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7,8-Dihydro-8-oxoguanosine Lesions Inhibit the Theophylline Aptamer or Change Its Selectivity.

ABSTRACT: Aptamers are attractive constructs due to their high affinity/selectivity towards a target. Here 7,8-dihydro-8-oxoguanosine (8-oxoG) has been used, due in part to its unique H-bonding capabilities (Watson-Crick or Hoogsteen), to expand the "RNA alphabet". Its impact on the theophylline RNA aptamer was explored by modifying its binding pocket at positions G11, G25, or G26. Structural probing, with RNases A and T₁ , showed that modification at G11 leads to a drastic structural change, whereas the G25-/G26-modified analogues exhibited cleavage patterns similar to that of the canonical construct. The recognition properties towards three xanthine derivatives were then explored through thermophoresis. Modifying the aptamer at position G11 led to binding inhibition. Modification at G25, however, changed the selectivity towards theobromine (K_d ≈160 μm), with a poor affinity for theophylline (K_d >1.5 mm) being observed. Overall, 8-oxoG can have an impact on the structures of aptamers in a position-dependent manner, leading to altered target selectivity.

SUBMITTER: Kiggins C

PROVIDER: S-EPMC7297664 | biostudies-literature |

REPOSITORIES: biostudies-literature

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An organometallic inhibitor for the human repair enzyme 7,8-dihydro-8-oxoguanosine triphosphatase.

Project description:The probe-based discovery of the first small-molecule inhibitor of the repair enzyme 8-oxo-dGTPase (MTH1) is presented, which is an unconventional cyclometalated ruthenium half-sandwich complex. The organometallic inhibitor with low-nanomolar activity displays astonishing specificity, as verified in tests with an extended panel of protein kinases and other ATP binding proteins. The binding of the organometallic inhibitor to MTH1 is investigated by protein crystallography.

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Short-term biological variation and Reference change values of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine and 8-oxo-7,8-dihydroguanosine.

Project description:AimThe DNA and RNA oxidative damage products urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-odGsn) and 8-oxo-7,8-dihydroguanosine (8-oGsn) have potential use in clinical practice. However, biological variation (BV) and reference change values (RCVs) have not been established. The aim of this study was to establish the short-term between-subject BV(CVG ), within-subject BV(CVI ), and RCVs for urinary 8-odGsn and 8-oGsn.MethodsFirst-morning midstream urine specimens were collected from 20 apparently healthy subjects(ten males and ten females) on five consecutive days. 8-odGsn and 8-oGsn were measured using LC-MS/MS, while urine creatinine (U-Cr) was also measured to correct their results. A two-level nested ANOVA was used to estimate the CVI and CVG. RESULTS: The values of CVG for 8-odGsn, 8-odGsn/U-Cr, 8-oGsn, and 8-oGsn/U-Cr were 31.2%, 39.6%, 35.3%, and 28.8%, respectively, while CVI for them were 40.5%, 9.0%, 33.5%, and 12.1%, respectively. The RCVs for 8-odGsn, 8-odGsn/U-Cr, 8-oGsn, and 8-oGsn/U-Cr were 112.5%, 26.7%, 93.7%, and 36.5%, respectively.ConclusionBV and RCVs were firstly established for 8-oxo-dGsn and 8-oGsn, and can be used in clinical practice.

| S-EPMC7755802 | biostudies-literature

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Project description:In the title compound, C(16)H(13)NO(2), the two benzene rings make a dihedral angle of 55.5 (2)°. The crystal packing is stabilized by inter-molecular C-H⋯O hydrogen bonds and weak π-π stacking inter-actions [centroid-centroid distance = 3.595 (3)Å], linking the mol-ecules into ladders of inversion dimers.

| S-EPMC2959899 | biostudies-literature

8-Oxo-7,8-dihydro-2'-deoxyguanosine and abasic site tandem lesions are oxidation prone yielding hydantoin products that strongly destabilize duplex DNA.

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| S-EPMC5636683 | biostudies-literature

Mutagenesis mechanism of the major oxidative adenine lesion 7,8-dihydro-8-oxoadenine.

