A BEAF dependent chromatin domain boundary separates myoglianin and eyeless genes of Drosophila melanogaster.

Precise transcriptional control is dependent on specific interactions of a number of regulatory elements such as promoters, enhancers and silencers. Several studies indicate that the genome in higher eukaryotes is divided into chromatin domains with functional autonomy. Chromatin domain boundaries are a class of regulatory elements that restrict enhancers to interact with appropriate promoters and prevent misregulation of genes. While several boundary elements have been identified, a rational approach to search for such elements is lacking. With a view to identifying new chromatin domain boundary elements we analyzed genomic regions between closely spaced but differentially expressed genes of Drosophila melanogaster. We have identified a new boundary element between myoglianin and eyeless, ME boundary, that separates these two differentially expressed genes. ME boundary maps to a DNaseI hypersensitive site and acts as an enhancer blocker both in embryonic and adult stages in transgenic context. We also report that BEAF and GAF are the two major proteins responsible for the ME boundary function. Our studies demonstrate a rational approach to search for potential boundaries in genomic regions that are well annotated.