How Does Methylation of CpG Sites Affect Gene Expression?
Methylation typically occurs at the 5' position of the cytosine ring, forming 5-methylcytosine. This modification can change the way DNA interacts with the cellular machinery, often leading to gene silencing. In cancer, hypermethylation of CpG islands at promoter regions of tumor suppressor genes can inhibit their expression, preventing the production of proteins that regulate cell growth and apoptosis.
