Direct Observation of Stalled Fork Restart via Fork Regression in the T4 Replication System

Abstract

DNA Repair in Vitro Accurate replication of the genome is critical to an organism's continued survival. Damaged DNA not repaired before the commencement of replication can cause the DNA replication fork to stall or collapse, which can result in mutation or recombination, with potentially serious consequences for cell and organism. Fork regression involving a so-called “chicken foot” structure (Holliday junction) is thought to provide one mechanism for dealing with unrepaired DNA damage during replication. Manosas et al. (p. 1217 ) analyzed the action of the T4 bacteriophage replisome and helicase UvsW on a stalled-fork mimic in vitro, using a magnetic trap. UvsW was able to switch migration directions, which was essential for remodeling the stalled fork. Together, UvsW and T4 holoenzyme were able to drive template switching and lesion bypass in vitro.