Role of DNA Damage Responses in Immune Development and Function

项目总结 淋巴细胞的发育受到精确的控制，以使克隆扩增和产生不同的 免疫球蛋白受体曲目，通过DNA双链断裂(DSB)进行。这两个 二分，但相互依赖的过程，是通过不同细胞信号的合作来管理的 防止带有DSB的细胞进入细胞周期，在细胞周期中，它们可能被异常修复为易位。在.期间 早期B细胞发育，前B细胞受体(Pre-BCR)，通过激活SYK激酶，协调 前B细胞的增殖和免疫球蛋白受体基因的组装。负性 需要对前bcr进行调控，以强制细胞周期停滞和限制产生的DNA断裂数量 在免疫球蛋白受体基因组装过程中。事实上，无人反对的BCR前信号，特别是增加了 SYK活性，驱动增殖和白血病转化。我们已经鉴定出一种新的细胞类型特异性 检查点通路被来自DSB的信号激活，从而抑制Pre-BCR信号。生理性DSB 在免疫球蛋白受体基因重排过程中产生的DNA损伤反应 SYK激酶活性位于Pre-BCR下游。令人惊讶的是，这个信号网络并不是由基因毒素触发的 DNA损伤，因此是特异的，在正常的B细胞分化过程中产生的双链断裂。在早期的B细胞中， 对生理性和遗传性毒性DSB的不同细胞反应是确保正常B细胞必不可少的 分化抑制白血病转化。我们的目标是确定来自DSB的信号 与发育计划相结合，以协调B细胞成熟。我们认为早期的B细胞 在来自前BCR和DSB的信号之间切换以订购免疫球蛋白受体基因组装和 通过阻止含有DSB的细胞的增殖来维持基因组的稳定性。利用创新的实验 允许分离DSB信号和表面受体信号的方法，我们建议：1)定义 调控DSB介导的检查点的转录抑制复合体，2)识别DSB依赖的 抑制Pre-BCR信号的翻译后通路，以及3)决定DSB特异的通路 决定了细胞对生理和遗传毒性侮辱的独特反应。完成这些研究后， 勾勒出一套对抑制Pre-BCR信号至关重要的机制，将为细胞- 为DSB键入特定的检查点，并将定义离散蜂窝响应的基本原则 生理性DSB与遗传毒性DSB。

PROJECT SUMMARY Lymphocyte development is precisely controlled to enable clonal expansion and generation of a diverse immunoglobulin receptor repertoire, which proceeds through DNA double-stranded breaks (DSBs). These two dichotomous, but interdependent processes, are managed through the cooperation of diverse cellular signals to prevent cells with DSBs from entering cell cycle where they could be aberrantly repaired as translocations. During early B cell development, the pre-B cell receptor (pre-BCR), through activation of the SYK kinase, coordinates both the proliferative expansion of pre-B cells and the assembly of immunoglobulin receptor genes. Negative regulation of the pre-BCR is required to enforce cell cycle arrest and limit the number of DNA breaks generated during immunoglobulin receptor gene assembly. Indeed, unopposed pre-BCR signaling, particularly increased SYK activity, drives proliferation and leukemic transformation. We have identified a novel cell-type specific checkpoint pathway activated by signals from DSBs that inhibits pre-BCR signaling. The physiologic DSBs generated during immunoglobulin receptor gene rearrangement trigger DNA damage responses that suppress SYK kinase activity downstream of the pre-BCR. Surprisingly, this signaling network is not triggered by genotoxic DNA injury and, thus, is specific to the DSBs generated during normal B cell differentiation. In early B cells, distinct cellular responses to physiologic and genotoxic DSBs are essential for ensuring normal B cell differentiation and inhibiting leukemic transformation. Our goal is to determine how signals from DSBs integrate with developmental programs to coordinate B cell maturation. We propose that early B cells toggle between signals from the pre-BCR and DSBs to order immunoglobulin receptor gene assembly and maintain genomic stability by preventing proliferation of cells with DSBs. Utilizing an innovative experimental approach that permits isolation of DSB signals and surface receptor signals, we propose to: 1) define the transcriptional repressor complex that regulates DSB-mediated checkpoints, 2) identify the DSB-dependent post-translational pathways that suppress pre-BCR signaling, and 3) determine the DSB-specific pathways that dictate the unique cellular responses to physiologic versus genotoxic insults. Completion of these studies will delineate a set of mechanisms critical for dampening pre-BCR signals, will establish novel paradigms for cell- type specific checkpoints to DSBs, and will define the underlying principles for discrete cellular responses to physiologic versus genotoxic DSBs.