Effects of cell cycle on telomerase activity and on hepatitis B virus replication in HepG2 2.2.15 cells.
BACKGROUND
It has been shown that telomerase activity and hepatitis B virus (HBV) replication are closely associated with cell cycle. This study aimed to further investigate the effects of cell cycle on telomerase activity and on HBV replication.


METHODS
Human hepatoma cells transfected with HBV DNA (HepG2 2.2.15 cell line) were treated respectively with serum deprivation, all-trans retinoic acid (RA), dimethyl sulfoxide (DMSO), or sodium butyrate. The cell cycle of HepG2 2.2.15 cells was analyzed by flow cytometry. The telomerase activities of the cells were detected by TRAP-PCR-ELISA. HBV DNA in culture medium was assayed by a fluorescent quantitative PCR assay and a semiquantitative dot blot hybridization technique. HBsAg and HBeAg in culture media were quantitatively examined by an ELISA assay.


RESULTS
Treatments with serum deprivation, RA, DMSO, or sodium butyrate inhibited the proliferation of HepG2 2.2.15 cells and led to cell arrest in the G0/G1 phase of cell cycle. The percentage of the G0/G1 phase in the groups of sodium butyrate, DMSO, RA and serum-free was 85.2%, 71.9%, 68.3% and 65.2%, respectively, but in the control group, 43.1% (P<0.01). The activities of telomerase of the cells were also significantly inhibited by 82.8%, 74.6%, 76.1% and 69.4% respectively. In addition, HBV replication of the HepG2 2.2.15 cells remarkably increased as shown by the contents of HBV DNA, HBsAg and HBeAg in the culture media of the cells treated with sodium butyrate, DMSO, RA or serum deprivation (P<0.01). The amounts of HBV DNA in the groups of sodium butyrate, DMSO, RA, serum deprivation and control were 6.7X10(6), 4.8X10(6), 4.4X10(6), 5.1X10(6) and 1.2X10(6) copies/ml, respectively (P<0.01). Telomerase was expressed mainly in the cells in S phase. HBV replication increased in quiescent cells (G0/G1 phase), and decreased in proliferating phase (S phase).


CONCLUSIONS
The current data approve that HBV replication is associated with the cellular proliferative activity.
Huang
Yan-Qing
YQ
Department of Infectious Diseases, Renmin Hospital, Wuhan University, Wuhan 430060, China.
Wang
Lu-Wen
LW
Yan
Shao-Nan
SN
Gong
Zuo-Jiong
ZJ
D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000276:immunology / Q000473:pathology* / Q000821:virology*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D004279:DNA, Viral / Q000032:analysis; D006514:Hepatitis B Surface Antigens / Q000032:analysis; D006513:Hepatitis B e Antigens / Q000032:analysis; D006515:Hepatitis B virus / Q000502:physiology*; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000276:immunology / Q000473:pathology / Q000821:virology; D019098:Telomerase / Q000378:metabolism*; D014779:Virus Replication
D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D006513:Hepatitis B e Antigens; D019098:Telomerase