Mismatch repair in V region mutation and isotype switching

描述（由申请方提供）：老年中心B细胞经历高速率的体细胞突变和其免疫球蛋白基因重组，其负责亲和力成熟和产生保护性抗体的同种型转换。这些过程由激活诱导的胞苷脱氨酶启动，其产生G：U错配，所述G：U错配通过复制、碱基切除修复和错配修复进行处理，以产生抗体可变区和开关区的体细胞超突变所需的突变。错配修复导致约60%的总突变和导致产生更有效抗体的A：T碱基中的大多数突变。虽然错配修复通常维持基因组的完整性和稳定性，但在IG基因处，它介导广泛的突变和重组。在这里，我们建议检查如何生殖中心B细胞使用错配修复招募错误倾向的修复免疫球蛋白基因的特定区域，同时继续保持基因组的其余部分的基因组稳定性，并检查错配修复在B细胞淋巴瘤发生的作用。为此，我们将：1）确定MSH 6和其它错配修复蛋白如何与PCNA相互作用以募集对免疫球蛋白可变区和转换区的易错修复，而不是对突变和转换的生殖中心B细胞中的其它基因的易错修复; 2）比较错配修复蛋白彼此之间的相互作用和与突变和转换的B细胞中的其它蛋白的相互作用以及与其它类型细胞中的那些相互作用;和3）检查MSH 6缺陷和突变小鼠中出现的淋巴瘤的特征，以了解MSH 6如何保护B细胞免于淋巴瘤发生。公共卫生相关性：为了保护我们免受病原体的侵害，我们有必要对每一种可能的抗原产生抗体，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，我们通过将许多突变引入编码抗体分子的基因来实现这一点，这种遗传不稳定性主要是通过一种称为错配修复的过程来实现的。我们将使用在错配修复中具有遗传缺陷的小鼠来检查抗体多样性的产生是如何完成的。

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.