Caenorhabditis elegans msh-5 is required for both normal and radiation-induced meiotic crossing over but not for completion of meiosis.
Crossing over and chiasma formation during Caenorhabditis elegans meiosis require msh-5, which encodes a conserved germline-specific MutS family member. msh-5 mutant oocytes lack chiasmata between homologous chromosomes, and crossover frequencies are severely reduced in both oocyte and spermatocyte meiosis. Artificially induced DNA breaks do not bypass the requirement for msh-5, suggesting that msh-5 functions after the initiation step of meiotic recombination. msh-5 mutants are apparently competent to repair breaks induced during meiosis, but accomplish repair in a way that does not lead to crossovers between homologs. These results combine with data from budding yeast to establish a conserved role for Msh5 proteins in promoting the crossover outcome of meiotic recombination events. Apart from the crossover deficit, progression through meiotic prophase is largely unperturbed in msh-5 mutants. Homologous chromosomes are fully aligned at the pachytene stage, and germ cells survive to complete meiosis and gametogenesis with high efficiency. Our demonstration that artificially induced breaks generate crossovers and chiasmata using the normal meiotic recombination machinery suggests (1) that association of breaks with a preinitiation complex is not a prerequisite for entering the meiotic recombination pathway and (2) that the decision for a subset of recombination events to become crossovers is made after the initiation step.
Kelly
K O
KO
Departments of Developmental Biology and Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
Dernburg
A F
AF
Stanfield
G M
GM
Villeneuve
A M
AM
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism*; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics / Q000648:ultrastructure; D003434:Crossing Over, Genetic / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D019077:Helix-Turn-Helix Motifs; D007814:Larva; D008297:Male; D008540:Meiosis; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D011995:Recombination, Genetic; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013090:Spermatocytes / Q000502:physiology
D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C552835:MSH-5 protein, C elegans; C094801:MSH5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins