SELEX to Identify Protein-Binding Sites on RNA

SELEX (systematic evolution of ligands by exponential enrichment) is a very powerful method for determining the binding site of a protein on RNA. It relies on the ability of an RNA-binding protein to select high-affinity RNA ligands from a randomized pool of RNAs. SELEX experiments are performed over several "rounds," with each round resulting in increased enrichment of RNAs capable of binding to the protein. There are many variations of SELEX strategies, but they all rely on the ability to separate bound RNA from unbound RNA. The method presented here uses tagged proteins; however, it is also possible to use other separation techniques (e.g., filter binding or antibodies).