Sixth DNA Base Discovered By Scientists?

Scientists may have discovered a sixth DNA base, changing the way we think about our genetic makeup, according to a new study.

DNA (deoxyribonucleic acid), the main component of our genetic material, is formed by combining four parts: A, C, G and T (adenine, cytosine, guanine and thymine). These parts, or bases, of DNA combine in thousands of possible sequences to provide the genetic variability that makes us human beings.

In the early 1980s, a fifth component was added to these four "classic" bases, called methyl-cytosine (mC), which is derived from cytosine. Then, in the late 1990s, mC was recognized as the main cause of epigenetic mechanisms. Meaning, it can switch genes on or off depending on the physiological needs of each tissue.

In recent years, researchers have studied this fifth DNA base in more detail because it seems alterations in the mC base contribute to the development of many human diseases, including cancer.

Now, according to new findings published in the journal Cell, a sixth possible DNA base may also exist. Called methyl-adenine (mA), this potential DNA base may also help determine the epigenome and would therefore be key in the life of the cells.

Although scientists have known for years the existence of mA in distantly-related bacteria - used to protect against the insertion of genetic material from other organisms - it was believed to be a phenomenon unique to primitive cells.

However, now this latest study suggests that "more complex cells called eukaryotes such as the human body cells, also present the sixth DNA base," Manel Esteller, director of the Epigenetics and Cancer Biology Program of the Bellvitge Biomedical Research Institute (IDIBELL), said in a statement.

Normally, levels of mA in described genomes are low, making them difficult to study. But Esteller and his team were able to make this discovery using unique analytical methods with high sensitivity, possibly leading to a rewrite of biology books.

"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," he added. "In addition it seems that mA would play a specific role in stem cells and early stages of development."

"Now," Esteller concluded, "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."

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