Down-regulation of Rad51 activity during meiosis in yeast prevents competition with Dmc1 for repair of double-strand breaks.
Interhomolog recombination plays a critical role in promoting proper meiotic chromosome segregation but a mechanistic understanding of this process is far from complete. In vegetative cells, Rad51 is a highly conserved recombinase that exhibits a preference for repairing double strand breaks (DSBs) using sister chromatids, in contrast to the conserved, meiosis-specific recombinase, Dmc1, which preferentially repairs programmed DSBs using homologs. Despite the different preferences for repair templates, both Rad51 and Dmc1 are required for interhomolog recombination during meiosis. This paradox has recently been explained by the finding that Rad51 protein, but not its strand exchange activity, promotes Dmc1 function in budding yeast. Rad51 activity is inhibited in dmc1Δ mutants, where the failure to repair meiotic DSBs triggers the meiotic recombination checkpoint, resulting in prophase arrest. The question remains whether inhibition of Rad51 activity is important during wild-type meiosis, or whether inactivation of Rad51 occurs only as a result of the absence of DMC1 or checkpoint activation. This work shows that strains in which mechanisms that down-regulate Rad51 activity are removed exhibit reduced numbers of interhomolog crossovers and noncrossovers. A hypomorphic mutant, dmc1-T159A, makes less stable presynaptic filaments but is still able to mediate strand exchange and interact with accessory factors. Combining dmc1-T159A with up-regulated Rad51 activity reduces interhomolog recombination and spore viability, while increasing intersister joint molecule formation. These results support the idea that down-regulation of Rad51 activity is important during meiosis to prevent Rad51 from competing with Dmc1 for repair of meiotic DSBs.
Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America.
Yan
Y
Liu
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America.
William A
WA
Gaines
Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America.
Tracy
T
Callender
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Valeria
V
Busygina
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, California, United States of America.
Ashwini
A
Oke
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Patrick
P
Sung
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, California, United States of America.
Jennifer C
JC
Fung
Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America.
Nancy M
NM
Hollingsworth
D018797:Cell Cycle Proteins / Q000235:genetics*; D002842:Chromatids / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D059765:Homologous Recombination / Q000235:genetics; D008540:Meiosis / Q000235:genetics*; D009154:Mutation; D051135:Rad51 Recombinase / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D013170:Spores / Q000254:growth & development
D018797:Cell Cycle Proteins; C513033:DMC1 protein, S cerevisiae; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D051135:Rad51 Recombinase