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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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Related in: MedlinePlus

Tankyrase 1 depletion leads to DNA damage and a senescence-like phenotype in normal human BJ fibroblast cells. (A) Immunoblot analysis of cell extracts from BJ or BJ + TERT cells harvested 48 h after infection with GFP or TNKS1 lentiviral shRNA. (B) Quantification of DNA damage foci. Cells with >10 foci that costained with 53BP1 and γ-H2AX were scored. Approximately 1,000 cells were scored for each sample. (C) Quantification of SA β-galactosidase–positive cells. Approximately 500 cells were scored for each sample. (D) Quantification of BrdU-positive cells. Approximately 1,000 cells were scored for each sample.
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fig2: Tankyrase 1 depletion leads to DNA damage and a senescence-like phenotype in normal human BJ fibroblast cells. (A) Immunoblot analysis of cell extracts from BJ or BJ + TERT cells harvested 48 h after infection with GFP or TNKS1 lentiviral shRNA. (B) Quantification of DNA damage foci. Cells with >10 foci that costained with 53BP1 and γ-H2AX were scored. Approximately 1,000 cells were scored for each sample. (C) Quantification of SA β-galactosidase–positive cells. Approximately 500 cells were scored for each sample. (D) Quantification of BrdU-positive cells. Approximately 1,000 cells were scored for each sample.

Mentions: To determine whether tankyrase 1 had a similar effect in normal human cells, primary human BJ fibroblasts or BJ cells immortalized with human telomerase reverse transcriptase (TERT; BJ + TERT) were infected with GFP or tankyrase 1 shRNA lentivirus. Immunoblot analysis shows efficient depletion of tankyrase 1 protein (Fig. 2 A). Depletion of tankyrase 1 in BJ or BJ + TERT cells led to induction of DNA damage foci (Fig. 2 B), an increase in SA β-galactosidase–positive cells (Fig. 2 C), and a concomitant decrease in BrdU incorporation (Fig. 2 D), which are consistent with DNA damage response and senescence-like G1 arrest.


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

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

Tankyrase 1 depletion leads to DNA damage and a senescence-like phenotype in normal human BJ fibroblast cells. (A) Immunoblot analysis of cell extracts from BJ or BJ + TERT cells harvested 48 h after infection with GFP or TNKS1 lentiviral shRNA. (B) Quantification of DNA damage foci. Cells with >10 foci that costained with 53BP1 and γ-H2AX were scored. Approximately 1,000 cells were scored for each sample. (C) Quantification of SA β-galactosidase–positive cells. Approximately 500 cells were scored for each sample. (D) Quantification of BrdU-positive cells. Approximately 1,000 cells were scored for each sample.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig2: Tankyrase 1 depletion leads to DNA damage and a senescence-like phenotype in normal human BJ fibroblast cells. (A) Immunoblot analysis of cell extracts from BJ or BJ + TERT cells harvested 48 h after infection with GFP or TNKS1 lentiviral shRNA. (B) Quantification of DNA damage foci. Cells with >10 foci that costained with 53BP1 and γ-H2AX were scored. Approximately 1,000 cells were scored for each sample. (C) Quantification of SA β-galactosidase–positive cells. Approximately 500 cells were scored for each sample. (D) Quantification of BrdU-positive cells. Approximately 1,000 cells were scored for each sample.
Mentions: To determine whether tankyrase 1 had a similar effect in normal human cells, primary human BJ fibroblasts or BJ cells immortalized with human telomerase reverse transcriptase (TERT; BJ + TERT) were infected with GFP or tankyrase 1 shRNA lentivirus. Immunoblot analysis shows efficient depletion of tankyrase 1 protein (Fig. 2 A). Depletion of tankyrase 1 in BJ or BJ + TERT cells led to induction of DNA damage foci (Fig. 2 B), an increase in SA β-galactosidase–positive cells (Fig. 2 C), and a concomitant decrease in BrdU incorporation (Fig. 2 D), which are consistent with DNA damage response and senescence-like G1 arrest.

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