H3K4me1

Histone H3 lysine 4 monomethylation (H3K4me1) is a post-translational modification of histone H3 where a single methyl group is added to lysine 4. It is a prominent chromatin feature associated with regulatory elements, most notably enhancers, and is examined in epigenomic maps to infer regulatory potential across genomes. In many cell types, H3K4me1 marks enhancers that are poised or primed for activation and is often found near transcription factor binding sites and accessible chromatin. Active enhancers typically display both H3K4me1 and H3K27ac, while promoters are more commonly enriched for H3K4me3.

Biogenesis and regulation: H3K4me1 is deposited by methyltransferases, primarily the MLL3/MLL4 family (KMT2C/KMT2D) within COMPASS-like complexes in mammals. Other methyltransferases may contribute in specific contexts. The mark can be removed by demethylases, including the KDM1A/LSD1 family and the KDM5 family, allowing dynamic regulation of enhancer activity during development and in response to signals.

Biological significance: H3K4me1 serves as a genomic tag that helps define regulatory landscapes, guiding the recruitment of chromatin remodelers and transcriptional machinery. It is a key component of enhancer identification and annotation in comparative and developmental studies. The balance between H3K4me1 and other marks such as H3K27ac contributes to the distinction between poised and active enhancers, influencing tissue-specific gene expression programs.

Detection: H3K4me1 is typically detected using chromatin immunoprecipitation followed by sequencing (ChIP-seq) with specific antibodies, enabling genome-wide mapping of enhancer-associated marks across cell types and conditions.