Representative EMSAs illustrating allelic DNA–protein interactions in the promoter region of BRCA1. Labeled double-stranded oligonucleotide (ds-oligo) probes containing either allele of rs4793204 (A) and rs799908 (B) were incubated with nuclear extracts from HeLa, MCF7 and MDA-MB-231 cells. (A) Lanes 1–6 represent binding to the labeled ds-oligo containing the major allele; lanes 7–12, binding to the ds-oligo containing the minor allele. Lanes 1 and 7, negative control (no extracts). Lanes 3 and 10, competition with unlabeled allelic probes (specific competitors). Lanes 4 and 9, competition with mismatched unlabeled probes. Lanes 5 and 11, competition with a non-specific probe (non-specific competitor). Lanes 6 and 12, pre-incubation with anti-BRG1 antibody. (B) Lanes 1–5 represent binding to the labeled ds-oligo containing the major allele; lanes 6–10, binding to the ds-oligo containing the minor allele. Lanes 1 and 6, negative control (no extracts). Lanes 3 and 9, competition with unlabeled allelic probes (specific competitors). Lanes 4 and 8, competition with mismatched unlabeled probes. Lanes 5 and 10, competition with a non-specific probe (non-specific competitor).