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Multistate structures of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosome

ABSTRACT: The human Mixed Lineage Leukemia-1 (MLL1) complex orchestrates methylation of histone H3K4 to promote transcription and is the target of chromosomal translocations in a variety of leukemias. The MLL1 core complex comprises the MLL1 methyltransferase and the WRAD complex, which contains WDR5, RbBp5, Ash2L, and DPY-30. Recent studies have shed light on the structure and organization of the human MLL1-WRAD complex bound to nucleosomes but were not able to resolve portions of the Ash2L subunit or DPY30. We used an integrated approach combining cryo-electron microscopy and mass spectrometry-cross linking to obtain models of the MLL1-WRAD complex bound to nucleosomes containing monoubiquitinated histone H2B, which is reported to stimulate H3K4 methylation. We constructed a model containing the Ash2L intrinsically disordered region (IDR), SPRY insertion region, and Sdc1-DPY30 interacting region (SDI-motif), as well as the DPY30 dimer, which were not resolved in previous structures. In addition to the model of the active state, we resolved three additional states of MLL1-WRAD lacking one or more subunits that may reflect different steps in the assembly of MLL1-WRAD. Our results provide a more complete picture of MLL1-WRAD and how it assembles on nucleosomes to form an active methyltransferase complex.

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Bruce A Knutson

PROVIDER: PXD036406 | JPOST Repository | Thu Aug 31 00:00:00 BST 2023

REPOSITORIES: jPOST

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Project description:In Arabidopsis, CHG DNA methylation is controlled by the H3K9 methylation mark through a self-reinforcing loop between DNA methyltransferase CHROMOMETHYLASE3 (CMT3) and H3K9 histone methyltransferase KRYPTONITE/SUVH4 (KYP). We report on the structure of KYP in complex with methylated DNA, substrate H3 peptide and cofactor SAH, thereby defining the spatial positioning of the SRA domain relative to the SET domain. The methylated DNA is bound by the SRA domain with the 5mC flipped out of the DNA, while the H3(1-15) peptide substrate binds between the SET and post-SET domains, with the epsilon-ammonium of K9 positioned adjacent to bound SAH. These structural insights complemented by in vivo functional data on key mutants of residues lining the 5mC and H3K9-binding pockets within KYP, establish how methylated DNA recruits KYP to the histone substrate. Together, the structures of KYP and previously reported CMT3 complexes provide insights into molecular mechanisms linking DNA and histone methylation. Plants homozygous for null mutations in the KRYPTONITE H3K9 methyltransferase were stably transformed with transgenes encoding the wildtype KYP protein or transgenes carrying induced point mutations in the KYP active site. The resulting lines were assayed for DNA methylation by whole-genome bisulfite sequencing to learn the efficiency with which wildtype and mutant versions of the KYP protein could restore DNA methylation lost in a kyp mutant. Samples 7 and 8 were run as single Illumina lanes and as such were compared to a previous Col sample (GSM881756), this Col sample was realigned to the TAIR10 genome for this study and as such updated processed files are available with this submission. These samples were used to define kyp mutant CHG context DMRs that were complemented upon introduction of the wildtype KYP protein. Samples 1-6 were run as multiplexed samples and were used to assay the degree of complementation for various point mutants. All plants are in the Col ecotype background.

			Action	DRS
	BK013116_020317_7.mgf	Mgf
	BK013116_020317_7.raw	Raw
	BK013116_020317_8.mgf	Mgf
	BK013116_020317_8.raw	Raw
	BK070717_072617_7.mgf	Mgf

Dataset Information

Multistate structures of the MLL1-WRAD complex bound to H2B-ubiquitinated nucleosome

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