The p65 domain from NF-kappa B is an efficient human activator in the tetracycline-regulatable gene expression system

The tc-responsive TetR protein allows the investigation of various transcri ptional activators in respective fusion proteins. We have fused eight well- known human activator domains to the C-terminus of TetR and determined the properties of the resulting transactivators using a tetracycline-responsive promoter in three human cell lines (HeLa, BJAB, and Jurkat). Several-hundr ed fold activation was exclusively obtained with the acidic p65 domain from NF-kappa B and with VP16, which served as a positive control. In contrast, at least 10-fold lower factors of activation were achieved with ITF-1, ITF -2, and MTF-1. The induction properties of the p65 domain are identical to those of VP16 in all three human cell lines and when fused to the reverse T etR. The combination of the novel reverse p65 fusion with the TetR(B/E)-KRA B construct resulted in active silencing and full activation. This is the f irst report of an expression system with minimal basal activity and high in duction levels without viral protein domains. (C) 2000 Elsevier Science B.V . All rights reserved.