DNA methylation is a biological process of epigenetic changes by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence
Methylation of cytosine to form 5-methylcytosine occurs at the same 5 position on the pyrimidine ring
Cytosine residues in the v2 region of the Septin9 gene are specifically methylated in colorectal cancer tissue but not in normal colon mucosa. The gene SEPT9 codes for the Septin9 protein, a member of a conserved family of GTP-binding proteins. Septins are multifunctional proteins, involved in vesicle trafficking, apoptosis, cytoskeletal remodelling, and mainly neoplasia (i. e. cancer), among other important cellular processes.
It was shown that septin 9 gene is methylated in colorectal adenoma-dysplasia-carcinoma sequence. As a result, mRNA expression is slowed down and production of septin protein is reduced.