Impact of Interactions between three Su(Hw)-Dependent Insulators and the White Gene Enhancer on Long-Distance Transcriptional Regulation in Drosophila melanogaster

Special regulatory elements, insulators, either block enhancer-promoter contacts or facilitate long-distance interactions between regulatory elements of the genome. Two identical DNA sequences containing four Su(Hw) protein binding sites were shown to interact in a transgenic system and ensure maximal activation of the yellow and white promoters by specific enhancers located 28 kb apart. We demonstrated that three Su(Hw) insulators are also capable of regulating specific enhancer-promoter contacts at a distance of 28 kb. The effect of multiple insulators on transcription depends on the relative positions of insulators, enhancers, and promoters. We confirmed that the eye enhancer directly interacts with the Su(Hw) insulator and participates in the formation of chromatin loops. These data indicate that insulators are multifunctional elements that organize chromatin structure and directly regulate gene activity.