Effects of Dietary Nutrients on DNA Methylation and Imprinting

Abstract

DNA methylation is an enzymatic modification carried out by DNA methyltransferases. Alterations in DNA methylation patterns are the best understood epigenetic cause of disease and were first discovered in studies during the 1980s that focused on X chromosome inactivation (Avner and Heard 2001), genomic imprinting (Verona et al. 2006) and cancer (Feinberg and Tycko 2004). DNA methylation involves the addition of a methyl group to cytosines in CpG (cytosine/guanine) pairs (Ehrlich and Wang 1981, Laird and Jaenisch 1994). The added methyl group does not affect the base pairing itself, but the protrusion of methyl groups into the DNA major groove can affect DNA–protein interactions. Methylated CpGs are usually associated with silenced DNA, can block methylation sensitive proteins from binding to the DNA and are subject to high mutation rates. DNA methylation patterns are established and maintained by DNMTs, enzymes that are essential for proper gene expression patterns (Robertson 2002) (Figure 1). DNA methylation is an essential epigenetic