DNA consists of different regions like intergenic regions, repetitive elements and CpG islands. CpG islands are rich in GC content. These CpG islands are prone to methylation. They are usually present in the promoter region of genes and in intergenic regions. Methylation of the promotor region plays an important role in the activation and silencing of the genes. In the promoter region, DNA methylation of these CpG islands inhibits the binding of transcription factors and thus leading to silencing of those specific genes. In normal conditions, CpG islands near genes are hypomethylated, while intergenic regions and repetitive elements are hypermethylated in order to ensure genomic stability and proper expression of genes. It is somehow ensured by the epigenetic machinery of the cell. Hypermethylation of these repetitive elements is necessary otherwise they can intervene with the rest of the genome and can cause several lethal complications. As in the case of cancer, epigenetic errors lead to hypermethylation of CpG islands of the promoter region and hypomethylation of that of repetitive elements. This can lead to epigenetic silencing of important regulatory genes and activation of oncogenes or repetitive elements, thus leading to cancer. On the other hand, reversing this condition can act as a potential treatment of cancer.
Keywords: Methylation, Transcription factors, Epigenetic machinery, Hypomethylation, Hypermethylation.