Acetylation

From Biomatics.org

In biology, i.e. in living cells, acetylation occurs as a post-translational modification of proteins, for example, histones and tubulins.

Histone Acetylation and Deacetylation

Histones are acetylated and deacetylated on lysine residues in the N-terminal tail as part of gene regulation. Typically, these reactions are catalyzed by enzymes with "histone acetyltransferase" (HAt) or "histone deacetylase" (HDAc) activity. The source of the acetyl group in histone acetylation is Acetyl-Coenzyme A, and in histone deacetylation the acetyl group is transferred to Coenzyme A.

Acetylated histones and nucleosomes represent a type of epigenetic tag within chromatin. Acetylation brings in a negative charge and neutralizes the interaction of the N termini of histones with the phosphate groups of DNA. As a consequence, the condensed chromatin is transformed into a transiently relaxed structure which allows genes to be transcribed. Acetylated chromatin is thought to be more "relaxed" and is called euchromatin. Methylated chromatin is more condensed (tightly packed), and referred to as heterochromatin.