Published: Wed, April 25, 2018
Medicine | By Brett Sutton

A New Structure of DNA Network Discovered by Researchers

A New Structure of DNA Network Discovered by Researchers

In a world first, Australian researchers have identified a new DNA structure - called the i-motif - inside cells.

Since the year 1953, the iconic "double helix" shape of DNA has captured imagination of the public, when Francis Crick and James Watson had famously uncovered the structure of DNA.

Biologists have recently discovered a new DNA structure in living cells.

"When most of us think of DNA, we think of the double helix", said Daniel Christ, head of the antibody therapeutics lab at Garvan and co-author of the research.

In order to locate the i-motifs inside human cells, the scientists designed tiny probes that could recognise the DNA knots. Now, scientists are identifying the objective of the unusual element.

Injecting the antibody into a variety of cells, the researchers found that the it zeroed in on several targets across the cells - mostly in parts that do not code for proteins - including the regulatory regions that switch genes on and off (known as promotors) and the chromosome tips (called telomeres).

DNA is traditionally thought of as an elegant double helix, twisting together billions of pairs of adenine, thymine, cytosine, guanine, and uracil - a infinitely complex code of A, T, C, G and U. But the deeper the look into this fundamental building block of life gets, the more complicated the picture becomes. They determined that the fleeting glimpses they were shown were due to the i-motif appearing for just brief times toward the end of the G1 phase of the cell cycle.

You're familiar with the famous double-helix structure of DNA (dsDNA) but that's not the only structure there is.

"What surprised us most is that we were able to see the green structures, the motifs in the form of the letter I, that appeared and disappeared so that we know that it is formed, dissolved, and re-formed", said Mahdi Zeraati, the study's leading author.

The researchers theorize that DNA could exist in short stretches in other shapes.

More recent work has shown that in some cases an i-motif shape could form even in environments that weren't so acidic, said Randy Wadkins, a biochemist at the University of MS in Oxford who was not involved with the new study. In this case, the antibody was engineered so that it would attach itself to i-motifs but not to any other form of DNA.

"We also think the transient nature of the i-motifs explains why they have been so very hard to track down in cells until now", added assistant prof Christ.

"We think the coming and going of the i-motifs is a clue to what they do", said Zeraati.

"It seems likely that they are there to help switch genes on or off, and to affect whether a gene is actively read or not", Zeraati explained.

"It's exciting to uncover a whole new form of DNA in cells", said Professor Dinger.

Researchers hope this finding will set the stage for a new push to understand what this new DNA shape is for and whether it will impact our understanding of health and disease.

The findings appeared in the journal Nature Chemistry.

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