H3K4me3

H3K4me3 is an abbreviation used in the field of epigenetics to denote a specific post-translational modification of the histone protein H3. Specifically, it refers to the trimethylation of lysine residue 4 on the histone H3 protein.

Histones are the main protein components of chromatin, around which DNA is wrapped. Post-translational modifications (PTMs) of histones, such as methylation, play a crucial role in regulating gene expression and other cellular processes. These modifications can alter chromatin structure, making DNA more or less accessible to transcription factors and other regulatory proteins.

In the case of H3K4me3, the "H3" stands for histone H3, "K4" indicates lysine residue number 4, and "me3" signifies trimethylation, meaning that three methyl groups have been added to the lysine residue. H3K4me3 is generally associated with active gene transcription and is often found at the promoter regions of actively transcribed genes. Its presence is typically correlated with an open chromatin conformation, facilitating access by transcription machinery.

The enzymes responsible for adding methyl groups to H3K4 are primarily histone methyltransferases (HMTs) of the COMPASS (Complex Proteins Associated with Set1) family in mammals. Conversely, histone demethylases can remove the methyl groups, reversing the modification.

The presence and levels of H3K4me3 are often used as a marker to identify active promoters and enhancers in genome-wide studies, providing insights into gene regulatory networks and cellular function. Studying H3K4me3 patterns can be valuable in understanding development, disease, and responses to environmental stimuli.