Figure 1: Distinct epigenetic signatures are related to enhancer functions in different cell types. Many enhancers are characterized by the presence of H3K4me1/2, H3.3/H2A.Z and the absence of an H3K4me3 mark. (A) In human ESCs, enhancers of actively transcribed genes are marked with H3K27ac. However, enhancers associated with poised genes contain (B) H3K27me3 in human ESCs or (C) H3K9me1 and H3K27me1 in human haematopoietic stem cells. (D) In Drosophila mesoderm cells, enhancers of actively transcribed genes are marked with H3K27ac and H3K79me3. Dark grey nucleosomes contain canonical histones. Pink nucleosomes are highly dynamic and contain histone variants. Green nucleosomes contain modified histones that are associated with many enhancers. ESC, embryonic stem cell; SC, stem cell.