¹Center for NeuroVirology and NeuroOncology, Department of Neurology, Allegheny University of the Health Sciences, Broad and Vine, MS 406, Philadelphia, Pennsylvania 19102, USA

²Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA

^aAuthor for correspondence:

Tetracycline controlled gene expression systems have become powerful tools in the analysis of gene function in mammalian cell culture as well as transgenic animals and plants. The original description of a tetracycline-regulated gene expression system is based on two plasmids, one of which constitutively expresses a tetracycline-controlled transactivator protein (tTA), a fusion protein between the tetracycline repressor of E. coli and the transcriptional activation domain of the VP16 protein of herpes simplex virus. The second plasmid contains the gene to be regulated by tTA under the control of an inducible promoter which consists of seven copies of the tetracycline resistance operator (tetO). Since this original description, many modifications have been described. In this report, we evaluate an autoregulatory tetracycline controlled system, in which the tTA is itself under the control of the tetO. We demonstrate that this autoregulatory tetracycline system produces adverse effects including cellular morphologic changes, growth rate attenuation and alterations in cell cycle distribution.

tetracycline; inducible promoter; gene expression regulation; transactivator