The charged patch hypothesis states that changing the charges on histone protein residues, namely lysines, allows the control of transcriptional activity.
Acetylation removes the positive charge present on lysine residues on histone proteins, causing disruption of the histone’s interactions with the DNA. Methylation does not disrupt positively charged lysine residues, and therefore does not have any effect on the histone protein’s interactions with DNA.
By controlling these interactions, it is possible to alter the transcriptional activity of the DNA.