https://phys.org/news/2018-07-supercoil-art-dna-maintenance.html

Supercoiled, twisted, and even knotted—far from the elegant and polished textbook images, DNA filaments in living cells is all crumpled and entangled, and to be functional, must be constantly unraveled, much like telephone cords that accumulate annoying curls or supercoils with careless use. Supercoils are present in DNA, too, and they are believed to be instrumental for keeping DNA compact and exposing or hiding genetic information to the cellular machinery that can process it, according to Lucia Coronel and Antonio Suma, young scientists and first authors of this study, which was coordinated by Cristian Micheletti.

At the same time, it has long been known that knots can accidentally form in DNA, with negative consequences for the cell. What had remained elusive until now was the dynamic interplay or coexistence on the same DNA filaments of complex knots and supercoiled regions. And this is what the researchers at SISSA set out to study using computer simulations, investigating the implications for DNA structure and its change in time, and whether such interplay might unlock new functional possibilities. They also sought to understand how the ensuing complex behaviour fits with what is already known about the molecular maintenance of DNA.