BACKGROUND: Telomeres, as elaborate nucleo-protein complexes, ensure chromosomal stability. When impaired, the ends of linear chromosomes can be recognised by cellular repair mechanisms as double-strand DNA breaks and can be healed by non-homologous-end-joining activities to produce dicentric chromosomes. During cell divisions, particularly during anaphase, dicentrics can break, thus producing naked chromosome tips susceptible to additional unwanted chromosome fusion. Many telomere-building protein complexes are associated with telomeres to ensure their proper capping function. It has been found however, that a number of repair complexes also contribute to telomere stability. RESULTS: We used Arabidopsis thaliana to study the possible functions of the DNA repair subunit, NBS1, in telomere homeostasis using knockout nbs1 mutants. The results showed that although NBS1-deficient plants were viable, lacked any sign of developmental aberration and produced fertile seeds through many generations upon self-fertilisation, plants also missing the functional telomerase (double mutants), rapidly, within three generations, displayed severe developmental defects. Cytogenetic inspection of cycling somatic cells revealed a very early onset of massive genome instability. Molecular methods used for examining the length of telomeres in double homozygous mutants detected much faster telomere shortening than in plants deficient in telomerase gene alone. CONCLUSIONS: Our findings suggest that NBS1 acts in concert with telomerase and plays a profound role in plant telomere renewal.

Department of Plant Developmental Genetics Institute of Biophysics of the Czech Academy of Sciences Brno Czech Republic

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de Lange T. Shelterin: the protein complex that shapes and safeguards human telomeres. Gene Dev. 2005;19:2100–2110. doi: 10.1101/gad.1346005. PubMed DOI

Blackburn EH. Telomeres and telomerase: their mechanisms of action and the effects of altering their functions. FEBS Lett. 2005;5579:859–862. PubMed

Verdun RE, Karlseder J. Replication and protection of telomeres. Nature. 2007;447:924–931. doi: 10.1038/nature05976. PubMed DOI

Palm W, de Lange T. How Shelterin Protects Mammalian Telomeres. Annu Rev Genet. 2008;42:301–334. doi: 10.1146/annurev.genet.41.110306.130350. PubMed DOI

Watson JM, Riha K. Comparative biology of telomeres: Where plants stand. FEBS Lett. 2010;584:3752–3759. doi: 10.1016/j.febslet.2010.06.017. PubMed DOI PMC

Lamarche BJ, Orazio NI, Weitzman MD. The MRN complex in double-strand break repair and telomere maintenance. FEBS Lett. 2010;584:3682–3695. doi: 10.1016/j.febslet.2010.07.029. PubMed DOI PMC

Stacker TH, Petrini JHJ. The MRE11 complex: starting from the ends. Nat Rev Mol Cell Bio. 2011;12:90–103. doi: 10.1038/nrm3047. PubMed DOI PMC

Hopfner KP, Craig L, Moncalian G, Zinkel RA, Usui T, Owen BA, Karcher A, Henderson B, Bodmer JL, McMurray CT, Carney JP, Petrini JH, Tainer JA. The Rad50 zinc-hook is a structure joining Mre11 complexes in DNA recombination and repair. Nature. 2002;418:562–566. doi: 10.1038/nature00922. PubMed DOI

Amiard S, Charbonnel C, Allain E, Depeiges A, White CI, Gallego ME. Distinct Roles of the ATR Kinase and the Mre11-Rad50-Nbs1 Complex in the Maintenance of Chromosomal Stability in Arabidopsis. Plant Cell. 2010;22:3020–3033. doi: 10.1105/tpc.110.078527. PubMed DOI PMC

Ueno M, Nakazaki T, Akamatsu Y, Watanabe K, Tomita K, Lindsay HD, Shinagawa H, Iwasaki H. Molecular Characterization of the Schizosaccharomyces pombe nbs1+ Gene Involved in DNA Repair and Telomere Maintenance. Mol Cell Biol. 2003;23:6553–6563. doi: 10.1128/MCB.23.18.6553-6563.2003. PubMed DOI PMC

Zhang Y, Zhou J, Lim CUK. The role of NBS1 in DNA double strand break repair, telomere stability, and cell cycle checkpoint control. Cell Res. 2006;16:45–54. doi: 10.1038/sj.cr.7310007. PubMed DOI

