Identification of Ku70 and Ku80 homologues in Arabidopsis thaliana: evidence for a role in the repair of DNA double-strand breaks
Article first published online: 26 MAR 2002
The Plant Journal
Volume 29, Issue 6, pages 771–781, March 2002
How to Cite
Tamura, K., Adachi, Y., Chiba, K., Oguchi, K. and Takahashi, H. (2002), Identification of Ku70 and Ku80 homologues in Arabidopsis thaliana: evidence for a role in the repair of DNA double-strand breaks. The Plant Journal, 29: 771–781. doi: 10.1046/j.1365-313X.2002.01258.x
- Issue published online: 26 MAR 2002
- Article first published online: 26 MAR 2002
- Received 6 November 2001; revised 7 December 2001; accepted 20 December 2001.
- DNA repair;
- Arabidopsis thaliana
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 ≈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.