If the binding activity was purified, suggest two experimental approaches that could be taken to verify that this factor is in fact a transcription factor? Explain. (4 marks) An electrophoretic mobility shift assay (EMSA) was performed using a radiolabeled DNA fragment from the sequence upstream of gene X . This DNA probe was incubated with (+) or without (-) nuclear extract isolated from tissues A (bone); B (lung); C (brain); and D (skin). The DNA-protein complexes were then fractionated on nondenaturing polyacrylamide gels. The gels were exposed to autoradiographic film; the results are presented in the figure. .