Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States; CR CNRS UMR5239, Team Genome Mechanics, Laboratory of Biology and Modelling of the Cell, Ecole Normale Supérieure de Lyon 46, Lyon, France
Vanessa Som
Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
William Wright
Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States; Mammoth Biosciences, South San Francisco, United States
Frédéric Chédin
Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States; Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
Displacement loops (D-loops) are critical intermediates formed during homologous recombination. Rdh54 (a.k.a. Tid1), a Rad54 paralog in Saccharomyces cerevisiae, is well-known for its role with Dmc1 recombinase during meiotic recombination. Yet contrary to Dmc1, Rdh54/Tid1 is also present in somatic cells where its function is less understood. While Rdh54/Tid1 enhances the Rad51 DNA strand invasion activity in vitro, it is unclear how it interplays with Rad54. Here, we show that Rdh54/Tid1 inhibits D-loop formation by Rad51 and Rad54 in an ATPase-independent manner. Using a novel D-loop Mapping Assay, we further demonstrate that Rdh54/Tid1 uniquely restricts the length of Rad51-Rad54-mediated D-loops. The alterations in D-loop properties appear to be important for cell survival and mating-type switch in haploid yeast. We propose that Rdh54/Tid1 and Rad54 compete for potential binding sites within the Rad51 filament, where Rdh54/Tid1 acts as a physical roadblock to Rad54 translocation, limiting D-loop formation and D-loop length.
