Automethylation Activities within the Mixed Lineage Leukemia-1 (MLL1) Core Complex Reveal Evidence Supporting a “Two-active Site” Model for Multiple Histone H3 Lysine 4 Methylation

Abstract

Background: The MLL1 core complex mono- and dimethylates histone H3 lysine 4 (H3K4).Results: MLL1 automethylates a conserved cysteine residue in its active site cleft.Conclusion: MLL1 automethylation is inhibited by unmodified histone H3 but not by histones previously mono-, di-, or trimethylated at H3K4.Significance: The pattern of automethylation inhibition is consistent with distinct active sites for mono- and dimethylation of H3K4.

Biochemical Reconstitution and Phylogenetic Comparison of Human SET1 Family Core Complexes Involved in Histone Methylation

“…4a). In addition, when MLL1 is assembled with WRAD, we previously found that MLL1 methylates ASH2L in an intramolecular (intra-complex) manner (60). In this investigation, we observed a similar ASH2L methylation reaction in complexes assembled with MLL1, MLL4, MLL2, SETd1A, and SETd1B proteins in the absence of UV light (Fig.…”

“…these studies is that we previously demonstrated that the isolated MLL1 SET domain undergoes a robust intramolecular automethylation activity in the absence of UV light (60). Indeed, in this investigation, we observed that the isolated MLL4 and MLL2 SET domains also undergo weaker automethylation reactions compared with that of MLL1 (Fig.…”

“…4c). In contrast, ASH2L methylation was unaffected in the presence or absence of UV light, indicating that it is the result of an enzymatic reaction that is catalyzed by the SET domain subunit, as suggested previously for MLL1 (60). The only complex that did not display ASH2L methylation was the MLL3 core complex (Fig.…”

Hijacked in cancer: the KMT2 (MLL) family of methyltransferases

“…21,33 It is likely that the RbBP5/ASH2L heterodimer facilitates and stabilizes the interaction between the SET domain and KMT2 substrates. 34 While transient interactions between RbBP5/ASH2L and the KMT2A SET domain are documented 34,35 , WDR5 stably bridges RbBP5 and KMT2A via direct binding to a conserved WDR5 interacting (WIN) motif in KMT2A 24,30,36 and a valine-aspartate-valine (VDV) motif in RbBP5 37 . Disruption of WDR5-KMT2A binding by the WIN peptides or their derivatives leads to disintegration of the KMT2A complex and inhibition of KMT2A catalytic activity in vitro 25,38,39 .…”

The histone methyltransferase activity of mll1 is dispensable for hematopoiesis and leukemogenesis

“…All MLL family members harbor a SET domain with specificity for H3K4 methylation, dependent upon associated cofactors or posttranslational modifications (Patel et al, 2014;Schuettengruber et al, 2011). Most Mll1 disruption alleles are embryonic lethal; however, homozygotes for a germline deletion of the SET domain of MLL1 (hereafter, ΔSET) survive into adulthood, providing an opportunity to assess the role of the SET domain, thus HMT activity of MLL1, in adult tissues (Terranova et al, 2006).…”