Yeast COMPASS (complex of proteins associated with Set1) and human MLL (mixed-lineage leukemia) complexes are histone H3 lysine 4 methyltransferases with critical roles in gene regulation and embryonic development. Both complexes share a conserved C-terminal SET domain, responsible for catalyzing histone H3 K4 methylation on nucleosomes. Notably, their catalytic activity toward nucleosomes is enhanced and optimized with assembly of auxiliary subunits. In this review, we aim to illustrate the recent X-ray and cryo-EM structures of yeast COMPASS and human MLL1 core complexes bound to either unmodified nucleosome core particle (NCP) or H2B mono-ubiquitinated NCP (H2Bub.NCP). We further delineate how each auxiliary component of the complex contributes to the NCP and ubiquitin recognition to maximize the methyltransferase activity.
Keywords: COMPASS; H2B K120 (K123 in yeast) mono-ubiquitinated nucleosome (H2Bub.NCP); H3 Lys4 methyltransferase; MLL; Nucleosomal core particle (NCP); SET domain; Single-particle electron cryomicroscopy (cryo-EM); X-ray crystallography.
© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.