Long range chromatin interactions involved in gene regulation.

Long-distance chromatin interaction has been proposed and demonstrated for enhancer elements separated from the gene by hundreds or thousands of base pairs. This paved the way for the detection of additional enhancer properties, such as the regulation of interaction, and the contacting of genes in trans on other chromosomes. The outspread arrangement of regulatory elements and transcription units requires insulators to prevent the functional interference of enhancer elements with inappropriate promoters. Apparently, insulators mediate differential chromatin folding to allow or to prevent enhancers from contacting specific promoters. The factor CTCF is often involved in bridging separated chromatin regions. In addition to interchromosomal contacts, intrachromosomal interactions have been demonstrated for genes with a similar regulation, such as active genes, estrogen induced genes and imprinted genes. With more sophisticated and sensitive methods combined with deep sequencing and array technology, a huge number of long range interactions can expected to be characterized in the near future.