The engagement of histone lysine methyltransferases with nucleosomes: structural basis, regulatory mechanisms, and therapeutic implications

Histone lysine methyltransferases (HKMTs) deposit methyl groups onto lysine residues on histones and play important roles in regulating chromatin structure and gene expression. The structures and functions of HKMTs have been extensively investigated in recent decades, significantly advancing our understanding of the dynamic regulation of histone methylation. Here, we review the recent progress in structural studies of representative HKMTs in complex with nucleosomes (H3K4, H3K27, H3K36, H3K79, and H4K20 methyltransferases), with emphasis on the molecular mechanisms of nucleosome recognition and trans-histone crosstalk by these HKMTs. These structural studies inform HKMTs’ roles in tumorigenesis and provide the foundations for developing new therapeutic approaches targeting HKMTs in cancers.