Post-translational modifications of histones regulate all DNA-templated processes, including replication, transcription and repair. These modifications function as platforms for the recruitment of specific effector proteins, such as transcriptional regulators or chromatin remodellers. Recent data suggest that histone modifications also have a direct effect on nucleosomal architecture. Acetylation, methylation, phosphorylation and citrullination of the histone core may influence chromatin structure by affecting histone–histone and histone–DNA interactions, as well as the binding of histones to chaperones.