Transactivator mutants with altered effector specificity allow selective regulation of two genes by tetracycline variants.

A set of Tet repressor (TetR) based eukaryotic transactivators that respond to 4-de(dimethylamino)-6-deoxy-6-demethyl-tetracycline (cmt3) but no longer to tetracycline (tc) is presented. The novel transactivators exhibit high activation in absence of an effector and a 200-fold reduction of reporter gene activity in the presence of cmt3. The most cmt3-sensitive mutant was coexpressed with a tc-responsive Tet transregulator harbouring an altered DNA recognition specificity. Use of cmt3 and tc yields independent control of expression of two genes in the same cell without crosstalk.