BEAF (Boundary Element-Associated Factor) was originally identified as a Drosophila melanogaster chromatin domain insulator binding protein, suggesting a role in gene regulation through chromatin organization and dynamics. Genome-wide mapping found that BEAF usually binds near transcription start sites, often of housekeeping genes, suggesting a role in promoter function. This would be a nontraditional role for an insulator binding protein. To gain insight into molecular mechanisms of BEAF function, we identified interacting proteins using yeast 2-hybrid assays. Here we focus on the transcription factor Sry-δ. Interactions were confirmed in pulldown experiments using bacterially expressed proteins, by bimolecular fluorescence complementation, and in a genetic assay in transgenic flies. Sry-δ interacted with promoterproximal BEAF both when bound to DNA adjacent to BEAF or over 2 kb upstream to activate a reporter gene in transient transfection experiments. The interaction between BEAF and Sry-δ was detected using both a minimal developmental promoter (y) and a housekeeping promoter (RpS12), while BEAF alone strongly activated the housekeeping promoter. These two functions for BEAF implicate it in playing a direct role in gene regulation at hundreds of BEAF-associated promoters.

No abstract

No abstract