Analysis for the Conflict between G2/M Phase Arrest in the Cell Cycle and Apoptosis Induction

When DNA is damaged by the irradiation or chemical agents in vitro, the damage signal activates the tumor suppressor protein p53 followed by the stimulation of the transcriptions of many related genes such as p21, 14-3-3, Bax, Bcl-2 and so fourth. These genes may determine the destination of the cell whether the cell cycle arrest or apoptosis induction. Thus, p53 is responsible for the conflict between the cell cycle arrest and apoptosis induction. Recently, it was reported that the protein levels of the p53/Mdm2 shows the oscillation under the condition of occurring some DNA damages [1, 2]. However, the physiological role of the oscillation in p53 level for the controlling the conflict between the cell cycle arrest and apoptosis induction is still unclear [2]. In this study, we proposed a novel mathematical model which can realize the qualitative temporal dynamics of both G2/M phase and apoptosis events involving the p53/Mdm2 oscillation. Then, we elucidated the influence that p53 plays an important role on the controlling the conflict between G2/M phase arrest and apoptosis with or without occurring low/high DNA damages.