title: Active cytosine demethylation triggered by a nuclear receptor involves DNA strand breaks.
abstract: Cytosine methylation at CpG dinucleotides contributes to the epigenetic maintenance of gene silencing. Dynamic reprogramming of DNA methylation patterns is believed to play a key role during development and differentiation in vertebrates. The mechanisms of DNA demethylation remain unclear and controversial. Here, we present a detailed characterization of the demethylation of an endogenous gene in cultured cells. This demethylation is triggered in a regulatory region by a transcriptional activator, the glucocorticoid receptor. We show that DNA demethylation is an active process, occurring independently of DNA replication, and in a distributive manner without concerted demethylation of cytosines on both strands. We demonstrate that the DNA backbone is cleaved 3' to the methyl cytidine during demethylation, and we suggest that a DNA repair pathway may therefore be involved in this demethylation.
authors.affiliation: Institut Jacques Monod du Centre National de la Recherche Scientifique, Universités Paris 6-7, Tour 43, 2 Place Jussieu, 75251 Paris Cedex 05, France.
authors.forename: Clémence
authors.initials: C
authors.lastname: Kress
authors.forename: Hélène
authors.initials: H
authors.lastname: Thomassin
authors.forename: Thierry
authors.initials: T
authors.lastname: Grange
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D018899:CpG Islands; D003596:Cytosine / Q000737:chemistry*; D004249:DNA Damage; D019175:DNA Methylation; D004742:Enhancer Elements, Genetic; D044127:Epigenesis, Genetic; D015696:Gene Products, tat / Q000235:genetics; D020868:Gene Silencing; D008969:Molecular Sequence Data; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry*; D012689:Sequence Homology, Nucleic Acid; D015533:Transcriptional Activation
chemical_list: D015696:Gene Products, tat; D018160:Receptors, Cytoplasmic and Nuclear; D003596:Cytosine