Insulators As Dynamic, Tunable Regulators of Enhancer-Promoter Coordination in Living Drosophila Embryos
The three-dimensional organization of the genome enables enhancers and promoters to interact across vast distances and direct transcription. Yet whether architectural elements, such as insulators, serve as rigid, passive barriers or as dynamic, active organizers of this communication remains unclear. Here, using single-cell, live imaging of a Drosophila transgene in which a single enhancer…
A Drosophila transgene was used to explore whether insulators are passive barriers or dynamic organizers of enhancer-promoter communication. The study confirmed that the enhancer interacts with two equidistant promoters simultaneously, and coordinated bursting of both promoters proved more productive than uncoordinated activity. Adding insulators to the system increased the frequency of coordinated bursting and overall transcriptional output, suggesting that insulators promote multi-way enhancer-promoter interaction.
Furthermore, the study found that bidirectionally-paired, homotypic insulators generated stronger coordination compared to unidirectional pairs. By inserting an intermediate insulator to create competing loop configurations and employing two-state promoter modeling, the researchers demonstrated that these chromatin loops are highly dynamic.
This finding challenges the notion that insulators are merely passive elements and instead positions them as active, tunable regulators that influence the frequency, coordination, and productivity of enhancer-promoter communication.
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