Aptamers as artificial gene regulation elements.

Conditional gene expression systems are important tools to identify the function of essential genes or in terms of gene therapy approaches. Small molecule-binding aptamers can be used for efficient control of gene expression by inserting them into the 5' untranslated region of an mRNA with the ligand-bound form inhibiting gene expression by interfering with translation initiation. However, only a small fraction of in vitro selected aptamers has the potential to act as regulator of gene expression which originates the necessity to develop screening systems for the identification of regulatory active aptamers. We describe here a simple and powerful yeast-based screening system which allows the rapid identification of small molecule-binding aptamers with the potential to act as artificial riboswitches for conditional control of gene expression.