Patent ID: 8236556

Claim:
A method of modulating the expression of a gene in a host cell comprising the gene to be modulated, the method comprising: a) introducing into the host cell a gene expression modulation system comprising i) a first gene expression cassette that is capable of being expressed in a host cell comprising a polynucleotide sequence that encodes a first hybrid polypeptide comprising: (A) a DNA-binding domain that recognizes a response element associated with a gene whose expression is to be modulated; and (B) an ecdysone receptor ligand binding domain; and ii) a second gene expression cassette that is capable of being expressed in the host cell comprising a polynucleotide sequence that encodes a second hybrid polypeptide comprising: (A) a transactivation domain; and (B) a chimeric retinoid X receptor ligand binding domain, comprising (i) helices 1-6 of a vertebrate retinoid X receptor and helices 7-12 of an invertebrate retinoid X receptor, (ii) helices 1-7 of a vertebrate retinoid X receptor and helices 8-12 of an invertebrate retinoid X receptor or (iii) helices 1-8 of a vertebrate retinoid X receptor and helices 9-12 of an invertebrate retinoid X receptor; and b) introducing into the host cell a ligand; wherein the gene to be modulated is a component of a gene expression cassette comprising: i) a response element recognized by the DNA binding domain from the first hybrid polypeptide; ii) a promoter that is activated by the transactivation domain of the second hybrid polypeptide; and iii) a gene whose expression is to be modulated; whereby upon introduction of the ligand into the host cell, expression of the gene of b)iii) is modulated.