Patent ID: 8232099

Claim:
A gene expression control system for controlling the expression of a target gene inside a cell in vitro or in a non-human transgenic animal by the presence or absence of a tetracycline antibiotic, comprising: (a) a cell (b) an expression vector that is introduced into the interior of said cell, and comprises expressibly (b1) a polynucleotide encoding a fusion protein of a mutant of a tetracycline repressor protein and a recombination enzyme, wherein said fusion protein mediates the recombination at a recombination sequence site, and is degraded inside said cell in the absence of said antibiotic, wherein said mutant has an amino acid sequence having at least two of the following mutations: substitution of aspartic acid at position 95 with asparagine, substitution of leucine at position 101 with serine and substitution of glycine at 102 with aspartic acid in the amino acid sequence of a wild-type tetracycline repressor protein encoded by SEQ ID NO: 2, and (b2) a polynucleotide to be introduced into the interior of said cell, encoding a protein that binds to the transcription control region of the polynucleotide in (b1) and controls the transcription of said polynucleotide, wherein the binding to said transcription control region is controlled by the presence or absence of said antibiotic, (c) an expression vector that is introduced into the interior of said cell, and comprises expressibly a target gene between and/or downstream of recombination sequences, and (d) a tetracycline antibiotic to be introduced into the interior of said cell, wherein the transcription of the polynucleotide in (b1) and the degradation of said fusion protein, which is the expression product of the polynucleotide in (b1), is controlled inside the cell by the presence or absence of the tetracycline antibiotic, and the expression of said target gene is controlled by the expressed amount of said fusion protein.