Decreased acetylation of associated histones

Acetylation is the process whereby an acety! group is transterred to a molecule. In this case the group donating the acety, group is acety coenzyme A which you may remember from the link reaction in respiration (Topic 12.2). Deacetylation is the reverse reaction where an acetyl group is removed from a molecule. Decreased acetylation increases the positive charges on histones and therefore increases their attraction to the phosphate groups of DNA. The association between DNA and histones is stronger and the DNA is not accessible to transcription factors. These transcription factors cannot initiate mRNA production from DNA. In other words, the gene is switched off.