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Delineation of joint molecule resolution pathways in meiosis identifies a crossover-specific resolvase |
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| Authors: | Zakharyevich Kseniya Tang Shangming Ma Yunmei Hunter Neil |
| Affiliation: | 1 Department of Microbiology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA 2 Microbiology Graduate Group, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA 3 Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA 4 Howard Hughes Medical Institute, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA 5 Department of Molecular and Cellular Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA 6 Department of Cell Biology and Human Anatomy, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA |
| Abstract: | At the final step of homologous recombination, Holliday junction-containing joint molecules (JMs) are resolved to form crossover or noncrossover products. The enzymes responsible for JM resolution in?vivo remain uncertain, but three distinct endonucleases capable of resolving JMs in?vitro have been identified: Mus81-Mms4(EME1), Slx1-Slx4(BTBD12), and Yen1(GEN1). Using physical monitoring of recombination during budding yeast meiosis, we show that all three endonucleases are capable of promoting JM resolution in?vivo. However, in mms4 slx4 yen1 triple mutants, JM resolution and crossing over occur efficiently. Paradoxically, crossing over in this background is strongly dependent on the Blooms helicase ortholog Sgs1, a component of a well-characterized anticrossover activity. Sgs1-dependent crossing over, but not JM resolution per se, also requires XPG family nuclease Exo1 and the MutLγ complex Mlh1-Mlh3. Thus, Sgs1, Exo1, and MutLγ together define a previously undescribed meiotic JM resolution pathway that produces the majority of crossovers in budding yeast and, by inference, in mammals. |
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