Supercoiled DNA Strands Wiggle And Morph Into Different Shapes

A group of researchers from Britain and the United States have discovered that supercoiled DNA is far more complex than the iconic double-helix DNA structure. The double-helix DNA was discovered by James Watson and Francis Crick in 1953. But a new study shows that double-helix structure is just a small part of DNA strands. Findings of the study were published in the latest issue of the journal Nature Communications.

It would help in developing better medicines

Biologists at the Baylor College of Medicine and University of Leeds imaged unusually supercoiled DNA in 3D form. They found that the supercoiled DNA strands are not only long, but they also wiggle and morph into a variety of shapes. In contrast, the double-helix DNA tends to be “rigid and static.” Dr. Sarah Harris of the University of Leeds said in a statement that the discovery would help in developing better medicines, especially cancer treatments and antibiotics.

That’s because drug molecules look for a specific molecular shape to act upon. The double-helix DNA is only a small part of the real genome, about 12 DNA base pairs. The new study looked at DNA at a grander scale of hundreds of base pairs. The DNA consists of about 3 billion base pairs, which would stretch out to measure about one meter if fully untangled and stretched.

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How researchers created 3D images of supercoiled DNA

And all this genetic information must fit into the nucleus of tiny cells measuring approximately 10 micrometers across. So, the DNA must be coiled precisely and tightly. Scientists simulated the coiling of DNA molecules in the lab to see how coiling changed the way the circles appeared. Then they wound and unwound DNA circles one round at a time.

Researchers used an enzyme called human topoisomerase II alpha to find out if the circles behaved the same way as full-length DNA strands inside the nucleus of a cell. The enzyme relieved all the stress caused by the twisting. It suggests that DNA in circles behave and appear in the same way as the longer strands in cells. Scientists used cryo-electron tomography to create 3D images of the supercoiled DNA and all its different shapes.