RNA-directed targeting of AID in immunity and genomic integrity

 描述（由申请人提供）：DNA双链断裂（DSB）是细胞中发生的毒性最大的损伤之一。未修复的DSB可以导致细胞死亡，也可以参与染色体易位，这是许多类型肿瘤的标志，包括淋巴瘤。尽管DSB具有毒性，但在类别转换重组（CSR）的免疫球蛋白（IG）基因多样化过程中，DSB被有意引入B细胞基因组的限定区域，称为转换（S）区域，并且未能引入此类DSB导致免疫缺陷综合征。DNA脱氨酶AID（活化诱导的胞苷脱氨酶）对于DSB的产生是必不可少的。虽然S区（和与IG基因相关的可变区基因片段）是主要靶点，但AID有可能在非IG基因（包括癌基因）处诱导DSB。这种脱靶DSB是大量成熟B细胞淋巴瘤个体发生背后的主要病变。尽管AID靶向免疫和癌症的相关性，但AID特异性的分子机制尚未完全阐明。我们现在已经证明，来自S区的非编码RNA作为分子向导将AID募集到S区。该提议检验了这样的假设，即转换转录物不仅将AID募集到S区域以促进CSR，而且还将AID与其他基因组区域隔离以防止B细胞基因多样化期间的附带损伤。在目标1中，我们测试了RNA引导的AID募集对体内CSR至关重要的概念。在目标2中，我们检查RNA引导的AID募集是否用于保护B细胞基因组免受附带的AIDS诱导的DNA损伤。在目标3中，我们设计嵌合RNA分子用于异位靶向AID。这些研究将对我们对免疫和免疫过程中简单的畸变如何导致B细胞淋巴瘤的基本理解产生深远的影响。

 DESCRIPTION (provided by applicant): DNA double strand breaks (DSBs) constitute one of the most toxic lesions to occur in a cell. Unrepaired DSBs can either lead to cell death or can participate in chromosomal translocations that are hallmarks of many kinds of tumors, including lymphomas. Despite the toxicity associated with DSBs, during the immunoglobulin (Ig) gene diversification process of class switch recombination (CSR), DSBs are deliberately introduced into defined regions, called switch (S) regions, of the B cell genome, and a failure to introduce such DSBs leads to immunodeficiency syndromes. The DNA deaminase AID (activation induced cytidine deaminase) is essential for the generation of DSBs. While S regions (and the Ig gene associated variable region gene segments) are primary targets, AID has the potential to induce DSBs at non-Ig genes, including oncogenes. Such off-target DSBs are the major lesions behind the ontogeny of a large number of mature B cell lymphomas. Despite the relevance of AID targeting to both immunity and cancer, the molecular mechanisms underlying AID specificity are yet to be fully elucidated. We have now shown that noncoding RNA emanating from S regions act as molecular guides to recruit AID to S regions. This proposal tests the hypothesis that switch transcripts not only recruit AID to S regions to facilitate CSR but also sequester AID from other genomic regions to prevent collateral damage during B cell gene diversification. In aim 1, we test the notion that the RNA-guided recruitment of AID is critical fo CSR in vivo. In aim 2, we examine if RNA-guided AID recruitment serves to shelter the B cell genome from collateral AID-induced DNA damage. In aim 3, we design chimeric RNA molecules for ectopic targeting of AID. These studies will have far-reaching implications into our fundamental understanding of both immunity and how simple aberrations in the process could lead to B cell lymphomas.