Epigenomics1
Epigenomics is the study of the complete set of epigenetic modifications on the genetic material of a cell, known as the epigenome. The field is analogous to genomics and proteomics, which are the study of the genome and proteome of a cell. Epigenetic modifications are reversible modifications on a cell’s DNA or histones that affect gene expression without altering the DNA sequence. Epigenomic maintenance is a continuous process and plays an important role in stability of eukaryotic genomes by taking part in crucial biological mechanisms like DNA repair.
Epigenomes provide information about the patterns in which structures such as methyl groups tag DNA and histones (the proteins around which DNA is packaged to form chromatin), and about interactions between distant sections of chromatin.
-histone modification : The basic and repeating units of chromatin, nucleosomes, consist of an octamer of histone proteins (H2A, H2B, H3 and H4) and a 146 bp length of DNA wrapped around it. Chromatin remodeling occurs via post-translational modifications of the N-terminal tails of core histone proteins (Russell 2010 p. 529-30). The collective set of histone modifications in a given cell is known as the histone code. Many different types of histone modification are known, including: acetylation, methylation, phosphorylation, ubiquitination, SUMOylation, ADP-ribosylation, deamination and proline isomerization; acetylation, methylation, phosphorylation and ubiquitination have been implicated in gene activation whereas methylation, ubiquitination, SUMOylation, deamination and proline isomerization have been implicated in gene repression.
Chromatin is the complex of DNA, RNA and proteins that packages DNA within the cell. At the core of chromatin is an eight-subunit protein complex composed of histones. Molecular modifications to either DNA or histones can affect the structure and function of chromatin.
The Roadmap Epigenomics Project has produced reference epigenomes that provide information on key functional elements controlling gene expression in 127 human tissues and cell types
Reference
Epigenomics: Roadmap for regulation
http://www.nature.com/nature/journal/v518/n7539/full/518314a.html
