Analysis of potential transcription factor binding sites within the functional Dβ1 promoter region. The sequence corresponding to −350 to +150 relative to Dβ1 was analyzed using the TFSEARCH program.39 The results were notable for a number of potential binding sites for Ikaros/Lyf-1 (shaded ovals) and GATA (shaded rectangles) transcription factors. Site-directed mutations of two of these sites (corresponding to m35 and m74 constructs in Fig 4) are indicated. In addition, a potential TATA motif is shown. The genomic fragments exhibiting promoter activity in the context of Eβ are indicated beneath.