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Publication Abstract from PubMed

The human Mixed Lineage Leukemia-1 (MLL1) complex methylates histone H3K4 to promote transcription and is stimulated by monoubiquitination of histone H2B. Recent structures of the MLL1-WRAD core complex, which comprises the MLL1 methyltransferase, WDR5, RbBp5, Ash2L, and DPY-30, have revealed variability in the docking of MLL1-WRAD on nucleosomes. In addition, portions of the Ash2L structure and the position of DPY30 remain ambiguous. We used an integrated approach combining cryoelectron microscopy (cryo-EM) and mass spectrometry cross-linking to determine a structure of the MLL1-WRAD complex bound to ubiquitinated nucleosomes. The resulting model contains the Ash2L intrinsically disordered region (IDR), SPRY insertion region, Sdc1-DPY30 interacting region (SDI-motif), and the DPY30 dimer. We also resolved three additional states of MLL1-WRAD lacking one or more subunits, which may reflect different steps in the assembly of MLL1-WRAD. The docking of subunits in all four states differs from structures of MLL1-WRAD bound to unmodified nucleosomes, suggesting that H2B-ubiquitin favors assembly of the active complex. Our results provide a more complete picture of MLL1-WRAD and the role of ubiquitin in promoting formation of the active methyltransferase complex.

Multistate structures of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosome.,Rahman S, Hoffmann NA, Worden EJ, Smith ML, Namitz KEW, Knutson BA, Cosgrove MS, Wolberger C Proc Natl Acad Sci U S A. 2022 Sep 20;119(38):e2205691119. doi: , 10.1073/pnas.2205691119. Epub 2022 Sep 12. PMID:36095189^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.