Fig. 7. Svp regulates the pros enhancer. (A) Alignment of the consensus Su(H)-binding sequence with the S1 site in the E(spl)m4 gene and the ten putative-binding motifs found in the core-enhancer. Mismatched residues are colored in red. Two of these motifs (pros7 and pros10) are also present within the mini-enhancer. (Right) A mobility-shift gel showing the complex that contains Su(H) protein and labeled E(spl)m4S1 DNA (m4S1). Each reaction contained a 100x molar excess of an unlabeled competitor DNA as indicated, except for the reaction loaded into the leftmost lane, which did not contain competitor. (B-C'') Transgenic mini-enhancer-β-gal reporter expression (green) in eye discs counterstained for Pros protein (purple). (B-B'') β-gal expression induced by the wild-type mini-enhancer is weakly variegated. (C-C'') β-gal expression induced by the mutated pros7 mini-enhancer is not variegated but is still restricted to R7 and cone cells. (D-D'') Transgenic core-enhancer-β-gal reporter (green) which has 10 mutated Su(H)-binding sites in a sev-N^act/+ mutant eye disc. sev-N^act induces ectopic β-gal expression in R1/R6 cells. Endogenous Pros protein (purple) is also induced ectopically in these cells. (E) Sequence alignment of a Svp-binding site in the pros mini-enhancer from D. melanogaster and D. simulans. Response elements correspond to two half-sites (consensus AGGTCA) spaced one bp apart as a direct repeat (Zelhof et al., 1995). The position of the three tandem half-sites in the enhancer is shown with a bar over each half-site. (F,G) Transgenic mini-enhancer-β-gal reporter expression (green) in eye discs counterstained for Pros protein (purple). (F) A wild-type eye disc. (G) An eye disc carrying four copies of the sev-Svp2 transgene. Although some cells are positive for both markers, other cells are positive for one marker but not the other.