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 端粒是核蛋白结构，其保护线性染色体的末端， 保持基因组的稳定性。端粒解决了末端保护和末端复制问题：1） 它们抑制染色体末端的DNA损伤，否则这将类似于断裂的DNA，2）由于 染色体末端在复制过程中缩短，端粒作为缓冲序列防止编码丢失 3）一旦端粒变得太短，它们就不能再抑制DNA损伤，导致 永久性细胞周期停滞（衰老）。这种“有丝分裂钟”是一种重要的肿瘤抑制屏障， 迫使老化细胞停止分裂要变成癌细胞必须获得无限的分裂潜能 通过激活端粒维持机制，或者重新激活端粒酶， 在发育过程中延长端粒，或通过端粒的替代性延长（ALT） 机制，这是基于重组。 端粒由5- 15 kb的（TTAGGG）n重复序列组成，这些重复序列被组织成紧密堆积的核小体， 由六种非组蛋白的复合物shelterin结合。端粒被认为是 H3 K9 me 3在异染色质中表达，并富含抑制性H3 K9 me 3“组蛋白标记”。强烈的关注一直是 重点是试图破译端粒的确切染色质状态，但更重要的是 一个问题被忽视了，仍然没有答案： 端粒的异染色质虽然shelterin蛋白的作用已被广泛研究， 异染色质在端粒中的功能仍在很大程度上未被探索。 我们使用一种新的方法来局部且特异性地调节端粒的组蛋白甲基化， 将彻底剖析H3 K9 me 3在端粒保护和维护中的功能。通过 将组蛋白修饰酶融合到shelterin蛋白TRF 1上，我们可以局部富集或耗尽 H3 K9 me 3在端粒上。 我们的初步数据显示，H3 K9 me 3的缺失导致严重的复制缺陷和去阻遏。 端粒的转录。这些数据表明，异染色质可能发挥意想不到的作用， 调节复制性衰老和衰老的开始。此外，虽然普遍共识是 ALT与端粒处较少的染色质凝聚有关，我们发现H3 K9 me 3是一个驱动因子， ALT活性。 使用这种独特的方法来操纵端粒上的H3 K9三甲基化，我们将有条不紊地 确定这种异染色质标记对端粒（末端）保护特性的作用， 保护，末端复制，进入衰老）以及端粒的ALT机制 上维护