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Strands of Four

Researchers have spotted a quadruple-stranded form of DNA within healthy human cells, New Scientist reports. It notes that such four-stranded DNA has been observed before in cancer cells and in some lab settings, but never in healthy human cells.

A team led by the University of Cambridge's Shankar Balasubramanian used a fluorescent probe to bind DNA G-quadruplexes, which they followed with single-molecule imaging of live cells. As they report in Nature Chemistry this week, the researchers found that the formation of DNA G-quadruplexes is cell-cycle dependent and related to transcription and replication, as when those processes are inhibited, quadruple-stranded DNA complexes could no longer be detected.

First author Marco Di Antonio from Imperial College London tells New Scientist that they suspect the complexes act similarly to epigenetic markers and affect the level of protein produced by holding various DNA regions open.

"We've undoubtedly demonstrated that the quadruple-strand DNA forms in living cells," Di Antonio tells it. "This forces us to rethink the biology of DNA."