Abstract: BACKGROUND AND AIM: To explore the effect on the function of 249 Arg to Ser mutation in the p53 gene in mice. MATERIALS AND METHODS: Arg to Ser mutation was introduced into the 249 position of the p53 gene by knock-in method. These ES cells with this mutation were selected according to the homologues-recombination with PCR and Southern blot. The positive ES cells without a selection marker were injected into blastocysts recovered from Hprt-/- mice, which were derived from Hprt-deficient ES cells. The injected blastocysts then were implanted into pseudopregnant females. At embryonic day 14, MEFs were recovered from the embryos and cultured under the selection of HAT (0.016 mg of hypoxanthine/ml, 0.01 mmol/L aminopterin, 0.0048 mg of thymidine thymidine/ml)，and the cell cycle, apoptosis, and the relative protein expressions were analyzed by flow cytometry and Western blot. RESULTS: The ES cells with 249 Arg to Ser mutation were more resistant to the IR-induced cell cycle arrest compared to the wild type ES cell(P<0.05).The ES and EF cell with 249 Arg to Ser mutation were more resistant to the IR- or UV-induced apoptosis compared to the wild type ES and EF cell(P<0.05). The mutation did not affect the expression of p53 after IR or UV, but decrease the expression bax and p21 after IR or UV. CONCLUSION: The p53 249 Arg to Ser mutation could disable the function of p53, but did not change the expression of p53.

Key words: hepatoma, carcinogenesis, p53 gene, mutation