Hepatitis B virus protein preS2 potentially promotes HCC development via its transcriptional activation of hTERT.
ABSTRACT Telomerase is significantly reactivated in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). Our previous studies showed that the transactivation unit of HBV surface (S) gene, preS2, could upregulate human telomerase reverse transcriptase (hTERT) expression and telomerase activity of HepG2 cells. Here, we aim to explore the functions, and the underlying mechanisms, of this preS2-mediated hTERT upregulation during HCC development.
An antisense blocking assay was performed on HBV-integrated HepG2.2.15 cells. The expression of hTERT was examined in clinical samples to test the role of the preS2-mediated hTERT upregulation in HCC development in vivo. In order to explore the mechanisms of preS2-mediated hTERT upregulation, co-transfection, reporter assays and electrophoretic mobility shift assays (EMSA) were performed.
Blocking preS2 expression reduced hTERT expression, telomerase activity, cell proliferation and tumorigenicity of HepG2.2.15. A region located between -349 and -329 bp upstream of the transcription initiation site of hTERT was identified as responsible for the preS2-mediated effect. preS2 interacted with the preS2-responsible region (PRR) and activated the hTERT promoter. Importantly, hTERT was also highly expressed in preS2-positive human HCC samples. All these findings strongly suggest that preS2 may promote HCC development via hTERT activation.
HBV protein preS2 upregulates hTERT via the PRR element in promoting HCC development.
Article: Hepatitis B virus induces G1 phase arrest by regulating cell cycle genes in HepG2.2.15 cells.[show abstract] [hide abstract]
ABSTRACT: To investigate the effect of HBV on the proliferative ability of host cells and explore the potential mechanism. MTT, colony formation assay and tumourigenicity in nude mice were performed to investigate the effect of HBV on the proliferative capability of host cells. In order to explore the potential mechanism, cell cycle and apoptosis were analysed. The cell cycle genes controlling the G1/S phase transition were detected by immunohistochemistry, westernblot and RT-PCR. HepG2.2.15 cells showed decreased proliferation ability compared to HepG2 cells. G1 phase arrest was the main cause but was not associated with apoptosis. p53, p21 and total retinoblastoma (Rb) were determined to be up-regulated, whereas cyclinE was down-regulated at both the protein and mRNA levels in HepG2.2.15 cells. The phosphorylated Rb in HepG2.2.15 cells was decreased. Our results suggested that HBV inhibited the capability of proliferation of HepG2.2.15 cells by regulating cell cycle genes expression and inducing G1 arrest.Virology Journal 01/2011; 8:231. · 2.34 Impact Factor