Eukaryotes may contain a sixth DNA base

Scientists have discovered a sixth DNA base, thus revolutionizing our long standing idea about our genetic makeup.

DNA (deoxyribonucleic acid), the main component of our genetic materialcontains four bases: A, C, G and T (adenine, cytosine, guanine and thymine). These basescombine in numerous possible combinations to provide the vast genetic variability.

However a fifth DNA base: methyl-cytosine (mC) derived from cytosine was discovered back in the early 80s and was recognized as the main cause of epigenetic mechanisms in late 90’s. The mC can switch genes on or off in order to meet the needs of each tissue, given that every cell contains the same DNA sequences. Such modifications are known as epigenetic changes, allowing the environment to affect gene expression. Epigenetic modifications play significant role in various diseases, like, cancer.

Now, scientists have discovered another potential candidate: N6-methyladenine (mA), adenine with a methyl group attached onto it. Researchers from IDIBELL-Bellvitge Biomedical Research Institute, University of Barcelona, demonstrated that mA also helped to determine the epigenome. For some time, it was thought that it exclusively existed in bacteria, where it palys a protective role against the unwanted addition of foreign DNA from other organisms. But the recent study provides evidence that 6mA is found in more complex eukaryotic cells. Eukaryotes are organisms within one of the three domains of life, the others being archaea and bacteria.

Moreover the researchers discovered the presence of 6mA in three different groups of eukaryotes: green algae, flies and worms, through the development of highly sensitive and sophisticated analytical techniques, which picked up the exceedingly low levels of this base that previously eluded detection. Interestingly, these findings indicate that, like mC, 6mA may also have a gene regulatory function in these animals, suggesting the newly discovered base’s epigenetic role.

The researchers now plan to scrutinize our own genomes to see if 6mC also exist in humans. This would be interesting given the fact that evidence seems to suggest that 6mA may play a role in early stages of development. Thus the findings could mean a huge breakthrough in understanding of epigenetics and could eventually help us to proceed in areas ranging from therapies to cloning.

Reference:Cell, 2015; DOI: 10.1016/j.cell.2015.04.021

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Arunima Maiti

Arunima Maiti

Biomedical scientist with special interest in reproductive biology.

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