FIG. 1.

Schemes of the distal part of the bithorax complex and the construct for testing the interaction between regulatory elements of the Abd-B locus. (A) The Abd-B gene and part of its 3′ cis-regulatory region. The horizontal line represents the DNA sequence of the bithorax marked off in kilobases (44). The only class A Abd-B transcript that is required for morphogenesis in PS10 to PS13 is drawn above the DNA line. Arrows marked “Proximal” and “Distal” point toward the centromere and the telomere, respectively. Horizontal brackets below the DNA indicate the extents of iab-5, iab-6, iab-7, and part of iab-8. Positions of the boundaries are indicated by filled squares. The promoter A region, marked off in kilobases, is indicated above the DNA line. The DNA fragments tested are shown as hatched boxes. The Fab-8 boundary is drawn below the DNA line. The PTS and Fab-8 insulator are indicated by white and black rectangles, respectively. The fragments taken for analysis are shown below the Fab-8 boundary. White and black ovals represent functional and mutant binding sites for dCTCF. (B) Reductive scheme of transgenic construct used to examine the interaction between regulatory elements at a distance. The yellow and white genes are shown as boxes, with arrows indicating the direction of their transcription. Downward arrows indicate the target sites of the Flp recombinase (frt) or Cre recombinase (lox); the same sites in construct names are denoted by parentheses. The GAL4 binding sites (indicated as G4) are at a distance of approximately 5 kb from the white promoter. Triangles indicate positions of elements tested for interaction.