p53 pro-apoptotic activity is regulated by the G2/M promoting factor Cdk1 in response to DNA damage

Exposure to genotoxic stress promotes cell-cycle arrest and DNA repair or apoptosis. These "life" or "death" cell fate decisions often rely on the activity of the tumor suppressor gene p53. Therefore, how p53 activity is precisely regulated is essential to maintain tissue homeostasis and to prevent cancer development. Here we demonstrate that Drosophila p53 pro-apoptotic activity is regulated by the G2/M kinase Cdk1. We find that cell cycle arrested or endocycle-induced cells are refractory to ionizing radiation induced apoptosis. We show that the p53 protein is not able to bind to and to activate the expression of the pro-apoptotic genes in experimentally arrested cells. Our results indicate that p53 genetically and physically interacts with Cdk1 and that p53 pro-apoptotic role is regulated by the cell cycle status of the cell. We propose a model in which cell cycle progression and p53 pro-apoptotic activity are molecularly connected to coordinate the appropriate response after DNA damage.