Mechanisms of AID-dependent Adaptive and Innate Immunity

描述（由申请人提供）：免疫球蛋白（Ig）基因多样化是针对病原体的有效抗体反应所必需的。激活诱导脱氨酶（AID）通过体细胞超突变（SHM）、类开关重组（CSR）和某些脊椎动物的Ig基因转换（IGC）等不同过程触发Ig基因多样化。大多数证据表明，AID通过破坏Ig基因胞嘧啶到尿嘧啶来触发这些过程。表达Ig基因可变区脱胺可导致SHM或IGC， Ig基因开关区脱胺可导致CSR。所产生的尿嘧啶的不同处理被认为会导致SHM， CSR或IGC的不同分子结果。这些观察结果提出了几个重要的问题：(i) DNA中尿嘧啶的存在如何导致IGC、CSR和可能的SHM所需的链断裂；（ii） AID如何特异性靶向Ig基因DNA（相对于任何其他细胞DNA）；（iii） AID是否通过参与相关的基于DNA脱氨的逆转录因子限制机制在先天免疫中发挥作用？第一个问题将通过确定脊椎动物细胞系DT40中IGC和SHM的遗传要求来回答，这支持正在进行的Ig基因多样化，并且可以很容易地进行操作。第二个问题的答案将通过先进的蛋白质组学方法来鉴定来自DT40和人类shm支持细胞系Ramos的保守的艾滋病相互作用蛋白来获得。第三个问题将通过对从鱼类到人类的脊椎动物树的关键分支编码的AID蛋白的逆转录限制能力进行全面的比较分析来解决。这里提出的基础研究将提高我们对Ig基因多样化机制的理解，人类免疫缺陷综合征的原因和几种B细胞癌的起源。与公共卫生有关。抗体是我们对细菌和病毒等病原体的免疫反应的重要组成部分。在DNA水平上，一种叫做AID的蛋白质帮助塑造抗体基因，从而产生高效的抗体反应。该建议侧重于如何在抗体产生细胞内控制和指导AID，因此这项研究将加强我们对抗体反应和一些人类抗体相关疾病（包括癌症）原因的理解。

DESCRIPTION (provided by applicant): Immunoglobulin (Ig) gene diversification is required for an effective antibody response toward pathogens. A single protein, activation-induced deaminase (AID), triggers Ig gene diversification by the distinct processes of somatic hypermutation (SHM), class switch recombination (CSR) and, in some vertebrates, Ig gene conversion (IGC). Most evidence indicates that AID triggers these processes by deaminating Ig gene cytosines to uracils. Deamination within the expressed Ig gene variable regions can lead to SHM or IGC, and deamination within the Ig gene switch regions can lead to CSR. Differential processing of the resulting uracils is proposed to result in the distinct molecular outcomes of SHM, CSR or IGC. These observations raise several important questions: (i) how does the presence of uracils in DNA lead to the strand breaks required for IGC, CSR and possibly for SHM; (ii) how is AID specifically targeted to the Ig gene DNA (as opposed to any other cellular DNA); and (iii) does AID play a role in innate immunity by participating in the related DNA deamination-based mechanism of retroelement restriction? The first question will be answered by determining the genetic requirements for IGC and SHM in the vertebrate cell line DT40, which supports ongoing Ig gene diversification and can be readily manipulated. The answer(s) to the second question will be obtained through advanced proteomic methods to identify conserved AID-interacting proteins from DT40 and a human SHM-supporting cell line Ramos. The third question will be addressed by performing a comprehensive comparative analysis of the retroelement restriction abilities of AID proteins encoded by key branches of the vertebrate tree, from fish to humans. The fundamental studies proposed here will improve our understanding of the mechanisms of Ig gene diversification, the causes of human immunodeficiency syndromes and the origins of several B cell cancers. Relevance to public health. Antibodies are a crucial part of our immune response to pathogens such as bacteria and viruses. At the DNA level, a single protein called AID helps to mold the antibody genes in such a way that a highly effective antibody response occurs. This proposal focuses on how AID is controlled and directed within an antibody-producing cell, and thereby this research will strengthen our understanding of the antibody response and the causes of some human antibody-associated diseases including cancers.