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Sister telomeres rendered dysfunctional by persistent cohesion are fused by NHEJ.

Hsiao SJ, Smith S - J. Cell Biol. (2009)

Bottom Line: Holtgreve-Grez, A.Curr.These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle.

View Article: PubMed Central - PubMed

Affiliation: Molecular Pathogenesis Program, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA.

ABSTRACT
Telomeres protect chromosome ends from being viewed as double-strand breaks and from eliciting a DNA damage response. Deprotection of chromosome ends occurs when telomeres become critically short because of replicative attrition or inhibition of TRF2. In this study, we report a novel form of deprotection that occurs exclusively after DNA replication in S/G2 phase of the cell cycle. In cells deficient in the telomeric poly(adenosine diphosphate ribose) polymerase tankyrase 1, sister telomere resolution is blocked. Unexpectedly, cohered sister telomeres become deprotected and are inappropriately fused. In contrast to telomeres rendered dysfunctional by TRF2, which engage in chromatid fusions predominantly between chromatids from different chromosomes (Bailey, S.M., M.N. Cornforth, A. Kurimasa, D.J. Chen, and E.H. Goodwin. 2001. Science. 293:2462-2465; Smogorzewska, A., J. Karlseder, H. Holtgreve-Grez, A. Jauch, and T. de Lange. 2002. Curr. Biol. 12:1635-1644), telomeres rendered dysfunctional by tankyrase 1 engage in chromatid fusions almost exclusively between sister chromatids. We show that cohered sister telomeres are fused by DNA ligase IV-mediated nonhomologous end joining. These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle.

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Tankyrase 1 depletion leads to sister chromatid fusions in multiple cell lines. (A–D) Quantification of the frequency of sister chromatid fusions in BJ (A) and BJ + TERT (B) cells analyzed 48 h after infection with GFP or TNKS1 lentivirus shRNA and in HeLa (C) and HTC75 (D) cells analyzed after 16-h transient transfection with GFP or TNKS1 siRNA. Colcemid was added for 12 h, and cells were collected by trypsinization, swollen in hypotonic buffer, and fixed in methanol/acetic acid. Metaphase spreads were analyzed by telomeric PNA FISH. Approximately 50 metaphase spreads were analyzed for each sample (Table I, experiments 3–6). (E) Schematic diagram showing the phenotypes of the four different human cell lines in response to tankyrase 1 depletion.
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fig5: Tankyrase 1 depletion leads to sister chromatid fusions in multiple cell lines. (A–D) Quantification of the frequency of sister chromatid fusions in BJ (A) and BJ + TERT (B) cells analyzed 48 h after infection with GFP or TNKS1 lentivirus shRNA and in HeLa (C) and HTC75 (D) cells analyzed after 16-h transient transfection with GFP or TNKS1 siRNA. Colcemid was added for 12 h, and cells were collected by trypsinization, swollen in hypotonic buffer, and fixed in methanol/acetic acid. Metaphase spreads were analyzed by telomeric PNA FISH. Approximately 50 metaphase spreads were analyzed for each sample (Table I, experiments 3–6). (E) Schematic diagram showing the phenotypes of the four different human cell lines in response to tankyrase 1 depletion.

Mentions: The preponderance of sister chromatid fusions uniquely in tankyrase 1–depleted HTC75 cells raised the possibility that these fusions were the direct result of the persistent sister telomere cohesion observed in these cells. Thus, we asked whether the other human cell lines (BJ, BJ + TERT, and HeLa) that showed persistent sister telomere cohesion also had sister telomere fusions. BJ and BJ + TERT cells were infected with GFP or tankyrase 1 shRNA lentivirus and subjected to metaphase spread analysis with a PNA FISH telomere repeat probe. As shown in Fig. 5 (A and B), we observed a modest but clear increase in sister telomere fusions in tankyrase 1–depleted BJ and BJ + TERT cells (Table I, experiments 3 and 4, respectively).


