Role of HELLS chromatin remodeler in genome maintenance

项目摘要 强大和严格调控的DNA修复对于维持基因组稳定和预防疾病发展至关重要。 真核细胞的DNA被包装成染色质，这种染色质对 DNA修复、复制和基因组维护。在理解DNA修复的方式上存在一个根本的差距 通路在结构不同的染色质内以及在异质性的 基因组图景。Hells(解旋酶淋巴特异性)是一种鲜为人知的与染色质相关的基因 蛋白质，在基因组维护中发挥着新的作用。小鼠地狱对于配子发生和 免疫系统的正常发育。人类地狱中的突变导致严重的免疫缺陷 ICF综合征(免疫缺陷、着丝粒不稳定、面部畸形)。尽管在以下方面取得了实质性进展 了解哺乳动物地狱在DNA甲基化和染色质重塑中的分子功能， 它在DNA修复和基因组维护中的作用还知之甚少，仍然难以捉摸。悬而未决的 问题仍然是地狱是否调节多条DNA修复途径，以及它是否具有特殊的作用 在修复和维持不同的基因组位置或结构域中。我们已经建立并验证了真菌 模型，粗糙脉孢菌促进了对Hells介导的机制的基本理解 基因组的稳定性。我们的研究揭示了地狱蛋白和细胞之间的一种新的、以前未知的联系 真菌和人类细胞对DNA烷基化损伤的反应。我们假设地狱保护细胞免受 烷基化诱导的毒性，在结构性异染色质的修复和稳定中起重要作用 域名。这一假说是建立在真菌模型脉孢子菌的强大初步数据和在 人类细胞表明，缺乏地狱的细胞对DNA烷基化损伤敏感，并 缺乏对构成异染色质的修复。此外，我们发现真菌WDR76的缺失 Hells突变细胞中的蛋白质导致烷基化敏感性表型的合成拯救，这意味着 WDR76是Hells缺乏症的基因抑制因子。在目标1中，我们将确定真菌和人类 Hells重构体在修复烷基化DNA损伤中的作用。在目标2中，我们将定义精确的基因组和 依赖地狱维持基因组的染色质环境。在目标3中，我们将确定功能 Hells与WDR76的关系，WDR76是参与DNA烷基化反应的WD40蛋白。成功 拟议研究的完成将确定地狱介导的基因组维持机制，以及 确定与地狱合作保护细胞免受有害物质伤害的其他调节剂和途径 基因毒性应激的后果。这些研究将为疾病的起源提供重要的见解- 导致许多人类疾病中出现的染色体重排和断裂，包括ICF综合征。

Project Summary Robust and tightly regulated DNA repair is critical to maintain genome stability and prevent disease development. Eukaryotic DNA is packaged into chromatin that has a profound, yet not well understood regulatory influence on DNA repair, replication and genome maintenance. There is a fundamental gap in understanding how DNA repair pathways are regulated and coordinated within structurally diverse chromatin, and across the heterogeneous genomic landscape. The HELLS (Helicase Lymphoid Specific) is a poorly understood chromatin-associated protein, with an emerging new role in genome maintenance. Mouse HELLS is essential for gametogenesis and proper development of the immune system. Mutations in human HELLS cause severe immunodeficiency syndrome ICF (Immunodeficiency Centromeric Instability Facial anomalies). Despite substantial progress in understanding the molecular functions of the mammalian HELLS in DNA methylation and chromatin remodeling, its role in DNA repair and genome maintenance is poorly understood and remains elusive. The unresolved questions remain whether HELLS regulates multiple DNA repair pathways, and whether it has specialized roles in the repair and maintenance of a distinct genomic loci or domains. We have established and validated fungal model, Neurospora crassa to advance the fundamental understanding of HELLS-mediated mechanisms of genome stability. Our studies reveal a new, previously unrecognized link between HELLS proteins and cellular responses to DNA alkylation damage in fungal and human cells. We hypothesize that HELLS protects cells form alkylation-induced toxicity and plays important roles in the repair and stability of the constitutive heterochromatin domains. This hypothesis is founded based on a strong preliminary data in the fungal model Neurospora and in human cells demonstrating that cells deficient in HELLS exhibit sensitivity to DNA alkylation damage and are deficient in the repair of the constitutive heterochromatin. In addition, we discovered that loss of fungal WDR76 protein in HELLS mutant cells leads to the synthetic rescue of the alkylation sensitivity phenotype, implying that WDR76 acts as genetic suppressor of HELLS deficiency. In Aim 1 we will determine the role of fungal and human HELLS remodelers in the repair of alkylation DNA damage. In Aim 2 we will define precise genomic and chromatin contexts that depend on HELLS for genome maintenance. In Aim 3 we will determine the functional relationship between HELLS and WDR76, a WD40 protein implicated in response to DNA alkylation. Successful completion of the proposed research will define HELLS-mediated mechanisms of genome maintenance, and identify additional regulators and pathways cooperating with HELLS in protecting the cells from detrimental consequences of genotoxic stress. These studies will provide important insights into the origin of the disease- causing chromosomal rearrangements and breaks found in many human diseases, including the ICF syndrome.