title: The F-Box DNA helicase Fbh1 prevents Rhp51-dependent recombination without mediator proteins.
abstract: A key step in homologous recombination is the loading of Rad51 onto single-stranded DNA to form a nucleoprotein filament that promotes homologous DNA pairing and strand exchange. Mediator proteins, such as Rad52 and Rad55-Rad57, are thought to aid filament assembly by overcoming an inhibitory effect of the single-stranded-DNA-binding protein replication protein A. Here we show that mediator proteins are also required to enable fission yeast Rad51 (called Rhp51) to function in the presence of the F-box DNA helicase Fbh1. In particular, we show that the critical function of Rad22 (an orthologue of Rad52) in promoting Rhp51-dependent recombination and DNA repair can be mostly circumvented by deleting fbh1. Similarly, the reduced growth/viability and DNA damage sensitivity of an fbh1(-) mutant are variously suppressed by deletion of any one of the mediators Rad22, Rhp55, and Swi5. From these data we propose that Rhp51 action is controlled through an interplay between Fbh1 and the mediator proteins. Colocalization of Fbh1 with Rhp51 damage-induced foci suggests that this interplay occurs at the sites of nucleoprotein filament assembly. Furthermore, analysis of different fbh1 mutant alleles suggests that both the F-box and helicase activities of Fbh1 contribute to controlling Rhp51.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
authors.forename: Fekret
authors.initials: F
authors.lastname: Osman
authors.forename: Julie
authors.initials: J
authors.lastname: Dixon
authors.forename: Alexis R
authors.initials: AR
authors.lastname: Barr
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Whitby
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D020090:Chromosome Segregation / Q000235:genetics / Q000502:physiology; D004249:DNA Damage / Q000235:genetics; D004265:DNA Helicases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics / Q000502:physiology; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D009154:Mutation; D051135:Rad51 Recombinase; D011995:Recombination, Genetic / Q000235:genetics* / Q000502:physiology; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D013489:Suppression, Genetic
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; C084232:RHP51 protein, S pombe; C121634:RHP55 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C483769:Swi5 protein, S pombe; C085412:rad52 protein, S pombe; D051135:Rad51 Recombinase; D004265:DNA Helicases; C504739:Fbh1 protein, S pombe; C106462:Rqh1 protein, S pombe; C468289:Srs2 protein, S pombe