Analysis of Cytosolic Proteins that Bind to the 5 Leader Sequence of the Angiotensin AT1 Receptor by RNA Electromobility Shift Assay

Electromobility shift assays (EMSAs) provide a way to study proteinnucleic acid interactions. This method is based on the observation that the electrophoretic mobility of nucleic acids through polyacrylamide gels is retarded when bound to proteins. The mobility of nucleic acid-protein complexes are thus “shifted“ with respect to the free nucleic acids. Typically, the nucleic acids are labeled with ³² P. Once the nucleic acid-protein complexes are separated from free radiolabeled nucleic acids, the electrophoresis is terminated and the gel dried. The radiolabeled nucleic acids in their free and complexed forms are visualized and quantified by phosphor autoradiography or by X-ray autoradiography. DNA-binding proteins are commonly identified by EMSA. EMSA also works well for studying purified RNA-binding proteins (1 –3 ) and this technique is currently being developed for identifying unknown RNA-binding proteins.