title: Evidence for non-CpG methylation in mammals.
abstract: In mammals, the existence of cytosine methylation on non-CpG sequences is controversial. Here, we adapted a LuminoMetric-based Assay (LUMA) to determine global non-CpG methylation levels in rodent and human tissues. We observed that <1% cytosines in non-CpG motifs were methylated in 3T3-L1 fibroblasts, whereas 7-13% cytosines in non-CpG motifs were methylated in mouse tissues or embryonic fibroblasts. Analysis of cytosine methylation in human, rat, and mouse tissues by bisulfite sequencing revealed non-CpG methylation levels up to 7.5% of all non-CpG cytosines. These levels dropped to 1.5% when a second round of PCR was performed prior to bisulfite sequencing, providing an explanation for the common underestimation of non-CpG methylation levels. Collectively, our results provide evidence that non-CpG methylation exists at substantial levels in mammals.
authors.affiliation: Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
authors.forename: Juleen R
authors.initials: JR
authors.lastname: Zierath
authors.forename: Romain
authors.initials: R
authors.lastname: Barrès
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D002478:Cells, Cultured; D018899:CpG Islands / Q000235:genetics*; D003596:Cytosine / Q000378:metabolism; D053837:DNA Cleavage; D019175:DNA Methylation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008163:Luminescent Measurements; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051381:Rats; D017422:Sequence Analysis, DNA; D013447:Sulfites / Q000737:chemistry
chemical_list: D013447:Sulfites; D003596:Cytosine