Deamination

Term in genetics that, like depuirinization, refers to spontaneous chemical changes in DNA. It is important to understand how this process can lead to mutations and what effects it can have on genetic information. During deamination, a base loses an amino group (one nitrogen and 2 hydrogen atoms - NH2) through hydrolysis.

For example, the base cytosine is converted into uracil by deamination. As uracil does not normally occur at all in DNA (uracil is a building block of RNA), it is replaced by thymine during the next replication. This results in an exchange mutation. If uracil is not cut out and replaced, it serves as a template during replication and pairs with its complementary base adenine. In this way, an original CG pair becomes a TA pair.

In repairing spontaneous damage caused by deamination, the repair mechanisms of cells play a crucial role in maintaining DNA integrity and ensuring genetic stability. However, if the repair mechanisms fail, potentially harmful mutations can occur that can lead to disease or genetic alterations. For example, genome sequencing of cancer cells from many tissues revealed a significant enrichment of the cytidine deaminase mutation signature in human cancers (Liu X et al. 2018). Thus, cytidine deamination, which can occur intensively in certain genomic regions in an enzyme-dependent manner, is a widespread source of genome instability in many tumor types.

1. Liu X et al. (2018) Generation of Genomic Alteration from Cytidine Deamination. Adv Exp Med Biol 1044:49-64.