Project description:Reactive oxygen species generate the genotoxic 8-oxoguanine (oxoG) and 8-oxoadenine (oxoA) as major oxidative lesions. The mutagenicity of oxoG is attributed to the lesion's ability to evade the geometric discrimination of DNA polymerases by adopting Hoogsteen base pairing with adenine in a Watson-Crick-like geometry. Compared with oxoG, the mutagenesis mechanism of oxoA, which preferentially induces A-to-C mutations, is poorly understood. In the absence of protein contacts, oxoA:G forms a wobble conformation, the formation of which is suppressed in the catalytic site of most DNA polymerases. Interestingly, human DNA polymerase η (polη) proficiently incorporates dGTP opposite oxoA, suggesting the nascent oxoA:dGTP overcomes the geometric discrimination of polη. To gain insights into oxoA-mediated mutagenesis, we determined crystal structures of polη bypassing oxoA. When paired with dGTP, oxoA adopted a syn-conformation and formed Hoogsteen pairing while in a wobble geometry, which was stabilized by Gln38-mediated minor groove contacts to oxoA:dGTP. Gln38Ala mutation reduced misinsertion efficiency ∼55-fold, indicating oxoA:dGTP misincorporation was promoted by minor groove interactions. Also, the efficiency of oxoA:dGTP insertion by the X-family polβ decreased ∼380-fold when Asn279-mediated minor groove contact to dGTP was abolished. Overall, these results suggest that, unlike oxoG, oxoA-mediated mutagenesis is greatly induced by minor groove interactions.

| S-EPMC7229865 | biostudies-literature

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.

| S-EPMC7448247 | biostudies-literature

Is pre-heat necessary for the measurement of 8-oxo-7,8-dihydroguanosine and 8-oxo-7,8-dihydro-2'-deoxyguanosine in urine samples.

Project description:BackgroundIt is currently unclear for the necessary of pre-heating urine samples for the accurate determination of 8-oxo-7,8-dihydroguanosine (8-oxoG) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). Thus, we conducted this study to evaluate the effect of pre-heat (i.e., to 37°C) on the accurate measurement of 8-oxoG and 8-oxodG in frozen urine samples.MethodsRandom urine samples from six healthy volunteers, six patients with renal dysfunction, and six patients with systematic diseases such as diabetes were collected, split, and stored at -80°C for up to 1 month. The frozen samples were thawed at room temperature (RT) or 37°C for different time, 10-fold diluted with ddH2O containing 1% formic acid, and determined by self-established LC-MS/MS method coupled with an ACQUITY™ Primer HSS T3 column.ResultsThawing the samples at RT for 30 or 120 min, or at 37°C for 15 or 90 min did not affect the determination of 8-oxoG and 8-oxodG in urine samples. Moreover, no significant difference between thawing the urine samples at RT and 37°C was found after storing at -80°C for 1-3 months.ConclusionIt is not always necessary to pre-heat the frozen urine samples to release 8-oxoG and 8-oxodG from precipitates, which is associated with different pre-treatment and determination methods.

| S-EPMC9550956 | biostudies-literature

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

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.

| S-EPMC4302245 | biostudies-literature

Quantitative detection of 8-Oxo-7,8-dihydro-2'-deoxyguanosine using chemical tagging and qPCR.

Project description:8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) is a commonly formed DNA lesion that is useful as a biomarker for oxidative stress. Although methods for selective quantification of 8-oxodGuo exist, there is room for additional methods that are sensitive and utilize instrumentation that is widely available. We previously took advantage of the reported reactivity of 8-oxodGuo to develop a method for detecting the lesion by selectively covalently tagging it with a molecule equipped with a biotin label that can be used subsequently with a reporting method ( Xue , L. and Greenberg , M. M. ( 2007 ) J. Am. Chem. Soc. 129 , 7010 ). We now report a method that can detect as little as 14 amol of 8-oxodGuo by tagging DNA with a reagent containing a disulfide that reduces background due to nonspecific binding. The reagent also contains biotin that enables capturing target DNA on streptavidin-coated magnetic beads. The captured DNA is quantified using quantitative PCR. The method is validated by comparing the amount of 8-oxodGuo detected as a function of Fe(2+)/H2O2/ascorbate-dose to that reported previously using mass spectrometry.

| S-EPMC4106692 | biostudies-literature

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