Roles of the Artemis nuclease in DNA repair and disease

描述(申请人提供)：在针对外来抗原的免疫反应的初始阶段，表达在B和T细胞表面的大量受体识别并结合无数外来分子。编码抗原受体识别区域的基因之间的多样性是通过V(D)J重组产生的，这是一个单独的V、D和J基因片段重排的过程。V(D)J重组需要两种类型的活性：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。Artemis的突变已知会导致一种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，Artemis的亚型突变也可能容易导致人类患者的淋巴瘤。Artemis是一种76 kDa的蛋白质，具有单链5‘-3’外切酶活性，并通过与DNA依赖的蛋白激酶催化亚单位(DNA-PKcs)相互作用和磷酸化而获得内切活性。除了在V(D)J重组中的作用外，Artemis也是一般DNA双链断裂修复(DSB)和抑制染色体异常(包括易位和端粒融合)所必需的。目前尚不清楚Artemis的多种功能中的每一项是否都需要内外核溶解活性或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的影响。因此，本提案中描述的特定目标的目标是使用组合的生化、细胞和遗传学方法来进一步阐明Artemis的催化谱系和在体内的作用。这些研究将使人们更清楚地了解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系统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.