The bithorax complex of Drosophila melanogaster as a model for studying specific long-distance interactions between enhancers and promoters

In higher eukaryotes regulation of the expression of genes responsible for the development of the organism is a complex process. Often, a single gene may be regulated in different cells and time intervals with the help of dozens of enhancers and promoters. It has recently become clear that enhancers directly interact with target promoters, and the intervening chromatin loops out. However, the mechanisms that ensure the specificity of long-distance interactions between enhancers and promoters remain unclear. One of the most convenient models for the study of remote interactions between the regulatory elements is the bithorax complex (BX-C) of Drosophila melanogaster. This review describes the regulation of the expression of the BX-C homeotic genes and discusses the existing models that explain the specificity of remote interactions between the enhancers and promoters at this locus.