Roles of the Artemis nuclease in DNA repair and disease

描述（由申请人提供）：在针对外来抗原的免疫反应的初始阶段，B细胞和T细胞表面表达的大量受体识别并结合无数的外来分子。编码抗原受体识别区的基因之间的多样性是通过V(D)J重组产生的，在这个过程中，单个的V、D和J基因片段被重新排列。V(D)J重组需要两种活性；淋巴特异性因子，如重组激活基因1和2 (RAG1/2)，以及普遍表达的非同源末端连接（NHEJ） DNA修复因子，如Artemis。已知Artemis突变可引起与细胞放射敏感性相关的人类严重联合免疫缺陷综合征（RS-SCID）。最近的证据表明，阿尔忒弥斯的亚型突变也可能使人类患者易患淋巴瘤。Artemis是一种76 kDa的蛋白，具有单链5‘至3’外切酶活性，并通过与dna依赖性蛋白激酶催化亚基（DNA-PKcs）相互作用和磷酸化而获得核内溶活性。除了在V(D)J重组中发挥作用外，Artemis还需要用于一般的DNA双链断裂修复（DSB）和抑制染色体畸变，包括易位和端粒融合。目前尚不清楚Artemis的多种功能是否需要外核和内核溶解活性或DNA-PKcs的调节，也不清楚在人类患者中发现的Artemis突变对其内在生化活性有何影响。因此，本提案中描述的具体目标是利用生物化学，细胞和遗传方法的结合来进一步阐明Artemis的催化功能和体内作用。这些研究将使我们更清楚地了解Artemis在DNA修复过程中的功能，并深入了解人类患者免疫系统缺陷和淋巴细胞恶性肿瘤易感性的分子机制。

DESCRIPTION (provided by applicant): During the initial stages of the immune response against foreign antigens, a vast array of receptors expressed on the surface of B and T cells recognize and bind the myriad of foreign molecules. Diversity amongst the genes encoding the recognition regions of antigen receptors is generated through V(D)J recombination, a process in which individual V, D, and J gene segments are rearranged. Two types of activities are required for V(D)J recombination; lymphoid-specific factors, such as recombination activating genes 1 and 2 (RAG1/2), and the ubiquitously expressed non-homologous end-joining (NHEJ) DNA repair factors, such as Artemis. Mutations in Artemis are known to cause a human severe combined immunodeficiency syndrome associated with cellular radiosensitivity (RS-SCID). Recent evidence suggests that hypomorphic mutations in Artemis may also predispose to lymphoma in human patients. Artemis, a 76 kDa protein, possesses single strand 5' to 3' exonuclease activity and acquires endonucleolytic activity upon interaction with and phosphorylation by the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). In addition to its role in V(D)J recombination, Artemis is also required for general DNA double strand break repair (DSB) and suppressing chromosomal aberrations, including translocations and telomeric fusions. It is not yet known whether both exo- and endonucleolytic activities or regulation by DNA-PKcs are required for each of the multiple functions of Artemis, nor is it clear what impact the Artemis mutations found in human patients have on its intrinsic biochemical activities. Thus, the goals of the specific aims described in this proposal are to use combined biochemical, cellular and genetic approaches to further elucidate the catalytic repertoire and in vivo roles of Artemis. These studies will provide a more clear understanding of the functions of Artemis in DNA repair processes and insights into the molecular mechanisms underlying immune system defects and predisposition to lymphoid malignancies in human patients.