Recently, scientists identified a new DNA structure inside human cells called the “i-motif”. It resembles a twisted knot quite different from the James Watson and Francis Crick double helix model.
Previous lab work had suggested the existence of this form of DNA. But only recently it was observed in living cells.
The function of the i-motif is not known exactly. But the scientists suspect its involvement in the process of reading DNA sequences and in their conversion to useful substances.
The study describing the newly discovered i-motif was co-led by Professor Daniel Christ, a molecular biologist at the Garvan Institute of Medical Research. He said that when we think of DNA, it reminds us only of the double helix model. But this new research now reminds us of an entirely different DNA structure which exists and can be important for our cells.
Previously i-motifs were observed in laboratories under artificial conditions. It was unclear whether they could exist in living cells prior to this work.
This new study led by Professor Christ and his team is published in the scientific journal Nature Chemistry.
Comparing Double Helix And i-motif
A traditional strand of DNA consists of base pairings. Bases such as adenine, thymine, cytosine, and guanine are the building blocks of the double helix DNA.
The structure of the molecule is due to the binding of adenine with thymine and cytosine with guanine. But i-motif has a different structure altogether.
According to Professor Marcel Dinger who is the study’s co-leader, i-motif is a four-stranded knot of DNA. Within the knot structure, cytosine binds to each other on the same strand of DNA unlike the double helix, where the bases on the opposite strands recognize each other and cytosines bind to guanines.
Research Approach For Identifying New DNA Form
The scientists designed tiny probes that could identify the DNA knots so as to locate the i-motifs inside the human cells. Antibodies which are Y-shaped molecules which have the ability to bind with specific substances were used to make the probes. For the study, the antibody was modified so that it could attach to the i-motifs and not to any other DNA form.
The antibody probes were colored with fluorescent dyes which could help the scientists to monitor the exact location of i-motifs in the cells.
For the study, the probes were applied to three different types of human cells. Scientists could identify the fluorescent green spots in the nucleus of each cell which they had a look at.
Dr. Mahdi Zeraati who was part of the study said that the green spots, the i-motifs appeared and disappeared over time. This means they form, dissolve and form again. The appearing and disappearing of the i-motifs can give a clue of what they can do. It appears that this i-motifs help to switch genes on or off and affects the process of reading a gene.
As per the researchers, this form of DNA eluded the scientists for so long because of their transient nature.
Professor Dinger opined that it is indeed exciting to discover a whole new DNA form in cells. These findings can set the stage for understanding what this new DNA shape is capable of and its overall impact on health and disease.