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X-ray structure of a DNA decamer containing 7,8-dihydro-8-oxoguanine.

ABSTRACT: We have determined the x-ray structure of a DNA fragment containing 7,8-dihydro-8-oxoguanine (G(O)). The structure of the duplex form of d(CCAGOCGCTGG) has been determined to 1.6-A resolution. The results demonstrate that GO forms Watson-Crick base pairs with the opposite C and that G(O) is in the anti conformation. Structural perturbations induced by C.G(O)anti base pairs are subtle. The structure allows us to identify probable elements by which the DNA repair protein MutM recognizes its substrates. Hydrogen bond donors/acceptors within the major groove are the most likely element. In that groove, the pattern of hydrogen-bond donors/acceptors of C.G(O)anti is unique. Additional structural analysis indicates that conversion of G to G(O) would not significantly influence the glycosidic torsion preference of the nucleoside. There is no steric interaction of the 8-oxygen of G(O) with the phospho-deoxyribose backbone.

SUBMITTER: Lipscomb LA

PROVIDER: S-EPMC42691 | biostudies-other | 1995 Jan

REPOSITORIES: biostudies-other

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X-ray structure of a DNA decamer containing 7,8-dihydro-8-oxoguanine.

Lipscomb L A LA Peek M E ME Morningstar M L ML Verghis S M SM Miller E M EM Rich A A Essigmann J M JM Williams L D LD

Proceedings of the National Academy of Sciences of the United States of America 19950101 3

We have determined the x-ray structure of a DNA fragment containing 7,8-dihydro-8-oxoguanine (G(O)). The structure of the duplex form of d(CCAGOCGCTGG) has been determined to 1.6-A resolution. The results demonstrate that GO forms Watson-Crick base pairs with the opposite C and that G(O) is in the anti conformation. Structural perturbations induced by C.G(O)anti base pairs are subtle. The structure allows us to identify probable elements by which the DNA repair protein MutM recognizes its substr ...[more]

PMID: 7846041

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Opposite base-dependent reactions of a human base excision repair enzyme on DNA containing 7,8-dihydro-8-oxoguanine and abasic sites.

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Substitution of Ala for Tyr567 in RB69 DNA polymerase allows dAMP to be inserted opposite 7,8-dihydro-8-oxoguanine .

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Kinetics, structure, and mechanism of 8-Oxo-7,8-dihydro-2'-deoxyguanosine bypass by human DNA polymerase ?.

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The polymerase eta translesion synthesis DNA polymerase acts independently of the mismatch repair system to limit mutagenesis caused by 7,8-dihydro-8-oxoguanine in yeast.

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UVA radiation is highly mutagenic in cells that are unable to repair 7,8-dihydro-8-oxoguanine in Saccharomyces cerevisiae.

Project description:UVA (320-400 nm) radiation constitutes >90% of the environmentally relevant solar UV radiation, and it has been proposed to have a role in skin cancer and aging. Because of the popularity of UVA tanning beds and prolonged periods of sunbathing, the potential deleterious effect of UVA has emerged as a source of concern for public health. Although generally accepted, the impact of DNA damage on the cytotoxic, mutagenic, and carcinogenic effect of UVA radiation remains unclear. In the present study, we investigated the sensitivity of a panel of yeast mutants affected in the processing of DNA damage to the lethal and mutagenic effect of UVA radiation. The data show that none of the major DNA repair pathways, such as base excision repair, nucleotide excision repair, homologous recombination, and postreplication repair, efficiently protect yeast from the lethal action of UVA radiation. In contrast, the results show that the Ogg1 DNA glycosylase efficiently prevents UVA-induced mutagenesis, suggesting the formation of oxidized guanine residues. Furthermore, sequence analysis of UVA-induced canavanine-resistant mutations reveals a bias in favor of GC-->TA events when compared with spontaneous or H(2)O(2)-, UVC-, and gamma-ray- induced canavanine-resistant mutations in the WT strain. Taken together, our data point out a major role of oxidative DNA damage, mostly 7,8-dihydro-8-oxoguanine, in the genotoxicity of UVA radiation in the yeast Saccharomyces cerevisiae. Therefore, the capacity of skin cells to repair 7,8-dihydro-8-oxoguanine may be a key parameter in the mutagenic and carcinogenic effect of UVA radiation in humans.

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Biophysical properties and thermal stability of oligonucleotides of RNA containing 7,8-dihydro-8-hydroxyadenosine.

Project description:Circular dichroism (CD) was used to assess the stabilization/destabilization imposed by oxidative lesion 7,8-dihydro-8-hydroxyadenosine (8-oxoA) on strands of RNA with different structural motifs. RNA:RNA homoduplex destabilization was observed in a position dependent manner using 10-mers as models that displayed differences between 12.7 and 15.1°C. We found that increasing the number of modifications resulted in depressed Tm values of about 12-15°C per lesion. The same effect was observed on RNA:DNA heteroduplex samples. We also tested the effects of this lesion in short hairpins containing the tetraloop UUCX (X?=?A, 8-oxoA). We found that the stem was hypersensitive to substitution of A by 8-oxoA and that it destabilized the structure by >23°C. Concomitant substitution at the stem and loop prevented formation of this secondary structure or lead to other less-stable hairpins. Incorporation of this lesion at the first base of the loop had no effect on either structure. Overall, we found that the effects of 8-oxoA on RNA structure are position dependent and that its stabilization may vary from sharp decreases to small increments, in some cases, leading to the formation of other more/less stable structures. These structural changes may have larger biological implications, particularly if the oxidatively modified RNA persists, thus leading to changes in RNA reactivity and function.

