Scientists Find New ‘Hidden’ Structure Inside Human DNA

“This new research reminds us that totally different DNA structures exist – and could well be important for our cells.”

Ladies and Gents, forget what you thought you knew about DNA. Scientists have just discovered a new, ‘hidden’ structure inside Human DNA.

An illustration of an i-motif embedded in a strand of DNA. (Mahdi Zeraati.)

The modern biological era began when Rosalind Franklin, James Watson, and Francis Crick discovered the twisted structure of DNA in 1953. Understanding that structure is what has allowed scientists to unravel the mysteries of the genetic code, but there was one part that was missing.

It turns out that the human DNA had a long-held secret: the popular double helix with which we interpret the DNA structure is not the only way it adopts.

In fact, and for the first time ever, a team of scientists has identified a new structure that resembles a twisted knot of four ropes.

The new structure has just been described in the journal Nature Chemistry, and it seems to play a crucial role in the way DNA is expressed.

Despite the fact that experts have long thought this structure (called imotif) may exist, never before had it been detected inside living human cells. The “i” stands for “intercalation,” which is a chemistry term for a layered structure.

The structure consists of four strands of DNA paired in a peculiar way.

Discovering the i-motif inside living cells indicates that it most likely plays a significant role in cell biology.

In the double helix, the nitrogenous bases of adenine (A) form pairs with thiamin (T), while the cytosine (C) does the same with guanine (G).

These bases are structured one on top of the other twisting in two rows of glucose and phosphate that form an elegant staircase in the form of a double helix.

This structure plays a determining role in the synthesis of proteins, note experts.

Discovering the hidden structure

“Our imaging suggests that this is a normal thing that happens,” said Marcel Dinger, a molecular biologist at the Garvan Institute for Medical Research in Sydney, Australia, who oversaw the research. “It is very likely that genomes in all the cells of our bodies are forming i-motifs at some point in time.”

In order to detect the i-motif, scientists used a fragment of an antibody capable of recognizing and adhering specifically to the i-motif forms.

We still know little about its function or importance, but it seems clear that, while the double helix is the predominant structure, the most common way that DNA has to store its information, there are other patterns whose role could be determinant for the control of the gene expression and, therefore, control diseases related to it, such as certain cancers.

“What excited us most is that we could see the green spots – the i-motifs – appearing and disappearing over time, so we know that they are forming, dissolving and forming again,” said Dr Mahdi Zeraati, a member of the team.

“We think the coming and going of the i-motifs is a clue to what they do. 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.”

The discovery was published in the scientific journal Nature Chemistry.

Featured Image Credit: Chris Hammang.

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