FIGURE 1.

Schematic model of the DDR that induces a mitosis bypass and cellular senescence in response to IR. (A) When irreparable DNA damage initiates, cell cycle can get interrupted by G2 arrest for long time, which is followed by mitotic bypass into G1 phase with replicated DNA and culminates in cellular senescence. ATM- p53- p21, ROS produced by mitochondria, SASP factors and cyclin-CDK complexes are pivots of this senescence progress. (B) The recruitment of ATM to DSBs activates the NF-κB signaling that induces SASP expression including IL-1α/β, IL-6, TGF-β, and TNF-α et al. With potent autocrine and paracrine activities, SASP factors are co-opted to affect surrounding cells.