Analysis for the binding affinity of GATA-1 and GATA-2 to the GATA consensus site in the MBP promoter by EMSA. (A) Competitor with the unlabeled oligonucleotides was added using increasing amounts of 0 to 160-fold molar excess as indicated. A double-stranded MBP promoter oligonucleotide extending from bp −93 to −58 was end-labeled and incubated with 1 μg of poly (dI-dC) in the absence of nuclear extract (lane 1) or in the presence of 8 μg of nuclear extracts from COS 7 cells which was transfected with GATA-1 (lanes 2 through 6) or GATA-2 (lanes 7 through 11) expression vectors. (B) Quantitation of the competition efficiency of the MBP promoter oligonucleotide for GATA-1 or GATA-2 binding. The radioactivity of each band was quantitated with a BAS-2000II radioanalysis imaging system (Fujix, Tokyo, Japan).