Résumé
Summary: In order to investigate the effect of small ubiquitin-like modifier-1 (SUMO-1) on the p53-induced HepG2 cell apoptosis, HepG2 cells were transfected by recombinant plasmids as pwtp53, pMDM2 and pSUMO-1 respectively. Western blot was employed to detect the protein expression of the transfected recombinant plasmids and the rate of apoptosis was measured by flow cytometry. The results showed that in cells transfected with pwtp53 and pwtp53+pSUMO-1, the apoptosis rate was (16.79±1.62) % and (18.15±1.36) % respectively, while transfected with pwtp53+pMDM2, the rate was decreased to (5.17±1.23) %. The apoptosis rate was (14.06±1.84) % in the cells transfected with pwtp53+pMDM2+pSUMO-1, significantly higher than that in the cells Transfected with pwtp53+pMDM2 (P<0.01). The apoptosis rates in the cells were all less than 2 % and had no significant difference among the groups. It was suggested that in the HepG2 cells, SUMO-1 can increase the apoptosis induced by wild-type p53 through binding to p53 protein, post-translational modification and inhibiting the p53 degradation by MDM2.
Résumé
Objective To investigate whether SUMO-1 enhances the apoptosis induced by wild-type p53 plasmid transfection in HepG2 cells. Methods The HepG2 cells were transfected respectively or simultaneouly with the following expressional plasmids as pcDNA3-wtp53(pwtp53,including human wild-type p53 gene),pCMV-HDM1B(pMDM2,including HDM2 gene, homologous gene as murine double minute gene 2),pcDNA3-His6-SUMO-1(pSUMO-1 ,including small ubiquitin-like modifier-1 gene)and plasmid pcDNA3.The proteins expressed in cells were detected by means of Western blotting and the apoptosis rates of cells were measured by flow cytometry. Results The protein bands of p53 and MDM2 could be seen in cells transfected with pwtp53 and pMDM2. Meanwhile,the relative larger molecular weight bands were also seen in cells transfected with pSUMO-1 which represented the p53 and MDM2 protein modification by SUMO-1. Merely the trace of p53 protein was detected in cells not transfected with any plasmid or only transfected with empty plasmid and pSUMO-1. In cells transfected with pwtp53 and pwtp53+pSUMO-1,the apoptosis rates were (16.79?1.62)% and (18.15?1.36)%. When transfected with pwtp53+pMDM2,the rate decreased to (5.17?1.23)%. The apoptosis rate would come up again to (14.06?1.84)% after transfected with pwtp53+pMDM2+pSUMO-1 and the difference of rates were significant compared to the cells transfected with pwtp53+pMDM2 (P