Molecular analysis of telomere fusions in Arabidopsis: multiple pathways for chromosome end-joining

• Published in: The EMBO journal 2004-06, Vol.23 (11), p.2304-2313
• Main Authors: Heacock, M, Spangler, E, Riha, K, Puizina, J, Shippen, D.E
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Catalytic Domain; chromosome fusion; Chromosomes, Plant; cytogenetics; Deoxyribonucleic acid; DNA; DNA Repair; DNA-binding proteins; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; EMBO13; EMBO30; enzyme activity; exodeoxyribonucleases; Ku70; length; Monitoring methods; Mre11; MRE11 Homologue Protein; Mre11 protein; Mutants; Mutation; NHEJ; nonhomologous end-joining; nucleotide sequences; polymerase chain reaction; telomerase; Telomerase - chemistry; Telomere; telomeres
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7600236

End‐to‐end fusion of critically shortened telomeres in higher eucaryotes is presumed to be mediated by nonhomologous end‐joining (NHEJ). Here we describe two PCR‐based methods to monitor telomere length and examine the fate of dysfunctional telomeres in Arabidopsis lacking the catalytic subunit of telomerase (TERT) and the DNA repair proteins Ku70 and Mre11. Primer extension telomere repeat amplification relies on the presence of an intact G‐overhang, and thus measures functional telomere length. The minimum functional telomere length detected was 300–400 bp. PCR amplification and sequence analysis of chromosome fusion junctions revealed exonucleolytic digestion of dysfunctional ends prior to fusion. In ku70 tert mutants, there was a greater incidence of microhomology at the fusion junction than in tert mutants. In triple ku70 tert mre11 mutants, chromosome fusions were still detected, but microhomology at the junction was no longer favored. These data indicate that both Ku70 and Mre11 contribute to fusion of critically shortened telomeres in higher eucaryotes. Furthermore, Arabidopsis processes critically shortened telomeres as double‐strand breaks, using a variety of end‐joining pathways.