Figure 9. Electrophoretic mobility shift assay comparing DNA binding of wild-type and three mutant Pax2 proteins.

A labeled Pax2 DNA-binding consensus sequence was incubated in the presence or absence of nuclear extract of COS-7 cells expressing equal amounts of the wild-type or mutant Pax2 protein; the same, unlabeled, competing DNA oligonucleotide; and/or a mutated version of the unlabeled oligonucleotide (Mut-Pax2). Nuclear extracts from mock transfected cells did not appreciably result in a shift of the labeled Pax2 DNA-binding site oligonucleotide, whereas wild-type and all three mutant Pax2 proteins bound the oligonucleotide with approximately equal affinity. Specificity for this binding was shown by competing the binding with the same, unlabeled oligonucleotide sequence and by failure of an unlabeled mutant oligonucleotide to compete for binding.