Yeast Mph1 helicase dissociates Rad51-made D-loops: implications for crossover control in mitotic recombination

Genes Dev. 2009 Jan 1;23(1):67-79. doi: 10.1101/gad.1737809.


Eukaryotes possess mechanisms to limit crossing over during homologous recombination, thus avoiding possible chromosomal rearrangements. We show here that budding yeast Mph1, an ortholog of human FancM helicase, utilizes its helicase activity to suppress spontaneous unequal sister chromatid exchanges and DNA double-strand break-induced chromosome crossovers. Since the efficiency and kinetics of break repair are unaffected, Mph1 appears to channel repair intermediates into a noncrossover pathway. Importantly, Mph1 works independently of two other helicases-Srs2 and Sgs1-that also attenuate crossing over. By chromatin immunoprecipitation, we find targeting of Mph1 to double-strand breaks in cells. Purified Mph1 binds D-loop structures and is particularly adept at unwinding these structures. Importantly, Mph1, but not a helicase-defective variant, dissociates Rad51-made D-loops. Overall, the results from our analyses suggest a new role of Mph1 in promoting the noncrossover repair of DNA double-strand breaks.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Crossing Over, Genetic / genetics*
  • DEAD-box RNA Helicases / metabolism*
  • DNA Breaks, Double-Stranded
  • DNA Repair
  • DNA, Fungal / chemistry
  • DNA, Fungal / metabolism
  • Mitosis / genetics*
  • Nucleic Acid Conformation
  • Rad51 Recombinase / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Saccharomyces cerevisiae* / chemistry
  • Saccharomyces cerevisiae* / enzymology
  • Saccharomyces cerevisiae* / genetics
  • Saccharomyces cerevisiae* / metabolism
  • Sister Chromatid Exchange / genetics


  • DNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • RAD51 protein, S cerevisiae
  • Rad51 Recombinase
  • MPH1 protein, S cerevisiae
  • DEAD-box RNA Helicases