The human OGG1 gene encodes a DNA glycosylase activity catalysing the excision of the mutagenic lesion 7,8-dihydro-8-oxoguanine from oxidatively damaged DNA. The OGG1 gene was localized to chromosome 3p25, a region showing frequent loss of heterozygosity (LOH) in lung and kidney tumours. In this study, we have analysed by RT ± PCR the expression of OGG1 in 25 small cell lung cancers, in 15 kidney carcinomas and the 15 normal kidney counterparts. The results show that OGG1 messenger RNA can be detected in all tumours tested and that no signi®cant di erence was observed in the level of expression between normal and tumoral kidney tissues. Denaturing gradient gel electrophoresis (DGGE) was used to screen this series of human tumours for alterations in the OGG1 cDNA. The study revealed homozygous mutations in three tumours, two from lung and one from kidney. Sequencing analysis of the mutants identi®ed a single base substitution in each of the three cases: two tranversions (GC to TA and TA to AT) and one transition (GC to AT). All three substitutions cause an amino acid change in the hOgg1 protein. For the mutant kidney tumour, the normal tissue counterpart shows a wild-type pro®le. These results suggest a role for OGG1 mutations in the course of the multistage process of carcinogenesis in lung or kidney.Keywords: oxidative DNA damage; DNA repair; missense mutations of OGG1 gene; human lung and kidney cancer; tumour suppressor gene Damage to DNA by oxygen-free radicals is postulated to cause mutations that are associated with the initiation or the progression of human cancers (Breimer, 1990;Loeb, 1997;Beckman and Ames, 1997). Oxidative damage-induced mutations can activate oncogenes or inactivate tumour suppressor genes altering the cell growth control (Fearon, 1997). An oxidatively damaged guanine, 7,, is abundantly produced in DNA as a consequence of the cellular oxidative metabolism or the exposure to ionizing radiation or chemical carcinogens (Dizdaroglu, 1991;Cadet et al., 1997). The presence of 8-OxoG in DNA has been shown to be mutagenic since, while this lesion does not impede DNA chain elongation, it preferentially pairs with adenine during in vitro DNA synthesis (Shibutani et al., 1991). The biological incidence of the presence of 8-OxoG in DNA has been unveiled by the study of two genes in E. coli, fpg (mutM) and mutY (micA) which code for DNA glycosylases that cooperate to prevent the mutagenic e ects of 8-OxoG in DNA (Boiteux et al., 1987;Cabrera et al., 1988;Radicella et al., 1988;Nghiem et al., 1988;Au et al., 1989). Inactivation of either gene leads to a spontaneous mutator phenotype characterized by the exclusive increase in GC to TA transversions (Michaels and Miller, 1992;Grollman and Moriya, 1993;Boiteux and Laval, 1997). In Saccharomyces cerevisiae the OGG1 gene was cloned as the functional eukaryotic homologue of the bacterial fpg gene (Au ret van der Kemp et al., 1996). The yeast Ogg1 protein is a DNA glycosylase/AP lyase which excises 8-OxoG, formamidopyrimidines and incizes apurinic/apyrimid...

8-Oxoguanine (8-oxoG), a common and mutagenic form of oxidized guanine in DNA, is eliminated mainly through base excision repair. In human cells its repair is initiated by human OGG1 (hOGG1), an 8-oxoG DNA glycosylase. We investigated the effects of an acute cadmium exposure of human lymphoblastoid cells on the activity of hOGG1. We show that coinciding with alteration of the redox cellular status, the 8-oxoG DNA glycosylase activity of hOGG1 was nearly completely inhibited. However, the hOGG1 activity returned to normal levels once the redox cellular status was normalized. In vitro, the activity of purified hOGG1 was abolished by cadmium and could not be recovered by EDTA. In cells, however, the reversible inactivation of OGG1 activity by cadmium was strictly associated with reversible oxidation of the protein. Moreover, the 8-oxoG DNA glycosylase activity of purified OGG1 and that from crude extracts were modulated by cysteine-modifying agents. Oxidation of OGG1 by the thiol oxidant diamide led to inhibition of the activity and a protein migration pattern similar to that seen in cadmiumtreated cells. These results suggest that cadmium inhibits hOGG1 activity mainly by indirect oxidation of critical cysteine residues and that excretion of the metal from the cells leads to normalization of the redox cell status and restoration of an active hOGG1. The results presented here unveil a novel redox-dependent mechanism for the regulation of OGG1 activity.

With the growing numbers of nanomaterials (NMs), there is a great demand for rapid and reliable ways of testing NM safety—preferably using in vitro approaches, to avoid the ethical dilemmas associated with animal research. Data are needed for developing intelligent testing strategies for risk assessment of NMs, based on grouping and read‐across approaches. The adoption of high throughput screening (HTS) and high content analysis (HCA) for NM toxicity testing allows the testing of numerous materials at different concentrations and on different types of cells, reduces the effect of inter‐experimental variation, and makes substantial savings in time and cost. HTS/HCA approaches facilitate the classification of key biological indicators of NM‐cell interactions. Validation of in vitro HTS tests is required, taking account of relevance to in vivo results. HTS/HCA approaches are needed to assess dose‐ and time‐dependent toxicity, allowing prediction of in vivo adverse effects. Several HTS/HCA methods are being validated and applied for NM testing in the FP7 project NANoREG, including Label‐free cellular screening of NM uptake, HCA, High throughput flow cytometry, Impedance‐based monitoring, Multiplex analysis of secreted products, and genotoxicity methods—namely High throughput comet assay, High throughput in vitro micronucleus assay, and γH2AX assay. There are several technical challenges with HTS/HCA for NM testing, as toxicity screening needs to be coupled with characterization of NMs in exposure medium prior to the test; possible interference of NMs with HTS/HCA techniques is another concern. Advantages and challenges of HTS/HCA approaches in NM safety are discussed. WIREs Nanomed Nanobiotechnol 2017, 9:e1413. doi: 10.1002/wnan.1413For further resources related to this article, please visit the WIREs website.