Molecular analysis of telomere fusions in Arabidopsis: multiple pathways for chromosome end-joining.
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.
Heacock
Michelle
M
Department of Biochemistry and Biophysics, Texas A&M University, TAMU, College Station, TX 77843-2128, USA.
Spangler
Elizabeth
E
Riha
Karel
K
Puizina
Jasna
J
Shippen
Dorothy E
DE
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D020134:Catalytic Domain; D032461:Chromosomes, Plant; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000076228:MRE11 Homologue Protein; D009154:Mutation; D019098:Telomerase / Q000737:chemistry; D016615:Telomere
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C463462:KU70 protein, Arabidopsis; C492900:Mre11 protein, Arabidopsis; D019098:Telomerase; D000076228:MRE11 Homologue Protein