H3K27ac

H3K27ac is an epigenetic modification of the DNA packaging protein histone H3. The designation H3K27ac indicates an acetylation of the lysine residue at the N-terminal position 27 of the histone H3 protein. H3K27ac is associated with higher transcriptional activation and is therefore defined as an active enhancer mark. (Huang, S et al. 2015). H3K27ac is located in both proximal and distal regions of the transcription start site (TSS).

Lysine acetylation: Proteins are usually acetylated at lysine residues. The acetylation reaction is based on acetyl coenzyme A as an acetyl group donor. In histone acetylation and deacetylation, histone proteins are acetylated and deacetylated at lysine residues in the N-terminal tail as part of gene regulation. Typically, these reactions are catalyzed by enzymes with histone acetyltransferase (HAT) or histone deacetylase (HDAC) activity, although HATs and HDACs can also alter the acetylation status of non-histone proteins.

The regulation of transcription factors, effector proteins, molecular chaperones and cytoskeletal proteins by acetylation and deacetylation is an important post-translational regulatory mechanism. These regulatory mechanisms are analogous to phosphorylation and dephosphorylation by kinases and phosphatases. The acetylation state of a protein can not only alter its activity, but also provides a recent indication that this post-translational modification can also interact with phosphorylation, methylation, ubiquitination, sumoylation and others to dynamically control cellular signaling.

1. F, Tie (2009) CBP-mediated acetylation of histone H3 lysine 27 antagonizes Drosophila Polycomb silencing. Development 136: 3131-3141.
2. Huang, S et al. (2015) Epigenetic Gene Expression and Regulation. Elsevier Science 30: 21-38.
3. Jenuwein T et al. (2001) Translating the histone code. Science 293: 1074-1080.
4. Masalha M et al. (2021) H3K27Ac modification and gene expression in psoriasis. J Dermatol Sci 103:93-100.
5. Ruthenburg AJ et al. (2007) Multivalent engagement of chromatin modifications by linked binding modules. Nature Reviews Molecular Cell Biology 8: 983-994.
6. Kouzarides T (2007). Chromatin modifications and their function. Cell 128: 693-705.)
7. Yao Q et al. (2021) Epigenetic Alterations in Keratinocyte Carcinoma. J Invest Dermatol141:1207-1218.