The term epigenetics defines heritable changes of gene expression that are not driven by the primary
nucleotide sequence of a gene, but rather by the reorganisation of chromatin structures. In eukaryotes,
chromatin allows the compaction of DNA into the nucleus via its basic structural subunit, the nucleosome, in
which DNA is wrapped around histone octamers. This structure is timely and spatially remodeled to fit the
needs of DNA replication and chromosome segregation during cell division processes, RNA transcription and
DNA repair. In this chapter, we describe the two major mechanisms of epigenetic regulation: DNA methylation
and covalent modifications of nucleosomal histone proteins, their crosstalk, and how their combinations
switch on and off gene expression.
Chromatin, Epigenetics, DNA methylation, CpG, CpNpG, Imprinting, Histone Code, Histone variants, posttranslational
modifications, Epigenomics, deacetylation, acetylation, ubiquitation.
Inserm, UMR837, Jean-Pierre Aubert Research Center, Team 5 "Mucins, epithelial differentiation and carcinogenesis", Lille, France.