Biochemical reconstitution and phylogenetic comparison of human SET1 family core complexes involved in histone methylation.
Mixed lineage leukemia protein-1 (MLL1) is a member of the SET1 family of histone H3 lysine 4 (H3K4) methyltransferases that are required for metazoan development. MLL1 is the best characterized human SET1 family member, which includes MLL1-4 and SETd1A/B. MLL1 assembles with WDR5, RBBP5, ASH2L, DPY-30 (WRAD) to form the MLL1 core complex, which is required for H3K4 dimethylation and transcriptional activation. Because all SET1 family proteins interact with WRAD in vivo, it is hypothesized they are regulated by similar mechanisms. However, recent evidence suggests differences among family members that may reflect unique regulatory inputs in the cell. Missing is an understanding of the intrinsic enzymatic activities of different SET1 family complexes under standard conditions. In this investigation, we reconstituted each human SET1 family core complex and compared subunit assembly and enzymatic activities. We found that in the absence of WRAD, all but one SET domain catalyzes at least weak H3K4 monomethylation. In the presence of WRAD, all SET1 family members showed stimulated monomethyltransferase activity but differed in their di- and trimethylation activities. We found that these differences are correlated with evolutionary lineage, suggesting these enzyme complexes have evolved to accomplish unique tasks within metazoan genomes. To understand the structural basis for these differences, we employed a "phylogenetic scanning mutagenesis" assay and identified a cluster of amino acid substitutions that confer a WRAD-dependent gain-of-function dimethylation activity on complexes assembled with the MLL3 or Drosophila trithorax proteins. These results form the basis for understanding how WRAD differentially regulates SET1 family complexes in vivo.
['Shinsky|Stephen A|SA|', 'Monteith|Kelsey E|KE|', 'Viggiano|Susan|S|', 'Cosgrove|Michael S|MS|']
D019943:Amino Acid Substitution D018360:Crystallography, X-Ray D011495:Histone-Lysine N-Methyltransferase D006657:Histones D006801:Humans D008239:Lysine D008745:Methylation D046912:Multiprotein Complexes D051788:Myeloid-Lymphoid Leukemia Protein D009687:Nuclear Proteins D010802:Phylogeny D011485:Protein Binding D014157:Transcription Factors
Phylogenetics SET1 Histone Methylation Leukemia WDR5 Ash2L Cancer Epigenetics MLL Product Specificity