Su(H) and bHLH A protein binding sites in the proximal promoter regions of the neural E(spl)-C, proneural bHLH A, and certain panneural genes. (A) Neural E(spl)-C genes. bHLH R (m8, m7, m5, m3, mγ, and mδ) and Brd-like (m4 and mα) genes are shown. (B) Proneural bHLH A genes (ac, amos, ase, ato, l'sc, and sc) as well as certain panneural genes (dpn and sna). Expansions of the proximal promoters for ac and m8 are shown, since they are model promoter regions for the proneural and E(spl)-C genes, respectively. The binding sites for the Su(H) and bHLH A proteins are indicated by “S” and “A,” respectively. Boxes with dashed lines indicate SPS elements, which are an inverted repeat of high-affinity S sites separated by 15 to 17 bp that are present in several E(spl)-C promoters. Promoter regions that have been used to drive reporter gene expression in proneural clusters in vivo are indicated by the gray boxes: m4 and mγ (32), m5 and m8 (22), mα (5), mδ (9), ac (41), ase (19), dpn (13), and sna (18). Reporter gene constructs with ato (38) and sc (11) used noncontiguous regulatory regions.