Synergistic decrease of DNA single-strand break repair rates in mouse neural cells lacking both Tdp1 and aprataxin

El-Khamisy, Sherif F, Katyal, Sachin, Patel, Poorvi, Ju, Limei, McKinnon, Peter J and Caldecott, Keith W (2009) Synergistic decrease of DNA single-strand break repair rates in mouse neural cells lacking both Tdp1 and aprataxin. DNA Repair, 8 (6). pp. 760-766. ISSN 1568-7864

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Ataxia oculomotor apraxia-1 (AOA1) is an autosomal recessive neurodegenerative disease that results from mutations of aprataxin (APTX). APTX associates with the DNA single- and double-strand break repair machinery and is able to remove AMP from 5'-termini at DNA strand breaks in vitro. However, attempts to establish a DNA strand break repair defect in APTX-defective cells have proved conflicting and unclear. We reasoned that this may reflect that DNA strand breaks with 5'-AMP represent only a minor subset of breaks induced in cells, and/or the availability of alternative mechanisms for removing AMP from 5'-termini. Here, we have attempted to increase the dependency of chromosomal single- and double-strand break repair on aprataxin activity by slowing the rate of repair of 3'-termini in aprataxin-defective neural cells, thereby increasing the likelihood that the T-termini at such breaks become adenylated and/or block alternative repair mechanisms. To do this, we generated a mouse model in which APTX is deleted together with tyrosyl DNA phosphodiesterase (TDP1), an enzyme that repairs T-termini at a subset of single-strand breaks (SSBs), including those with 3'-topoisomerase-1 (Top1) peptide. Notably, the global rate of repair of oxidative and alkylation-induced SSBs was significantly slower in Tdp1(-/-)/Aptx(-/-) double knockout quiescent mouse astrocytes compared with Tdp1(-/-) or Aptx(-/-) single knockouts. In contrast, camptothecin-induced Top1-SSBs accumulated to similar levels in Tdp1(-/-) and Tdp1(-/-)/Aptx(-/-) double knockout astrocytes. Finally, we failed to identify a measurable defect in double-strand break repair in Tdp1(-/-),Aptx(-/-) or Tdp1(-/-)/Aptx(-/-) astrocytes. These data provide direct evidence for a requirement for aprataxin during chromosomal single-strand break repair in primary neural cells lacking Tdp1. (C) 2009 Elsevier B.V. All rights reserved.

Item Type: Article
Schools and Departments: School of Life Sciences > Sussex Centre for Genome Damage and Stability
Subjects: Q Science
Depositing User: Sherif El-Khamisy
Date Deposited: 06 Feb 2012 21:21
Last Modified: 09 Oct 2012 13:04
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