DNA Methylation is an epigenetic mechanism with addition of methyl group into nitrogenous bases of DNA. The mechanism involves the transfer of methyl group into the C5 position of the cytosine and formation of 5-methylcystosine (Moore et al., 2013). DNA Methylation facilitates X-chromosome inactivation, imprinting and suppression of parasitic DNA sequences however methylation increases the rate of mutation (Robertson and Jones, 1999). Cell functions are affected by epigenetic regulation of gene expression. Genomic stability and mammalian development have been associated with methylation pattern (Tost, 2009).
Prediction and monitoring the response to antineoplastic treatment, detection of cancer at early stages and classification of tumour can be carried out with the help of DNA methylation pattern (Tost, 2009). Enzymes responsible for DNA methylation have been categorised into writers, erasers and readers by Moore et al (2012). Addition of methyl groups onto cytosine is categorised by writers, modification and removal of the methyl group is conducted by erasers and readers influence gene expression (Moore et al., 2012).
In the human genome, CpG or Cytosine (C) linked by a phosphate bond to the base Guanine (G) dinucleotide is methylated and methylation causes suppression of gene expression in the cells. (Lim and Maker, 2010; Robertson and Jones, 1999). Methylation and epigenetic changes has adverse effects on cancer cells. DNA Methylation has been believed to have direct role in carcinogenesis (Robertson and Jones, 1999). Deamination of methylated cytosine converts cytosine to thymine leading to inactivation of tumour suppression genes (TSGs), a vital factor for normal growth and differentiation (Lim and Maker, 2010).
Moore, L.D., Le, T., Fan, G. (2012) DNA Methylation and Its Basic Function Neuropsychopharmacology Reviews, pp 1-16.
Robertson, K.D. and Jones, P.A. (1999) DNA Methylation: Past, Present and Future Directions, Carcinogenesis, Vol. 21 (3), pp. 461-467.
Lim, D.H.K. and Maker, E.R. (2010) The Obstetrician and Gynaecologist. Vol 12, pp. 37-42.
Tost,J. (2009) DNA Methylation: An Introduction to the Biology and Disease-Associated Changes of a Promising Bio-marker Methods, Molecular Biology, Vol 507, pp. 3-20.