DNA repair and lg class switching

DNA 修复和 LG 类别转换

• 批准号: 7172597
• 负责人: Janet M. Stavnezer
• 金额: $ 30.82万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7172597
• 关键词: APEXL2 Gene; Antibodies; Antigens; B-Cell Activation; Base Excision Repairs; CD80 Antigens; Class; Condition; DNA; DNA Polymerase I; DNA Repair; DNA Single Strand Break; DNA polymerase iota; DNA-(apurinic or apyrimidinic site) lyase; DNA-Directed DNA Polymerase; Data; Deamination; ERCC1 gene; Enzymes; Event; Excision; Genes; Genetic Recombination; Goals; Grant; Human; IgE; Immune response; Immunoglobulin A; Immunoglobulin Class Switching; Immunoglobulin G; Immunoglobulin M; Immunoglobulin Somatic Hypermutation; Immunoglobulin Switch Recombination; Infectious Agent; Left; Lesion; Mus; Mutation; Nucleotide Excision Repair; Pathway interactions; Polymerase; Process; Regulation; Role; Site; Specificity; Structure; XPA gene; activation-induced cytidine deaminase; base; constant region gene; cytokine; endonuclease; human APEX1 protein; protein expression; repair enzyme; repaired; uracil-DNA glycosylase; variable region gene

DESCRIPTION (provided by applicant): Upon activation by antigen, B cells undergo antibody class (isotype) switching, changing from expression of IgM to expression of IgG, IgA or IgE, while maintaining specificity for the same antigen. Since the isotype determines the effector function of the antibody, class switching allows the humoral immune response to adaptively respond to different infectious organisms. Class switching occurs by a DNA recombination event between switch (S) region sequences located upstream of each heavy chain constant (CH) region gene. This process has mechanistic similarities to somatic hypermutation of Ig variable region genes. It has recently become clear that activation-induced cytidine deaminase (AID) initiates class switch recombination (CSR) by deamination of dC residues within S regions, creating dU residues. The resulting dU residues are excised by uracil DNA glycosylase (UNG) leaving a basic residues, and mice and humans without UNG have greatly reduced abilities to undergo CSR. However, in order to initiate CSR, the abasic site must be converted to a single strand DNA break. This has been hypothesized to be due to AP endonuclease (APE) but which of the two APEs might be involved are unknown. Another possibility is supported by data from this group, suggesting that the endonuclease ERCC1/XPF might also have this role. One of the goals of this grant is to determine how the initiating DNA breaks are introduced. A related goal is to determine the mechanisms for introduction of mutations into S regions during the DNA repair processes accompanying CSR. There are 4 specific aims directed towards these goals. Aim 1: to determine if components of the nucleotide excision repair (NER) pathway, in addition to ERCC1/XPF, are involved in CSR and to determine their role. Aim 2: to determine if the base excision repair (BER) enzymes APE1 or APE2 create the initiating DNA breaks in the Su segments. Aim 3: to determine if the BER and NER pathways are redundant for creation of the initiating DNA breaks and if there is a competition between these pathways. We will also explore if the competition is altered by activation of B cells in the presence of different induction conditions. In Aim 4 we will explore how the mutations are introduced into Ig S regions by determining if the translesion DNA polymerase iota is involved in the error-prone repair of S regions and if this involvement is regulated by cytokines.

描述（由申请人提供）：抗原激活后，B细胞会经历抗体类（同种型）切换，从IgM的表达转换为IgG，IgA或IgE的表达，同时保持对同一抗原的特异性。由于同种型决定抗体的效应函数，因此类切换允许体液免疫反应适应对不同的感染生物的反应。类开关是通过位于每个重链常数（CH）区域基因上游的开关区域序列之间的DNA重组事件发生的。该过程与Ig变量区域基因的体细胞超伪标具有机械相似性。最近很明显，激活诱导的胞苷脱氨酶（AID）通过在S区域内的直流残基脱氨基来启动类开关重组（CSR），从而产生DU残基。由尿嘧啶DNA糖基化酶（UNG）切除所得的DU残基，留下基本残基，而没有UNG的小鼠和人类具有大大降低CSR的能力。但是，为了启动企业社会责任，无asic部位必须转换为单链DNA断裂。这是由于AP核酸内切酶（APE）造成的，但可能涉及的两只猿中的哪个尚不清楚。该组的数据支持了另一种可能性，这表明核酸内切酶ERCC1/XPF也可能具有此角色。这笔赠款的目标之一是确定如何引入启动DNA断裂。一个相关的目标是确定在CSR伴随的DNA修复过程中将突变引入S区域的机制。针对这些目标有4个具体目标。目标1：确定除ERCC1/XPF之外，核苷酸切除修复（NER）途径的组件是否参与了CSR并确定其作用。目标2：确定基础切除修复（BER）酶APE1或APE2是否会在SU段中产生启动DNA断裂。 AIM 3：确定BER和NER途径是否是为了创建启动DNA断裂以及这些途径之间是否存在竞争。我们还将在存在不同的诱导条件下B细胞的激活改变竞争是否会改变竞争。在AIM 4中，我们将通过确定转移DNA聚合酶IOTA是否参与S区域的易于修复以及该参与是否受细胞因子的调节来探讨如何将突变引入Ig S区域。