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Promutagenic bypass of 7,8-dihydro-8-oxoadenine by translesion synthesis DNA polymerase Dpo4.

Project description:Reactive oxygen species induced by ionizing radiation and metabolic pathways generate 7,8-dihydro-8-oxoguanine (oxoG) and 7,8-dihydro-8-oxoadenine (oxoA) as two major forms of oxidative damage. The mutagenicity of oxoG, which promotes G to T transversions, is attributed to the lesion's conformational flexibility that enables Hoogsteen base pairing with dATP in the confines of DNA polymerases. The mutagenesis mechanism of oxoA, which preferentially causes A to C transversions, remains poorly characterized. While structures for oxoA bypass by human DNA polymerases are available, that of prokaryotic DNA polymerases have not been reported. Herein, we report kinetic and structural characterizations of Sulfolobus solfataricus Dpo4 incorporating a nucleotide opposite oxoA. Our kinetic studies show oxoA at the templating position reduces the replication fidelity by ?560-fold. The catalytic efficiency of the oxoA:dGTP insertion is ?300-fold greater than that of the dA:dGTP insertion, highlighting the promutagenic nature of oxoA. The relative efficiency of the oxoA:dGTP misincorporation is ?5-fold greater than that of the oxoG:dATP misincorporation, suggesting the mutagenicity of oxoA is comparable to that of oxoG. In the Dpo4 replicating base pair site, oxoA in the anti-conformation forms a Watson-Crick base pair with an incoming dTTP, while oxoA in the syn-conformation assumes Hoogsteen base pairing with an incoming dGTP, displaying the dual coding potential of the lesion. Within the Dpo4 active site, the oxoA:dGTP base pair adopts a Watson-Crick-like geometry, indicating Dpo4 influences the oxoA:dGTP base pair conformation. Overall, the results reported here provide insights into the miscoding properties of the major oxidative adenine lesion during translesion synthesis.

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Unexpected behavior of DNA polymerase Mu opposite template 8-oxo-7,8-dihydro-2'-guanosine.

Project description:DNA double-strand breaks (DSBs) resulting from reactive oxygen species generated by exposure to UV and ionizing radiation are characterized by clusters of lesions near break sites. Such complex DSBs are repaired slowly, and their persistence can have severe consequences for human health. We have therefore probed DNA break repair containing a template 8-oxo-7,8-dihydro-2'-guanosine (8OG) by Family X Polymerase ? (Pol ?) in steady-state kinetics and cell-based assays. Pol ? tolerates 8OG-containing template DNA substrates, and the filled products can be subsequently ligated by DNA Ligase IV during Nonhomologous end-joining. Furthermore, Pol ? exhibits a strong preference for mutagenic bypass of 8OG by insertion of adenine. Crystal structures reveal that the template 8OG is accommodated in the Pol ? active site with none of the DNA substrate distortions observed for Family X siblings Pols ? or ?. Kinetic characterization of template 8OG bypass indicates that Pol ? inserts adenosine nucleotides with weak sugar selectivity and, given the high cellular concentration of ATP, likely performs its role in repair of complex 8OG-containing DSBs using ribonucleotides.

| S-EPMC6755092 | biostudies-literature

DNA interstrand cross-links induced by the major oxidative adenine lesion 7,8-dihydro-8-oxoadenine.

Project description:Oxidative damage to DNA generates 7,8-dihydro-8-oxoguanine (oxoG) and 7,8-dihydro-8-oxoadenine (oxoA) as two major lesions. Despite the comparable prevalence of these lesions, the biological effects of oxoA remain poorly characterized. Here we report the discovery of a class of DNA interstrand cross-links (ICLs) involving oxidized nucleobases. Under oxidative conditions, oxoA, but not oxoG, readily reacts with an opposite base to produce ICLs, highlighting a latent alkylating nature of oxoA. Reactive halogen species, one-electron oxidants, and the myeloperoxidase/H2O2/Cl- system induce oxoA ICLs, suggesting that oxoA-mediated cross-links may arise endogenously. Nucleobase analog studies suggest C2-oxoA is covalently linked to N2-guanine and N3-adenine for the oxoA-G and oxoA-A ICLs, respectively. The oxoA ICLs presumably form via the oxidative activation of oxoA followed by the nucleophilic attack by an opposite base. Our findings provide insights into oxoA-mediated mutagenesis and contribute towards investigations of oxidative stress-induced ICLs and oxoA-based latent alkylating agents.

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