Table 2

Response of rtTA and of the new rtTA variants toward Dox

Dox, ng/mlResponse in arbitrary light units of rtTA alleles
rtTAS219/56RM1M2
00.67  ± 0.281.24  ± 0.410.62  ± 0.482.54  ± 2.051.02  ± 1.163.02  ± 1.26
50.52  ± 0.0657.27  ± 6.661.26  ± 0.173.24  ± 2.721.24  ± 1.5417.07  ± 5.58
500.64  ± 0.55229.72  ± 35.3426.52  ± 12.40.91  ± 0.3230.94  ± 25.751,517.37  ± 169.94
5000.94  ± 0.63696.27  ± 70.31,726.75  ± 110.64112.68  ± 6.982,428.19  ± 254.4210,746.33  ± 1,272.97
  • Dox-dependent gene activation of various rtTAs was measured in HeLa X1/6 cells that were transiently transfected with plasmids containing the genes for the transactivators rtTA and rtTA-S2, -19/56R, -M1, and -M2, all of which were controlled by PCMV. For standardization of transfection efficiencies, each transfection mixture contained also a vector that constitutively produces β-galactosidase. Cells were grown in absence of or in presence of 5, 50, and 500 ng/ml Dox. Twenty-four hours post transfection, luciferase activity was measured from cell extracts and normalized to β-galactosidase activity. Values given are arbitrary light units.