[HBx promotes ubiquitination and degradation of ZO1 and increases the migration and invasion of liver cancer cells].

Objective: To study the effect of hepatitis B virus X protein (HBx) expression level on migration and invasion of zonula occludens protein-1 (ZO-1) in HepG2 liver cancer cells. Methods: Liver cancer cells were transfected with HBV full gene plasmid (pcDNA3.1-HBV1. 1 or pcDNA3.1-HBV1.3), empty plasmid (pcDNA3.1) and HBV-encoded protein plasmids (pHBc, pHBs, pHBp and pHBx), respectively. Western blot and RT-PCR were used to detect ZO1 protein and mRNA levels. Immunoprecipitation was used to detect transfected pHBx. Western blot was used to detect ZO1 ubiquitination levels. Transwell chambers were used to assess cell migration and invasion. Cell proliferation and lactate dehydrogenase assay was used to detect siRNA transfecting targeting ZO1. Flow cytometry was used to detect cell apoptosis and cycle. The data was compared between two and multiple groups by using an independent sample t-test and one-way analysis of variance. Results: Compared with the empty plasmid, ZO1 protein level in HepG2 cells after transiently transfected with pHBV1.1 and pHBV1.3 was decreased by 42.99% ± 6.8% and 55.0% 5 ± 4.56%, respectively, and their mRNA levels did not change significantly. ZO1 protein level in Huh7 cells was decreased by 17.46% ± 4.94% and 47.53% ± 3.38%, respectively. ZO1 protein level after transfection with pHBx was decreased by 47.02% ± 3.4%, while the ZO1 protein level after transfection with pHBc, pHBs and pHBp did not change significantly. ZO1 mRNA level was unaffected with pHBx transfection. ZO1 ubiquitin level and cell migration and invasion ability in HepG2 cells was significantly increased with transfected pHBx. HepG2 cells proliferation, apoptosis and cycle after transfection with ZO1-targeted siRNA did not change significantly, but the migration and invasion ability were significantly increased. Conclusion: HBx can increase the migration and invasion of liver cancer cells by promoting the ubiquitination and degradation of ZO1 protein level.