Objective: To explore possible relationship among expression of human high density lipoprotein binding protein(VIGILIN), H19 and the insulin-like growth factor 2 (IGF2) mRNA in HepG2 cell cycle and investigate the role of VIGILIN in controlling imprinting genes of H19 and IGF2 mRNA expression.
Methods: We investigated time course cell cycle distribution of HepG2 cells by FACS, analyzed VIGILIN, H19 and IGF2 mRNA expression at the indicated times using RT-PCR, RNAi and real-time PCR.
Results: Cell-cycle of HepG2 cells was approximately 20 h. 0 h-9 h and 20 h-28 h, 9 h-20 h and 28 h-39 h were S-phase and G2/M-G1-phase, respectively. Firstly, cells were synchronized by serum-starvation for 24 h. As expected, VIGILIN transcription was up-regulated with expression peaks at 20 h and 60 h after serum stimulating by the addition of 10% fetal calf serum. In parallel, H19 mRNA had a high expression level at 6 h and 43 h, and IGF2 mRNA was also increasing with cell-cycle. The expression profiles of human VIGILIN, H19, and IGF2 mRNA were ascending with cell-cycle. In addition, the knock-down of VIGILIN expression by transfecting HepG2 cells with shRNA expression plasmid pSIREN-VIG inhibited the expression of human VIGILIN, which led to the expression of H19 mRNA decrease by 12.08%, and IGF2 mRNA increase by 30.13%.
Conclusion: The expression of VIGILIN and H19 mRNA was the cell-cycle dependent and had something to do with each other. The results clearly shed light on the roles of VIGILIN in controlling expression of the imprinted H19 and IGF2 genes.