Analysis of Immunodeficiencies with defective DNA damage response

我们试图分析由DNA损伤反应缺陷引起的免疫缺陷的分子机制，这些缺陷作用于包括共济失调毛细血管扩张症（AT）、阿尔忒弥斯缺乏症和奈梅亨断裂综合征（NBS1缺乏症）在内的疾病细胞。到目前为止，我们已经发现Artemis的S645在DNA损伤试剂上被ATM磷酸化。通过本研究，我们发现70kda分子与Artemis有关，并控制着Artemis的稳定性。这种相互作用需要Artemis的磷酸化，但位点不在迄今已知的区域。阿尔忒弥斯的新角色也被展示出来。研究表明，当DNA复制在断裂链中停滞时，双链DNA断裂需要Artemis的内切酶活性。此过程依赖于ATM。目前正在进行进一步调查。DNA损伤反应（DDR）是免疫受体多样化的必要条件；在这个过程中，DDR被破坏会导致染色体畸变。我们分析了DDR分子在肿瘤发生中的作用，发现DDR在癌前阶段被激活。在某些情况下，DDR的缺失导致p53突变的细胞发生恶性转化（白血病，2006）。ATM和Ku70/80在氧化应激下被降解导致细胞凋亡（Ann NY Acad Sci 2006, Int J Biochem Cell Biol. 2008）。细胞免于凋亡可能导致染色体畸变的获得。我们诊断出14例AT， 2例DNA连接酶IV缺乏症，2例mre11缺乏症（ATLD）和1例Cernunnos缺乏症。最后，我们对AT进行了第一次全国范围的调查。我们观察到兄弟姐妹AT病例之间的表型差异。10%的患者出现Hyper-IgM，表明ATM参与了类转换重组。

We sought to analyze molecular mechanism of immunodeficiency caused by defective DNA damage response working on cells from disorders including ataxia-telangiectasia (AT), Artemis deficiency, and Nijmegen breakage syndrome (NBS1 deficiency).We have so far revealed that S645 of Artemis is phosphorylated by ATM upon DNA damaging reagent. Through this study, we have shown 70-kDa molecule is associated with Artemis and controls stability of Artemis. The interaction requires phosphorylation of Artemis, but the site is not in the hitherto-known region. A new role of Artemis was also demonstrated. Endonuclease activity of Artemis was shown to be required for double strand DNA break when DNA replication is stalled in a ragging strand. This process was dependent on ATM. Further investigation is currently in progress.DNA damage response (DDR) is absolutely required for diversification of immune receptors; and disrupted DDR during the process leads to chromosomal aberration. We analyzed involvement of the DDR molecules in tumorigenesis, and found that DDR is activated in pre-malignant stage. The loss of DDR led to malignant transformation of the cells with mutation in p53 in some cases (Leukemia 2006).ATM and Ku70/80 were shown to be degraded upon oxidative stress leading to cellular apoptosis (Ann NY Acad Sci 2006, Int J Biochem Cell Biol. 2008)。 The cells escaped from apoptosis may lead to acquisition of chromosomal aberration.We diagnosed 14 patients with AT, 2 DNA ligase IV deficiency, 2 Mre11deficiency (ATLD) and one Cernunnos deficiency. Finally, we carried out the first nation-wide survey for AT. We observed phenotypic variety between sibling cases with AT. Hyper-IgM was noted in 10% of the patients indicating involvement of ATM in class switch recombination.