H3K27ac is an epigenetic modification to the DNA packaging protein histone H3. It is a mark that indicates acetylation of the lysine residue at N-terminal position 27 of the histone H3 protein. H3K27ac is associated with the higher activation of transcription and therefore defined as an active enhancer mark. H3K27ac is found at both proximal and distal regions of transcription start site (TSS). H3K27ac is also enriched in the regulatory regions of genes implicated in Alzheimer's disease, including those in tau and amyloid neuropathology.