It is thought that higher eukaryotes possess factors that facilitate remote enhancer-promoter interactions.
Enhancers can interact with proximal promoters from distances of thousands of base pairs.
To identify putative enhancer facilitators, a screen for mutations that reduce activity of the remote wing margin enhancer in the cut gene was performed. A TEA DNA-binding domain in the Scalloped protein binds the cut wing margin enhancer. Interactions among scalloped, mastermind and Chip mutations indicate that Mastermind and Chip act synergistically with Scalloped to regulate the wing margin enhancer. Chip is essential and also affects expression of a gypsy insertion in Ultrabithorax . Relative to mutations in scalloped or mastermind, a Chip mutation hypersensitizes the wing margin enhancer in cut to gypsy insertions.