Zhu J, Petersen S, Tessarollo L, Nussenzweig A. Targeted disruption of the Nijmegen breakage syndrome gene NBS1 leads to early embryonic lethality in mice. Curr Biol. 2001;11:105–109. doi: 10.1016/S0960-9822(01)00019-7. PubMed DOI

Wu G, Lee W-H, Chen P-L. NBS1 and TRF1 Colocalize at Promyelocytic Leukemia Bodies during Late S/G2 Phases in Immortalized Telomerase-negative Cells. J Biol Chem. 2000;275:30618–30622. PubMed

Zhu XD, Kuster B, Mann M, Petrini JH, de Lange T. Cell-cycle-regulated association of RAD50/MRE11/NBS1 with TRF2 and human telomeres. Nat Genet. 2000;25:347–352. doi: 10.1038/77139. PubMed DOI

Dimitrova N, de Lange T. Cell Cycle-Dependent Role of MRN at Dysfunctional Telomeres: ATM Signaling-Dependent Induction of Nonhomologous End Joining (NHEJ) in G1 and Resection-Mediated Inhibition of NHEJ in G2. Mol Cell Biol. 2009;29:5552–5563. doi: 10.1128/MCB.00476-09. PubMed DOI PMC

Zellinger B, Riha K. Composition of plant telomeres. Biochim Biophys Acta. 2007;1769:399–409. doi: 10.1016/j.bbaexp.2007.02.001. PubMed DOI

Siroky J. Cytogenetics for the study of telomere function in plants. Cytogenet Genome Res. 2008;122:374–379. doi: 10.1159/000167825. PubMed DOI

Bleuyard J-Y, Gallego ME, White CI. Meiotic defects in the Arabidopsis rad50 mutant point to conservation of the MRX komplex function in early stages of meiotic recombination. Chromosoma. 2004;113:197–203. PubMed

Vannier JB, Depeiges A, White C, Gallego ME. Two roles for Rad50 in telomere maintenance. EMBO J. 2006;25:4577–4585. doi: 10.1038/sj.emboj.7601345. PubMed DOI PMC

Puizina J, Siroky J, Mokros P, Schweizer D, Riha K. Mre11 deficiency in Arabidopsis is associated with chromosomal instability in somatic cells and Spo11-dependent genome fragmentation during meiosis. Plant Cell. 2004;16:1968–1978. doi: 10.1105/tpc.104.022749. PubMed DOI PMC

Heacock M, Spangler E, Riha K, Puizina J, Shippen DE. Molecular analysis of telomere fusions in Arabidopsis. multiple pathways for chromosome end-joining. EMBO J. 2004;23:2304–2313. doi: 10.1038/sj.emboj.7600236. PubMed DOI PMC

Akutsu N, Iijima K, Hinata T, Tauchi H. Characterization of the plant homolog of Nijmegen breakage syndrome 1: Involvement in DNA repair and recombination. Biochem Biophys Res Co. 2007;353:394–398. doi: 10.1016/j.bbrc.2006.12.030. PubMed DOI

Waterworth WM, Altun C, Armstrong SJ, Roberts N, Dean PJ, Young K, Weil CF, Bray CM, West CE. NBS1 is involved in DNA repair and plays a synergistic role with ATM in mediating meiotic homologous recombination in plants. Plant J. 2007;52:41–52. doi: 10.1111/j.1365-313X.2007.03220.x. PubMed DOI

Riha K, McKnight TD, Griffing LR, Shippen DE. Living with genome instability: plant responses to telomere dysfunction. Science. 2001;291:1797–1800. doi: 10.1126/science.1057110. PubMed DOI

Newcombe RG. Two-Sided Confidence Intervals for the Single Proportion: Comparison of Seven Methods. Stat Med. 1998;17:857–872. doi: 10.1002/(SICI)1097-0258(19980430)17:8<857::AID-SIM777>3.0.CO;2-E. PubMed DOI

Mokros P, Vrbsky J, Siroky J. Identification of chromosomal fusion sites in Arabidopsis mutants using sequential bicolour BAC-FISH. Genome. 2006;49:1036–1042. doi: 10.1139/G06-082. PubMed DOI

