Journal Article

Age-related and tissue-specific accumulation of oxidative DNA base damage in 7,8-dihydro-8-oxoguanine-DNA glycosylase (Ogg1) deficient mice

Marcel Osterod, Stephan Hollenbach, Jan G. Hengstler, Deborah E. Barnes, Tomas Lindahl and Bernd Epe

in Carcinogenesis

Volume 22, issue 9, pages 1459-1463
Published in print September 2001 | ISSN: 0143-3334
Published online September 2001 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/22.9.1459
Age-related and tissue-specific accumulation of oxidative DNA base damage in 7,8-dihydro-8-oxoguanine-DNA glycosylase (Ogg1) deficient mice

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Mutations that influence the repair of oxidative DNA modifications are expected to increase the steady-state (background) levels of these modifications and thus create a mutator phenotype that predisposes to malignant transformation. We have analysed the steady-state levels and repair kinetics of oxidative DNA modifications in cells of homozygous ogg1–/– null mice, which are deficient in Ogg1 protein, a DNA repair glycosylase that removes the miscoding base 8-hydroxyguanine (8-oxoG) from the genome. Oxidative purine modifications including 8-oxoG were quantified by means of an alkaline elution assay in combination with Fpg protein, the bacterial functional analogue of Ogg1 protein. In primary hepatocytes of adult ogg1–/– mice aged 9–12 months, the steady-state level of the lesions was 2.8-fold higher than in wild-type control mice. In contrast, no difference between ogg1–/– and wild-type mice was observed in splenocytes, spermatocytes and kidney cells. In hepatocytes of ogg1–/– mice, but not in wild-type controls, the steady-state levels increased continuously over the whole lifespan. No significant accumulation of the oxidative base modifications was observed in ogg1–/– fibroblasts in culture when they were kept confluent for 8 days. Both in confluent and proliferating ogg1–/– fibroblasts, the global repair of additional oxidative base modifications induced by photosensitization was 4-fold slower than in wild-type cells. The results suggest that the consequences of an Ogg1 defect are restricted to slowly proliferating tissues with high oxygen metabolism such as liver, because of a back-up mechanism for the repair of 8-oxoG residues that is independent of transcription and replication.

Keywords: Fpg protein; formamidopyrimidine-DNA glycosylase; 8-oxoG; 7,8-dihydro-8-oxoguanine; Ro19-8022, [R]-1-[(10-Chloro-4-oxo-3-phenyl-4H-benzo[a]quinolizin-1-yl)-carbonyl]-2-pyrrolidinemethanol; ROS; reactive oxygen species.

Journal Article.  3621 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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