Figure 3.

Dox-dependent gene regulation by transregulators. Cells were cotransfected transiently with plasmid pUHC13-3 carrying the luciferase gene under P_tet-1 control and plasmids encoding the indicated transactivators. Cells were grown in the absence (–) or presence (+) of 5 µg/ml dox. Luciferase activity was determined as described in Figure 1. (A) Characterization of the transactivator variants tTA2, tTA2^s, sc tTA2ⁱ and sc tTA2 in HeLa cells. The dimeric and the monomeric transactivators are identical, respectively, but encoded by different DNA sequences. (B) Characterization of the reverse transactivator variants rtTA2^s-S2, sc rtTA2-S2, rtTA2^s-M2 and sc rtTA2-M2 in HeLa cells. (C) Dox-dependent repression by the transsilencers tTS^s, sc tTS and tTS^E in HeLa cells and (D) in HEK293 cells.