Breaking the silence : the interplay between transcription factors and DNA methylation

Abstract

DNA methylation is best known for its role in gene silencing through a methyl group (CH3) being added to the 5' carbon of cytosine bases (giving 5-methylcytosine) in the promoters of genes leading to supression of transcription. De novo methylation, which involves the addition of a methyl group to unmodified DNA, is described as an epigenetic change because it is a chemical modification to DNA not a change brought about by a DNA mutation. Unlike mutations, methylation changes are potentially reversible. Epigenetic changes also include changes to DNA-associated molecules such as histone modifications, chromatin-remodelling complexes and other small non-coding RNAs including miRNAs and siRNAs. These changes have key roles in imprinting (gene-ex‐ pression dependent on parental origin), X chromosome inactivation and heterochromatin formation among others [3-5].