The GeneSwitch™ System for inducible mammalian expression is ideal for experiments that require the absolute lowest uninduced expression levels. The expression vector pGene/V5-His provides a minimal promoter, GAL4-E1b, consisting of the binding sites for the yeast Gal4 DNA binding protein followed by the TATA sequence from the Adenovirus E1b promoter. Without additional factors, the GAL4-E1b promoter is transcriptionally silent.To activate transcription from the GAL4-E1b promoter, the GeneSwitch™ regulatory protein is expressed from a minimal TK promoter on the pSwitch vector. The GeneSwitch™ protein has three functional domains:

• Gal4 DNA Binding Domain (Gal4-DBD) to bind the regulatory protein to the GAL4-E1b promoter
• Truncated human Progesterone Receptor Ligand Binding Domain (hPR-LBD) that undergoes a conformational change when it binds the progesterone antagonist, mifepristone