Figure 1.1.

Various sites and effects of DNA methylation throughout the genome

DNA methylation is found at inter- and intragenic regions throughout the genome. DNA methylation dependent transcriptional activity is contingent on CpG dinucleotide genic location and density. Normal methylation events and subsequent effects are shown on the left. (a) CpG islands at promoters are normally unmethylated resulting in gene expression. However, aberrant hypermethylation at the same promoter results in corepressor complex recruitment and subsequent gene repression. (b) Intragenic regions characterized by scattered CpG dinucleotides located 2kb upstream of the promoter called CpG island shores are regulated in the same manner as (a). (c) DNA methylation within the gene body prevents initiation of transcription from spurious sites in the gene. If unmethylated, these sites become transcriptional start sites resulting in an incorrect product. (Portela and Estellar 2010)