When cytosine is methylated, a methyl group (—CH₃) from the acceptor of S-adenosylmethionine is added to cytosine, this process is catalyzed by methyltransferase, the number of electrons increases, DNA is twisted more strongly as a result of electrostatic forces (F).

With the subsequent transition of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) with the participation of Tet-proteins, the number of electrons increases again, respectively, the repulsive forces increase, which leads to stronger DNA twisting and stress in chemical bonds. Next, 5-formylcytosine (5-fC) is formed, then 5-carboxycytosine (5-caC).

An important merit in the study of the stages of demethylation belongs to a group of researchers led by Professor Yi Zhang. They discovered intermediate nitrogenous bases of demethylation.

Cytosine → 5-methylcytosine → 5-hydroxymethylcytosine → 5-formylcytosine →5-carboxycytosine →Cytosine

When demethylating the entire DNA (after the transition of 5-carboxycytosine to cytosine) the molecule spins up sharply, the energy necessary for replication and other biochemical processes is formed. This can be compared to a strongly twisted rope: if you release one end, it unwinds.

The catalysts are enzymes, and the main one will be the methyltransferase —responsible for starting the demethylation process. Tet-proteins are involved in subsequent reactions. When the genes encoding the synthesis of these enzymes are hyperactivated, the accumulation of enzymes in the cell will occur, which will cause the DNA to constantly double.

Therefore, it can be assumed that the principle of tumor formation is mainly based on the hyperactive state of these genes, which leads to the accumulation of methyltransferase, Tet-proteins in cells.

This is important for understanding one of the mechanisms of the occurrence of cancer and other malignant neoplasms!

If the promoter region of the cytosine(C5)-DNA-methyltransferase gene is activated in any way, as well as the promoters of other genes involved in demethylation, then the processes that activate DNA replication are triggered. As a result, this will lead to an unrestrained reproduction of cells with the subsequent formation of a tumor.