Lukas Claudia, Falck Jacob, Bartkova Jirina, Bartek Jiri, Lukas Jiri
Danish Cancer Society, Institute of Cancer Biology, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
Nat Cell Biol. 2003 Mar;5(3):255-60. doi: 10.1038/ncb945.
Cell cycle checkpoints are signal transduction pathways activated after DNA damage to protect genomic integrity. Dynamic spatiotemporal coordination is a vital, but poorly understood aspect, of these checkpoints. Here, we provide evidence for a strikingly different behaviour of Chk2 versus Nbs1, key mediators of the ataxia-telangiecatesia-mutated (ATM)-controlled checkpoint pathways induced by DNA double-strand breaks (DSBs). In live human cells with DSBs restricted to small sub-nuclear areas, Nbs1 was rapidly recruited to the damaged regions and underwent a dynamic exchange in the close vicinity of the DSB sites. In contrast, Chk2 continued to rapidly move throughout the entire nucleus, irrespective of DNA damage and including the DSB-free areas. Although phosphorylation of Chk2 by ATM occurred exclusively at the DSB sites, forced immobilization of Chk2 to spatially restricted, DSB-containing nuclear areas impaired its stimulating effect on p53-dependent transcription. These results unravel a dynamic nature of Nbs1 interaction with DSB lesions and identify Chk2 as a candidate transmitter of the checkpoint signal, allowing for a coordinated pan-nuclear response to focal DNA damage.
细胞周期检查点是DNA损伤后被激活以保护基因组完整性的信号转导通路。动态时空协调是这些检查点至关重要但却知之甚少的一个方面。在此，我们提供证据表明，共济失调毛细血管扩张症突变基因（ATM）控制的由DNA双链断裂（DSB）诱导的检查点通路的关键介质Chk2与Nbs1的行为存在显著差异。在DSB局限于小核内亚区域的活的人类细胞中，Nbs1迅速被招募到受损区域，并在DSB位点附近进行动态交换。相反，Chk2继续在整个细胞核中快速移动，无论有无DNA损伤，包括无DSB的区域。尽管ATM对Chk2的磷酸化仅发生在DSB位点，但将Chk2强制固定在空间受限的、含有DSB的核区域会损害其对p53依赖性转录的刺激作用。这些结果揭示了Nbs1与DSB损伤相互作用的动态性质，并将Chk2确定为检查点信号的候选传递者，从而允许对局部DNA损伤做出协调的全核反应。
