The invention relates to a composition for inhibiting the expression of a target gene in a eukaryotic cell by RNA interference, the composition comprising a genetic construct and the target gene being introduced into the eukaryotic cell by means of said construct, and the construct having a first target gene and a first siRNA tag. The invention also relates to a composition for inhibiting the expression of one or more target genes in a eukaryotic cell by RNA interference. The composition comprises at least two genetic constructs and the target genes are introduced into the eukaryotic cell by means of said constructs, a) the first construct containing a first target gene and a first siRNA tag and b) the second construct containing a second target gene and a second siRNA tag, and the first and the second siRNA tag having different nucleic acid sequences. The invention finally relates to a method for inhibiting the expression of a target gene in a eukaryotic cell. Said method comprises the following steps: a) providing at least one eukaryotic cell, said cell being capable of RNA interference, b) transfecting the cells with a composition according to the invention and c) introducing at least one siRNA that is complementary to a siRNA tag of a transfected construct to inhibit the expression of the target gene that forms a transcription unit together with the siRNA tag.