Telomere stability and development of ctc1 mutants are rescued by inhibition of EJ recombination pathways in a telomerase-dependent manner

Nucleic Acids Res. 2014 Oct 29;42(19):11979-91. doi: 10.1093/nar/gku897. Epub 2014 Oct 1.


The telomeres of linear eukaryotic chromosomes are protected by caps consisting of evolutionarily conserved nucleoprotein complexes. Telomere dysfunction leads to recombination of chromosome ends and this can result in fusions which initiate chromosomal breakage-fusion-bridge cycles, causing genomic instability and potentially cell death or cancer. We hypothesize that in the absence of the recombination pathways implicated in these fusions, deprotected chromosome ends will instead be eroded by nucleases, also leading to the loss of genes and cell death. In this work, we set out to specifically test this hypothesis in the plant, Arabidopsis. Telomere protection in Arabidopsis implicates KU and CST and their absence leads to chromosome fusions, severe genomic instability and dramatic developmental defects. We have analysed the involvement of end-joining recombination pathways in telomere fusions and the consequences of this on genomic instability and growth. Strikingly, the absence of the multiple end-joining pathways eliminates chromosome fusion and restores normal growth and development to cst ku80 mutant plants. It is thus the chromosomal fusions, per se, which are the underlying cause of the severe developmental defects. This rescue is mediated by telomerase-dependent telomere extension, revealing a competition between telomerase and end-joining recombination proteins for access to deprotected telomeres.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / physiology*
  • DNA End-Joining Repair*
  • DNA Helicases / genetics
  • DNA Repair
  • Mutation
  • Recombination, Genetic*
  • Repetitive Sequences, Nucleic Acid
  • Telomerase / genetics
  • Telomerase / physiology*
  • Telomere / chemistry
  • Telomere Homeostasis*
  • Telomere Shortening
  • Telomere-Binding Proteins / genetics*


  • Arabidopsis Proteins
  • CTC1 protein, Arabidopsis
  • Telomere-Binding Proteins
  • TERT protein, Arabidopsis
  • Telomerase
  • DNA Helicases
  • Ku80 protein, Arabidopsis