Abstract: Objective To determine p53 with R213 mutation impacts on the expression of its downstream target gene p21 in HCT116-/- colorectal cancer cell line. Methods Mutations of p53 at R213Q (R/Q) and R213K (R/K) were respectively constructed and transfected into the p53 null HCT116 cells. The promoter activitydrivedby p53 was detected by dual-luciferase reporter system. EMSA assay was used to detect the ability of p53 binding to the promoter of its target gene p21.The expression of p53 downstream target genes p21 wasexamined by Real time PCR and Western blot experiments. Results The mutation of R213K disrupted the efficiency of p53 transactivation(P<0.05). The mutants were less efficient in targeting the consensus binding sequences of p53 in the regulatory region of p21 gene(P<0.05), In addition, The R/K mutant attenuated the expression of p21gene(P<0.05). The mobility of R213Q was increased.Conclusion The different mutations of Arginine 213 have different impact on p21 in colorectal cancer cells. It could exist diverse mechanism to regulate.

Key words: Key words: p53, Arginine213, p21, Mutation