Acetylation has the effect of changing the overall charge of the histone tail from positive to neutral. Nucleosome formation is dependent on the positive charges of the H4 histones and the negative charge on the surface of H2A histone fold domains.

Why does acetylation happen?

Acetylation occurs with the transfer of acetyl groups from acetyl coenzyme A (acetyl CoA) to lysine residues by acetyltransferase leading to neutralization of their positive charge. As discussed in Section 15.7. 1.1, acetylation can alter gene expression epigenetically.

What is the function of acetylation?

Acetylation neutralizes the positive charge of lysine and thus affects diverse aspects of protein function, such as stability, enzymatic activity, subcellular localization and interaction with other macromolecules in the cell.