TETRACYCLINE REPRESSOR, TETR, RATHER THAN THE TETR-MAMMALIAN CELL TRANSCRIPTION FACTOR FUSION DERIVATIVES, REGULATES INDUCIBLE GENE-EXPRESSION IN MAMMALIAN-CELLS

This article describes the first (to our knowledge) tetracycline-induc ible regulatory system that demonstrates that the tetracycline repress or (tetR) alone, rather than tetR-mammalian cell transcription factor fusion derivatives, can function as a potent trans-modulator to regula te gene expression in mammalian cells. With proper positioning of tetr acycline operators downstream of the TATA element and of human epiderm al growth factor (hEGF) as a reporter, we show that gene expression fr om the tetracycline operator-bearing hCMV major immediate-early enhanc er-promoter (pcmvtetO) can be regulated by tetR over three orders of m agnitude in response to tetracycline when (1) the reporter was cotrans fected with tetR-expressing plasmid in transient expression assays, an d (2) the reporter unit was stably integrated into the chromosome of a tetR-expressing cell line, This level of tetR-mediated inducible gene regulation is significantly higher than that of other repression-base d mammalian cell transcription switch systems. In an in vivo porcine w ound model, close to 60-fold tetR-mediated regulatory effects were det ected and it was reversed when tetracycline was administered. Collecti vely, this study provides a direct implementation of this tetracycline -inducible regulatory switch for controlling gene expression in vitro, in vivo, and in gene therapy.