Gallego ME, White CI. DNA repair and recombination functions in Arabidopsis telomere maintenance. Chromosome Res. 2005;13:481–491. doi: 10.1007/s10577-005-0995-4. PubMed DOI

Bundock P, Hooykaas P. Severe developmental defects, hypersensitivity to DNA-damaging agents, and lengthened telomeres in Arabidopsis MRE11 mutants. Plant Cell. 2002;14:2451–2462. doi: 10.1105/tpc.005959. PubMed DOI PMC

Gallego ME, White CI. RAD50 function is essential for telomere maintenance in Arabidopsis. P Natl Acad Sci USA. 2001;98:1711–1716. doi: 10.1073/pnas.98.4.1711. PubMed DOI PMC

Gallego ME, Jeanneau M, Granier F, Bouchej D, Bechtold N, White CI. Disruption of the Arabidopsis RAD50 gene leads to plant sterility and MMS sensitivity. Plant J. 2001;25:31–41. doi: 10.1046/j.1365-313x.2001.00928.x. PubMed DOI

Fitzgerald MS, Riha K, Gao F, Ren SX, McKnight TD, Shippen DE. Disruption of the telomerase catalytic subunit gene from Arabidopsis inactivates telomerase and leads to a slow loss of telomeric DNA. P Natl Acad Sci USA. 1999;96:14813–14818. doi: 10.1073/pnas.96.26.14813. PubMed DOI PMC

Siroky J, Zluvova J, Riha K, Shippen DE, Vyskot B. Rearrangements of ribosomal DNA clusters in late generation telomerase-deficient Arabidopsis. Chromosoma. 2003;112:116–123. doi: 10.1007/s00412-003-0251-7. PubMed DOI

Vespa L, Ross T, Warrington RT, Mokros P, Siroky J, Shippen DE. ATM regulates the length of individual telomere tracts in Arabidopsis. P Natl Acad Sci USA. 2007;104:18145–18150. doi: 10.1073/pnas.0704466104. PubMed DOI PMC

Ranganathan V, Heine WF, Ciccone DN, Rudolph KL, Wu X, Chang S, Hai H, Ahearn IM, Livingston DM, Resnick I, Rosen F, Seemanova E, Jarolim P, DePinho RA, Weaver DT. Rescue of a telomere length defect of Nijmegen breakage syndrome cells requires NBS and telomerase catalytic subunit. Curr Biol. 2001;11:962–966. doi: 10.1016/S0960-9822(01)00267-6. PubMed DOI

Lim DS, Kim ST, Xu B, Maser RS, Lin J, Petrini JH, Kastan MB. ATM phosphorylates p95/nbs1 in an S-phase checkpoint pathway. Nature. 2000;404:613–617. doi: 10.1038/35007091. PubMed DOI

Lee JH, Paull TT. ATM activation by DNA double-strand breaks through the Mre11-Rad50-Nbs1 complex. Science. 2005;308:551–554. doi: 10.1126/science.1108297. PubMed DOI

Williams GJ, Lees-Miller SP, Tainer JA. Mre11–Rad50–Nbs1 conformations and the control of sensing, signaling, and effector responses at DNA double-strand breaks. DNA Repair. 2010;9:1299–1306. doi: 10.1016/j.dnarep.2010.10.001. PubMed DOI PMC

Rosso MG, Li Y, Strizhov N, Reiss B, Dekker K, Weisshaar B. An Arabidopsis thaliana T-DNA mutagenized population (GABI-Kat) for flanking sequence tag-based reverse genetics. Plant Mol Biol. 2003;53:247–259. PubMed

Dellaporta SL, Wood J, Hicks JB. A plant DNA minipreparation. Version II. Plant Mol Biol Rep. 1983;1:19–21. doi: 10.1007/BF02712670. DOI

Watson JM, Shippen DE. Telomere rapid deletion regulates telomere length in Arabidopsis thaliana. Mol Cell Biol. 2007;27:1706–1715. doi: 10.1128/MCB.02059-06. PubMed DOI PMC

Kiss T, Kiss M, Solymosy F. Nucleotide sequence of a 25S rRNA gene from tomato. Nucleic Acids Res. 1989;17:796. doi: 10.1093/nar/17.2.796. PubMed DOI PMC

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