Mechanism and regulation of V(D)J repair

项目摘要 连接酶IV在非同源末端连接（NHEJ）、V（D）J重组中起关键作用 和免疫系统的发展，干细胞衰竭，衰老和神经生长和发育， 例如具有连接酶IV中的亚型突变的患者的表型。许多蛋白质具有 已显示调节连接酶IV活性。其中，XRCC 4和Cernunnos/XLF可能是 最好/最具决定性的特点。这两种因子，如连接酶IV，是核心NHEJ的一部分， 机械. XRCC 4中的人类突变尚未被描述，但有趣的是，Cernunnos/XLF 人类的突变导致生长缺陷、小头畸形和免疫缺陷，类似于 观察到连接酶IV突变。我们最近的研究发现，阿耳忒弥斯，一个因素也与 作为一种与连接酶IV直接相互作用的蛋白质，我们还观察到， 通过连接酶IV调节XRCC 4。在这个项目中，我们建议分析这些功能的相关性， 新型连接酶IV/Artemis复合物在基因组稳定性和V（D）J重组中的作用。的机制 连接酶IV调节XRCC 4功能，以及在XRCC 4中内源性连接酶IV复合物的组成和功能。 还将研究淋巴细胞。我们的初步工作与连接酶IV重组蛋白和蛋白 片段导致含有连接酶IV DNA结合结构域的连接酶IV片段结晶。 提出实验来解决连接酶IV和/或与Artemis复合的连接酶IV的结构。所有 这些都是具有挑战性但非常相关的实验，我们在这些实验中取得了重大进展。此外，委员会认为， 在LIG 4综合征患者中鉴定的突变对Artemis调节其功能的影响， 这些突变的连接酶IV蛋白如何影响XRCC 4功能也将被研究。获得的信息 将有助于对NHEJ、V（D）J的分子和结构的理解 重组和人类疾病与这两个过程中的缺陷有关。

Project Summary Ligase IV has been shown to play critical roles in Non-Homologous End Joining (NHEJ), V(D)J recombination and development of the immune system, stem cell exhaustion, ageing and neural growth and development, as exemplified by the phenotype of patients with hypomorphic mutations in Ligase IV. Numerous proteins have been shown to modulate Ligase IV activity. Among them, XRCC4 and Cernunnos/XLF are perhaps the best/most conclusively characterized. Both of these factors, like Ligase IV, are part of the core-NHEJ machinery. Human mutations in XRCC4 have not been described yet, but interestingly, Cernunnos/XLF mutations in humans result in growth defects, microcephaly and immunodeficiency, similar to what has been observed for Ligase IV mutations. Our recent findings have identified Artemis, a factor also linked to immunodeficiency in humans, as a protein that directly interacts with Ligase IV, in addition we have observed regulation of XRCC4 by Ligase IV. In this project we propose to analyze the functional relevance of these novel Ligase IV/Artemis complex in genomic stability and V(D)J recombination. The mechanism by which Ligase IV regulates XRCC4 function, and the composition and function of endogenous Ligase IV complexes in lymphocytes will also be investigated. Our preliminary work with Ligase IV recombinant protein and protein fragments has resulted in crystallization of a Ligase IV fragment containing the Ligase IV DNA binding domain. Experiments are proposed to solve the structure of Ligase IV and/or Ligase IV in complex with Artemis. All these are challenging yet very relevant experiments for which we show significant progresses. Furthermore, the impact of mutations identified in patients with LIG4 syndrome on regulation of its function by Artemis and on how these mutant Ligase IV proteins affect XRCC4 function will also be investigated. Information gained from the proposed studies will contribute to a molecular and structural understanding of NHEJ, V(D)J recombination and human diseases linked to defects in both of these processes.