Methods and compositions are provided which employ polypeptides having a SU-dependent stabilization domain, and nucleotide sequences encoding the same. Such SU-dependent stabilization domains can be employed a part of a fusion protein comprising a polypeptide of interest. The presence of the SU-dependent stabilization domain in such a fusion protein serves as a method of modulating the level of the protein of interest through the presence of or the absence of a SU ligand. Further provided are methods and compositions employing the SU-dependent stabilization domain in a SuR or revSuR. Such polypeptides can be employed in combination with a chemical-gene switch system to allow for a sophisticated level of transcriptional control.
