ELUCIDATION OF IMMUNOGLOBULIN CLASS SWITCH RECOMBINATION AND SOMATIC HYPERMUTATIO

项目摘要 为了产生最佳的免疫应答，成熟的B淋巴细胞在其免疫球蛋白中经历两个遗传改变。 类别转换重组（CSR）和体细胞超突变（SHM）的形式。企业社会责任导致生产 各种同种型（IgG、IgE、伊加）的抗体，而SHM导致产生具有 对抗原的亲和力更高。B细胞特异性蛋白AID（活化诱导的脱氨酶）对于 两个过程。AID通过使细胞核转录区域内的胞苷脱氨基来启动CSR和SHM。 免疫球蛋白位点。这些病变然后在SHM期间转化为点突变或转化为DNA双链突变。 在CSR过程中作为强制性中间体的链断裂。艾滋病的灭活导致人类 免疫缺陷综合征（Hyper-IgM 2），患者对细菌性免疫缺陷综合征 感染.另一方面，对AID的放松管制将其转化为一般的增变因子并导致突变， 与成熟B细胞淋巴瘤发生有关的癌基因易位。的理解 因此，规范援助活动的程序至关重要。本研究的总体目标 的建议是阐明机制，其中AID活动的调节，在CSR和SHM。最近 研究表明，蛋白激酶A（PKA）在体外使AID磷酸化，以激活其结合其受体的能力。 辅助因子，单链DNA结合蛋白复制蛋白A，介导转录的 DNA底物。为了阐明AID磷酸化在体内的作用，在AID磷酸化基因突变的小鼠中， 将生成磷酸化位点的所有片段，并分析CSR和SHM。突变小鼠也将用于 细胞和生物化学测定来描述磷酸化AID在CSR和SHM中的功能。最后， 现有的PKA突变体将被分析，以测试由PKA引起的AID磷酸化本身是一种高度磷酸化的假说。 调节事件，并可能有助于艾滋病的目标特异性。成功完成项目 在这个提案中概述的将提供对免疫反应的机制性见解，以及如何 这种生理反应中的畸变可引起成熟的B细胞肿瘤。

PROJECT SUMMARY To mount an optimum immune response, mature B lymphocytes undergo two genetic alterations in the forms of class switch recombination (CSR) and somatic hypermutation (SHM). CSR leads to the production of antibodies of various isotypes (IgG, IgE, IgA) while SHM results in the generation of antibody molecules with a much higher affinity for antigens. The B cell specific protein AID (activation induced deaminase) is essential to both processes. AID initiates CSR and SHM by deaminating cytidines within transcribed regions of the immunoglobulin locus. These lesions are then converted into point mutations during SHM or into DNA double strand breaks that serve as obligatory intermediates during CSR. Inactivation of AID leads to human immunodeficiency syndromes (Hyper-IgM2) where patients suffer from profound susceptibility to bacterial infections. On the other hand, deregulation of AID converts it into a general mutator and leads to mutations and translocations of oncogenes that have been implicated in mature B cell lymphomagenesis. An understanding of the processes that regulate AID activity is thus of utmost importance. The overall objective of this research proposal is to elucidate the mechanism by which AID activity is regulated during CSR and SHM. Recent studies have shown that protein kinase A (PKA) phosphorylates AID in vitro to activate its ability to bind its cofactor, the single-stand DNA binding protein Replication Protein A and mediate deamination of transcribed DNA substrates. To elucidate the role of AID phosphorylation in vivo, mice with a mutation in the AID phosphorylation site will be generated and analyzed for CSR and SHM. The mutant mouse will also be used in cellular and biochemical assays to delineate the function of phosphorylated AID in CSR and SHM. Finally, existing PKA mutants will be analyzed to test the hypothesis that AID phosphorylation by PKA is itself a highly regulated event and could potentially contribute to AID target specificity. Successful completion of the projects outlined in this proposal will provide mechanistic insights into reactions central to immunity and how aberrations in such physiological reactions can cause mature B cell tumors.