Electrophoretic Mobility Shift Assays for the Analysis of DNA-Protein Interactions

Several nuclear mechanisms involve specific DNA-protein interactions. The electrophoretic mobility shift assay (EMSA, also known as the gel mobility shift or gel retardation assay), first described almost two decades ago (1 ,2 ), provides a simple, efficient and widely used method to study such interactions. Its ease of use, its versatility, and especially its high sensitivity (10⁻¹⁸ mol of DNA [2 ]) make it a powerful method that has been successfully used in a variety of situations not only in gene regulation analyzes but also in studies of DNA replication, repair, and recombination. Although very useful for qualitative purposes, EMSA has the added advantage of being suitable for quantitative and kinetic analyzes (3 ). Furthermore, because of its very high sensitivity, EMSA makes it possible to resolve complexes of different protein or DNA stoichiometry (4 ) and even to detect conformational changes.