Combinatorial expression of a ftz-zen fusion promoter suggests the occurrence of cis interactions between genes of the ANT-C.

The nine homeobox genes contained within the Antennapedia gene complex (ANT-C) are precisely regulated during embryonic development. It is not known to what extent the physical linkage of these genes contributes to their normal patterns of expression. Here we show that cis regulatory elements associated with one homeobox gene can act over a long distance (approximately 20 kb) to influence the expression of another homeobox gene. Specifically, fushi tarazu (ftz) promoter elements can direct the periodic expression of the z2 gene, which normally shows a simple 'dorsal on/ventral off' pattern of expression. An 80 kb deletion within the ANT-C [Df(3R)LIN] juxtaposes the z2 and ftz promoters, resulting in a hybrid expression pattern whereby z2 transcripts are distributed within periodic stripes that are confined to dorsal and lateral tissues and not observed in the ventral mesoderm. This observation suggests that separate promoter elements of different genes can function in a combinatorial manner, and that the patterns of ANT-C gene expression might depend on cis regulatory interactions.