Effects of HDF1 (Ku70) and HDF2 (Ku80) on spontaneous and DNA damage-induced intrachromosomal recombination in Saccharomyces cerevisiae

Mol Gen Genet. 2000 Sep;264(1-2):56-63. doi: 10.1007/s004380000280.


The Ku heterodimer binds to the ends of double-stranded breaks (DSBs) in DNA, and is involved in nonhomologous end joining. HDF1 and HDF2, which have been identified in Saccharomyces cerevisiae as homologues of the Ku70 and Ku80 proteins of mammals, reduce radiosensitivity only when homologous recombination repair is impaired and, therefore, affect DSB repair via nonhomologous recombination. Although it has been reported that homologous recombination is defective in the hdf1 null mutant, the roles of HDF1 and HDF2 in this process are not completely clear. We investigated the effect of HDF1 and HDF2 on intrachromosomal recombination by measuring rates of deletion between direct repeats caused by spontaneous and DNA damage-induced events (DEL recombination). We found a decrease in spontaneous DEL recombination in both TCY5 (hdf1delta) and TCY6 (hdf2delta) strains, suggesting that HDF1 and HDF2 play a role in homologous recombination. As DEL recombination events may occur by sister chromatid conversion and/or single-strand annealing, which is initiated by DSBs, HDF1 and HDF2 may be required to recruit proteins to the damaged ends so as to promote single-strand annealing. The strains TCY5 and TCY6 are also defective in methylmethane sulfonate (MMS)- and X-ray-induced, but not in UV-induced DEL recombination. This confirms that HDF1 and HDF2 are required for the completion of DEL recombination by single strand annealing.

MeSH terms

  • Antigens, Nuclear*
  • Chromosomes, Fungal
  • DNA / drug effects
  • DNA / genetics
  • DNA / radiation effects
  • DNA Damage / drug effects
  • DNA Damage / genetics*
  • DNA Damage / radiation effects
  • DNA Helicases*
  • DNA Repair / drug effects
  • DNA Repair / genetics
  • DNA Repair / radiation effects
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Ku Autoantigen
  • Methyl Methanesulfonate / toxicity
  • Mutagens / toxicity
  • Mutation
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Recombination, Genetic*
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / radiation effects
  • Saccharomyces cerevisiae Proteins*
  • X-Rays


  • Antigens, Nuclear
  • DNA-Binding Proteins
  • Mutagens
  • Nuclear Proteins
  • Saccharomyces cerevisiae Proteins
  • YKU70 protein, S cerevisiae
  • YKU80 protein, S cerevisiae
  • high affinity DNA-binding factor, S cerevisiae
  • DNA
  • Methyl Methanesulfonate
  • DNA Helicases
  • XRCC5 protein, human
  • Xrcc6 protein, human
  • Ku Autoantigen