Enhancers

Enhancers act as transcription factor binding sites; further activating the target gene. Genes with similar functions in different species depend on an enhancer that does not bear similarities. The enhancer can transcribe into RNAs that do not code for protein. They also act as cis-regulatory elements. The functional definition of enhancers varies because of their flexibility of action, genomic location and position. Genes with similar functions in different species depend on an enhancer that does not bear similarities. Histone tails modification amongst genomic DNA via DNase I is the more reliable means of identification of these enhancers. These DNases occupy around 200bp of open-chromatin. ‘Open’ chromatin indicates the DNase-sensitive and they are flanked by regions rich in mono- and/or dimethylated lysine 4 of histone H3 (H3K4me1/H3K4me2) and acetylated lysine 27 of histone H3 (H3K27ac (bind with p300). Previously researchers have attempted to classify enhancers based on their role in development (active, intermediate and poised enhancers and additional markers include H3K27me3 orH3K36me3). β-globin locus is the first and most studied gene in regard to gene regulation via enhancers. The locus Control Region of the β-globin locus is located 40 to 60kb upstream from the promoter it regulates. During Transcription, these enhancers are transcribed into non-coding RNA (eRNA) and their sequence length stabilises the enhancer-promoter interaction.