Mechanisms of heterochromatin replication

项目总结 异染色域，如着丝粒、端粒和其他卫星dna，对 DNA复制。致密的染色质被认为抑制了复制的启动和阻碍了 复制机器。毫不奇怪，最近对各种体细胞和癌细胞的分析表明， 抑制染色质与晚期复制区域和高突变密度相关。然而，几乎没有什么是 了解控制和促进异染色域DNA复制的分子机制。 重要的是，癌细胞可能利用这些机制来促进异染色质复制和 维持他们日益增长的扩散需求。例如，去甲基酶KDM4A/JMJD2的过表达 它消除了异染色标H3K9的三甲基化，使染色质解压和 加速卵巢癌的复制。值得注意的是，KDM4A的过度表达也导致了 在卵巢癌和多发性骨髓瘤中，特定的基因组位点经常被扩增，进一步加强了这种联系 去调节的异染色质复制和基因组不稳定性之间的关系。这些观察结果突显了 需要阐明适当的异染色质复制所需的机制，以便了解 基因组维持和细胞增殖控制的基本方面。 这项建议是以METTL13(类似甲基转移酶的13)为中心的，它是一个鲜为人知的 含有可能的腺苷甲硫氨酸结合结构域的蛋白质家族。而METTL13是 在癌症中发现了扩增和过度表达，以前对它的细胞学几乎一无所知 功能。本文给出的初步结果提供了关于METTL13如何维持细胞的第一个见解 增殖，揭示了在DNA复制和染色质动力学中的关键作用。更具体地说，我们发现 METTL13是一种新的异染色质复制的关键介质，对 着丝粒。据我们所知，这是第一个被描述的人类着丝粒的调节器 复制计时。这项提案将结合尖端基因组和蛋白质组技术 生化和细胞生物学方法剖析METTL13的作用并确定其在 控制染色质动态、DNA复制和基因组完整性。生成的结果将显示一个 异染色质复制的基本机制和复制时机控制，将建立新的 调节染色质动力学和癌细胞增殖能力的药物靶点。

PROJECT SUMMARY Heterochromatic domains, such as centromeres, telomeres and other satellite DNA, pose a major challenge for DNA replication. Compacted chromatin is thought to inhibit replication initiation and obstruct progression of the replication machinery. Not surprisingly, recent analyses of various somatic and cancer cells have revealed that repressive chromatin is associated with regions of late replication and high mutation density. Little, however, is known about the molecular mechanisms that control and facilitate DNA replication at heterochromatic domains. Of importance, cancer cells may harness these mechanisms to facilitate heterochromatin replication and sustain their increased proliferative demands. For example, overexpression of KDM4A/JMJD2, a demethylase that removes the heterochromatic mark H3K9 tri-methylation, enables chromatin de-compaction and accelerated replication in ovarian cancers. Strikingly, KDM4A overexpression also resulted in copy gain of specific genomic loci often amplified in ovarian cancers and multiple myeloma, further strengthening the link between de-regulated heterochromatin replication and genomic instability. These observations highlight the need to elucidate the mechanisms required for proper heterochromatin replication so as to understand fundamental aspects of genome maintenance and the control of cell proliferation. This proposal is centered on METTL13 (Methyltransferase-like 13), a member of a poorly understood family of proteins containing putative SAM (S-adenosylmethionine)-binding domains. While METTL13 was found amplified and overexpressed in cancers, virtually nothing was previously known about its cellular functions. Preliminary results presented here provide the first insights on how METTL13 sustains cell proliferation, revealing crucial roles in DNA replication and chromatin dynamics. More specifically, we find that METTL13 is a novel key mediator of heterochromatin replication that is particularly important for replication of centromeres. To the best of our knowledge this is the first described regulator of human centromere replication timing. This proposal will combine cutting edge genomic and proteomic techniques with biochemical and cell biological approaches to dissect the action of METTL13 and establish its role in controlling chromatin dynamics, DNA replication and genome integrity. Generated results will reveal a fundamental mechanism of heterochromatin replication and replication timing control, and will establish novel drug targets for modulating chromatin dynamics and the proliferative capacity of cancer cells.