Insulators, long range interactions, and genome function

Insulators are DNA–protein complexes that can mediate interactions in cis or trans between different regions of the genome. Although originally defined on the basis of their ability to block enhancer–promoter communication or to serve as barriers against the spreading of heterochromatin in reporter systems, recent information suggests that their function is more nuanced and depends on the nature of the sequences brought together by contacts between specific insulator sites. Here we provide an overview of new evidence that has uncovered a wide range of functions for these sequences in addition to their two classical roles.