NF-E2 AND GATA BINDING MOTIFS ARE REQUIRED FOR THE FORMATION OF DNASE-I HYPERSENSITIVE SITE-4 OF THE HUMAN BETA-GLOBIN LOCUS-CONTROL REGION

The beta-like globin genes require the upstream locus control region ( LCR) for proper expression. The active elements of the LCR coincide wi th strong erythroid-specific DNase I-hypersensitive sites (HSs). We ha ve used 5' HS4 as a model to study the formation of these HSs. Previou sly, we identified a 101 bp element that is required for the formation of this HS. This element binds six proteins in vitro. We now report a mutational analysis of the HS4 HS-forming element (HSFE). This analys is indicates that binding sites for the hematopoietic transcription fa ctors NF-E2 and GATA-1 are required for the formation of the character istic chromatin structure of the HS following stable transfection into murine erythroleukemia cells. Similarly arranged NF-E2 and GATA bindi ng sites are present in the other HSs of the human LCR, as well as in the homologous mouse and goat sequences and the chicken beta-globin en hancer. A combination of DNase I and micrococcal nuclease sensitivity assays indicates that the characteristic erythroid-specific hypersensi tivity of HS4 to DNase I is the result of tissue-specific alterations in both nucleosome positioning and tertiary DNA structure.