Erna

More recently, in 2010, researchers discovered that these enhancers are transcribed into RNA molecules, known as enhancer RNA or eRNA.

This raised the possibility that measuring eRNA transcription levels could help researchers determine when an enhancer is active, as well as which genes it's targeting.

However, this kind of mapping has proven difficult to perform because eRNA is produced in very small quantities and does not last long in the cell.

Additionally, eRNA lacks a modification known as a poly-A tail, which is the "hook" that most techniques use to pull RNA out of a cell.

One way to capture eRNA is to add a nucleotide to cells that halts transcription when incorporated into RNA.