Histone Acetylation
Histone acetylation is the addition of an acetyl group to lysine residues on histone proteins, mainly on their N-terminal tails. It is broadly associated with open, transcriptionally active chromatin: by neutralising the positive charge of lysine it loosens histone-DNA contacts, and it creates docking sites for reader proteins that activate transcription.
Definition
Histone acetylation is the reversible, enzymatically catalysed addition of an acetyl group to the epsilon-amino group of lysine residues on histones, generally relaxing chromatin and promoting transcription, and removed by histone deacetylases.
Scope
The entry covers the chemistry and location of histone lysine acetylation, the writer and eraser enzymes (acetyltransferases and deacetylases), the reader modules that recognise the mark, and its general link to active chromatin. It is reference-educational and does not cover therapeutic dosing or individualised treatment.
Core questions
- How does acetylation of a lysine alter histone-DNA interaction and chromatin compaction?
- Which enzymes add and remove the mark, and which modules read it?
- Why is histone acetylation broadly associated with active transcription?
- How is the balance between acetylation and deacetylation regulated?
Key concepts
- Lysine acetylation
- Histone acetyltransferases (writers)
- Histone deacetylases (erasers)
- Bromodomain readers
- Charge neutralisation and chromatin relaxation
- Acetylation-associated active chromatin
Mechanisms
Acetyl groups are transferred from acetyl-CoA to the epsilon-amino group of specific lysines on histone tails by histone acetyltransferases (writers). Acetylation neutralises the lysine's positive charge, weakening the electrostatic attraction between histones and the negatively charged DNA backbone and thereby loosening nucleosome packing. Acetyl-lysines are also recognised by bromodomain-containing reader proteins, which recruit transcriptional and remodelling machinery. The mark is reversed by histone deacetylases (erasers), which restore the positive charge and favour compaction. The dynamic balance of acetyltransferase and deacetylase activity sets local chromatin accessibility and transcriptional competence.
Clinical relevance
Histone acetylation enzymes are studied as regulators of gene expression and as drug targets in research settings, and disruption of acetylation balance is described in various diseases. This entry is descriptive background for understanding the mark and is not a basis for individual treatment decisions.
Evidence & guidelines
The association of histone acetylation with transcriptionally permissive chromatin, the writer-eraser-reader organisation, and bromodomain recognition of acetyl-lysine are well established in reviews by Shahbazian and Grunstein, Seto and Yoshida, and Fujisawa and Filippakopoulos. Site-specific functional consequences vary by residue and context and remain an active area of mapping.
History
A link between histone acetylation and transcriptional activity was proposed in the 1960s, but the field advanced sharply in the 1990s when histone acetyltransferases and deacetylases were identified as enzymes that, respectively, activate and repress transcription. The later characterisation of bromodomains as acetyl-lysine readers completed the writer-reader-eraser picture for this mark.
Key figures
- Michael Grunstein
- C. David Allis
- Edward Seto
- Tony Kouzarides
- Panagis Filippakopoulos
Related topics
Seminal works
- shahbazian-grunstein-2007
- seto-yoshida-2014
- kouzarides-2007
Frequently asked questions
- Why does histone acetylation tend to activate transcription?
- Acetylation neutralises the positive charge on histone lysines, loosening the histone-DNA grip and opening chromatin, and it recruits bromodomain reader proteins that bring in activating machinery.
- What removes histone acetylation?
- Histone deacetylases (HDACs) remove acetyl groups, restoring the lysine's positive charge and favouring chromatin compaction and transcriptional repression.