Institute of Medical Radiation Biology, University Hospital Essen, University of Duisburg-Essen, 45147 Essen, Germany.
Division of Experimental Radiation Biology, Department of Radiation Therapy, University Hospital Essen, University of Duisburg-Essen, 45147 Essen, Germany.
Cells. 2023 May 14;12(10):1387. doi: 10.3390/cells12101387.
We have recently reported that in G-phase cells (but not S-phase cells) sustaining low loads of DNA double-strand break (DSBs), ATM and ATR regulate the G-checkpoint epistatically, with ATR at the output-node, interfacing with the cell cycle through Chk1. However, although inhibition of ATR nearly completely abrogated the checkpoint, inhibition of Chk1 using UCN-01 generated only partial responses. This suggested that additional kinases downstream of ATR were involved in the transmission of the signal to the cell cycle engine. Additionally, the broad spectrum of kinases inhibited by UCN-01 pointed to uncertainties in the interpretation that warranted further investigations. Here, we show that more specific Chk1 inhibitors exert an even weaker effect on G-checkpoint, as compared to ATR inhibitors and UCN-01, and identify the MAPK p38α and its downstream target MK2 as checkpoint effectors operating as backup to Chk1. These observations further expand the spectrum of p38/MK2 signaling to G-checkpoint activation, extend similar studies in cells exposed to other DNA damaging agents and consolidate a role of p38/MK2 as a backup kinase module, adding to similar backup functions exerted in p53 deficient cells. The results extend the spectrum of actionable strategies and targets in current efforts to enhance the radiosensitivity in tumor cells.
我们最近报道称，在 G 期细胞（而非 S 期细胞）中持续承受低水平的 DNA 双链断裂（DSBs）时，ATM 和 ATR 呈上位性调控 G 检验点，ATR 处于输出节点，通过 Chk1 与细胞周期相互作用。然而，尽管抑制 ATR 几乎完全消除了检验点，但使用 UCN-01 抑制 Chk1 仅产生部分反应。这表明 ATR 下游的其他激酶参与了信号向细胞周期引擎的传递。此外，UCN-01 抑制的广泛的激酶谱表明，需要进一步研究以解释存在的不确定性。在这里，我们表明，与 ATR 抑制剂和 UCN-01 相比，更特异的 Chk1 抑制剂对 G 检验点的作用更弱，并鉴定出 MAPK p38α及其下游靶标 MK2 作为作为 Chk1 的备份的检验点效应物。这些观察结果进一步扩展了 p38/MK2 信号向 G 检验点激活的范围，将类似的研究扩展到暴露于其他 DNA 损伤剂的细胞中，并巩固了 p38/MK2 作为备份激酶模块的作用，类似于在 p53 缺陷细胞中发挥的类似备份功能。这些结果扩展了当前提高肿瘤细胞放射敏感性的可行策略和靶标的范围。
