title: Polarity and bypass of DNA heterology during branch migration of Holliday junctions by human RAD54, BLM, and RECQ1 proteins.
abstract: Several proteins have been shown to catalyze branch migration (BM) of the Holliday junction, a key intermediate in DNA repair and recombination. Here, using joint molecules made by human RAD51 or Escherichia coli RecA, we find that the polarity of the displaced ssDNA strand of the joint molecules defines the polarity of BM of RAD54, BLM, RECQ1, and RuvAB. Our results demonstrate that RAD54, BLM, and RECQ1 promote BM preferentially in the 3'→5' direction, whereas RuvAB drives it in the 5'→3' direction relative to the displaced ssDNA strand. Our data indicate that the helicase activity of BM proteins does not play a role in the heterology bypass. Thus, RAD54 that lacks helicase activity is more efficient in DNA heterology bypass than BLM or REQ1 helicases. Furthermore, we demonstrate that the BLM helicase and BM activities require different protein stoichiometries, indicating that different complexes, monomers and multimers, respectively, are responsible for these two activities. These results define BM as a mechanistically distinct activity of DNA translocating proteins, which may serve an important function in DNA repair and recombination.
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102-1192, USA.
authors.forename: Olga M
authors.initials: OM
authors.lastname: Mazina
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Rossi
authors.forename: Julianna S
authors.initials: JS
authors.lastname: Deakyne
authors.forename: Fei
authors.initials: F
authors.lastname: Huang
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Mazin
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D004265:DNA Helicases / Q000737:chemistry; D004260:DNA Repair; D004261:DNA Replication; D004270:DNA, Circular / Q000737:chemistry; D045566:DNA, Cruciform / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D004268:DNA-Binding Proteins; D057075:Enzyme Assays; D029968:Escherichia coli Proteins / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D009687:Nuclear Proteins / Q000737:chemistry*; D010957:Plasmids / Q000737:chemistry; D053484:RecQ Helicases / Q000737:chemistry*; D011995:Recombination, Genetic; D051716:Replication Protein A / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D004270:DNA, Circular; D045566:DNA, Cruciform; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009687:Nuclear Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; C061260:RuvB protein, Bacteria; C071059:Holliday junction DNA helicase, E coli; C097151:Bloom syndrome protein; C506725:RECQL protein, human; D004265:DNA Helicases; C103532:RAD54L protein, human; D053484:RecQ Helicases; D008274:Magnesium