A cis DNA element that regulates long-range enhancer promoter communications

Large gene complexes frequently use cis DNA elements to ensure proper regulation of gene activities. The transcriptional enhancers in these large gene complexes activate promoters over huge distances, yet little is known about the mechanism of these long-range interactions. The Promoter Targeting Sequence (PTS) from the Abdominal-B locus of the Drosophila Bithorax complex facilitates the enhancer promoter interaction. In this report, the experiments indicated that the PTS overcomes enhancer-blocking insulator, and facilitates a distant enhancer and restricts the transcription activation to only one of the two available promoters. The results further showed that the PTS could overcome multiple insulators. It can be hypothesized that the PTS establishes a stable chromatin structure between an enhancer and a promoter, which facilitates yet restricts an enhancer to a single promoter. These findings offer significant insights into the mechanism of PTS function and provide a new window to examine the fundamental questions about enhancer-promoter interaction and the mechanism of insulator function.