The Regulation of Somatic Hypermutation

项目摘要/摘要 脊椎动物能够产生大量的抗体分子来对抗 感染。人类在生命周期中能产生的抗体特异性的数量 寿命估计超过109，这个数字大大超过了编码 基因组的容量。相反，抗体库的大小是 在产生抗体的B淋巴细胞中发生的基因多样化过程。这个 初级B细胞库是由骨骼中的体细胞(V(D)J)重组产生的 B细胞发育过程中的骨髓。然而，这个曲目既不够大，也不够 具有足够的特异性，以提供针对一系列抗原和 动物可能会遇到。因此，抗体多样性的产生在很大程度上取决于 关于V(D)J重组后发生的二级多元化过程。 二次抗体多样化是由胞苷残基(TO)的脱氨基引发的 产生尿嘧啶)在免疫球蛋白基因内。这个过程是由胞苷催化的。 脱氨酶AID，被认为是结合和脱氨暴露在 转录的免疫球蛋白基因，产生U：G错配，在 产生点突变、基因转换或开关重组的多种方式。 然而，艾滋病引起的尿嘧啶损伤也可以通过以下方式导致永久性的基因组损伤 作为染色体易位的底物或通过诱变非Ig基因， 包括癌基因。因此，对艾滋病的严格监管对维持 基因组稳定性。这项建议的长期目标是了解艾滋病是如何 通过延伸抗体多样化，是受调控的。因此，这项提案将侧重于 以下专题：a)艾滋病的转录调控(我们建议 将确定导致AID转录诱导的程序的实验)； B)在蛋白质水平上调节AID(我们使用了一种新的筛查来 确定与脱氨酶相互作用的一整套细胞因子；以及 我们建议对其中一个辅因子进行详细研究，一种名为RNF126的蛋白质，它 似乎满足脱氨酶靶向因子的要求)。 体细胞超突变与自身免疫性疾病以及 B细胞淋巴瘤的发生。因此，这里提出的实验对于 更好地了解自身免疫性和B细胞淋巴瘤。

Project Summary/Abstract Vertebrates are able to produce a vast repertoire of antibody molecules to combat infection. The number of antibody specificities that a human can produce during their lifetime is estimated to be in excess of 109, a number that greatly exceeds the coding capacity of the genome. Instead, the size of the antibody repertoire is the product of gene diversification processes that take place in antibody producing B lymphocytes. The primary B cell repertoire is generated by somatic (V(D)J) recombination in the bone marrow during B cell development. However, this repertoire is neither large enough nor specific enough to provide high affinity antibodies against the range of antigens an animal may encounter. Thus the generation of antibody diversity depends in a major way on secondary diversification processes that occur following V(D)J recombination. Secondary antibody diversification is triggered by deamination of cytidine residues (to yield uracil) within the immunoglobulin locus. This process is catalyzed by the cytidine deaminase AID, which is thought to bind and deaminate ssDNA exposed on the transcribed immunoglobulin gene, generating U:G mismatches that are resolved in a variety of ways to generate point mutations, gene conversion or switch recombination. However, AID-induced uracil lesions can also lead to permanent genomic damage by serving as substrates for chromosometranslocations or by mutagenizing non-Ig genes, includingoncogenes. Therefore, strict regulation of AID is importantfor maintaining genomic stability. The long term objective of this proposal is to understand how AID, and by extension antibody diversification, is regulated. This proposal will therefore focus on the following topics: a) the transcriptional regulation of AID (where we propose experiments that will determine the program that leads to induction of AID transcription); b) the regulation of AID at the protein level (where we have used a novel screen to identify the entire set of cellular factors that interact with the deaminase; and also, where we propose detailed studies on one of these cofactors, a protein termed RNF126, which appears to satisfy the requirements of a targeting factor for the deaminase). Somatic hypermutation has been implicated in autoimmune diseases as well as in the generation of B cell lymphomas. Thus the experiments proposed here are important for a better understanding of both autoimmunity and B cell lymphomas.