Gel retardation assays of the strong in vitro DNaseI footprinted regions in 5′HS1. (A) Gel retardation assay on Sp1/Sp3 factors bound to the E probe corresponding to the strongest footprint E. Competitors: E, self-competition with HS1FpE site; 4.0, wild-type Sp1 site from 5′HS2; 4.4, mutant Sp1 site from 5′HS2. Antibodies: G, Gata-1. B. Gel retardation assay on the GATA factors bound to the A, C, F, and G footprints. Competitors: Sp1, Sp1-Cruz consensus site; G, GATA-Cruz dimer GATA-1 site; F, self-competition with HS1FpF site. C. Summary of factors bound to each footprint as deduced by gel retardation assays and in vitro DNaseI footprinting. Filled circles, erythroid-specific factors; open circles, ubiquitous factors. {/ANNT;4224n;;0n;0n}A {/ANNT;4224n;;84480n;0n}B {/ANNT;4224n;;0n;103488n}C