A new type of human DNA that does not resemble the double helix shape has emerged in a study performed in a laboratory in Australia.
Scientists at the Garvan Institute of Medical Research discovered that human DNA may not necessarily take the shape and structure of the double helix. Instead, a twisted "knot" called i-motif exists inside the human cells — a phenomenon that only previously occurred during an artificial lab manipulation.
"When most of us think of DNA, we think of the double helix. This new research reminds us that totally different DNA structures exist — and could well be important for our cells," said lead author Daniel Christ, who also heads the Antibody Therapeutics Lab at Garvan.
Studying the four-stranded i-motif will help researchers understand its role in decoding DNA. The double helix provides information on the exact structure of DNA strands, designated by letters A, C, G, and T.
DNA is the building block of how cells are formed, how the body is built, and how it works. I-motif, on the other hand, has different genetic sequences compared to the double helix.
"In the knot structure, C letters on the same strand of DNA bind to each other — so this is very different from a double helix, where 'letters' on opposite strands recognize each other, and where Cs bind to Gs [guanines]," said coauthor Marcel Dinger, who heads the Kinghorn Center for Clinical Genomics at Garvan.
Looking Inside The New Type Of DNA
To identify locations of i-motifs in a living cell, the researchers used a precise fluorescence technique that will pinpoint green spots inside the nucleus, which would indicate i-motifs.
Interestingly, scientists observed that the green spots constantly appeared and disappeared over time, suggesting that i-motifs have formed and dissolved before it formed again.
Researcher Dr. Mahdi Zeraati said that the behavior of i-motifs could provide clues on their genetic role. He said that it is likely that i-motifs exist to determine which genes are "actively read or not" or "to help switch genes on or off."
Dinger said that the discovery of i-motifs opens whole new possibilities in the field of genomics. He explained that since i-motifs folds are fewer than the double helix, it is possible that drugs that bind DNA can be developed in the future.
These drugs could improve cancer treatment. However, researchers said they have to find a way to prevent cancer cells from attaching to other parts of DNA.
"This provides a firm foundation for a major therapeutic effort around these new structures," said Laurence Hurley, a professor at the University of Arizona.
Details of the study can be found in the April 23 edition of the journal Nature Chemistry.