Abstract: The present invention relates to a tetracycline dependent gene regulatory system or composition controlling the expression of a target gene in a cell and to methods using said system or composition. The present invention more specifically discloses compositions, vectors and methods allowing tetracycline-controlled expression of short-hairpin RNAs (shRNAs), and demonstrates inducible, reversible and stable RNA interference (RNAi) using the same in a cell. The invention can be used to cause reversible control of the expression of any gene and may therefore find applications in the fields of mammalian, in particular human, genetics and molecular therapeutics, in cell and gene therapy, research as well as in genetic studies using transgenic animals.