Gel mobility shift assays of the AP-2 and Sp1 sites of thehKCC1gene promoter. Gel mobility shift assays using oligonucleotide probes corresponding to the AP-2 site 2 and Sp1 site 1 consensus-binding sequences of the human KCC1 promoter were performed using K562 nuclear extracts. (A) The probe used in lanes 1 to 5 corresponds to wild-type KCC1 AP-2, the probe used in lanes 6 to 10 corresponds to mutant KCC1 AP-2, and the probe used in lanes 11 to 15 corresponds to a control AP-2. Unlabeled, double-stranded oligonucleotide was added to the reactions as competitor where indicated. (B) The probe used in lanes 1 to 5 corresponds to wild-type KCC1 AP-2, and the probe used in lanes 6 and 7 corresponds to control AP-2. Specific AP-2 antibody was added to the reaction mixtures where indicated. (C) The probe used in lanes 1 to 3 corresponds to wild-type KCC1 Sp1, the probe used in lanes 4 to 6 corresponds to mutant KCC1 Sp1, and the probe used in lanes 7 to 9 corresponds to control Sp1. Specific Sp1 antibody was added to the reaction mixtures where indicated.