DNA methylation of repetitive elements. (A) Distribution profiles of DNA methylation over three distinct repeat tracks demonstrate an enrichment of repetitive elements for DNA methylation. Microsatellite DNA lacks CpG dinucleotides and therefore is not methylated. However, the RepeatMasker track is depleted for CpG dinucleotides but enriched for DNA methylation, while in the case of the Simple Repeats track DNA, methylation positively correlates with CpG density. (B) Extent of overlap between repeat types and DNA methylation (merged MethylCap peaks). (Top panel) Percentage of methylated genomic copies. (Bottom panel) CpG density of different repeat types. There is an overall correlation of DNA methylation and CpG density. However, some repeats such as Sat1 are highly methylated in spite of their low CpG density.
