More than a mirror-image: left-handed nucleic acids

Biology encodes its genetic instructions in sequences of base pairs within the backbone of DNA’s right-handed double helix and through the RNA molecules subsequently transcribed. But what if the helices of these nucleic acids twisted in the opposite left-handed direction? It’s sometimes seen by mistake in stock images, but a crystal structure for this DNA conformer, known as Z-DNA, was published in the 1970s. It looks a little different to the right handed version - rather than a smooth corkscrew, the backbone forms a zig-zag shape, giving rise to its name. Investigations led to suggestions that Z-nucleic acids could play a role in biology, but these were widely met with scepticism.

In the last five years, clear evidence has shown that both DNA and RNA do form left-handed double helices in biology, and that these structures are involved in our immune responses to viral infection and inflammation. Z-DNA may even have a fundamental role in genetic control. Now a growing community of researchers are looking at ways this new biology can be exploited to fight cancer and other diseases.