The yeast Ku heterodimer is essential for protection of the telomere against nucleolytic and recombinational activities

Curr Biol. 1998 Jul 2;8(14):831-4. doi: 10.1016/s0960-9822(98)70325-2.


The Ku heterodimer, conserved in a wide range of eukaryotes, plays a multiplicity of roles in yeast. First, binding of Ku, which is composed of a 70 kDa (Hdf1p) and an 80 kDa (Hdf2p) subunit [1-3], to double-strand breaks promotes non-homologous end-to-end joining of DNA [3]. Second, Ku appears to participate in DNA replication, regulating both the number of rounds of replication permissible within the cell cycle and the structure of the initiation complex [3,4]. Furthermore, mutations in HDF1 or HDF2 rapidly reduce telomeric poly (TG1-3) tract size [1-3], hinting also at a possible telomeric function of Ku. We show here that the two subunits of the Ku heterodimer play a key role in maintaining the integrity of telomere structure. Mutations in either Ku subunit increased the single-strandedness of the telomere in a cell-cycle-independent fashion, unlike wild-type cells which form 3' poly(TG1-3) overhangs exclusively in late S phase [5]. In addition, mutations enhanced the instability of elongated telomeres to degradation and recombination. Both Ku subunits genetically interacted with the putative single-stranded telomere-binding protein Cdc13p. We propose that Ku protects the telomere against nucleases and recombinases.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antigens, Nuclear*
  • Base Sequence
  • Chromosomes, Fungal
  • Crosses, Genetic
  • Cyclin B / chemistry
  • Cyclin B / genetics
  • Cyclin B / metabolism
  • DNA Helicases*
  • DNA Replication
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Dimerization
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Heterozygote
  • Ku Autoantigen
  • Macromolecular Substances
  • Mutagenesis, Site-Directed
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism*
  • Oligodeoxyribonucleotides / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Recombination, Genetic*
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / physiology
  • Saccharomyces cerevisiae Proteins*
  • Telomere / genetics
  • Telomere / metabolism*
  • Telomere / ultrastructure
  • Transcription Factors / metabolism


  • Antigens, Nuclear
  • Cyclin B
  • DNA-Binding Proteins
  • Fungal Proteins
  • Macromolecular Substances
  • Nuclear Proteins
  • Oligodeoxyribonucleotides
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • YKU70 protein, S cerevisiae
  • YKU80 protein, S cerevisiae
  • high affinity DNA-binding factor, S cerevisiae
  • DNA Helicases
  • XRCC5 protein, human
  • Xrcc6 protein, human
  • Ku Autoantigen