Epigenetics: scope and mechanisms

dinucleotides are the rarest dinucleotides in genomes, Ficz says that 75–85% of these dinucleotides are methylated in mammals (p. 14). However, when they group together to form CpG islands at promoter regions, they are generally unmethylated. Adding that this so-called ‘hypermethylation’ effectively shuts down genes, Ficz says that promoter hypermethylation is rare during development, yet increases with age and in cancer. Describing the signalling pathways and enzymes that regulate CpG methylation, Ficz explains that altered DNA methylation patterns are potential key trigger factors in many cancers, saying, ‘It is highly likely that epigenetic aberrations are at the root of subsequent genomic instabilities that enable genetic mutations to occur’.