Rec'd and repaired

DNA replication stalls when the polymerase encounters lesions in the DNA, but recovers soon after lesion repair. In a recent work, Justin Courcelle and colleagues (Mississippi State University, Mississippi State, MS) examine what happens to the replication fork during this downtime. The results show that maintaining the correct fork structure depends on recombination proteins that may help to prevent illegitimate strand exchanges.

Courcelle's group used two-dimensional gel electrophoresis to examine the shapes of a replicating bacterial plasmid. Advancing replication forks yielded the expected Y-shaped structure. But UV-induced lesions stalled the replication fork and produced X-shaped structures. These structures represent the nascent DNA backing up from the apex of a Y-shaped fork. The stalled structures were processed by RecQ and RecJ and maintained by RecA and RecF, which are the same proteins...