Protocol to detect nucleotide-protein interaction in vitro using a non-radioactive competitive electrophoretic mobility shift assay

Summary: Electrophoretic mobility shift assay (EMSA) is a classical and popular approach for DNA/RNA protein-binding affinity detection in vitro. This protocol describes a competitive EMSA assay using digoxigenin (DIG)-labeled probe, which solves the safety issues and limitations attributed to the short lifespan of the 32P-radiolabeled DNA probe. We detail steps for DNA probe preparation, protein-DNA mixture coincubation, EMSA, and competitive EMSA process. We optimize the standard DIG-ddUTP-labeling EMSA protocol to high sensitivity with reproducible results.For complete details on the use and execution of this protocol, please refer to Feng et al. (2022). : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.