REGULATION OF V(D)J RECOMBINATION IN CELL CYCLE AND IN DEVELOPMENT

类肉瘤是儿童最常见的恶性肿瘤， 重排涉及许多这些癌症的产生。这一长期目标 该项目仍然是为了了解基因组可塑性及其控制的机制， 发展免疫系统。抗原受体多肽链的可变区编码于 在淋巴发育过程中由V（D）J聚集在一起的单独的DNA片段 重组，一种位点特异性DNA重排的形式。蛋白质RAG-1和RAG-2启动 通过在特异性重组信号序列处切割参与基因片段的V（D）J重组 （RSS）。重组的完成利用了非同源DNA末端的细胞机制 NHEJ是DNA双链断裂修复（DSBR）的一种形式。V（D）J复合耦合到 通过RAG-2的周期性破坏细胞周期。V（D）J重组酶活性与 NHEJ是维持基因组完整性所必需的;当RAG诱导的DNA断裂被破坏时， 如果检测和修复不当，所产生的基因组重排可能导致淋巴肿瘤。 相应地，越来越多的证据表明，异常的V（D）J重组有助于 淋巴恶性肿瘤的发病机制。要求继续提供资金， 调节V（D）J重组的机制以及这些机制对抑制的贡献 肿瘤的发生。建议的目的如下：（1）界定一个详细的机制， 通过结合生化分析和验证，V（D）J重组与细胞周期相关 （2）了解从细胞中解偶联V（D）J重组的生理后果 周期，通过使用逃避调节的RAG-2表达形式的小鼠;（3）阐明RAG-2的表达形式， 通过开发V（D）J重组中间体分解的机制， （4）建立一个新的、可调控的系统来研究V（D）J的反馈控制 重组，采用小鼠B祖细胞中突变激酶活性的化学拯救。

Lymphoid tumors are the most common malignancies in children, and aberrant chromosomal rearrangements are implicated in the generation of many of these cancers. The long term goals of this project remain to understand the mechanisms underlying genomic plasticity and its control in the developing immune system. The variable regions of antigen receptor polypeptide chains are encoded in separate DNA segments that are brought together during lymphoid development by V(D)J recombination, a form of site-specific DNA rearrangement. The proteins RAG-1 and RAG-2 initiate V(D)J recombination by cleaving participating gene segments at specific recombination signal sequences (RSSs). Completion of recombination employs the cellular machinery for non-homologous DNA end joining (NHEJ), a form of DNA double strand break repair (DSBR). V(D)J recombination is coupled to the cell cycle by the periodic destruction of RAG-2. Coordination of V(D)J recombinase activity with NHEJ is required for the maintenance of genomic integrity; when RAG-induced DNA breaks are improperly sensed and repaired, the resulting genomic rearrangements can give rise to lymphoid tumors. Correspondingly, a growing body of evidence indicates that aberrant V(D)J recombination contributes to the pathogenesis of lymphoid malignancies. Renewed funding is requested for continued study of mechanisms that regulate V(D)J recombination and the contributions of these mechanisms to suppression of tumorigenesis. The proposal has the following aims: (1) to define a detailed mechanism by which V(D)J recombination is linked to the cell cycle, by a combination of biochemical analysis and validation in vivo; (2) to understand the physiologic consequences of uncoupling V(D)J recombination from cell cycle, through the use of mice expressing forms of RAG-2 that escape regulation; (3) to elucidate the mechanism by which V(D)J recombination intermediates are disassembled, through development of a cell-free system; and (4) to build a novel, regulable system to study the feedback control of V(D)J recombination, employing chemical rescue of mutant kinase activites in mouse B cell progenitors.