Huang Ruixue, Gao Shanshan, Han Yanqin, Ning Huacheng, Zhou Yao, Guan Hua, Liu Xiaodan, Yan Shuang, Zhou Ping-Kun
Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, 410078 Changsha, Hunan Province China.
Department of Radiation Biology, Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, AMMS, 100850 Beijing, China.
Cell Death Discov. 2020 Aug 5;6:70. doi: 10.1038/s41420-020-00301-2. eCollection 2020.
Authophagy and G2/M arrest are two important mechanistic responses of cells to ionizing radiation (IR), in particular the IR-induced fibrosis. However, what interplayer and how it links the autophagy and the G/M arrest remains elusive. Here, we demonstrate that the autophagy-related protein BECN1 plays a critical role in ionizing radiation-induced G/M arrest. The treatment of cells with autophagy inhibitor 3-methyladenine (3-MA) at 0-12 h but not 12 h postirradiation significantly sensitized them to IR, indicating a radio-protective role of autophagy in the early response of cells to radiation. 3-MA and BECN1 disruption inactivated the G/M checkpoint following IR by abrogating the IR-induced phosphorylation of phosphatase CDC25C and its target CDK1, a key mediator of the G/M transition in coordination with CCNB1. Irradiation increased the nuclear translocation of BECN1, and this process was inhibited by 3-MA. We confirmed that BECN1 interacts with CDC25C and CHK2, and which is mediated the amino acids 89-155 and 151-224 of BECN1, respectively. Importantly, BECN1 deficiency disrupted the interaction of CHK2 with CDC25C and the dissociation of CDC25C from CDK1 in response to irradiation, resulting in the dephosphorylation of CDK1 and overexpression of CDK1. In summary, IR induces the translocation of BECN1 to the nucleus, where it mediates the interaction between CDC25C and CHK2, resulting in the phosphorylation of CDC25C and its dissociation from CDK1. Consequently, the mitosis-promoting complex CDK1/CCNB1 is inactivated, resulting in the arrest of cells at the G/M transition. Our findings demonstrated that BECN1 plays a role in promotion of radiation-induced G2/M arrest through regulation of CDK1 activity. Whether such functions of BECN1 in G2/M arrest is dependent or independent on its autophagy-related roles is necessary to further identify.
自噬和G2/M期阻滞是细胞对电离辐射（IR），尤其是IR诱导的纤维化的两种重要机制反应。然而，它们之间的相互作用因子以及该因子如何连接自噬和G2/M期阻滞仍不清楚。在此，我们证明自噬相关蛋白BECN1在电离辐射诱导的G2/M期阻滞中起关键作用。在照射后0至12小时而非12小时用自噬抑制剂3-甲基腺嘌呤（3-MA）处理细胞，可显著使它们对IR敏感，表明自噬在细胞对辐射的早期反应中具有辐射保护作用。IR后，3-MA和BECN1的破坏通过消除IR诱导的磷酸酶CDC25C及其靶点CDK1（与CCNB1协同作用的G2/M转换的关键介质）的磷酸化，使G2/M检查点失活。照射增加了BECN1的核转位，而该过程被3-MA抑制。我们证实BECN1分别与CDC25C和CHK2相互作用，且分别由BECN1的89-155和151-224氨基酸介导。重要的是，BECN1缺陷破坏了照射后CHK2与CDC25C的相互作用以及CDC25C与CDK1的解离，导致CDK1去磷酸化和CDK1过表达。总之，IR诱导BECN1转位至细胞核，在细胞核中它介导CDC25C与CHK2之间的相互作用，导致CDC25C磷酸化及其与CDK1解离。因此，有丝分裂促进复合物CDK1/CCNB1失活，导致细胞在G2/M转换期停滞。我们的研究结果表明，BECN通过调节CDK1活性在促进辐射诱导的G2/M期阻滞中发挥作用。BECN1在G2/M期阻滞中的这种功能是否依赖或独立于其自噬相关作用有待进一步确定。
