Molecular mechanism of HCV NS5A on p53's inhibition of AFP expression in hepatocellular carcinoma cells / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To explore hepatitis C virus (HCV) non-structural protein 5A (NS5A)'s influence on inhibition of AFP expression executed by p53 protein and its possible molecular mechanism.</p><p><b>METHODS</b>Plasmid transfection and MEIA were employed to observe p53's inhibitive effect on AFP expression of Huh7 cells and the HCV NS5A's influence on p53 function. Western blot was employed to find out if HCV NS5A affects p53 protein expression and GST pull down assay was applied to examine the interaction between HCV NS5A and p53.</p><p><b>RESULTS</b>The AFP concentration in the supernatant of the culture of the Huh7 cells transfected with pRc/CMV was (14322+/-2412) ng/ml, and that of the Huh7 cells transfected with pCNS5A was (13843+/-3218) ng/ml; no significant difference existed between these two groups (t = 1.42, P > 0.05). After transfection with pC53-NS3, the AFP level was decreased to (10 241+/-1326) ng/ml, and in comparison to the above two groups it had a statistically significant difference (t values were 2.41 and 2.38, P < 0.05). When co-transfected with pCNS5A and pC53-NS3, the AFP expression (14582+/-1238) ng/ml returned to the level of pRc/CMV transfected, and there was a remarkably significant difference between this and that of the pC53-NS3 transfected cells (t = 3.12, P < 0.01). HCV NS5A had no function on the p53 protein expression with Western blot experiment. In the GST pull down assay, an HCV NS5A protein band was found after GST-p53 was added, but not detected with GST only.</p><p><b>CONCLUSION</b>We found that p53 has an inhibitive function on the AFP expression in Huh7 cells and HCV NS5A minimized this p53 function. HCV NS5A did not affect p53 protein expression, but was able to form a complex with p53, by which HCV NS5A inactivated this p53 function.</p>

Regulation mechanism of HCV NS5A on p53 protein transactivity / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To study the inhibition effect of HCV NS5A on p53 protein transactivity and its possible mechanism.</p><p><b>METHODS</b>Luciferase reporter gene system was used for the study of p53 transactivity on p21 promoter and electrophorectic mobility-shift assay (EMSA) was applied to observe whether HCV NS5A could suppress the binding ability of p53 protein to its specific DNA sequence.</p><p><b>RESULTS</b>Endogenous p53 protein could stimulate p21 promoter activity, and the relative luciferase activity increased significantly (3.49 x 10(5) vs 0.60 x 10(5), t = 5.92, P<0.01). Exogenous p53 protein also up-regulated p21 promoter driving luciferase expression, comparing to the control group (0.47 x 10(5)), the relative luciferase activity increased (5.63 x 10(5)) obviously (t = 10.12, P<0.01). HCV NS5A protein inhibited both endogenous and exogenous p53 transactivity on p21 promoter in a dose-dependent manner (F > or = 20.71, P<0.01). In the experiment of EMSA, p53 could bind to its specific DNA sequence, but when co-transfected with HCV NS5A expressing vector, the p53 binding affinity to its DNA decreased.</p><p><b>CONCLUSION</b>HCV NS5A can inhibit p53 protein transactivity on p21 promoter through its inhibiting of p53 binding ability to the specific DNA sequence.</p>