PET Imaging of Epigenetic Influences on Alzheimer’s Disease

Figure 1

Histone regulation of gene expression. Positively charged histone octamers bind to the negatively charged phosphate backbone of DNA, condensing it into transcriptionally inactive heterochromatin. Histone acetyltransferase (HAT) enzymes donate acetyl groups from acetyl-coenzyme A to histone proteins, thereby neutralizing its positive charge, resulting in its dissociation from DNA, making it transcriptionally active. This relaxed form of chromatin, euchromatin, can then reassociate with DNA through the action of histone deacetylases (HDACs), which remove acetyl groups from the neutralized histone protein, returning it to transcriptionally inactive cationic heterochromatin.