In a new DNA twist, Australian scientists have found another structure in living human cells besides the familiar double helix. Called the “i-motif,” it’s a four-stranded knot of DNA thought to have regulatory properties.
Researchers at the Garvan Institute of Medical Research said the i-motif structure had never been seen before directly inside living cells. Their research was detailed in the Tuesday's issue of the medical journal Nature Chemistry.
"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. "This new research reminds us that totally different DNA structures exist – and could well be important for our cells."
The double helix shape of DNA has been around since 1953 but the new research reveals that in short stretches DNA can take other shapes and scientists believe that the different shapes might play an important role in how and when the DNA code is “read.”
"… We provide evidence that i-motif structures are formed in regulatory regions of the human genome, including promoters and telomeric regions," the study’s abstract read. "Our results support the notion that i-motif structures provide key regulatory roles in the genome."
The DNA code provides exact instructions to how our bodies are constructed and how they are to work over time, the researchers said. Within the human genome, the i-motif stands out.
"The i-motif is a four-stranded 'knot' of DNA," said Marcel Dinger, head of Kinghorn Center for Clinical Genomics at Garvan and another of the study's co-authors.
"In the knot structure, C 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]," Dinger said.
Researchers found the i-motifs by designing tiny probes that could recognize the DNA knots, made of using antibodies that bind with specific substances, The Independent reported. The scientists then added fluorescent dyes to the antibody probes so they could monitor where exactly the i-motifs were located in the cells.
"It's exciting to uncover a whole new form of DNA in cells – and 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," Dinger said in the Garvan statement.