Chen Benjamin P C, Uematsu Naoya, Kobayashi Junya, Lerenthal Yaniv, Krempler Andrea, Yajima Hirohiko, Löbrich Markus, Shiloh Yosef, Chen David J
Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.
J Biol Chem. 2007 Mar 2;282(9):6582-7. doi: 10.1074/jbc.M611605200. Epub 2006 Dec 21.
The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is rapidly phosphorylated at the Thr-2609 cluster and Ser-2056 upon ionizing radiation (IR). Furthermore, DNA-PKcs phosphorylation at both regions is critical for its role in DNA double strand break (DSB) repair as well as cellular resistance to radiation. IR-induced DNA-PKcs phosphorylation at Thr-2609 and Ser-2056, however, exhibits distinct kinetics indicating that they are differentially regulated. Although DNA-PKcs autophosphorylates itself at Ser-2056 after IR, we have reported here that ATM mediates DNA-PKcs phosphorylation at Thr-2609 as well as at the adjacent (S/T)Q motifs within the Thr-2609 cluster. In addition, our data suggest that DNA-PKcs- and ATM-mediated DNA-PKcs phosphorylations are cooperative and required for the full activation of DNA-PKcs and the subsequent DSB repair. Elimination of DNA-PKcs phosphorylation at both regions severely compromises radioresistance and DSB repair. Finally, our result provides a possible mechanism for the direct involvement of ATM in non-homologous end joining-mediated DSB repair.
在受到电离辐射（IR）后，DNA依赖性蛋白激酶（DNA-PKcs）的催化亚基会在苏氨酸-2609簇和丝氨酸-2056处迅速发生磷酸化。此外，DNA-PKcs在这两个区域的磷酸化对于其在DNA双链断裂（DSB）修复以及细胞对辐射的抗性方面所起的作用至关重要。然而，IR诱导的DNA-PKcs在苏氨酸-2609和丝氨酸-2056处的磷酸化表现出不同的动力学，这表明它们受到不同的调节。尽管IR后DNA-PKcs会在丝氨酸-2056处自身发生自磷酸化，但我们在此报告，ATM介导DNA-PKcs在苏氨酸-2609以及苏氨酸-2609簇内相邻的（丝氨酸/苏氨酸）谷氨酰胺基序处的磷酸化。此外，我们的数据表明，DNA-PKcs介导的和ATM介导的DNA-PKcs磷酸化是协同的，并且是DNA-PKcs完全激活以及随后的DSB修复所必需的。消除这两个区域的DNA-PKcs磷酸化会严重损害辐射抗性和DSB修复。最后，我们的结果为ATM直接参与非同源末端连接介导的DSB修复提供了一种可能的机制。
