title: Molecular basis for the methylation specificity of ATXR5 for histone H3.
abstract: In plants, the histone H3.1 lysine 27 (H3K27) mono-methyltransferases ARABIDOPSIS TRITHORAX RELATED PROTEIN 5 and 6 (ATXR5/6) regulate heterochromatic DNA replication and genome stability. Our initial studies showed that ATXR5/6 discriminate between histone H3 variants and preferentially methylate K27 on H3.1. In this study, we report three regulatory mechanisms contributing to the specificity of ATXR5/6. First, we show that ATXR5 preferentially methylates the R/F-K*-S/C-G/A-P/C motif with striking preference for hydrophobic and aromatic residues in positions flanking this core of five amino acids. Second, we demonstrate that post-transcriptional modifications of residues neighboring K27 that are typically associated with actively transcribed chromatin are detrimental to ATXR5 activity. Third, we show that ATXR5 PHD domain employs a narrow binding pocket to selectively recognize unmethylated K4 of histone H3. Finally, we demonstrate that deletion or mutation of the PHD domain reduces the catalytic efficiency (kcat/Km of AdoMet) of ATXR5 up to 58-fold, highlighting the multifunctional nature of ATXR5 PHD domain. Overall, our results suggest that several molecular determinants regulate ATXR5/6 methyltransferase activity and epigenetic inheritance of H3.1 K27me1 mark in plants.
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Elisa
authors.initials: E
authors.lastname: Bergamin
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Sabina
authors.initials: S
authors.lastname: Sarvan
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Josée
authors.initials: J
authors.lastname: Malette
authors.affiliation: Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5J 1L7, Canada.
authors.forename: Mohammad S
authors.initials: MS
authors.lastname: Eram
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Yeung
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Mongeon
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Monika
authors.initials: M
authors.lastname: Joshi
authors.affiliation: Northwestern Synchrotron Research Center, Life Sciences Collaborative Access Team, Northwestern University, Argonne, IL 60439, USA.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Brunzelle
authors.affiliation: Department of Biology, Indiana University, 915 East Third Street, Bloomington, IN 47405, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Michaels
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Blais
authors.affiliation: Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5J 1L7, Canada.|Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Masoud
authors.initials: M
authors.lastname: Vedadi
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Couture
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000502:physiology; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D018506:Gene Expression Regulation, Plant; D006657:Histones / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008745:Methylation; D008780:Methyltransferases / Q000737:chemistry* / Q000502:physiology; D008958:Models, Molecular; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D006657:Histones; C542364:ATXR5 protein, Arabidopsis; D008780:Methyltransferases