Role of ncRNA Surveillance Complex "RNA Exosome" in Class Switch Recombination an

描述(由申请人提供)：本提案旨在了解在适应性免疫反应过程中管理抗体多样化的机制。抗体是脊椎动物体液中B淋巴细胞产生的多肽复合体，被免疫系统用来识别和中和各种外来抗原。新产生的B细胞从骨髓迁移到次级淋巴器官，在那里它们遇到抗原，并被刺激进一步经历两种免疫球蛋白(Ig)基因改变，即类切换重组(CSR)和体细胞过度突变(SHM)。CSR是一种B细胞特异性的DNA重排反应，它将Cβ中的Ig重链恒定区基因(CH)与下游的CH外显子替换，从而产生具有不同效应功能的次级同功型(Ig G、Ig A等)。另一方面，SHM以非常高的比率将点突变引入V基因，最终导致抗体亲和力增加。虽然CSR和SHM两个不同的过程绝对需要通过相应的Ig基因座转录和单链DNA脱氨酶的活性，但激活诱导的胞苷脱氨酶(AID)。AID在特定Ig基因座的DNA序列(开关(S)序列或可变区(V)基因)中引入点突变，然后转化为DNA损伤(双链断裂或突变)，启动CSR和SHM。AID以一种受调控的方式在Ig基因座上引入这些突变的机制是一个活跃的研究领域。我们最近的研究表明，AID利用细胞内非编码素RNA降解/处理复合体，RNA外体，突变底物DNA序列的两条链。利用现代蛋白质组学、高通量基因组学和小鼠遗传学相结合的方法，我们继续研究RNAexosome/AID复合体在CSR和SHM中的作用机制。了解AID的作用机制是至关重要的。AID基因失活突变的人类患者会患上高免疫球蛋白M综合征(HIGM2)，而AID基因的异常表达可能会导致多种B和T细胞恶性肿瘤。对B淋巴细胞中AID功能的了解将有助于指导临床治疗这些患者。 公共卫生相关性：本提案研究了非编码RNA降解复合体--RNA外切体对原癌基因激活诱导的胞苷脱氨酶(AID)的调节机制。AID对于启动类切换重组(CSR)和体细胞超突变(SHM)是必不可少的，这两个过程是产生抗体所必需的，抗体通过适应性免疫反应参与生物防御。

DESCRIPTION (provided by applicant): This proposal is directed towards the understanding of the mechanisms that govern antibody diversification during an adaptive immune response. Antibodies are polypeptide complexes produced from B-lymphocytes that are present in the bodily fluids of vertebrates, and are used by the immune system to identify and neutralize various foreign antigens. Newly generated B cells migrate from bone- marrow to secondary lymphoid organs where they encounter antigens, and are stimulated to further undergo two Immunoglobulin (Ig) gene alterations known as class switch recombination (CSR) and somatic hypermutation (SHM). CSR is a B cell-specific DNA rearrangement reaction that replaces an Ig heavy chain constant region gene (CH) from C¿ with other downstream CH exons so that secondary isotypes (IgG, IgA etc) with different effector functions are generated. SHM, on the other hand, introduces point mutations into V genes at a very high rate, ultimately leading to increased antibody affinity. Though two distinct processes, CSR and SHM absolutely require transcription through the relevant Ig loci and activity of a single-strand DNA deaminase, Activation Induced cytidine Deaminase (AID). AID introduces point mutations in the at specific Ig locus DNA sequences (switch (S) sequences or variable regions (V) genes) that are then converted to DNA lesions (double-strand breaks or mutations) to initiate CSR and SHM. The mechanism by which AID introduces these mutations in the Ig locus in a regulated fashion is an active field of investigation. Our recent studies indicate that AID utilizes the cellular non-codin RNA degradation/processing complex, RNA exosome, to mutate both strands of substrate DNA sequences. Using a combination of modern proteomic approaches, high- throughput genomics and mouse genetics we continue to study the mechanism of function of RNA exosome/AID complex function during CSR and SHM. Understanding the mechanism of AID function is of paramount importance. Human patients with inactivating mutations in the AID gene suffer from Hyper-IgM syndrome (HIGM2), whereas aberrant expression of AID may lead to various B and T cell malignancies. Understanding of AID function in B-lymphocytes will allow treatment of these patients with directed clinical therapies. PUBLIC HEALTH RELEVANCE: This proposal investigates the mechanism of regulation of the proto-oncogene Activation Induced cytidine Deaminase (AID) by the non-coding RNA degradation complex, RNA exosome. AID is essential for initiating the class switch recombination (CSR) and somatic hypermutation (SHM), two processes required for generation of antibodies that participate in bio-defense via adaptive immune response.