Sister telomeres rendered dysfunctional by persistent cohesion are fused by NHEJ.

Hsiao SJ, Smith S - J. Cell Biol. (2009)

Tankyrase 1 depletion leads to sister chromatid fusions in multiple cell lines. (A–D) Quantification of the frequency of sister chromatid fusions in BJ (A) and BJ + TERT (B) cells analyzed 48 h after infection with GFP or TNKS1 lentivirus shRNA and in HeLa (C) and HTC75 (D) cells analyzed after 16-h transient transfection with GFP or TNKS1 siRNA. Colcemid was added for 12 h, and cells were collected by trypsinization, swollen in hypotonic buffer, and fixed in methanol/acetic acid. Metaphase spreads were analyzed by telomeric PNA FISH. Approximately 50 metaphase spreads were analyzed for each sample (Table I, experiments 3–6). (E) Schematic diagram showing the phenotypes of the four different human cell lines in response to tankyrase 1 depletion.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2654126&req=5

fig5: Tankyrase 1 depletion leads to sister chromatid fusions in multiple cell lines. (A–D) Quantification of the frequency of sister chromatid fusions in BJ (A) and BJ + TERT (B) cells analyzed 48 h after infection with GFP or TNKS1 lentivirus shRNA and in HeLa (C) and HTC75 (D) cells analyzed after 16-h transient transfection with GFP or TNKS1 siRNA. Colcemid was added for 12 h, and cells were collected by trypsinization, swollen in hypotonic buffer, and fixed in methanol/acetic acid. Metaphase spreads were analyzed by telomeric PNA FISH. Approximately 50 metaphase spreads were analyzed for each sample (Table I, experiments 3–6). (E) Schematic diagram showing the phenotypes of the four different human cell lines in response to tankyrase 1 depletion.
Mentions: The preponderance of sister chromatid fusions uniquely in tankyrase 1–depleted HTC75 cells raised the possibility that these fusions were the direct result of the persistent sister telomere cohesion observed in these cells. Thus, we asked whether the other human cell lines (BJ, BJ + TERT, and HeLa) that showed persistent sister telomere cohesion also had sister telomere fusions. BJ and BJ + TERT cells were infected with GFP or tankyrase 1 shRNA lentivirus and subjected to metaphase spread analysis with a PNA FISH telomere repeat probe. As shown in Fig. 5 (A and B), we observed a modest but clear increase in sister telomere fusions in tankyrase 1–depleted BJ and BJ + TERT cells (Table I, experiments 3 and 4, respectively).

Bottom Line: Holtgreve-Grez, A.Curr.These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle.

View Article: PubMed Central - PubMed

Affiliation: Molecular Pathogenesis Program, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA.

ABSTRACT
Telomeres protect chromosome ends from being viewed as double-strand breaks and from eliciting a DNA damage response. Deprotection of chromosome ends occurs when telomeres become critically short because of replicative attrition or inhibition of TRF2. In this study, we report a novel form of deprotection that occurs exclusively after DNA replication in S/G2 phase of the cell cycle. In cells deficient in the telomeric poly(adenosine diphosphate ribose) polymerase tankyrase 1, sister telomere resolution is blocked. Unexpectedly, cohered sister telomeres become deprotected and are inappropriately fused. In contrast to telomeres rendered dysfunctional by TRF2, which engage in chromatid fusions predominantly between chromatids from different chromosomes (Bailey, S.M., M.N. Cornforth, A. Kurimasa, D.J. Chen, and E.H. Goodwin. 2001. Science. 293:2462-2465; Smogorzewska, A., J. Karlseder, H. Holtgreve-Grez, A. Jauch, and T. de Lange. 2002. Curr. Biol. 12:1635-1644), telomeres rendered dysfunctional by tankyrase 1 engage in chromatid fusions almost exclusively between sister chromatids. We show that cohered sister telomeres are fused by DNA ligase IV-mediated nonhomologous end joining. These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle.

Show MeSH
Related in: MedlinePlus