Regulatory features

Regions that have epigenomic marks associated with non-coding regulatory function are called regulatory features in Ensembl. The different types of regulatory features annotated include:

• Promoters
• Enhancers
• Open chromatin regions (without evidence to classify as a promoter or enhancer)
• Transcription factor binding (enriched for TF binding, but lacking evidence to be classified as open chromatin, enhancer or promoter)
• CTCF binding sites

Currently in human and mouse, promoters and enhancers share similar epigenomic features, but promoters are more likely to be found near a Transcription Start Site. For other vertebrates, promoters are open chromatin regions that overlap a transcription start site.

For each cell type (epigenome) regulatory features are assigned labels to describe their activity levels. These include:

• ACTIVE, when the feature displays an active epigenetic signature, which can include evidence of open chromatin.
• POISED, when the feature displays a epigenetic signature with the potential to be activated.
• REPRESSED, when the feature is epigenetically repressed.
• INACTIVE, when the region bears no epigenetic modifications from the ones included in the Regulatory Build.
• NA, when there is no available data in the cell type for this feature.