Humans have another type of DNA inside our cells

Scientists have identified an entirely new kind of DNA inside humans.

This new DNA, known as the “i-motif,” was suggested in previous research, but had only been identified under artificial conditions in a lab. But research published in Nature Chemistry^[1] is the first study to confirm its existence inside living beings.

The i-motif looks like a twisted knot, as opposed to DNA’s well-known double helix structure.

In a double helix strand of DNA, there are four compounds that form “bases” — adenine, thymine, cytosine and guanine. Adenine typically binds with thymine while the cytosine binds with guanine, but this isn’t the case in the i-motif.

“The i-motif is a four-stranded ‘knot’ of DNA,” Marcel Dinger, a co-author on the study, said in a press release.^[2] “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 recognize each other and where Cs bind to Gs [guanines].”

To find the i-motifs, the scientists engineered antibodies into tiny probes that would attach themselves only to i-motifs. They added fluorescent dye to the probes so they could track exactly where the i-motifs were.

These antibody probes were then placed in three variations of human cells where scientiests had hoped to identify the i-motifs in the nucleus of each cell.

More research is needed to determine the i-motif’s purpose, but the researchers believe the structures help to switch genes “on or off.”

“It’s exciting to uncover a whole new form of DNA in cells,” said Dinger. “These findings will set the stage for a whole new push to understand what this new DNA shape is really for and whether it will impact on health and disease.”