Page "Epigenetics" Paragraph 19

Although histone modifications occur throughout the entire sequence, the unstructured N-termini of histones ( called histone tails ) are particularly highly modified.

These modifications include acetylation, methylation, ubiquitylation, phosphorylation and sumoylation.

Acetylation is the most highly studied of these modifications.

For example, acetylation of the K14 and K9 lysines of the tail of histone H3 by histone acetyltransferase enzymes ( HATs ) is generally correlated with transcriptional competence.