A double-strand break repair defect in ATM-deficient cells contributes to radiosensitivity

Kuhne, M., Riballo, E., Rief, N., Rothkamm, K., Jeggo, P. A. and Lobrich, M. (2004) A double-strand break repair defect in ATM-deficient cells contributes to radiosensitivity. Cancer Research, 64 (2). pp. 500-508. ISSN 0008-5472

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Abstract

The ATM protein, which is mutated in individuals with ataxia telangiectasia (AT), is central to cell cycle checkpoint responses initiated by DNA double-strand breaks (DSBs). ATM's role in DSB repair is currently unclear as is the basis underlying the radiosensitivity of AT cells. We applied immunofluorescence detection of gamma-H2AX nuclear foci and pulsed-field gel electrophoresis to quantify the repair of DSBs after X-ray doses between 0.02 and 80 Gy in confluence-arrested primary human fibroblasts from normal individuals and patients with mutations in ATM and DNA ligase IV, a core component of the nonhomologous end-joining (NHEJ) repair pathway. Cells with hypomorphic mutations in DNA ligase IV exhibit a substantial repair defect up to 24 h after treatment but continue to repair for several days and finally reach a level of unrepaired DSBs similar to that of wild-type cells. Additionally, the repair defect in NHEJ mutants is dose dependent. ATM-deficient cells, in contrast, repair the majority of DSBs with normal kinetics but fail to repair a subset of breaks, irrespective of the initial number of lesions induced. Significantly, after biologically relevant radiation doses and/or long repair times, the repair defect in AT cells is more pronounced than that of NHEJ mutants and correlates with radiosensitivity. NHEJ-defective cells analyzed for survival following delayed plating after irradiation show substantial recovery while AT cells fail to show any recovery. These data argue that the DSB repair defect underlies a significant component of the radiosensitivity of AT cells.

Item Type: Article
Additional Information: GDSC82
Depositing User: Gee Wheatley
Date Deposited: 20 Mar 2007
Last Modified: 12 Jun 2012 14:29
URI: http://sro.sussex.ac.uk/id/eprint/979
Google Scholar:204 Citations
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