Enhancers are cis-acting elements capable of regulating transcription in a 
distance and orientation-independent manner. A subset of enhancers are occupied 
by RNA polymerase II (RNAP II) and transcribed to produce long non-coding RNAs 
termed eRNAs. We thoroughly investigated the association between eRNA 
productivity and various chromatin marks and transcriptional regulators in mouse 
embryonic stem cells (ESCs) through an integrative approach. We found that 
eRNA-producing enhancers exhibited elevated levels of the active mark H3K27Ac, 
decreased DNA methylation, and enrichment for the DNA hydroxylase Tet1. Many 
eRNA-producing enhancers have recently been characterized as "super-enhancers," 
suggesting an important role in the maintenance of pluripotency. Using 
experimental methods, we focally investigated a well-characterized enhancer 
linked to the Nanog locus and confirmed its exclusive eRNA productivity in ESCs. 
We further demonstrate that the binding of Sall4 and Tet family proteins were 
required for eRNA productivity at this locus. Collectively, we demonstrate that 
Tet1 binding and DNA hypomethylation are hallmarks of eRNA production.