title: Activation of an alternative, rec12 (spo11)-independent pathway of fission yeast meiotic recombination in the absence of a DNA flap endonuclease.
abstract: Spo11 or a homologous protein appears to be essential for meiotic DNA double-strand break (DSB) formation and recombination in all organisms tested. We report here the first example of an alternative, mutationally activated pathway for meiotic recombination in the absence of Rec12, the Spo11 homolog of Schizosaccharomyces pombe. Rad2, a FEN-1 flap endonuclease homolog, is involved in processing Okazaki fragments. In its absence, meiotic recombination and proper segregation of chromosomes were restored in rec12Delta mutants to nearly wild-type levels. Although readily detectable in wild-type strains, meiosis-specific DSBs were undetectable in recombination-proficient rad2Delta rec12Delta strains. On the basis of the biochemical properties of Rad2, we propose that meiotic recombination by this alternative (Rec*) pathway can be initiated by non-DSB lesions, such as nicks and gaps, which accumulate during premeiotic DNA replication in the absence of Okazaki fragment processing. We compare the Rec* pathway to alternative pathways of homologous recombination in other organisms.
authors.affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 11200 Fairview Avenue North, Seattle, WA 98109-1024, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Farah
authors.forename: Gareth
authors.initials: G
authors.lastname: Cromie
authors.forename: Luther
authors.initials: L
authors.lastname: Davis
authors.forename: Walter W
authors.initials: WW
authors.lastname: Steiner
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Smith
mesh_terms: D020090:Chromosome Segregation / Q000235:genetics*; D003433:Crosses, Genetic; D004247:DNA / Q000235:genetics*; D004271:DNA, Fungal / Q000737:chemistry*; D004706:Endodeoxyribonucleases / Q000235:genetics; D005434:Flow Cytometry; D005819:Genetic Markers / Q000235:genetics; D008540:Meiosis / Q000235:genetics / Q000502:physiology*; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D012568:Schizosaccharomyces / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics; D000099257:Meiotic Recombination Protein SPO11
chemical_list: D004247:DNA; D004271:DNA, Fungal; D004706:Endodeoxyribonucleases; D005819:Genetic Markers; D029702:Schizosaccharomyces pombe Proteins; C022262:Okazaki fragments; C456270:rec12 protein, S pombe; D000099257:Meiotic Recombination Protein SPO11; C445562:Rad2 protein, S pombe