The promoter targeting sequence facilitates and restricts a distant enhancer to a single promoter in the Drosophila embryo.

Transcriptional enhancers in large gene complexes activate promoters over huge distances, yet little is known about the mechanism of these long-range interactions. We report that the promoter targeting sequence (PTS) from the Abdominal-B locus of the Drosophila bithorax complex facilitates the activity of a distantly located enhancer in transgenic embryos and that it restricts the enhancer to a single promoter. These functions are heritable in all successive generations. We also show that the PTS functions only when itself and an insulator are located between the enhancer and the promoter. These findings suggest that the PTS may facilitate long-range enhancer-promoter interactions in the endogenous Abdominal-B locus. We propose that the PTS establishes a stable chromatin structure between an enhancer and a promoter, which facilitates yet restricts an enhancer to a single promoter.