Fig. 7. Electrophoretic mobility shift assay of the Cdx1b protein. The biotin-labeled wild-type oligonucleotide was mixed with buffer (lane 1) or 10 µg of nuclear extract prepared from COS-1 cells transfected with pcDNA3-cdx1b-Myc-His plasmid (lanes 2-4). Binding was completely abolished by the addition of an unlabeled wild-type oligonucleotide competitor in a 50-fold molar excess (lane 3), whereas specific binding was maintained when the same amount of the excess mutant oligonucleotide competitor was added (lane 4).