Factors and DNA Motifs in Ig Class Switch

描述(申请人提供)：体液免疫依赖于免疫球蛋白(Ig)的表达来抵御致病挑战。体液免疫系统已经进化到产生具有广泛结合特异性的Ig。类切换重组(CSR)用于获得免疫球蛋白效应器功能和组织定位的多样性。小鼠IgH恒定区基因座组成为：5‘-V(D)J-C？Cd-C？3-C？1-C？2B-C？2a-Ce-Ca-3’。CSR涉及染色体内的缺失重排，主要集中在位于每个CH基因(CD除外)上游的重复开关(S)DNA区域。企业社会责任的形成过程可分为发起、S/S突触和分解与修复三个阶段。AID诱导的S区域的DNA损伤启动了这一过程。我建议研究导致S/S突触的事件，并识别与转录和DNA修复相关的染色质修饰。利用染色体构象捕获技术(3C)，我的实验室最近研究了位于VH和CH基因之间的5个内含子增强子(Eé)和位于IgH基因3‘端的3’EA增强子与各种GLT启动子之间的远程相互作用。我们发现，在B细胞中，E和3‘EA增强子在空间上非常接近，形成了独特的染色体环状构型。B细胞激活导致生殖线转录(GLT)启动子以细胞因子依赖的方式重新聚集到E？：3‘EA复合体。这种结构促进了S/S的突触，因为S位于E的近端，下游的S区域与靶向启动子共同招募到E：3‘EA复合体。我们认为，GLT启动子与E？：3‘EA复合体的结合创建了一个在CSR期间促进S/S突触的建筑支架，这些相互作用依赖于艾滋病的稳定作用。染色质重塑是控制S DNA对艾滋病的可及性的重要调控机制。我们已经定义了在S和C区不同发现的组蛋白修饰。我们的研究表明，染色质可及性与S区域组蛋白乙酰化和H3K4me3的增加相关，而染色质可及性的降低与S区域下游的低Ac和H3K36me3标记相关。我们将研究可访问性和这些组蛋白修饰之间的常见关系。叙述：体液免疫依赖于免疫球蛋白(Ig)的表达来抵御致病挑战。体液免疫系统已经进化到产生具有广泛结合特异性的Ig。我们研究了表达新型免疫球蛋白的分子过程。

DESCRIPTION (provided by applicant): Humoral immunity is dependent on the expression of immunoglobulin (Ig) to fend off pathogenic challenges. The humoral immune system has evolved to produce Ig with a broad repertoire of binding specificities. Class switch recombination (CSR) is used to attain diversity of Ig effector function and tissue localization. The murine IgH constant region locus is organized: 5'-V(D)J-C¿-Cd-C?3-C?1-C?2b-C?2a-Ce-Ca-3'. CSR involves an intra-chromosomal deletional rearrangement that focuses on regions of repetitive switch (S) DNA located upstream of each CH gene (with the exception of Cd). The process of CSR can be thought of as composed of three phases including, initiation, S/S synapsis and resolution and repair. AID induced DNA lesions at S regions initiates the process. I propose to examine events leading to S/S synapsis, and discern chromatin modifications associated with transcription and DNA repair. Using the chromosome conformation capture technique (3C), my laboratory has newly investigated the long- range interactions between the 5 intronic enhancer (E¿) located between the VH and CH genes and the 3'Ea enhancer located at the 3'-end of the IgH locus together with the various GLT promoters. We find that in B cells, the E¿ and 3'Ea enhancers are in close spatial proximity forming a unique chromosomal loop configuration. B cell activation leads to recruitment of the germline transcript (GLT) promoters to the E¿: 3'Ea complex in a cytokine dependent fashion. This structure facilitates S/S synapsis since S¿ is proximal to E¿ and the downstream S region are co-recruited with the targeted GLT promoter to the E¿: 3'Ea complex. We propose that GLT promoter association with the E¿: 3'Ea complex creates an architectural scaffolding that promotes S/S synapsis during CSR and these interactions are dependent on the stabilizing influence of AID. Chromatin remodeling is an important regulatory mechanism controlling the accessibility of S DNA to AID. We have defined histone modifications differentially found in the S and C regions. Our studies indicate chromatin accessibility is correlated with increased histone acetylation and H3K4me3 at the S regions whereas reduced accessibility is associated with hypoAc and the H3K36me3 mark downstream of the S region. We will study the causual relationship between accessibility and these histone modifications. NARRATIVE: Humoral immunity is dependent on the expression of immunoglobulin (Ig) to fend off pathogenic challenges. The humoral immune system has evolved to produce Ig with a broad repertoire of binding specificities. We study the molecular processes by which new types of Ig are expressed.