title: Robust crossover assurance and regulated interhomolog access maintain meiotic crossover number.
abstract: Most organisms rely on interhomolog crossovers (COs) to ensure proper meiotic chromosome segregation but make few COs per chromosome pair. By monitoring repair events at a defined double-strand break (DSB) site during Caenorhabditis elegans meiosis, we reveal mechanisms that ensure formation of the obligate CO while limiting CO number. We find that CO is the preferred DSB repair outcome in the absence of inhibitory effects of other (nascent) recombination events. Thus, a single DSB per chromosome pair is largely sufficient to ensure CO formation. Further, we show that access to the homolog as a repair template is regulated, shutting down simultaneously for both CO and noncrossover (NCO) pathways. We propose that regulation of interhomolog access limits CO number and contributes to CO interference.
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Simona
authors.initials: S
authors.lastname: Rosu
authors.forename: Diana E
authors.initials: DE
authors.lastname: Libuda
authors.forename: Anne M
authors.initials: AM
authors.lastname: Villeneuve
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D023902:Chromosome Pairing; D003434:Crossing Over, Genetic; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D018509:DNA, Helminth / Q000235:genetics*; D008540:Meiosis; D011995:Recombination, Genetic
chemical_list: D018509:DNA, Helminth