The invention is related to a fusion polypeptide involving transcription regulation of a target gene. Said fusion polypeptide consists of (i) a zinc finger domain that recognizes and binds to the corresponding nucleic acid recognition sequence in the vicinity of a promoter of the target gene; (ii) a dimerization domain of a tetracycline (tet) repressor which contains a drug (e.g., tetracycline)-dependent switch, and (iii) an accessory domain which alters the expression of the target gene (such as an transcriptional activation or repression domain). This fusion polypeptide can be administered to, or expressed in, a cell harboring the target gene to be regulated.