DNA Damage Responses in B Cell Development

描述（由申请人提供）：在免疫应答过程中，免疫球蛋白座内的B系细胞具有独特的经历发育程序性DNA双链断裂（DSB）的能力，以便在称为类开关重组（CSR）的过程中产生功能性抗体。因此，切换B细胞为研究细胞对生理DSB的反应提供了一个很好的模型。经历CSR的B细胞触发DNA损伤反应（DDR）途径，该途径向细胞发出暂停和修复DNA断裂的信号，或者如果无法解决损伤，则进行凋亡。DDR通路是对DNA损伤的初始细胞反应，在肿瘤发生早期被激活，但在癌症进展过程中经常丢失。CSR过程中DDR通路的破坏导致B细胞免疫球蛋白转换受损，并导致涉及IgH位点的染色体易位。共济失调毛细血管扩张突变基因（ATM）是感知和响应DNA损伤的关键协调者。缺乏ATM的B细胞损害了CSR，并且经常产生涉及免疫球蛋白重链位点的染色体易位。在这方面，在许多淋巴细胞恶性肿瘤中发现了ATM的改变。ATM在维持B系细胞基因组稳定性中的确切作用尚不清楚。在本提案中，我们寻求开发方法来研究在B细胞进行类别转换时调节ATM招募到程序性DNA断裂的机制。DSB修复复合体的定位和分子评估将阐明CSR过程中DDR的组成。此外，我们将检查参与主动免疫应答的特定B细胞群，以确定ATM和DDR的其他成员被招募到IgH位点的特定群体。在我们的第二个目标中，我们将进一步测试促进ATM招募到IgH位点的确切DNA序列。综上所述，这些研究将进一步确定调节atm缺陷B细胞基因组稳定性维持的机制，为治疗靶点的开发提供见解。公共卫生相关性：B细胞淋巴瘤是共济失调毛细血管扩张患者死亡的主要原因。本研究旨在了解促进B细胞致癌事件的基本机制，这也适用于AT患者发生的其他癌症。这些发现可能会导致开发新的和合理的治疗靶点的癌症患者的AT。

DESCRIPTION (provided by applicant): B lineage cells of the immune are unique in their ability to undergo developmentally programmed DNA double strand breaks (DSB) within their immunoglobulin loci during an immune response in order to generate functional antibodies in a process termed class switch recombination (CSR). Switching B cells thus offer an excellent model to study cellular responses to physiologic DSB. B cells undergoing CSR trigger the DNA damage response (DDR) pathway, which signals cells to pause and repair DNA breaks, or if unable to resolve the damage to then undergo apoptosis. The DDR pathway is the initial cellular response to DNA damage, which is activated early in tumorigenesis but is frequently lost during progression to cancer. Disruption of the DDR pathway during CSR leads to impaired immunoglobulin switching in B cells and to chromosomal translocations involving the IgH locus. The ataxia-telangiectasia mutated gene (ATM) is the key coordinator of sensing and responding to DNA damage. B cells deficient for ATM have impaired CSR and frequently generate chromosomal translocations involving the immunoglobulin heavy chain locus. In this regard, ATM alterations have been detected in many lymphoid malignancies. The exact role of ATM in maintaining genomic stability in B lineage cells remains unknown. In this proposal we seek to develop methods to study the mechanisms that regulate ATM recruitment to programmed DNA breaks in B cells undergoing class switching. Localization and molecular assessment of the DSB repair complex will elucidate the components of the DDR during CSR. In addition we will examine defined populations of B cells participating in an active immune response to determine the specific populations in which ATM and other members of the DDR are recruited to the IgH locus. In our second aim, we will further test the exact DNA sequences that facilitate recruitment of ATM to the IgH locus. Taken together, these studies will further define the mechanisms that regulate the maintenance of genomic stability in ATM-deficient B cells, providing insights towards the development of therapeutic targets. PUBLIC HEALTH RELEVANCE: B cell lymphoma is a major cause of death in patients with ataxia-telangiectasia. The studies in this proposal seek to understand the basic mechanisms that promote oncogenic events B cells, which is also applicable towards other cancers that develop in AT patients. These findings may lead to the development of novel and rational therapeutic targets for cancer in patients with AT.