Genotype-dependent binding of nuclear proteins to the human BCL2 promoter. Electrophoretic mobility shift assays (EMSAs) were performed using nuclear extracts (10 μg) from human follicular lymphoma cells (Karpas 422). Nuclear extracts were incubated with DIG-labeled oligonucleotides. Assays were performed in the absence (−) or presence (+) of 100-fold molar excess of unlabeled oligonucleotide. Arrow indicates a specifically retarded band observed upon addition of nuclear extracts from Karpas cells. These extracts contain nuclear proteins that specifically bind to the construct with the BCL2−938C allele compared with the BCL2−938A allele. Moreover, addition of an Sp-1 antibody competed this band almost completely away, suggesting that this band was specific for Sp-1 binding sites.