[The effect of hepatitis B virus x protein on cell cycling].
OBJECTIVE
To study the effect of HBx protein on cell cycle progression and its molecular mechanism.


METHODS
The eucaryotic expression vector pCEP4 of HBx gene was constructed and introduced into HepG2 cells. The HepG2 cells transfected with X gene (X cell) were synchronized in a quiescent state by culture of serum deprivation. Flow cytometry, immunohistochemical and Western Blot analysis were performed.


RESULTS
70% HepG2 cells transfected with pCEP4 (X0 cells) was induced in G0-G1 phase, only 56% X cells in G0-G1 phase, almost identical to its parental HepG2 cells cultured in serum medium. To further understand the molecular mechanism of cell cycle progression, the p21CIP1/WAF1 and PCNA were examined. HBx was found to strongly increase the level of PCNA in X cells (86 +/- 3)% compared with X0 cells (9 +/- 5)%, and greatly decrease the level of p21CIP1/WAF1 protein in X cells (16 +/- 6)% compared with X0 cells (86 +/- 8)% (P < 0.001).


CONCLUSIONS
These data suggest a molecular mechanism by which HBx likely contributes to viral carcinogenesis. By deregulating cell cycle checkpoint control, HBx could participate in the selection of cells that are genetically unstable, some of which would accumulate unrepaired transforming mutations.
Tao
X
X
Chongqing University of Medical Sciences, Chongqing 400010.
Ren
H
H
Shen
D
D
D048868:Adaptor Proteins, Signal Transducing; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics*; D002453:Cell Cycle; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D018274:Electroporation; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D014407:Tumor Cells, Cultured; D017361:Viral Nonstructural Proteins / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C110719:LAMTOR5 protein, human; D017361:Viral Nonstructural Proteins