Mismatch repair in V region mutation and isotype switching

描述（由申请人提供）：生发中心B细胞经历高速率的体细胞突变和免疫球蛋白基因重组，负责亲和成熟和同型转换，产生保护性抗体。这些过程由激活诱导胞苷脱氨酶启动，该酶产生G:U错配，G:U错配经过复制、碱基切除修复和错配修复处理，产生抗体可变区和开关区体细胞超突变所需的突变。错配修复导致了约60%的突变和大部分导致产生更有效抗体的A:T碱基突变。虽然错配修复通常维持基因组的完整性和稳定性，但在Ig基因上，它介导广泛的突变和重组。在这里，我们建议研究生发中心B细胞如何利用错配修复将容易出错的修复招募到免疫球蛋白基因的特定区域，同时继续保持基因组其余部分的基因组稳定性，并研究错配修复在B细胞淋巴瘤发生中的作用。我们将通过：1)确定MSH6和其他错配修复蛋白如何与PCNA相互作用，将容易出错的修复招募到免疫球蛋白变量和开关区域，而不是突变和切换生发中心B细胞中的其他基因；2)比较错配修复蛋白在突变和切换B细胞中的相互作用和与其他蛋白质的相互作用，以及与其他类型细胞中的相互作用；3)检测MSH6缺陷和突变小鼠淋巴瘤的特征，以了解MSH6如何保护B细胞免受淋巴瘤的发生。公共卫生相关性：为了保护我们免受病原生物的侵害，我们有必要生产针对每种可能抗原的抗体，并随着病原体的变化迅速改变这些抗体。当我们对感染做出反应时，我们通过向编码抗体分子的基因中引入许多突变来做到这一点，这种遗传不稳定性主要是通过一个称为错配修复的过程来实现的。我们将使用在错配修复中有遗传缺陷的小鼠来研究抗体多样性是如何产生的。

DESCRIPTION (provided by applicant): Germinal center B cells undergo a high rate of somatic mutation and recombination of their immunoglobulin genes that is responsible for the affinity maturation and isotype switching that generates protective antibodies. These processes are initiated by activation induced cytidine deaminase which generates G:U mismatches that are processed by replication, base excision repair and mismatch repair to produce the mutations required for somatic hypermutation of antibody variable and switch regions. Mismatch repair is responsible for ~60% of the total mutations and most of the mutations in A:T bases that lead to production of more effective antibodies. While mismatch repair normally maintains the integrity and stability of the genome, at the Ig gene it mediates extensive mutation and recombination. Here we propose to examine how germinal center B cells use mismatch repair to recruit error prone repair to specific regions of the immunoglobulin genes while continuing to maintain genomic stability in the rest of genome and to examine role of mismatch repair in the B cell lymphomagenesis. We will do this by: 1) determining how MSH6 and the other mismatch repair proteins interact with PCNA to recruit error prone repair to the immunoglobulin variable and switch regions, but not to other genes in mutating and switching germinal center B cells; 2) comparing the interactions of the mismatch repair proteins with each other and with other proteins in mutating and switching B cells and with those interactions in other types of cells; and 3) examining the characteristics of the lymphomas that arise in MSH6 deficient and mutant mice in order to understand how MSH6 protects B cells from lymphomagenesis. PUBLIC HEALTH RELEVANCE: To protect us from pathogenic organisms, it is necessary for us to produce antibodies to every possible antigen and to rapidly change those antibodies as the pathogen changes. We do this by introducing many mutations into the genes that encode the antibody molecules as we respond to infection and this genetic instability is accomplished mostly through a process called mismatch repair. We will use mice that have genetic defects in mismatch repair to examine how the generation of antibody diversity is accomplished.