An erythroid cell nuclear factor specifically binds a PAR motif overlapping the Ebox site in the LMO2 promoter. (A) EMSA was performed with a labeled oligonucleotide spanning the Ebox and PAR sites and nuclear extracts from K562 cells. Specific protein-DNA complexes are labeled A-D. (B) The double-stranded oligos listed were used as competitors. Mutations in the sequence are shown in bold. Critical nucleotides are indicated by the inability of a mutant oligomer to compete for the radiolabeled binding to the wild-type 30-mer. (C) A similar EMSA using the Ebox wild-type probe and nuclear extracts from K562 and MEL cells and carried out in the presence and absence of an antibody directed against GATA-1. The disappearance of the band labeled C in the presence of the antibody indicates a GATA-1 binding complex.