H3K27ac

H3K27ac refers to the acetylation of lysine residue 27 on the histone H3 protein. Histones are proteins that package DNA into structural units called nucleosomes. The post-translational modification of histones, such as acetylation, plays a crucial role in regulating gene expression. Acetylation of histones generally leads to a more open chromatin structure, making the DNA more accessible to transcription machinery and thereby promoting gene activation.

H3K27ac specifically is a mark associated with active enhancers and promoters. Enhancers are regulatory DNA elements that can increase the transcription of a gene, often from a distance. Promoters are regions of DNA located near the transcription start site of a gene where transcription initiation is controlled. The presence of H3K27ac at these sites is a strong indicator of transcriptional activity.

This epigenetic mark is deposited by histone acetyltransferases (HATs), such as p300 and CBP, and removed by histone deacetylases (HDACs). The dynamic regulation of H3K27ac levels is important for various cellular processes, including cell differentiation, development, and response to stimuli. Aberrant H3K27ac patterns have been implicated in diseases like cancer, where they can contribute to uncontrolled cell growth and altered gene expression profiles. Researchers utilize techniques like ChIP-seq (Chromatin immunoprecipitation sequencing) to map H3K27ac across the genome and study its functional significance.