The effect of radiation on DNA methylation and its links to cancer

One of the most widely studied areas of epigenetics is DNA methylation. Methylation has been linked to a number of different phenomena, including gene silencing, chromosomal stability and carcinogenesis.

DNA methylation occurs when a methyl group is added to a Cytosine-Guanine base pair. As mentioned previously, one of the outcomes of DNA methylation is gene silencing. Methylation is thought to silence a gene by switching off its promoter, through the methylation of GpG islands located in the promoter sequence.

CpG islands are simply a Cytosine nucleotide followed by a Guanine nucleotide, with the “p” representing the phosphate located between the two nucleotides.

Igor Pogribny et al. (2004) of carried out a study to examine the effect of radiation on the DNA methylation state of three different types of tissue; liver, spleen and lung. After the tissue was exposed to varying doses of radiation, the proportion of methylation in the treated tissue was compared with control samples.

Results from the study indicated that exposure to radiation can cause demethylation of DNA. Based on the results it was suggested that demethylation is DNA-repair related. It was also suggested the demethylation, and the subsequent undesirable activation of certain genes, may be part of the pathway by which certain types of radiation cause cancer.

Reference:

Pogribny I, Raiche J, Slovack M, Kovalchuk O (2004) Dose-dependence, sex- and tissue-specificity, and persistence of radiation-induced genomic DNA methylation changes. Biochem Biophys Res Commun. 2004 Aug 6;320(4):1253-61