The formation of four-stranded DNA has been tracked in living human cells, allowing scientists to see how it works, and its possible role in cancer.

DNA usually forms the classic double helix shape discovered in 1953 – two strands wound around each other. Several other structures have been formed in test tubes, but this does not necessarily mean they form within living cells.

Quadruple helix structures, called DNA G-quadruplexes (G4s), have previously been detected in cells. However, the technique used required either killing the cells or using high concentrations of chemical probes to visualize G4 formation, so their actual presence within living cells under normal conditions has not been tracked, until now.

A research team from the University of Cambridge, Imperial College London and Leeds University have invented a fluorescent marker that is able to attach to G4s in living human cells, allowing them to see for the first time how the structure forms and what role it plays in cells.
The study is published today in Nature Chemistry.