Methylation of DNA at cytosine residues as well as post-translational modifications of histones, including phosphorylation, acetylation, methylation and ubiquitylation, contribute to the epigenetic information carried by chromatin. These changes play an important role in the regulation of gene expression by modulating the access of regulatory factors to the DNA. The use of a combination of biochemical, genetic and structural approaches has allowed demonstration of the role of chromatin stru ...