Histone H3 (acetyl K4) refers to the acetylation of lysine 4 on the histone H3 protein, which is a post-translational modification that plays a critical role in gene regulation. This modification is associated with active transcription, as it weakens the interaction between histones and DNA, leading to a more open chromatin structure that is accessible to the transcription machinery. Histone H3 acetylation at lysine 4 (H3K4ac) is enriched at the transcription start sites (TSSs) of active genes and enhancers, contributing to transcription by promoting H3K4 trimethylation (H3K4me3) and facilitating histone eviction. Moreover, H3K4ac is positively correlated with H3K4 methylation, and both modifications are important for marking active chromatin regions that dictate transgene expression or silencing. The dynamic turnover of acetylation on K4-methylated histone H3 is also significant for efficient gene induction, as inhibition of this turnover can lead to immediate inhibition of gene expression. In summary, Histone H3 (acetyl K4) is a key epigenetic marker that influences gene transcription and chromatin structure.