[A study of the down-regulation effect of hepatitis B virus pre-protein S2 on inducible nitric oxide synthase gene promoter].

Objectives: To investigate the regulating effect of HBV pre-S2 protein on iNOS gene promoter and the molecular biological mechanisms of pre-S2 protein in HBV pathogenicity.

Methods: Polymerase chain reaction (PCR) technique was employed to amplify the sequence of iNOS promoter and 3 deletion mutants using HepG2 genomic DNA as the template, and the products were cloned into the pGEM-T vector. The iNOS gene and 3 deletion mutants were cut from T- iNOS by Kpn I and Xho I, and then cloned into pCAT3-Basic. The resulting vectors were named p1-iNOSp, p2-iNOSp, p3-iNOSp, and p4-iNOSp. Each of the reporter vectors was transfected into the HepG2 cell line and cotransfected into HepG2 cells with pcDNA3.1(-)-pre-S2 by FuGENE 6 transfection reagents. The HepG2 cells transfected with pCAT3-Basic were used as a negative control. The activity of CAT in HepG2 cells transfected was detected by an ELISA kit 48 hours after the transfection, which reflected the regulating effect of HBV pre-S2 protein on iNOS gene promoter activity.

Results: The expressive vector pcDNA3.1(-)-pre-S2 and report vector pCAT3-iNOSp were constructed and confirmed by restriction enzyme digestion and sequencing. The expression of pcDNA3.1(-)-pre-S2 in HepG2 cells could down-regulate the activity of p1-iNOSp, p3-iNOSp, and the inhibition rate was 54.7% and 79.5%, respectively. The expression of pcDNA3.1(-)-pre-S2 in HepG2 cells had no regulatory effects on p2-iNOSp and p4-iNOSp.

Conclusion: It is suggested that HBV pre-S2 protein can down-regulate iNOS gene promoter.