Role of Target DNA sequences in mutation and DNA Break Generation

描述（由申请方提供）：在对抗原的应答中，活化的B细胞经历体细胞超突变（SHM）和类别转换重组（CSR）以增强抗体多样性。SHM和CSR各自需要活化诱导脱氨酶（AID），其催化DNA特异性胞苷脱氨酶活性。AID靶向免疫球蛋白重链（Igh）基因座的高度重复开关（S）区域以诱导DNA双链断裂（DSB），DSB是CSR的中间体。当靶向IgH和IgL基因座的可变（V）区外显子时，AID主要诱导称为SHM的点突变，导致抗体对抗原的亲和力增加。大量的努力已经确定了潜在的AID辅因子，其可以结合Igh基因座的S区DNA或RNA转录物。这表明AID靶向与S区的转录暂停或RNA加工之间存在联系。 与研究得相对较好的 尽管对CSR的靶向机制的研究较少，但对AID靶向V区基因座的机制的了解要少得多。尽管AID具有在体外对任何转录底物脱氨基的能力，并且可能广泛地进入基因组以诱导B细胞中的基因组不稳定性，但其在SHM期间的生理靶点几乎仅限于IG基因座的V区。然而，由于缺乏强有力的实验系统，在很大程度上仍然不知道AID是如何专门针对V区的，这是目前最有趣的未解决问题之一。 在援助管理方面。因此，我们建立了一个独特的实验系统，并提出解决这些基本问题。本研究的完成将为研究艾滋病介导的SHM在B细胞免疫应答中的调控提供新的思路，并阐明B细胞淋巴瘤基因组不稳定性的分子机制。

DESCRIPTION (provided by applicant): In response to antigens, activated B cells undergo somatic hypermutation (SHM) and class switch recombination (CSR) to enhance antibody diversity. SHM and CSR each require the Activation Induced Deaminase (AID), which catalyses DNA-specific cytidine deaminase activity. AID targets the highly repetitive switch (S) regions of immunoglobulin heavy chain (Igh) loci to induce DNA double strand breaks (DSBs), which are intermediates in CSR. When targeting to variable (V) region exons of IgH and IgL loci, AID predominantly induces point mutations, termed SHM, resulting in the increased affinity of antibody for antigen. Intensive efforts have identified potential AID co-factors, which could bind S region DNA or RNA transcripts of Igh loci. This suggests a link between AID targeting and transcriptional pausing or RNA processing of S regions. In contrast to the relatively well studied targeting mechanisms for CSR, the mechanism of AID targeting to V region locus is much less well understood. Although AID has the ability to deaminate any transcribed substrate in vitro and could potentially access the genome widely to induce genomic instability in B cells, its physiological targets during SHM are almost exclusively restricted to V regions of Ig loci. However, due to the lack of robust experimental systems, it remains largely unknown how AID is specifically targeted to V regions, which is one of the most interesting unresolved questions in the field of AID regulation. Thus, we have established a unique experimental system, and propose to address these fundamental questions. The completion of our proposal will provide novel insights into the regulation of AID-mediated SHM in B cell immune responses and elucidate molecular mechanism of genomic instability in B cell lymphomas.