I am looking for a pair of strong transactivator and promoter squences. Somehow like the tet on system: I plan to express the transactivator in cells, which could turn on the promoter and in turn the protein expression.

Tet-off system would work for me, but my cells already have tet system. And tet inducible feature is not required in this case. The Cre-loxp system won't work me either.

Could anyone suggest an alternative?

Thank you very much.