重组。 端粒由5-15kb的（ttaggg）n重复组成，被组织成紧密包装的核小体和 由庇护素约束，六个非固定蛋白的复合物。端粒被认为是 异染色质，并富含反射性H3K9me3“组蛋白标记”。强烈的重点是 试图破译端粒的确切染色质状态，但更重要的是 问题已被忽视，并且仍未得到答复： 端粒的异染色质？虽然庇护素蛋白的作用已广泛研究，但 异染色质在端粒上的功能在很大程度上仍然是出乎意料的。 使用一种新颖的方法来局部和专门调节端粒的组蛋白甲基化，我们 将彻底剖析H3K9me3在端粒保护和维护中的功能。经过 将组蛋白融合到庇护素蛋白TRF1中，我们可以局部富集或复制 H3K9me3在端粒上。 我们的初步数据表明，H3K9me3的损失导致严重的复制缺陷和抑制 端粒转录。这些数据表明异染色质可以在 调节复制衰老和感应的发作。而且，一般共识是 该ALT与端粒处的浓缩染色质较少有关，我们发现H3K9me3是驱动器 Alt活动。 使用这种独特的方法来操纵端粒的H3K9三甲基化，我们将有条不紊 确定该异染色质标记在端粒受保护特性上的功能（end- 保护，终端复制，进入感应）以及端粒的ALT机理 维护。