Effect of X-ray Radiation on Cell Cycle Regulated by P53 and Its Related Proteins in HepG2 Cells

HepG2 cells were irradiated with X-ray at the doses of 0,1.0,2.0,4.0 or 8.0 Gy and separately maintained in DMEM at 37 ℃ for 0,6,12 or 24 h.Colony-forming assay showed that cell survival decreased with the irradiation dose increasing.Cell cycle was detected by FACS,the arrest of S phase was found after 12 h irradiation and arrest of G2 phase took place at 24 h after all irradiation doses,which suggested that cell cycle distribution was different in groups gathered after different maintaining time.The results of Western blotting showed that the expression of P53,MDM2 and P21 increased more after irradiation than the control.The expression of P53 remained high at 24 h after irradiation,while the levels of MDM2 or P21 arrived at the highest at 6 h or 12 h after irradiation respectively.The expressions of P21 after irradiation were in corresponding with the cell cycle distribution in the groups of different maintaining time.In conclusion,irradiation change the distribution of cell cycle by effecting the expression of P53 and its related proteins.