What is acetylation, and how does it affect DNA transcription?

The amount of binding between DNA and histones can be altered by a process called acetylation. HAT enzymes transfer a two carbon acetyl group to the ends of particular amino acids in the histone proteins. The addition of the acetyl group to positively charged amino acids such as lysine removes the charge and reduces the overall affinity of the histones for the negatively charged DNA. In this configuration, the DNA is more accessible for transcription factors and transcription is increased. Similarly, deacetylation leads to a repression of transcription.