Enhancers as non-coding RNA transcription units: recent insights and future perspectives

The observation that many, if not all, functional enhancers generate non-coding enhancer RNAs (eRNAs) has raised critical questions regarding the potential biological roles of the enhancer transcription process and, indeed, of eRNAs. This article reviews fundamental insights into the inter-regulation of enhancers and promoters and discusses unresolved questions regarding the functional role of enhancers as transcription units in genome regulation.