Figure 3

Regulational luciferase expression by the novel Tet-On system. (A) The comparison of different Tet-On systems. 293 cells were transfected with different Tet-On systems as well as the negative control pAd5-E1 and the positive control pCMV-Luciferase, in the presence or absence of Dox (2 μg Dox/ml). Forty-eight hours post-transfection, the activities of firefly luciferase and the internal control, Renilla luciferase, were quantified. The ratio of firefly luciferase to Renilla luciferase activity (FL/RL) was used to represent normalized luciferase activity. Experiments were repeated three times; *P < 0.05. (B) Time course of luciferase expression by pAd5-KRAB-Bi-Tet-On-Luciferase following Dox induction. CHO-K1 cells were transfected with pAd5-KRAB-Bi-Tet-On-Luciferase in the presence of 2 μg Dox/ml. Cells were collected every 4 h and normalized luciferase activities were obtained. Experiments were repeated three times. Data represent mean ± SD. (C) Dose–response curve demonstrating regulational expression of luciferase by the pAd5-KRAB-Bi-Tet-On vector. CHO-K1 cells were transfected with pAd5-KRAB-Bi-Tet-on-Luciferase in the presence of Dox at the final concentrations of 10 ng/ml, 100 ng/ml, 1000 ng/ml, 2000 ng/ml, 4000 ng/ml, 8000 ng/ml, and 10000 ng/ml. Forty-eight hours post-transfection, the cells were collected, and normalized luciferase activities were obtained. Experiments were repeated three times. Data represent mean ± SD.