Co-ordination of recombination and allelic exclusion at IgH and Igk loci

描述(由申请人提供)：B和T淋巴细胞的发育是由V(D)J重组推动的，通过V(D)J重组，抗原受体位点的基因片段重复重排，创建大量的抗原受体基因库。因为V(D)J重组需要广泛分布的基因片段每天数百万次的切割和连接，甚至一个 极小的错误率仍然会带来相当大的移位风险。鉴于这种风险，V(D)J重组在三个主要水平上受到严格调控：谱系特异性、给定谱系内的有序重排和等位基因排斥。我的实验室对等位基因排斥以及它如何与给定谱系内的有序重排相协调特别感兴趣。我们最新的工作，由父母资助(《免疫球蛋白和免疫球蛋白K基因座重组和等位基因排除的协调》)为这些问题提供了一些惊人的见解。简而言之，我们发现同源免疫球蛋白等位基因以一种阶段特定的方式配对，这与这些基因座重组的顺序阶段平行。IL-7R及其下游信号转导元件STAT5在免疫球蛋白重排过程中介导基因座可及性，促进免疫球蛋白等位基因的同源配对，抑制免疫球蛋白/免疫球蛋白K关联和免疫球蛋白基因座去牵引力。此外，我们发现Ig基因座的等位基因间关联是由V(D)J重组酶(即RAG1和RAG2蛋白)和DNA损伤检查点蛋白ATM介导的：一个等位基因上的RAG裂解会导致另一个等位基因重新定位到着丝粒周围的异染色质，以防止进一步的切割，而这种重新定位在没有ATM(自然免疫学)的情况下不会发生。DNA损伤传感机制在等位基因排除中的参与是相当令人惊讶的，并将我的实验室带入了一个与肿瘤发生直接相关的有前途的新研究领域。我们现在想扩展我们现有的目标，询问在协调T细胞中抗原受体基因座的重组和等位基因排斥方面涉及哪些共同机制。考虑到每个基因座的独特功能，我们预计这些因素和过程在T细胞中可能受到非常不同的调节(例如，我们已经看到IgH和IgK之间的差异，因为前者必须经历两个重排步骤，D到J，然后V到DJ)。我们相信，这些实验提供了一个极好的机会，以一种非常合乎逻辑的方式显著扩大父母赠款的范围。 公共卫生评论：我们一直在研究免疫球蛋白和免疫球蛋白K基因座有序、有序重组的调节。我们最近的研究揭示了新的监管方面 免疫球蛋白重排，涉及STAT5、RAG1和ATM。在这个项目中，我们的目标是确定是否有共同的机制参与协调Tcrb和TCRA基因座的重组和等位基因排斥。

DESCRIPTION (provided by applicant): B and T lymphocyte development is driven by V(D)J recombination, a process by which gene segments at the antigen receptor loci are repeatedly rearranged to create a vast repertoire of antigen receptor genes. Because V(D)J recombination entails the cleavage and joining of widely dispersed gene segments many millions of times each day, even a miniscule error rate would still carry considerable risk of translocation. Given this risk, V(D)J recombination is tightly regulated at three main levels: lineage specificity, ordered rearrangement within a given lineage, and allelic exclusion. My lab has been particularly interested in allelic exclusion and how it might be coordinated with ordered rearrangement within a given lineage. Our most recent work, funded by the parent grant ("Co-ordination of recombination and allelic exclusion at Igh and Igk loci") has provided some striking insights into these questions. In brief, we discovered that homologous Ig alleles pair up in a stage-specific manner that parallels the sequential stages of recombination at those loci. IL-7R and STAT5, its downstream signaling component, mediate locus accessibility during Igh rearrangement, promote homologous pairing of Igh alleles, and inhibit Igh/Igk association and Igh locus decontraction. Moreover, we found that interallelic association of Ig loci is mediated by the V(D)J recombinase (i.e., the RAG1 and RAG2 proteins) and the DNA damage checkpoint protein ATM: RAG cleavage on one allele induces repositioning of the other allele to pericentromeric heterochromatin to prevent further cleavage, and this repositioning does not occur in the absence of ATM (Nature Immunology, in press). The involvement of the DNA damage sensing machinery in allelic exclusion is quite surprising and takes my lab into a promising new area of research with direct relevance to oncogenesis. We would now like to expand our existing aims to ask what common mechanisms are involved in coordinating recombination and allelic exclusion of the antigen receptor loci in T cells. Given the unique features of each locus, we expect that these factors and processes could be regulated quite differently in T cells (we already see differences between Igh and Igk, for example, because the former must undergo two rearrangement steps, D to J and then V to DJ). We believe these experiments present a superb opportunity to significantly expand the scope of the parent grant in an eminently logical way. PUBLIC HEALTH REVELANCE: We have been investigating the regulation of ordered, sequential recombination of Igh and Igk loci. Our recent studies have brought to light new regulatory aspects of immunoglobulin rearrangement, that involve STAT5, RAG1 and ATM. In this project we aim to determine whether common mechanisms are involved in coordinating recombination and allelic exclusion of the Tcrb and Tcra loci.