Close interactions between DNA methylation and histone modifications. (a) Relaxed chromatin is accessible for transcription factors (TFs). Chemical modifications (green) on the core histones (yellow) result in a relaxed chromatin structure. (b) DNA methyltransferases (Dnmts) add methyl groups (grey triangle) to CpG dinucleotides, resulting in gene silencing that can affect the former modification of the histones. (c) The chemical modification (red) to the core histone results in a condensed and inactive chromatin structure. TFs are sterically hindered and cannot bind to their recognition sequence on the DNA.