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Hypomethylation of DNA

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Encyclopedia of Cancer

Synonyms

DNA demethylation; DNA undermethylation

Definition

DNA hypomethylation refers to the loss of the methyl group in the 5-methylcytosine nucleotide. Methylation is a natural modification of DNA, and mainly affects the cytosine base (C) when it is followed by a guanosine (G) in mammals (Methylation). The term hypomethylation can be applied to describe the unmethylated state of most CpG sites in a specific sequence that is normally methylated, or as a general phenomenon affecting the bulk of the genome; this is a decrease in the proportion of methylated versus unmethylated cytosines.

Characteristics

In human, DNA methylation mainly occurs at CpG sites. Up to 80% of all CpG sites in human DNA are methylated. However, this methylation occurs primarily in areas where CpG density is low, or at repeat DNA sites, such as Alu elements. CpG islands are regions where CpG density is high and most of them are unmethylated. Patterns of DNA methylation have been linked to control of gene...

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References

  1. Ehrlich M (2002) DNA methylation in cancer: too much, but also too little. Oncogene 21:5400–5413

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  2. Feinberg AP, Tycko B (2004) The history of cancer epigenetics. Nat Rev Cancer 4:143–153

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Correspondence to Miguel A. Peinado .

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© 2011 Springer-Verlag Berlin Heidelberg

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Peinado, M.A. (2011). Hypomethylation of DNA. In: Schwab, M. (eds) Encyclopedia of Cancer. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-16483-5_2923

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