Requirement of insulator for the functions of promoter targeting sequence in vivo of Drosophila Bithorax

In complex genomes, insulators set up chromatin domain boundaries, and protect promoters from unwanted activation by enhancers from neighboring genes. The Promoter Targeting Sequence (PTS) from the Abdominal-B locus of the Drosophila Bithorax complex overcomes an insulator, and facilitates, but restricts, distant enhancers to a single promoter. Experiments showed that this promoter targeting activity required an insulator for its establishment, but could be maintained by the PTS in the absence of an insulator. These results sequence suggest that PTS is established independently of enhancer activity and is maintained epigenetically throughout development and subsequent generations.