title: Nucleosomes protect DNA from DNA methylation in vivo and in vitro.
abstract: Positioned nucleosomes limit the access of proteins to DNA. However, the impact of nucleosomes on DNA methylation in vitro and in vivo is poorly understood. Here, we performed a detailed analysis of nucleosome binding and nucleosomal DNA methylation by the de novo methyltransferases. We show that compared to linker DNA, nucleosomal DNA is largely devoid of CpG methylation. ATP-dependent chromatin remodelling frees nucleosomal CpG dinucleotides and renders the remodelled nucleosome a 2-fold better substrate for Dnmt3a methyltransferase compared to free DNA. These results reflect the situation in vivo, as quantification of nucleosomal DNA methylation levels in HeLa cells shows a 2-fold decrease of nucleosomal DNA methylation levels compared to linker DNA. Our findings suggest that nucleosomal positions are stably maintained in vivo and nucleosomal occupancy is a major determinant of global DNA methylation patterns in vivo.
authors.affiliation: Institut für Biochemie III, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Felle
authors.forename: Helen
authors.initials: H
authors.lastname: Hoffmeister
authors.forename: Julia
authors.initials: J
authors.lastname: Rothammer
authors.forename: Andreas
authors.initials: A
authors.lastname: Fuchs
authors.forename: Josef H
authors.initials: JH
authors.lastname: Exler
authors.forename: Gernot
authors.initials: G
authors.lastname: Längst
mesh_terms: D042002:Chromatin Assembly and Disassembly; D004247:DNA / Q000378:metabolism; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D006367:HeLa Cells; D006801:Humans; D009707:Nucleosomes / Q000378:metabolism*
chemical_list: C000717967:DNMT3A protein, human; D009707:Nucleosomes; D004247:DNA; D004248:DNA (Cytosine-5-)-Methyltransferases; C541545:DNA (cytosine-5-)-methyltransferase 3b2, human; D000090205:DNA Methyltransferase 3A