Fig. 2
From: Histone H3 lysine K4 methylation and its role in learning and memory
H3K4 methylation marks and their genomic distributions. a Histone octamers, comprised of two of each histone H2A, H2B, H3, and H4 subunits, are wrapped by DNA to form nucleosomes. An N-terminal tail protrudes from each histone subunit, containing residues amenable to posttranslational modification. Lysine residue K4 on H3 can be mono- (orange), di- (green), or tri- (blue) methylated, forming H3K4me1, H3K4me2, or H3K4me3, respectively. b H3K4me1, H3K4me2, and H3K4me3 are located in different regions throughout the genome. H3K4me3, H3K4me2, and H3K4me1 are found in increasingly broad distributions about the TSSs of actively transcribed genes. Additionally, H3K4me1 is found at distal regions acting as enhancers