A Tetracycline-Regulated Expression System without Viral Transactivators
The T-REx™ System yields higher levels of induced expression than any other regulated mammalian expression system. It utilizes the complete CMV promoter and adds control elements from the bacterial tetracycline resistance operon to effectively repress and derepress transcription from one of the strongest mammalian promoter sequences known (1,2).

Specific Activation
The T-REx™ System uses a repressor mechanism that blocks transcription from the powerful CMV promoter in the absence of tetracycline. Because the T-REx™ System elements do not use viral transactivators, you can achieve high-level expression from the complete CMV promoter without secondary, non-specific activation of host genes.

The T-REx™ Mechanism
The T-REx™ transcriptional control elements are illustrated in Figure 1. Two tetracycline operator sequences (TetO2) have been inserted between the TATA box of the CMV promoter and the