DNA (deoxyribonucleic acid) is the main component of human genetic material. It is formed by combining four parts known as Adenine (A), Cytosine (C), Guanine (G) and Thymine (T) respectively. These ‘parts’ are called bases of DNA and they combine in thousands of possible sequences to provide genetic variability. In the early 80s, a fifth base was added to the four classic bases of DNA. This new fifth base, methyl-cytosine, is derived from cytosine and is recognized as the main cause of epigenetic mechanisms.
Not only is methyl-cytosine able to switch genes on or off depending on the physiological needs of each tissue, in recent years interest has increased in the is base, with methyl-cytosine mutations linked to the development of many human diseases, including cancer.
Now, researchers from the Institut d’Investigació Biomèdica de Bellvitge (IDIBELL) and the University of Barcelona describe the possibility of the existence of a sixth DNA base, methyl-adenine, which also helps to determine the epigenome and would therefore be key in the life of the cells.
The team explain that it has long been known that certain bacteria have methyl-adenine in their 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.
However, three new papers suggest that more complex cells called eukaryotes which make up the human body, also present the sixth DNA base. These studies suggest that algae, worms and flies possess methyl-adenine which acts to regulate the expression of certain genes, thus constituting a new epigenetic tag or mark.
Eukaryotic cells have an organized nucleus with a nuclear envelope, explain the team. They have a ‘brain’ for the cell. They have a discreet area where they keep their DNA. It is also said that they have a ‘true nucleus’. Eukaryotic cells usually have organelles. They might have mitochondria, maybe a chloroplast, or some endoplasmic reticulum. They have parts that work to make the cell a self-sufficient organism. All multicellular organisms are eukaryotes, including humans, animals, plants and fungi.
This team state that these results have been made possible thanks to the development of analytical methods with high sensitivity because levels of methyl-adenine in the mapped genomes are low. In addition, the data findings show that methyl-adenine also plays a specific role in stem cells and early stages of development.
The researchers plan to confirm this data and find out whether humans have this sixth DNA base, whilst mapping the exact role of methyl-adenine within the human genome.