[2] The genomic DNA of eukaryotic cells is wrapped around special protein molecules known as Histones.
[5] The current understanding and interpretation of histones comes from two large scale projects: ENCODE and the Epigenomic roadmap.
This led to chromatin states which define genomic regions by grouping the interactions of different proteins and/or histone modifications together.
Chromatin states were investigated in Drosophila cells by looking at the binding location of proteins in the genome.
[8] A look in to the data obtained led to the definition of chromatin states based on histone modifications.
This additional level of annotation allows for a deeper understanding of cell specific gene regulation.
It results in good optimization and is used in vivo to reveal DNA-protein binding occurring in cells.
ChIP-Seq can be used to identify and quantify various DNA fragments for different histone modifications along a genomic region.