Branch migration and Holliday junction resolution catalyzed by activities from mammalian cells

During homologous recombination, DNA strand exchange leads to Holliday junc tion formation. The movement, or branch migration, of this junction along D NA extends the length of the heteroduplex joint. In prokaryotes, branch mig ration and Holliday junction resolution are catalyzed by the RuvA and RuvB proteins, which form a complex with RuvC resolvase to form a "resolvasome". Mammalian cell-free extracts have now been fractionated to reveal analogou s activities. An ATP-dependent branch migration activity, which migrates ju nctions through >2700 bp, cofractionates with the Holliday junction resolva se during several chromatographic steps. Together, the two activities promo te concerted branch migration/resolution reactions similar to those catalyz ed by E. coli RuvABC, highlighting the preservation of this essential pathw ay in recombination and DNA repair from prokaryotes to mammals.