Role of HELLS chromatin remodeler in genome maintenance

项目摘要 稳健和严格调控的DNA修复对于维持基因组稳定性和预防疾病发展至关重要。 真核细胞DNA被包装成染色质，染色质对DNA的表达有着深刻的，但还没有很好地理解的调控影响。 DNA修复、复制和基因组维护。在理解DNA修复如何 在结构多样的染色质内，以及在异质性染色质中， 基因组景观HELLS（Helicase cytophoid Specific）是一种知之甚少的染色质相关蛋白， 蛋白质，在基因组维护中发挥着新的作用。小鼠HELLS对于配子发生至关重要， 免疫系统的正常发育。人类HELLS突变导致严重免疫缺陷 综合征ICF（免疫缺陷着丝粒不稳定性面部异常）。尽管取得了重大进展， 了解哺乳动物HELLS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知之甚少，仍然难以捉摸。悬而未决的 问题仍然是，HELLS是否调节多个DNA修复途径，以及它是否有专门的作用 修复和维持不同的基因组位点或结构域。我们已经建立并验证了真菌 模型，粗糙脉孢菌，以推进对HELLS介导的 基因组稳定性我们的研究揭示了地狱蛋白与细胞之间一种新的、以前未被认识到的联系 对真菌和人类细胞中DNA烷基化损伤的反应。我们假设地狱保护细胞形成 在组成性异染色质的修复和稳定中起重要作用 域.这一假设是基于真菌模型脉孢菌和 人类细胞证明缺乏HELLS的细胞表现出对DNA烷基化损伤的敏感性， 在组成性异染色质的修复中有缺陷。此外，我们发现真菌WDR 76的缺失 HELLS突变细胞中的蛋白导致烷基化敏感性表型的合成拯救，这意味着 WDR 76是HELLS缺陷的遗传抑制基因。在目标1中，我们将确定真菌和人类 在烷基化DNA损伤修复中的HELS重塑。在目标2中，我们将定义精确的基因组和 依赖于HELLS进行基因组维护的染色质环境。在目标3中，我们将确定函数 HELLS和WDR 76之间的关系，WDR 76是一种参与DNA烷基化反应的WD 40蛋白。成功 完成拟议的研究将确定HELLS介导的基因组维持机制， 确定与HELLS合作的其他调节因子和途径，以保护细胞免受有害物质的侵害。 遗传毒性应激的后果。这些研究将为了解这种疾病的起源提供重要的见解- 导致在许多人类疾病中发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.