Processing of Holliday junctions by the Escherichia coli RuvA, RuvB, RuvC and RecG proteins.

Recent work has led to significant advances in our understanding of the late steps of genetic recombination and the post-replicational repair of DNA. The RuvA and RuvB proteins have been shown to interact with recombination intermediates and catalyse the branch migration of Holliday junctions. Although both proteins are required for branch migration, each plays a defined role with RuvA acting as a specificity factor that directs RuvB (an ATPase) to the junction. The RuvB ATPase provides the motor for branch migration. The next step is catalysed by RuvC protein which recognises Holliday junctions and promotes their resolution by endonucleolytic cleavage. New data indicates an alternative pathway for Holliday junction processing. This pathway involves RecG, a branch migration protein which is functionally analogous to RuvAB, and a protein (activated by a rus mutation) which works with RecG to process intermediates independently of RuvA, RuvB and RuvC.