Factors and DNA Motifs in Ig Class Switch

描述（由申请方提供）：体液免疫依赖于免疫球蛋白（IG）的表达来抵御病原体的攻击。体液免疫系统已经进化到产生具有广泛结合特异性的IG。类别转换重组（CSR）用于获得IG效应子功能的多样性和组织定位。鼠IgH恒定区基因座的结构为：5 '-V（D）J-C <$-Cd-C？3-C 1-C？2b-C？2a-Ce-Ca-3 '。CSR涉及染色体内缺失重排，其集中于位于每个CH基因上游的重复开关（S）DNA区域（除了Cd）。CSR的过程可分为起始、S/S突触和消退与修复三个阶段。AID诱导的S区DNA损伤启动了这一过程。我建议检查导致S/S突触的事件，并辨别与转录和DNA修复相关的染色质修饰。利用染色体构象捕获技术（3C），我的实验室新近研究了位于VH和CH基因之间的5内含子增强子（E？）和位于IgH基因座3 '末端的3' Ea增强子与各种GLT启动子之间的长程相互作用。我们发现，在B细胞中，E？和3 'Ea增强子在空间上非常接近，形成了独特的染色体环构型。B细胞活化导致种系转录本（GLT）启动子以细胞因子依赖性方式募集至E ²：3 'Ea复合物。这种结构有利于S/S突触，因为S <$接近E <$，下游S区与靶向GLT启动子共同募集到E <$：3 'Ea复合物。我们认为GLT启动子与E：3 'Ea复合物的结合创造了一个建筑支架，在CSR过程中促进S/S突触，这些相互作用依赖于AID的稳定影响。染色质重构是控制S DNA与AID可及性的重要调节机制。我们已经定义了在S和C区发现的组蛋白修饰差异。我们的研究表明，染色质可及性与S区组蛋白乙酰化和H3 K4 me 3增加相关，而可及性降低与S区下游的hypoAc和H3 K36 me 3标记相关。我们将研究可及性和这些组蛋白修饰之间的因果关系。叙述：体液免疫依赖于免疫球蛋白（IG）的表达来抵御病原体的挑战。体液免疫系统已经进化到产生具有广泛结合特异性的IG。我们研究了新型IG表达的分子过程。

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.