Replication forks are known to stall due to replication stress, and electron microscopy observation has revealed the occurrence of the fork reversal structure, also known as the chicken-foot structure. It was previously known that the RAD51 recombinase is required for the formation of the reversed forks. However, it was unclear whether CMG helicase, which was responsible for moving the replication fork, remained present in the reversed forks and, if so, where it was located. This study analyzed RAD51 mutants and found that the reversed fork structure forms behind the CMG helicase and that the requirement for RAD51 in fork reversal formation disappears when CMG helicase is absent.
Figure: A schematic diagram of the formation of the reversed fork structure. When CMG helicase stalls, DNA annealing is promoted by the annealing activity of RAD51 behind it.
This study was conducted as collaborative research between Professor David Cortez at Vanderbilt University and the Kanemaki Laboratory at NIG. The Kanemaki Laboratory generated AID2 cells that can degrade MCM proteins, which is a main component of the CMG helicase.
