Our genetic makeup is actually much more complex than we ever imagined. A ground-breaking discovery reveals that there’s more to our DNA than the double helix structure everyone is familiar with.
This mysterious form of DNA is called the intercalated motif (i-motif) and has been described as a “twisted knot” because, unlike the elegantly woven double helix, this structure looks like a four-stranded tangle of genetic code.
Although its existence had been theorized in the 1990s, many scientists were convinced the i-motif could not exist in living human cells due to its affinity for acidic environments.
According to Science Alert, this new DNA component had only been encountered in lab experiments, where the acidic conditions it thrives in had been created in vitro.
For the first time ever, the i-motif has now been spotted in living human cells, and researchers are trying to glean the role of this newfound DNA structure in cell biology.
“Before this, it was kind of an academic idea that DNA could [fold like this], but it wasn’t known at all what it meant for biology,” said senior study author Marcel Dinger, from the Garvan Institute of Medical Research in Sydney, Australia.
Daniel Christ, another one of the study authors and an antibody therapeutics researcher at the Garvan Institute, pointed out that the discovery of the i-motif in living cells is an important reminder of the vast complexity of our DNA.
“This new research reminds us that totally different DNA structures exist — and could well be important for our cells.”
Dinger, who runs the institute’s Kinghorn Centre for Clinical Genomics, explained the major differences between the i-motif and the double helix.
“In the knot structure, C [cytosine] 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 recognise each other, and where Cs bind to Gs [guanines],” Dinger said in a statement.
— Live Science (@LiveScience) April 23, 2018
The Australian team was finally able to identify the four-stranded structure in living cells by engineering an antibody fragment that could recognize and bind with this type of structure. The antibody pinpointed the location of i-motif structures with an immunofluorescent glow, allowing the researchers to watch them sparkle inside the cells.
“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,” says Mahdi Zeraati, one of the study authors.
And if finding out that you have a completely unique and never before seen structure in your DNA is somewhat of a shock, then it must be completely mind-blowing to fathom that there could be others as well.
Zeraati, also from the Gavan institute, reveals that the i-motif could be just one of many other unknown genetic code structures that could be present in our DNA.
— Melanie Kron (@MedNewsProducer) April 23, 2018
After all, human DNA contains a number of other known structures that don’t follow the double helix conformation, such as A-DNA, Z-DNA, triplex DNA, and Cruciform DNA, ScienceAlert notes.
“There’s so much of the genome that we don’t understand, probably like 99 percent of it,” says Dinger.
As for the reason why the i-motif exists in our DNA, the team speculates that it might play an important role in regulating our genes.
The scientists observed that these structures tend to form later in the cells’ life cycle and that they particularly appear in the areas of our DNA responsible for determining whether genes are activated or turned off.
“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.