title: A novel function of Rad54 protein. Stabilization of the Rad51 nucleoprotein filament.
abstract: Homologous recombination is important for the repair of double-stranded DNA breaks in all organisms. Rad51 and Rad54 proteins are two key components of the homologous recombination machinery in eukaryotes. In vitro, Rad51 protein assembles with single-stranded DNA to form the helical nucleoprotein filament that promotes DNA strand exchange, a basic step of homologous recombination. Rad54 protein interacts with this Rad51 nucleoprotein filament and stimulates its DNA pairing activity, suggesting that Rad54 protein is a component of the nucleoprotein complex involved in the DNA homology search. Here, using physical criteria, we demonstrate directly the formation of Rad54-Rad51-DNA nucleoprotein co-complexes that contain equimolar amounts of each protein. The binding of Rad54 protein significantly stabilizes the Rad51 nucleoprotein filament formed on either single-stranded DNA or double-stranded DNA. The Rad54-stabilized nucleoprotein filament is more competent in DNA strand exchange and acts over a broader range of solution conditions. Thus, the co-assembly of an interacting partner with the Rad51 nucleoprotein filament represents a novel means of stabilizing the biochemical entity central to homologous recombination, and reveals a new function of Rad54 protein.
authors.affiliation: Department of Biochemistry, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102-1192, USA.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Mazin
authors.forename: Andrei A
authors.initials: AA
authors.lastname: Alexeev
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Kowalczykowski
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D019921:Biotinylation; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases; D045643:DNA Repair Enzymes; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D008954:Models, Biological; D009698:Nucleoproteins / Q000378:metabolism; D011137:Polystyrenes / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051135:Rad51 Recombinase; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D012492:Salts / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D019809:Streptavidin / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009698:Nucleoproteins; D011137:Polystyrenes; D029701:Saccharomyces cerevisiae Proteins; D012492:Salts; D012965:Sodium Chloride; D004247:DNA; D019809:Streptavidin; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D004262:DNA Restriction Enzymes; D000251:Adenosine Triphosphatases; C075468:RAD54 protein, S cerevisiae; D004265:DNA Helicases; D045643:DNA Repair Enzymes