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

描述（由申请人提供）：本提案旨在了解适应性免疫应答期间控制抗体多样化的机制。抗体是由存在于脊椎动物体液中的B淋巴细胞产生的多肽复合物，并被免疫系统用于识别和中和各种外源抗原。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，并被刺激以进一步经历两种免疫球蛋白（IG）基因改变，称为类别转换重组（CSR）和体细胞超变（SHM）。CSR是一种B细胞特异性DNA重排反应，其将来自C？的IG重链恒定区基因（CH）替换为其他下游CH外显子，从而产生具有不同效应子功能的二级同种型（IgG、伊加等）。另一方面，SHM以非常高的速率将点突变引入V基因，最终导致抗体亲和力增加。尽管CSR和SHM是两个不同的过程，但它们绝对需要通过相关的IG基因座和单链DNA脱氨酶（激活诱导的胞苷脱氨酶（AID））的活性进行转录。AID在特定的IG基因座DNA序列（开关（S）序列或可变区（V）基因）中引入点突变，然后将其转化为DNA损伤（双链断裂或突变）以启动CSR和SHM。AID以调节的方式在IG基因座中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利用细胞非编码RNA降解/加工复合物，RNA外泌体，突变底物DNA序列的两条链。使用现代蛋白质组学方法、高通量基因组学和小鼠遗传学的组合，我们继续研究RNA外泌体/AID复合物在CSR和SHM期间的功能机制。了解艾滋病的作用机制至关重要。在AID基因中具有失活突变的人类患者患有高IgM综合征（HIGM 2），而AID的异常表达可导致各种B和T细胞恶性肿瘤。了解B淋巴细胞中的AID功能将允许用定向临床疗法治疗这些患者。

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.