Carcinogenesis Advance Access published online on January 6, 2009
Carcinogenesis, doi:10.1093/carcin/bgp004
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The DNA repair protein NBS1 influences the base excision repair pathway
1 Institute of Radiation Biology, Helmholtz Centre Munich - German Research Centre for Environmental Health, Ingolstaedter Landstrasse 1, 85758 Neuherberg, Germany
2 Radiological Technology Department, Faculty of Allied Health Sciences, Naresuan University, 65000 Phitsanulok, Thailand
Corresponding author: Daniel Sagan, Radiological Technology Department, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok 65000, Thailand, Tel.: +66 55 26 10 00 ext. 62 79, Fax: +66 55 26 19 35, E-mail: daniel.sagan{at}helmholtz-muenchen.de
NBS1 fulfills important functions for the maintenance of genomic stability and cellular survival. Mutations in the NBS1 gene are responsible for the Nijmegen breakage syndrome (NBS) in humans. The symptoms of this disease and the phenotypes of NBS1 defective cells, especially their enhanced radiosensitivity, can be explained by an impaired DNA double strand break (DSB)-induced signaling and a disturbed repair of these DNA lesions. We now provide evidence that NBS1 is also important for cellular survival after oxidative or alkylating stress where it is required for the proper initiation of base excision repair (BER). NBS1 down-regulated cells show reduced activation of poly-(ADP-ribose)-polymerase-1 (PARP1) following genotoxic treatment with H2O2 or methyl methanesulfonate (MMS), indicating impaired processing of damaged bases by BER as PARP1 activity is stimulated by the single strand breaks intermediately generated during this repair pathway. Furthermore, extracts of these cells have a decreased capacity for the in vitro repair of a double-stranded (ds)-oligonucleotide containing either uracil or 8-oxo-7,8-dihydroguanine (8-oxoG) to trigger base excision repair. Our data presented here, highlight for the first time a functional role for NBS1 in DNA maintenance by the BER pathway.
Key Words: base excision repair NBS1 oxidative stress PARP1
Received August 31, 2008; revised November 25, 2008; accepted December 22, 2008.