Pathways of DNA double-strand break repair during the mammalian cell cycle.
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It is shown here that NHEJ-defective hamster cells (CHO mutant V3 cells) have strongly reduced repair in all cell cycle phases after 1 Gy of irradiation, and HR is particularly important in late S/G2, where both pathways contribute to repair and radioresistance.Abstract:
Little is known about the quantitative contributions of nonhomologous end joining (NHEJ) and homologous recombination (HR) to DNA double-strand break (DSB) repair in different cell cycle phases after physiologically relevant doses of ionizing radiation. Using immunofluorescence detection of -H2AX nuclear foci as a novel approach for monitoring the repair of DSBs, we show here that NHEJ-defective hamster cells (CHO mutant V3 cells) have strongly reduced repair in all cell cycle phases after 1 Gy of irradiation. In contrast, HR-defective CHO irs1SF cells have a minor repair defect in G1, greater impairment in S, and a substantial defect in late S/G2. Furthermore, the radiosensitivity of irs1SF cells is slight in G1 but dramatically higher in late S/G2, while V3 cells show high sensitivity throughout the cell cycle. These findings show that NHEJ is important in all cell cycle phases, while HR is particularly important in late S/G2, where both pathways contribute to repair and radioresistance. In contrast to DSBs produced by ionizing radiation, DSBs produced by the replication inhibitor aphidicolin are repaired entirely by HR. irs1SF, but not V3, cells show hypersensitivity to aphidicolin treatment. These data provide the first evaluation of the cell cycle-specific contributions of NHEJ and HR to the repair of radiation-induced versus replication-associated DSBs.read more
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Inhibition of homologous recombination by variants of the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs).
Erin Convery,Euy Kyun Shin,Qi Ding,Wei Wang,Pauline Douglas,Laurie S. Davis,Jac A. Nickoloff,Susan P. Lees-Miller,Katheryn Meek +8 more
TL;DR: Two conserved splice variants of a catalytic subunit of DNA-PK (DNA-PKcs) that are expressed predominately in nondividing cells are described that are able to inhibit repair by means of HR when sister chromatids are not available as templates for accurate repair with low risk of genome rearrangement.
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Homologous recombination protects mammalian cells from replication-associated DNA double-strand breaks arising in response to methyl methanesulfonate.
TL;DR: The data indicate that agents producing N-alkylpurines in the DNA induce replication-dependent DSBs and show that HR is the major pathway of protection of cells against DSB formation, killing and genotoxicity following S(N)2-alksylating agents.
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Human Rad51C Deficiency Destabilizes XRCC3, Impairs Recombination, and Radiosensitizes S/G2-phase Cells
TL;DR: Direct cellular evidence is provided for the function of human Rad51C in homologous recombinational repair by the use of RNA interference to deplete expression of Rad 51C protein in human HT1080 and HeLa cells.
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Direct involvement of retinoblastoma family proteins in DNA repair by non-homologous end-joining.
Rebecca S. Cook,Georgia Zoumpoulidou,Maciej T. Luczynski,Simone Rieger,Jayne Moquet,Victoria J. Spanswick,John A. Hartley,Kai Rothkamm,Paul H. Huang,Sibylle Mittnacht,Sibylle Mittnacht +10 more
TL;DR: It is reported that the retinoblastoma tumor suppressor protein (RB1) is required for DNA DSB repair by canonical non-homologous end-joining (cNHEJ).
ATM and Artemis promote homologous recombination of radiation-induced DNA double-strand breaks in G2 This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits distribution,andreproductioninanymedium,providedtheoriginalauthorandsourcearecredited.Thislicensedoesnot permit commercial exploitation without specific permission.
Andrea Beucher,Julie Birraux,Leopoldine Tchouandong,Olivia Barton,Atsushi Shibata,Sandro Conrad,Aaron A. Goodarzi,Andrea Krempler,Penny A. Jeggo,Markus Löbrich +9 more
TL;DR: In this paper, the authors show that in G2, NHEJ represents the major DSB-repair pathway whereas HR is only essential for repair of B15% of X- or c-ray-induced DSBs.
References
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TL;DR: The results offer direct visual confirmation that γ-H2AX forms en masse at chromosomal sites of DNA double-strand breaks and suggest the possible existence of units of higher order chromatin structure involved in monitoring DNA integrity.
Journal ArticleDOI
Evidence for a lack of DNA double-strand break repair in human cells exposed to very low x-ray doses
Kai Rothkamm,Markus Löbrich +1 more
TL;DR: Evidence is presented that foci of γ-H2AX (a phosphorylated histone), detected by immunofluorescence, are quantitatively the same as DSBs and are capable of quantifying the repair of individual D SBs, allowing the investigation of DSB repair after radiation doses as low as 1 mGy, an improvement by several orders of magnitude over current methods.
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