Mechanistic Elucidation of Class Switch Recombination and Somatic Hypermutation

摘要 当遇到抗原时，成熟的B细胞表达活化诱导的胞苷脱氨酶（AID），并经历 免疫球蛋白重链（Igh）类别转换重组（CSR）和体细胞超突变（SHM）。CSR 通过DNA双链断裂（DSB）的专性产生进行，这构成了 大多数毒性损伤都可能发生在细胞中。单个未修复的DSB可导致细胞死亡或增强 染色体易位是许多类型癌症的标志，包括淋巴瘤。因此，在本发明中， 促进DSB产生和促进DSB修复的机制与免疫和 保持基因组的完整性。在这个建议中，我们测试的概念，单一的蛋白质可以协调两者 DSB形成和介导末端连接以有效地产生和修复DSB。我们检验了一个假设， 核小体重塑蛋白CHD 4协调Igh DSB的产生和修复（aim 1），而C- AID末端介导Igh DSB的有效DNA修复（目的2）。成功完成实验 将对我们理解B细胞免疫和B细胞淋巴瘤产生深远的影响。

ABSTRACT Upon encountering antigens, mature B cells express activation induced cytidine deaminase (AID) and undergo immunoglobulin heavy chain (Igh) class switch recombination (CSR) and somatic hypermutation (SHM). CSR proceeds through the obligate generation of DNA double strand breaks (DSBs), which constitute one of the most toxic lesions that can occur in a cell. A single unrepaired DSB can cause cell death or potentiate chromosomal translocations that are hallmarks of many types of cancer, including lymphomas. Thus, mechanisms that promote generation of DSBs and facilitate DSB repair are intergral to both immunity and preservation of genomic integrity. In this proposal we test the notion that single proteins can coordinate both DSB formation and mediate end-joining to efficiently generate and repair DSBs. We test the hypothesis that the nucleosomal remodeling protein CHD4 co-ordinates generation and repair of Igh DSBs (aim 1) and the C- terminus of AID mediates efficient DNA repair of Igh DSBs (aim 2). Successful completion of the experiments will have far reaching implications in our understanding of both B cell immunity and B cell lymphomas.