title: Methylation of a euchromatin-heterochromatin transition region in Arabidopsis thaliana chromosome 5 left arm.
abstract: Cytosine methylation was studied at the level of the euchromatin/heterochromatin transition genomic region of the Arabidopsis chromosome 5 left arm. It has been shown using a monoclonal antibody against 5-methylcytosines that the density of DNA methylation increases from the euchromatin towards the heterochromatin. YACs mapped along this region were characterized for their repeated sequences content. Some of them, corresponding to euchromatin, euchromatin/heterochromatin border and heterochromatin regions, were used as probes for a Southern blot analysis of methylation. This revealed that the degree of mCmCGG and GATmC methylation increases significantly from the euchromatin towards the heterochromatin. Moreover, an analysis of cytosine methylation levels (% of 5-methylcytosine) of different DNA fragments, inside the same genomic region, was performed using PCR and/or Southern blot approaches. There is a gradual increase of methylation along the genomic region analyzed: CpG methylation in the euchromatic fraction, CpG and CpNpG methylation at the euchromatin/heterochromatin transition and an additional asymmetrical methylation in the repeated-heterochromatic fraction. The most methylated repeated family at CpG, CpNpG and asymmetrical sites is the 5S ribosomal DNA, highly methylated even though it is transcribed.
authors.affiliation: U.M.R. CNRS 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Mathieu
authors.forename: Georges
authors.initials: G
authors.lastname: Picard
authors.forename: Sylvette
authors.initials: S
authors.lastname: Tourmente
mesh_terms: D044503:5-Methylcytosine; D017360:Arabidopsis / Q000235:genetics*; D015139:Blotting, Southern; D002875:Chromosomes / Q000235:genetics*; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics; D018899:CpG Islands; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D019175:DNA Methylation; D018744:DNA, Plant / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D022041:Euchromatin / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D006570:Heterochromatin / Q000378:metabolism*; D017404:In Situ Hybridization, Fluorescence; D009154:Mutation; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal; D022041:Euchromatin; D006570:Heterochromatin; D044503:5-Methylcytosine; D003596:Cytosine