DNA (deoxyribonucleic acid) is the main component of our genetic material. It is formed by combining four parts: A, C, G and T (adenine, cytosine, guanine and thymine), called bases of DNA combine in thousands of possible sequences to provide the genetic variability that enables the wealth of aspects and functions of living beings.

Two more bases: the Methyl- cytosine and Methyl-adenine

In the early 80s, to these four "classic" bases of DNA was added a fifth: the methyl-cytosine (mC) derived from cytosine. And it was in the late 90's when mC was recognized as the main cause of epigenetic mechanisms: it is able to switch genes on or off depending on the physiological needs of each tissue.

In recent years, interest in this fifth DNA base has increased by showing that alterations in the methyl-cytosine contribute to the development of many human diseases, including cancer.

Today, an article published in Cell by Manel Esteller, director of the Epigenetics and Cancer Biology Program of the Bellvitge Biomedical Research Institute (IDIBELL), ICREA researcher and Professor of Genetics at the University of Barcelona, describes the possible existence of a sixth DNA base, the methyl-adenine (mA), which also help determine the epigenome and would therefore be key in the life of the cells.

In bacteria and in complex organisms

"It was known for years that bacteria, evolutionarily very distant living organisms of us, had mA in its genome with a protective function against the insertion of genetic material from other organisms. But it was believed that this was a phenomenon of primitive cells and it was very static" describes Manel Esteller.

"However, this issue of Cell publishes three papers suggesting that more complex cells called eukaryotes such as the human body cells, also present the sixth DNA base. These studies suggest that algae, worms and flies possess mA and it acts to regulate the expression of certain genes, thus constituting a new epigenetic mark. This work has been possible thanks to the development of analytical methods with high sensitivity because levels of mA in described genomes are low. In addition it seems that mA would play a specific role in stem cells and early stages of development, "explains the researcher.

"Now the challenge we face is to confirm this data and find out whether mammals, including humans, we also have this sixth DNA base, and consider what its role is."