title: Traceless Synthesis of Asymmetrically Modified Bivalent Nucleosomes.
abstract: Nucleosomes carry extensive post-translational modifications (PTMs), which results in complex modification patterns that are involved in epigenetic signaling. Although two copies of each histone coexist in a nucleosome, they may not carry the same PTMs and are often differently modified (asymmetric). In bivalent domains, a chromatin signature prevalent in embryonic stem cells (ESCs), namely H3 methylated at lysine 4 (H3K4me3), coexists with H3K27me3 in asymmetric nucleosomes. We report a general, modular, and traceless method for producing asymmetrically modified nucleosomes. We further show that in bivalent nucleosomes, H3K4me3 inhibits the activity of the H3K27-specific lysine methyltransferase (KMT) polycomb repressive complex 2 (PRC2) solely on the same histone tail, whereas H3K27me3 stimulates PRC2 activity across tails, thereby partially overriding the H3K4me3-mediated repressive effect. To maintain bivalent domains in ESCs, PRC2 activity must thus be locally restricted or reversed.
authors.affiliation: Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
authors.forename: Carolin C
authors.initials: CC
authors.lastname: Lechner
authors.affiliation: Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
authors.forename: Ninad D
authors.initials: ND
authors.lastname: Agashe
authors.affiliation: Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland. beat.fierz@epfl.ch.
authors.forename: Beat
authors.identifier: http://orcid.org/0000-0002-2991-3044
authors.initials: B
authors.lastname: Fierz
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D053595:Embryonic Stem Cells / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D009707:Nucleosomes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006657:Histones; D009707:Nucleosomes
keywords: PRC2; bivalent domains; chromatin; epigenetics; expressed protein ligation