Mechanisms of formation, genotoxicity, and mutation of guanine oxidation products

Department of Chemistry and Biological Engineering Division, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Chemical Research in Toxicology (Impact Factor: 4.19). 05/2006; 19(4):491-505. DOI: 10.1021/tx0600043
Source: PubMed
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    ABSTRACT: Ultraviolet radiation can damage biomolecules, with detrimental or even lethal effects for life. Even though lower wavelengths are filtered by the ozone layer, a significant amount of harmful UV-B and UV-A radiation reach Earth's surface, particularly in high altitude environments. high-altitude Andean lakes (HAALs) are a group of disperse shallow lakes and salterns, located at the Dry Central Andes region in South America at altitudes above 3,000 m. As it is considered one of the highest UV-exposed environments, HAAL microbes constitute model systems to study UV-resistance mechanisms in environmental bacteria at various complexity levels. Herein, we present the genome sequence of Acinetobacter sp. Ver3, a gammaproteobacterium isolated from Lake Verde (4,400 m), together with further experimental evidence supporting the phenomenological observations regarding this bacterium ability to cope with increased UV-induced DNA damage. Comparison with the genomes of other Acinetobacter strains highlighted a number of unique genes, such as a novel cryptochrome. Proteomic profiling of UV-exposed cells identified up-regulated proteins such as a specific cytoplasmic catalase, a putative regulator, and proteins associated to amino acid and protein synthesis. Down-regulated proteins were related to several energy-generating pathways such as glycolysis, beta-oxidation of fatty acids, and electronic respiratory chain. To the best of our knowledge, this is the first report on a genome from a polyextremophilic Acinetobacter strain. From the genomic and proteomic data, an "UV-resistome" was defined, encompassing the genes that would support the outstanding UV-resistance of this strain.
    Frontiers in Microbiology 04/2015; 6:328. DOI:10.3389/fmicb.2015.00328 · 3.94 Impact Factor
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    ABSTRACT: Oxidative damage to DNA constitutes a major threat to the faithful replication of DNA in all organisms and it is therefore important to understand the various mechanisms that are responsible for repair of such damage, and the consequences of unrepaired damage. In these experiments, we make use of a reporter system in Saccharomyces cerevisiae that can measure the specific increase of each type of base pair mutation by measuring reversion to a Trp+ phenotype. We demonstrate that increased oxidative damage due to the absence of the superoxide dismutase gene, SOD1, increases all types of base pair mutations and that mismatch repair (MMR) reduces some, but not all, types of mutations. By analyzing various strains that can revert only via a specific CG→AT transversion in backgrounds deficient in Ogg1 (encoding an 8-oxoG glycosylase), we can study mutagenesis due to a known 8 oxoG base. We show as expected that MMR helps prevent mutagenesis due to this damaged base, and that Pol η is important for its accurate replication. In addition we find that its accurate replication is facilitated by template switching, as loss of either RAD5 or MMS2 leads to a significant decrease in accurate replication. We observe that these ogg1 strains accumulate revertants during prolonged incubation on plates, in a process most likely due to retromutagenesis.
    Genetics 07/2013; 195(2). DOI:10.1534/genetics.113.153874 · 4.87 Impact Factor
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    ABSTRACT: The oxidation of guanine to 8-oxo-2'-deoxyguanosine (8-oxo-dG) is one of the most abundant and best studied oxidative DNA lesions and is commonly used as a biomarker for oxidative stress. Over the last decades, various methods for the detection of DNA oxidation products have been established and optimized. However, some of them lack sensitivity or are prone to artifact formation, while others are time-consuming, which hampers their application in screening approaches. In this study, we present a formamidopyrimidine glycosylase (Fpg)-based method to detect oxidative lesions in isolated DNA using a modified protocol of the automated version of the fluorimetric detection of alkaline DNA unwinding (FADU) method, initially developed for the measurement of DNA strand breaks [Moreno-Villanueva et al. (2009) BMC Biotechnol, 9, 39]. The FADU-Fpg method was validated using a plasmid DNA model, mimicking mitochondrial DNA, and the results were correlated to 8-oxo-dG levels as measured by LC-MS/MS. The FADU-Fpg method can be applied to analyze the potential of compounds to induce DNA strand breaks and oxidative lesions, as exemplified here by treating plasmid DNA with the peroxynitrite-generating molecule Sin-1. Moreover, this method can be used to screen DNA-protective effects of antioxidant substances, as exemplified here for a small-molecule, i.e. uric acid, and a protein, i.e. manganese superoxide dismutase, both of which displayed a dose-dependent protection against the generation of oxidative DNA lesions. In conclusion, the automated FADU-Fpg method offers a rapid and reliable measurement for the detection of peroxynitrite-mediated DNA damage in a cell-free system, rendering it an ideal method for screening the DNA-protective effects of antioxidant compounds.
    Toxicology 05/2013; DOI:10.1016/j.tox.2013.05.006 · 3.75 Impact Factor