BECN1 promotes radiation-induced G2/M arrest through regulation CDK1 activity: a potential role for autophagy in G2/M checkpoint

Abstract

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 2 /M arrest remains elusive. Here, we demonstrate that the autophagy-related protein BECN1 plays a critical role in ionizing radiation-induced G 2 /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 2 /M checkpoint following IR by abrogating the IR-induced phosphorylation of phosphatase CDC25C and its target CDK1, a key mediator of the G 2 /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 2 /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.

Tissue-Specific Knockdown of Genes of the Argonaute Family Modulates Lifespan and Radioresistance in Drosophila Melanogaster

“…Similarly, genes encoding heat shock proteins are activated under acute radiation and provide an adaptive response to stress [38,39,85]. We also expected changes in the expression of genes of autophagy and ER stress response-since, in studies on rodent and human cell lines, a connection between these mechanisms and the response to radiation has been established [86][87][88][89][90]. However, their changes in our study were small and inconsistent.…”

Tissue-Specific Knockdown of Genes of the Argonaute Family Modulates Lifespan and Radioresistance in Drosophila melanogaster

“…Similarly, genes encoding heat shock proteins are activated under acute radiation and provide an adaptive response to stress [ 38 , 39 , 85 ]. We also expected changes in the expression of genes of autophagy and ER stress response—since, in studies on rodent and human cell lines, a connection between these mechanisms and the response to radiation has been established [ 86 , 87 , 88 , 89 , 90 ]. However, their changes in our study were small and inconsistent.…”

Tight association of autophagy and cell cycle in leukemia cells

“…Yet some papers have reported highly active autophagy in mitosis [ 33 – 36 ], and others have related autophagy activation to a halt of the cell cycle in G2 or mitosis. Concurrent induction of autophagy and G2/M cell cycle arrest was observed in response to agents such as plumbagin, resveratrol, artesunate, and a boswellic acid analog [ 37 – 40 ] as well as after ionizing radiation [ 41 , 42 ]. In addition, removal of damaged mitochondria by autophagy can be associated with cell cycle arrest in G2/M [ 43 ].…”