H3K27ac

H3K27ac

Lysine acetylation process

H3K27ac refers to the acetylation of the 27th lysine residue on the histone H3 protein. This post-translational modification is a key epigenetic marker associated with active gene transcription. H3K27ac is commonly found at enhancer and promoter regions of the genome, where it plays a crucial role in regulating gene expression.

Structure and Function

Histone proteins, including histone H3, are essential components of chromatin, the complex of DNA and protein found in the nucleus of eukaryotic cells. The acetylation of lysine residues on histones, such as H3K27, is a reversible modification that influences chromatin structure and gene activity.

H3K27ac is specifically associated with open chromatin and is a marker of active enhancers and promoters. The acetylation neutralizes the positive charge of the lysine residue, reducing the interaction between histones and DNA, thereby facilitating access for transcription factors and the transcriptional machinery.

Biological Significance

H3K27ac is a critical marker for identifying active regulatory elements in the genome. It is often used in chromatin immunoprecipitation (ChIP) assays to map active enhancers and promoters. The presence of H3K27ac at a genomic region suggests that the region is actively involved in regulating gene expression.

In addition to its role in normal cellular processes, aberrant patterns of H3K27ac have been implicated in various diseases, including cancer. Changes in the acetylation status of H3K27 can lead to dysregulation of gene expression, contributing to oncogenesis and tumor progression.

Enzymes Involved

The acetylation of H3K27 is catalyzed by histone acetyltransferases (HATs), which transfer an acetyl group from acetyl-CoA to the lysine residue. Conversely, the removal of the acetyl group is mediated by histone deacetylases (HDACs). The balance between these opposing activities determines the acetylation status of H3K27 and, consequently, the transcriptional activity of associated genes.

Research and Applications

H3K27ac is a valuable marker in epigenomic studies aimed at understanding gene regulation. Techniques such as ChIP-seq (chromatin immunoprecipitation followed by sequencing) are used to map H3K27ac across the genome, providing insights into the regulatory landscape of cells.

The study of H3K27ac is also important in the field of epigenetic therapy, where modulating histone acetylation is explored as a therapeutic strategy for diseases like cancer. Inhibitors of HDACs, for example, are being investigated for their potential to reactivate silenced genes by increasing histone acetylation levels.

Related Pages

• Histone modification
• Epigenetics
• Chromatin
• Gene expression
• Histone acetyltransferase
• Histone deacetylase