| Acetyl-histone H3 (Lys23), often denoted H3K23ac, is a specific post-translational modification on the N‑terminal tail of histone H3 generated by histone lysine acetyltransferases and removed by histone deacetylases, and it contributes to the broader epigenetic program that regulates chromatin structure and gene transcription. Histone H3 carries a globular core domain and an extended tail with multiple modifiable lysine residues, including Lys4, 9, 14, 18, 23, 27, 36 and 56, and acetylation at these positions neutralizes the positive charge of the lysine side chain, reducing electrostatic interactions between histone tails and the DNA backbone and weakening internucleosomal contacts, which promotes a more open chromatin configuration. Acetylation at Lys23 fits into this general mechanism, contributing to relaxation of chromatin and facilitating access of transcriptional machinery to DNA by allowing DNA-binding proteins, including transcription factors and coactivators, to engage their target sequences within nucleosomal regions more efficiently. Acetylated lysine residues on histone H3, including H3K23ac, also create recognition sites for reader proteins containing bromodomains or YEATS domains; these readers recruit additional transcriptional regulators, chromatin remodelers or coactivator complexes to acetylated nucleosomes, integrating H3 tail acetylation into multistep signaling cascades that reinforce transcriptional activation. Within epigenetic histone H3 pathways, H3K23ac participates alongside other acetyl marks in coordinating nuclear organization and chromatin domain states, acting as part of combinatorial PTM patterns that distinguish active promoters, enhancers and transcriptionally engaged gene bodies from repressed regions. In cancer, global changes in histone H3 acetylation, including shifts in tail acetylation, associate with altered gene expression, and dysregulated acetylation contributes to oncogenic signaling by modifying accessibility at loci controlling proliferation, apoptosis and DNA repair; histone acetylation levels, as assessed by site-specific antibodies such as anti–acetyl-H3K23, have been explored as prognostic indicators and as pharmacodynamic readouts for HDAC inhibitor therapy. At a structural level, H3K23ac marks can be monitored with modification-specific antibodies that recognize histone H3 only when Lys23 is acetylated and do not cross-react with other acetylated lysines, providing tools for chromatin immunoprecipitation, immunohistochemistry or western blotting to map or quantify H3K23ac distribution across genomes and tissues. |
