An autonomously replicating eukaryotic expression vector with a tetracycline-responsive promoter

The control elements of the tetracycline-resistance operon encoded in Tn 10 of Escherichia coli have previously been utilized by Gossen and Bujard [Proc. Natl. Acad. Sci. 89 (1992) 5547–;5551] to establish an efficient transcription regulatory system in mammalian cells. We describe here a modification of this vector system that encodes all required elements, including a neomycin-resistance gene, on an autonomously replicating episome. This, thereby, allows for improved transfection frequency and episome stability, providing an easily selectable marker gene and a promoter whose activity can be easily modulated to control gene expression.