Embryonic Stem Cells: A Perfect Tool for Studying Mammalian Transcriptional Enhancers.

Transcriptional enhancers are DNA elements capable of regulating gene expression in-cis over great distances. With the recent availability of genomic approaches to define epigenetic marks and RNA levels, these previously difficult to study elements are now being extensively examined for their critical role in lineage-specific transcriptional regulation. This review sets out to highlight the use of embryonic stem cells (ESCs) in the study of enhancers, emphasizing that ESC have become an ideal model system for questions regarding mammalian transcriptional regulation. This review highlights the epigenetic "signature" of enhancers, their mechanism of action, and the role of non-coding RNAs (ncRNAs) on enhancer function. We briefly review insulators, a sub-type of enhancers, and a novel model system for studying enhancer function in vivo. We conclude with some ongoing questions within the field.