Su(Hw) interacts with Combgap to establish long-range chromatin contacts
Insulator-binding proteins (IBPs) play a critical role in genome architecture by forming and maintaining contact domains. While the involvement of several IBPs in organising chromatin architecture in Drosophila has been described, the specific contribution of the Suppressor of Hairy wings (Su(Hw)) IBP to genome topology remains unclear. In this study, we provide evidence for the existence of long-range interactions (LRIs) between Su(Hw) and Combgap ChIP-Seq peaks, reflected in the indirect binding of these proteins to chromatin in ChIP experiments. Loss of Su(Hw) binding results in the disappearance of Su(Hw)-Combgap LRIs and a decrease in spatial self-interactions among a subset of Su(Hw) sites. Our findings suggest that Su(Hw)-Combgap LRIs are associated with active chromatin rather than Polycomb-directed repression. Furthermore, we observe that the majority of transcription start sites that are down-regulated upon loss of Su(Hw) binding to chromatin are located within 2 kb of Combgap peaks and exhibit Su(Hw)-dependent changes in Combgap and transcriptional regulators' binding. Overall design: All flies were raised at 25°C on standard agar medium. Ovaries were dissected from recently eclosed 15 hour-old flies (contain only egg chamber stages 1-8).