title: Top3-Rmi1 dissolve Rad51-mediated D loops by a topoisomerase-based mechanism.
abstract: The displacement loop (D loop) is a DNA strand invasion product formed during homologous recombination. Disruption of nascent D loops prevents recombination, and during synthesis-dependent strand annealing (SDSA), disruption of D loops extended by DNA polymerase ensures a non-crossover outcome. The proteins implicated in D loop disruption are DNA motor proteins/helicases that act by moving DNA junctions. Here we report that D loops can also be disrupted by DNA topoisomerase 3 (Top3), and this disruption depends on Top3's catalytic activity. Yeast Top3 specifically disrupts D loops mediated by yeast Rad51/Rad54; protein-free D loops or D loop mediated by bacterial RecA protein or human RAD51/RAD54 resist dissolution. Also, the human Topoisomerase IIIa-RMI1-RMI2 complex is capable of dissolving D loops. Consistent with genetic data, we suggest that the extreme growth defect and hyper-recombination phenotype of Top3-deficient yeast cells is partially a result of unprocessed D loops.
authors.affiliation: Department of Microbiology & Molecular Genetics, University of California, Davis, Davis, CA 95616-8665, USA.
authors.forename: Clare L
authors.initials: CL
authors.lastname: Fasching
authors.affiliation: Department of Microbiology & Molecular Genetics, University of California, Davis, Davis, CA 95616-8665, USA.
authors.forename: Petr
authors.initials: P
authors.lastname: Cejka
authors.affiliation: Department of Microbiology & Molecular Genetics, University of California, Davis, Davis, CA 95616-8665, USA; Department of Molecular & Cellular Biology, University of California, Davis, Davis, CA 95616-8665, USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Kowalczykowski
authors.affiliation: Department of Microbiology & Molecular Genetics, University of California, Davis, Davis, CA 95616-8665, USA; Department of Molecular & Cellular Biology, University of California, Davis, Davis, CA 95616-8665, USA. Electronic address: wdheyer@ucdavis.edu.
authors.forename: Wolf-Dietrich
authors.initials: WD
authors.lastname: Heyer
mesh_terms: D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D059765:Homologous Recombination / Q000502:physiology*; D006801:Humans; D008957:Models, Genetic; D051135:Rad51 Recombinase / Q000378:metabolism / Q000502:physiology*; D053484:RecQ Helicases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity
chemical_list: D004268:DNA-Binding Proteins; C502206:Rmi1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C502374:TOP3 protein, S cerevisiae; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; C075468:RAD54 protein, S cerevisiae; C090472:SGS1 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; D045643:DNA Repair Enzymes