Single Holliday junctions are intermediates of meiotic recombination.
Crossing-over between homologous chromosomes facilitates their accurate segregation at the first division of meiosis. Current models for crossing-over invoke an intermediate in which homologs are connected by two crossed-strand structures called Holliday junctions. Such double Holliday junctions are a prominent intermediate in Saccharomyces cerevisiae meiosis, where they form preferentially between homologs rather than between sister chromatids. In sharp contrast, we find that single Holliday junctions are the predominant intermediate in Schizosaccharomyces pombe meiosis. Furthermore, these single Holliday junctions arise preferentially between sister chromatids rather than between homologs. We show that Mus81 is required for Holliday junction resolution, providing further in vivo evidence that the structure-specific endonuclease Mus81-Eme1 is a Holliday junction resolvase. To reconcile these observations, we present a unifying recombination model applicable for both meiosis and mitosis in which single Holliday junctions arise from single- or double-strand breaks, lesions postulated by previous models to initiate recombination.
Cromie
Gareth A
GA
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, P.O. Box 19024, Seattle, WA 98109, USA.
Hyppa
Randy W
RW
Taylor
Andrew F
AF
Zakharyevich
Kseniya
K
Hunter
Neil
N
Smith
Gerald R
GR
D015825:Chromosomes, Fungal / Q000235:genetics / Q000502:physiology; D003434:Crossing Over, Genetic; D045566:DNA, Cruciform / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology; D004720:Endonucleases / Q000502:physiology; D008540:Meiosis; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000502:physiology; D012854:Sister Chromatid Exchange / Q000502:physiology; D000099257:Meiotic Recombination Protein SPO11
D045566:DNA, Cruciform; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D004720:Endonucleases; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C495865:MUS81 protein, S pombe; C456270:rec12 protein, S pombe; D000099257:Meiotic Recombination Protein SPO11; C411624:MUS81 protein, S cerevisiae