Mechanism of the inhibitory effect of HBx on IGFBP3 transcription

Abstract:

[Objective] To study the mechanism of HBx regulating the transcription of insulin growth factor binding protein 3 (IGFBP3).[Methods] RNA-sequencing method was used to screen differently expressing genes in HepG2 and HBV transgenic cell line HepG2-4D14. The mRNA of IGFBP3 was measured by reverse transcription and real-time PCR. To verify the activity of IGFBP3 promoter, cells were analyzed by luciferase assay. The binding of p53 and IGFBP3 promoter was measured by ChIP Assay.[Results] The level of IGFBP3 mRNA in HBV transgenic cell line HepG2-4D14 was significantly lower than that in HepG2 cells. The data of real-time PCR indicated that HBV HBx can down regulate the transcription of IGFBP3. By taking the approach of promoter luciferase assay on HCT116 and HCT116-p53^-/- cell lines, we found that HBx can inhibit the promoter activity of IGFBP3 in a p53-dependent manner. Our data also showed that HBx can significantly interfere with the binding of p53 to the promoter of IGFBP3. As IGFBP3 is a suppressor for cell growth, we postulate that HBx promotes the cell proliferation by reducing the level of IGFBP3.[Conclusion] HBx can inhibit the transcription of IGFBP3 in a p53-dependent manner.