H3K4me3

H3K4me3 stands for tri-methylation of the fourth lysine residue on histone protein H3, which is part of the DNA packaging structure in cells. This chemical modification is commonly found near the start of active genes and signals that a gene is "turned on" or accessible for making proteins. By marking specific areas of the genome, H3K4me3 helps regulate gene activity, playing a key role in processes like development, cell differentiation, and response to environmental cues. It is a crucial component of the epigenetic mechanisms that control how genes are expressed without altering the underlying DNA sequence.