Fig. 3. The divergent Lab/Exd/Hth-binding site is crucial for in vivo activity of EVIII enhancer of CG11339. (A) Sequence alignment of the Drosophila melanogaster (Dm) 150 bp fragment EVIII with the corresponding genomic region of Drosophila pseudoobscura (Dp). Identical nucleotides are outlined in red. The putative Lab/Exd- and Hth-binding sites are indicated (broken boxes), as well as the oligonucleotide used for gel mobility experiments in Fig. 4 (broken blue lines). (B-I) All embryos are shown at stages 12 (B,D,F,H) and 14 (C,E,G,I). (B,C) Expression of ß-Gal protein under the control of wild-type enhancer EVIII. This expression was lost when fragment EVIII carried mutations in the two putative Lab/Exd-binding sites (D,E) or in the divergent Lab/Exd/Hth-binding site (F,G); and was diminished with mutations in the atypically oriented Hox/Exd-like binding site (H,I).