Abstract: Objective To establish Tetracycline-induced gene expression system for gene therapy based on third generation lentivirus system.Methods The mutant of the reverse Tet transactivator (rtTA and M2rtTA) was subcloned into a lentiviral vector with neo selection marker named as pELNS-rtTA-IRES-Neo and pELNS-M2rtTA-IRES-Neo. The Tet-responsive element (TETO and TREpitt) and green fluorescence proteint (GFP) were subcloned into a lentiviral vector with blasticidin selection marker named as plenti6-TETO-GFP and plenti6-TREpitt-GFP.293 cells were contransfect with pELNS-rtTA-IRES-Neo and plenti6-TETO-GFP, or with pELNS-M2rtTA-IRES-Neo and plenti6-TREpitt -GFP. Cells were treated by Dox to induce GFP expression. After 48hours, GFP expression in the co-transfected cells was observed under a fluorescent microscope.Results The first generation of Tetracycline-induced gene expression system named pELNS-rtTA-IRES-Neo and plenti6-TETO-GFP vectors were successfully set up. GFP expression in cotransfected cells induced with Dox was about 90% positive, while there was 30% positive GFP expression observed in no Dox inducing group. The second generation of Tetracycline-induced gene expression system named pELNS-M2rtTA-IRES-Neo and plenti6-TREpitt-GFP vectors were successfully set up. GFP expression in cotransfected cells induced with Dox was about 95% positive, while there was no positive GFP expression observed in no Dox inducing group.Conclusion Tetracycline-induced gene expression system based on lentivirus was successfully set up, which can induce gene expression effectively and tightly without obvious side-effects on cells by using the second Tetracycline-induced elements.

Key words: Tetracycline, Lentiviral vector, Gene regulation, Gene engineering, Gene cloning, Fluorescent microscopy