ATM-dependent phosphorylation of nibrin in response to radiation exposure
ATM-dependent phosphorylation of nibrin in response to radiation exposure
复制标题
DOI：
10.1038/75508
复制
发表时间：
2000-05-01
期刊：
影响因子：
30.8
通讯作者：
Khanna, K
中科院分区：
文献类型：
--
作者：
Gatei, M;Young, D;Khanna, K
ATM基因的突变导致遗传性疾病共济失调-毛细血管扩张症(A-T)，其特征是小脑功能障碍、辐射敏感性、染色体不稳定和癌症易感性。ATM蛋白的A-T表型和与其他DNA损伤感受器的相似性都表明ATM在参与识别、信号和修复DNA双链断裂(DSB)的生化途径中发挥了作用。A-T患者的放射敏感性、染色体不稳定性和癌症易感性与奈梅亨断裂综合征(NBS)患者的辐射敏感性、染色体不稳定性和癌症易感性有很强的相似性。NBS中的缺陷蛋白Nibrin(由NBS1编码)与Mre11和Rad50形成复合体(参考文献1，2)。这种复合体在细胞暴露于电离辐射(1R)后30分钟内定位于DSB，并在较长时间后在染色鲜艳的核灶中观察到(3)。A-T和NBS的临床和细胞表型的重叠表明ATM和Nibrin可能在同一生化途径中发挥作用。在这里，我们证明了Nibrin在IR处理细胞的一小时内被磷酸化。这种反应在不表达ATM蛋白或表达接近全长突变蛋白的A-T细胞中被取消。我们还表明，在体内和体外，ATM都与丝氨酸343上的Nibrin发生物理相互作用并使其磷酸化。该位点的磷酸化似乎具有重要的功能，因为突变的Nibrin(S343A)不能完全补充NBS细胞的放射敏感性。辐射诱导的病灶形成表明，Nibrin的ATM磷酸化不影响Nibrin-Mre11-Rad50的结合。我们的数据为A-T和NBS在表型上的相似性提供了生化解释。
Mutations in the gene ATM are responsible for the genetic disorder ataxia-telangiectasia (A-T), which is characterized by cerebellar dysfunction, radiosensitivity, chromosomal instability and cancer predisposition. Both the A-T phenotype and the similarity of the ATM protein to other DNA-damage sensors suggests a role for ATM in biochemical pathways involved in the recognition, signalling and repair of DNA double-strand breaks (DSBs). Them are strong parallels between the pattern of radiosensitivity, chromosomal instability and cancer predisposition in A-T patients and that in patients with Nijmegen breakage syndrome (NBS). The protein defective in NBS, nibrin (encoded by NBS1), forms a complex with MRE11 and RAD50 (refs 1,2). This complex localizes to DSBs within 30 minutes after cellular exposure to ionizing radiation (1R) and is observed in brightly staining nuclear foci after a longer period of time(3). The overlap between clinical and cellular phenotypes in A-T and NBS suggests that ATM and nibrin may function in the same biochemical pathway. Here we demonstrate that nibrin is phosphorylated within one hour of treatment of cells with IR. This response is abrogated in A-T cells that either do not express ATM protein or express near full-length mutant protein. We also show that ATM physically interacts with and phosphorylates nibrin on serine 343 both in vivo and in vitro. Phosphorylation of this site appears to be functionally important because mutated nibrin (S343A) does not completely complement radiosensitivity in NBS cells. ATM phosphorylation of nibrin does not affect nibrin-MRE11-RAD50 association as revealed by radiation-induced foci formation. Our data provide a biochemical explanation for the similarity in phenotype between A-T and NBS.