Uziel Tamar, Lerenthal Yaniv, Moyal Lilach, Andegeko Yair, Mittelman Leonid, Shiloh Yosef
The David and Inez Myers Laboratory for Genetic Research, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
EMBO J. 2003 Oct 15;22(20):5612-21. doi: 10.1093/emboj/cdg541.
The ATM protein kinase is a primary activator of the cellular response to DNA double-strand breaks (DSBs). In response to DSBs, ATM is activated and phosphorylates key players in various branches of the DNA damage response network. ATM deficiency causes the genetic disorder ataxia-telangiectasia (A-T), characterized by cerebellar degeneration, immunodeficiency, radiation sensitivity, chromosomal instability and cancer predisposition. The MRN complex, whose core contains the Mre11, Rad50 and Nbs1 proteins, is involved in the initial processing of DSBs. Hypomorphic mutations in the NBS1 and MRE11 genes lead to two other genomic instability disorders: the Nijmegen breakage syndrome (NBS) and A-T like disease (A-TLD), respectively. The order in which ATM and MRN act in the early phase of the DSB response is unclear. Here we show that functional MRN is required for ATM activation, and consequently for timely activation of ATM-mediated pathways. Collectively, these and previous results assign to components of the MRN complex roles upstream and downstream of ATM in the DNA damage response pathway and explain the clinical resemblance between A-T and A-TLD.
ATM蛋白激酶是细胞对DNA双链断裂（DSB）作出反应的主要激活因子。响应DSB时，ATM被激活并磷酸化DNA损伤反应网络各个分支中的关键因子。ATM缺陷会导致遗传性疾病共济失调毛细血管扩张症（A-T），其特征为小脑变性、免疫缺陷、辐射敏感性、染色体不稳定和癌症易感性。MRN复合物的核心包含Mre11、Rad50和Nbs1蛋白，它参与DSB的初始处理过程。NBS1和MRE11基因的亚效突变分别导致另外两种基因组不稳定疾病：尼曼-匹克氏综合征（NBS）和共济失调毛细血管扩张症样疾病（A-TLD）。ATM和MRN在DSB反应早期发挥作用的顺序尚不清楚。在此我们表明，功能性MRN是ATM激活所必需的，因此也是ATM介导的信号通路及时激活所必需的。总体而言，这些结果以及先前的结果确定了MRN复合物的组分在DNA损伤反应途径中位于ATM上下游的作用，并解释了A-T和A-TLD之间的临床相似性。
