title: Identification of Ku70 and Ku80 homologues in Arabidopsis thaliana: evidence for a role in the repair of DNA double-strand breaks.
abstract: In higher organisms such as mammals and plants, DNA double-strand breaks (DSBs) are repaired preferentially by non-homologous end joining (NHEJ) rather than by homologous recombination. The NHEJ pathway is mediated by Ku, a heterodimer of approximately 70 and 80 kDa subunits, which contributes to various aspects of the metabolism of DNA ends in eukaryotic cells. On the basis of their predicted sequence similarity to human Ku70 and Ku80, cDNAs encoding the first plant homologues of these proteins (AtKu70 and AtKu80, respectively) have now been isolated from Arabidopsis thaliana. AtKu70 and AtKu80 share 28.6 and 22.5% amino acid sequence identity with human Ku70 and Ku80, respectively. Yeast two-hybrid analysis demonstrated that AtKu70 and AtKu80 form a heterodimer, and electrophoretic mobility-shift assays revealed that this heterodimer binds to double-stranded telomeric and non-telomeric DNA sequences, but not to single-stranded DNA. The AtKu heterodimer also possesses single-stranded DNA-dependent ATPase and ATP-dependent DNA helicase activities. Reverse transcription and the polymerase chain reaction revealed that AtKu70 and AtKu80 genes are expressed widely but at low levels in plant tissues. The expression of these two genes in cultured cells was markedly increased in response to the generation of DSBs by bleomycin or methylmethane sulfonate. These results suggest that the evolutionarily conserved Ku70-Ku80 heterodimer functions in DSB repair by the NHEJ pathway in A. thaliana.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Tamura
authors.forename: Yugo
authors.initials: Y
authors.lastname: Adachi
authors.forename: Keiko
authors.initials: K
authors.lastname: Chiba
authors.forename: Keiko
authors.initials: K
authors.lastname: Oguchi
authors.forename: Hideo
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001761:Bleomycin / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics* / Q000502:physiology; D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008969:Molecular Sequence Data; D010802:Phylogeny; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C463462:KU70 protein, Arabidopsis; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D001761:Bleomycin; D049452:Green Fluorescent Proteins; D008741:Methyl Methanesulfonate; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C469228:Ku80 protein, Arabidopsis