Intertwining of DNA molecules frequently results in the formation of ‘ultrafine bridges’ between sister chromatids that need to be resolved during segregation of the chromatids into daughter cells. Although it has been established that these DNA bridges are coated by the helicase PICH, it has remained unknown how PICH assists in their resolution. A study now reveals that PICH directs the formation of positive DNA supercoiling in the presence of type I topoisomerases to promote the subsequent disentanglement of these DNA helices by type II topoisomerases. Remarkably, PICH might be able to reconfigure DNA topology by extruding loops of DNA while it moves along the double helix.
- Shveta Bisht
- Christian H. Haering