A phosphorylation switch on RbBP5 regulates histone H3 Lys4 methylation

Pamela Zhang; Chandra-Prakash Chaturvedi; Veronique Tremblay; Myriam Cramet; Joseph S. Brunzelle; Georgios Skiniotis; Marjorie Brand; Ali Shilatifard; Jean-François Couture

doi:10.1101/gad.254870.114

A phosphorylation switch on RbBP5 regulates histone H3 Lys4 methylation

¹Department of Biochemistry, Microbiology, and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada;
²The Sprott Center for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario K1H 8L6, Canada;
³Department of Cellular and Molecular Medicine, University of Ottawa, Ontario K1H 8L6, Canada;
⁴Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA;
⁵Life Sciences Institute,
⁶Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA;
⁷Department of Biochemistry and Molecular Genetics, Northwestern University, Chicago, Illinois 60611, USA

Corresponding author: jean-francois.couture{at}uottawa.ca

Abstract

The methyltransferase activity of the trithorax group (TrxG) protein MLL1 found within its COMPASS (complex associated with SET1)-like complex is allosterically regulated by a four-subunit complex composed of WDR5, RbBP5, Ash2L, and DPY30 (also referred to as WRAD). We report structural evidence showing that in WRAD, a concave surface of the Ash2L SPIa and ryanodine receptor (SPRY) domain binds to a cluster of acidic residues, referred to as the D/E box, in RbBP5. Mutational analysis shows that residues forming the Ash2L/RbBP5 interface are important for heterodimer formation, stimulation of MLL1 catalytic activity, and erythroid cell terminal differentiation. We also demonstrate that a phosphorylation switch on RbBP5 stimulates WRAD complex formation and significantly increases KMT2 (lysine [K] methyltransferase 2) enzyme methylation rates. Overall, our findings provide structural insights into the assembly of the WRAD complex and point to a novel regulatory mechanism controlling the activity of the KMT2/COMPASS family of lysine methyltransferases.

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Footnotes

Supplemental material is available for this article.
Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.254870.114.

Received October 27, 2014.
Accepted December 15, 2014.

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