The Role of Base Excision Repair in Regulating DNA-Mediated Inflammatory Signaling Pathways

项目摘要 DNA修复缺陷是许多人类遗传疾病的基础，这些疾病影响各种各样的遗传疾病。 这可能会影响生理系统，并导致不良表型，如加速老化和易患癌症。 忠实的DNA修复对于保持基因组完整性和预防癌症是必要的。碱基切除修复 (BER)这条通路负责修复每个细胞每天至少20，000个损伤。如果不修理， 损伤可引起基因组不稳定性和肿瘤发生。BER也是主要的修复途径， 非庞大的受损碱基，脱碱基位点，和DNA单链断裂后，用不同的DNA处理， 破坏剂。BER途径涉及几个基因，包括DNA糖基化酶、XRCC 1、DNA 聚合酶β（Polβ）、DNA连接酶III、瓣状核酸内切酶1（FEN 1）和DNA连接酶I。BER缺陷可以 导致累积的未修复的DNA损伤，产生细胞质DNA，可能激活DNA依赖性 先天免疫途径环GMP-AMP合酶（cGAS）是产生多核苷酸的关键胞质DNA传感器。 环二核苷酸cGMP-AMP（cGAMP）激活后，触发激活的刺激剂， 干扰素基因（STING），导致I型干扰素产生。然而，BER的不足如何促进 cGAS/STING介导的炎症尚未完全了解。这项探索性的R21提案的目标是 揭示自发DNA损伤和BER失败如何刺激宿主炎症反应。我们最近 开发了一种新的小鼠模型，使用人类遗传变异，我们将使用它来阐明分子 炎症机制。利用Cre-flox靶向系统，我们构建了一个L22 P条件性基因敲入系统， 缺乏在Rosa 26 a基因座表达的dRP裂解酶功能并且不能支持BER的小鼠模型。我们 初步数据显示，在我们的小鼠模型中，BER缺陷显著诱导基因组不稳定性， 慢性炎症因此，我们假设BER缺乏积累了来自于 自发DNA损伤，从而引发先天免疫反应。 在这项研究中，我们提出了两个 具体目的：（1）确定异常BER诱导炎症的分子机制。 使用BER缺陷细胞（ Polβ -/-; XRCC 1; PARP 1-/-; L22 P（dRP裂解酶缺陷型 Polβ），我们将研究如何 BER缺陷引发先天免疫应答介导的炎症。(2)确定BER是否失败 刺激小鼠中cGAS/STING介导的炎症。使用体外和体内模型（L22 P小鼠 模型），我们将研究细胞溶质DNA传感途径如何触发炎症免疫反应。的 本研究的结果将定义异常BER如何诱导先天免疫系统的新范例， 并将对cGAS/STING功能背后的分子机制以及 未来的免疫导向癌症疗法。

PROJECT SUMMARY Defects in DNA repair underlie a number of human genetic diseases that affect a wide variety of physiological systems and cause adverse phenotypes such as accelerated aging and predisposition to cancer. Faithful DNA repair is necessary to maintain genomic integrity and prevent cancer. The base excision repair (BER) pathway is responsible for repairing at least 20,000 lesions per cell per day. If left unrepaired, the lesions can give rise to genomic instability and tumorigenesis. BER is also the major repair pathway for nonbulky damaged bases, abasic sites, and DNA single-strand breaks after treatment with different DNA- damaging agents. Several genes are involved in BER pathways, including DNA glycosylase, XRCC1, DNA polymerase beta (Polβ), DNA ligase III, flap endonuclease 1 (FEN1), and DNA ligase I. BER deficiency can lead to accumulated unrepaired DNA damage, generating cytosolic DNA that likely activates DNA-dependent innate immune pathways. Cyclic GMP-AMP synthase (cGAS) is a key cytosolic DNA sensor that produces the cyclic dinucleotide cGMP-AMP (cGAMP) upon activation, which triggers the activation of stimulator of interferon genes (STING), leading to type I Interferon production. However, how deficiency in BER promotes cGAS/STING-mediated inflammation is not yet fully understood. The goal of this exploratory R21 proposal is to uncover how spontaneous DNA damage and failed BER stimulate host inflammatory response. We recently developed a novel mouse model using a human genetic variant, which we will use to elucidate the molecular mechanism of inflammation. Using a Cre-flox targeting system, we constructed an L22P conditional knock-in mouse model that lacks dRP lyase function expressed at Rosa26a locus and cannot support BER. Our preliminary data revealed that BER deficiency in our mouse model markedly induces genomic instability and chronic inflammation. Thus, we hypothesize that BER deficiency accumulates cytosolic DNA that derives from spontaneous DNA damage, thereby triggering the innate immune response. In this study, we propose two Specific Aims: (1) Determine the molecular mechanisms through which aberrant BER induces inflammation. Using BER-deficient cells ( Polβ -/-; XRCC1; PARP1-/-; L22P (dRP lyase-deficient Polβ), we will study how BER deficiency triggers innate immune response-mediated inflammation. (2) Determine whether failed BER stimulates cGAS/STING-mediated inflammation in mice. Using in vitro and in vivo models (L22P mouse models), we will examine how cytosolic DNA-sensing pathways trigger inflammatory immune responses. The outcomes of this study will define a novel paradigm for how aberrant BER induces the innate immune system, and will have broad implications for the molecular mechanisms behind cGAS/STING function, as well as for future immune-directed cancer therapies.