Protein-binding sites within the 5' DNase I-hypersensitive region of the chicken alpha D-globin gene

Abstract

We mapped at high resolution and as a function of development the hypersensitive domain in the 5'-flanking region of the chicken alpha D-globin gene and determined the specific protein-binding sites within the domain. The domain extends from -130 to +80 nucleotides (nt) relative to the cap site. DNase I footprinting within intact embryonic erythrocyte nuclei revealed a strongly protected area from -71 to -52 nt. The same area was weakly protected in adult nuclei. A factor was present in extracts of erythrocyte nuclei from both embryos and adults that protected the sequence AAGATAAGG (-63 to -55 nt) in DNase I footprinting experiments; at higher concentrations of extract, sequences immediately adjacent (-73 to -64 and -53 to -38) were also protected. The same pattern of binding was revealed by gel mobility shift assays. The identical AAGATAAGG sequence is found in the 5'-flanking region of the beta rho gene; it competed for binding of the alpha D-specific factor, suggesting that regulatory elements are shared.