ASH2 like, histone lysine methyltransferase complex subunit (ASH2L)

ASH2 like, histone lysine methyltransferase complex subunit (ASH2L), is a **core component of the COMPASS/MLL family of histone methyltransferase complexes** responsible for methylation of histone H3 at lysine 4 (H3K4), a critical mark for active gene transcription[1][2][3]. ASH2L enables the catalytic activity of the MLL family enzymes by serving as a scaffold and regulator within multiprotein complexes that include WDR5, RBBP5, and DPY30[3]. It contains a plant homeodomain (PHD) finger and a SPRY domain, with an atypical PHD that does not directly bind histone tails, as well as a DNA-binding winged-helix motif critical for chromatin localization and gene regulation[1]. ASH2L functions both in general chromatin accessibility and in **direct transcriptional enhancement** by associating with specific transcription factors (e.g., Ap2δ) that recruit MLL/COMPASS complexes to particular gene promoters, facilitating targeted H3K4 trimethylation and gene activation[2]. Loss or mutation of ASH2L disrupts H3K4 methylation, represses gene expression (especially at CpG island promoters), alters chromatin architecture, and can lead to cellular senescence or developmental defects[3].

Other names

ASH2LASH2L1ASH2L2Bre2Set1/Ash2 histone methyltransferase complex subunit ASH2ASH2-like proteinash2 (absent, small, or homeotic)-like

Involved in recruitment of methyltransferase complexes (e.g., MLL complex) for H3K4 methylation Complexes with transcription factors (e.g., Ap2δ) to mediate specific promoter methylation/gene activation