Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin

Vock, Esther; Wolfe, Alan R.; Meehan, Thomas

doi:10.1016/s0027-5107(01)00153-1

Cited by 8 publications

(3 citation statements)

References 15 publications

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“…Its reaction at N 2 of guanine gives the major BP DE DNA adduct (trans 10S BP-N 2 -dG, Fig. 1A) in mammalian cells (9,10). This adduct induces mainly base substitutions as well as Ϫ1 frameshift mutations in vivo (11,12).…”

Section: Biochemistrymentioning

confidence: 99%

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

Bauer

Xing²,

Yagi³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

139

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Erroneous replication of lesions in DNA by DNA polymerases leads to elevated mutagenesis. To understand the molecular basis of DNA damage-induced mutagenesis, we have determined the x-ray structures of the Y-family polymerase, Dpo4, in complex with a DNA substrate containing a bulky DNA lesion and incoming nucleotides. The DNA lesion is derived from an environmentally widespread carcinogenic polycyclic aromatic hydrocarbon, benzo[ a ]pyrene (BP). The potent carcinogen BP is metabolized to diol epoxides that form covalent adducts with cellular DNA. In the present study, the major BP diol epoxide adduct in DNA, BP- N 2 -deoxyguanosine (BP–dG), was placed at a template–primer junction. Three ternary complexes reveal replication blockage, extension past a mismatched lesion, and a −1 frameshift mutation. In the productive structures, the bulky adduct is flipped/looped out of the DNA helix into a structural gap between the little finger and core domains. Sequestering of the hydrophobic BP adduct in this new substrate-binding site permits the DNA to exhibit normal geometry for primer extension. Extrusion of the lesion by template misalignment allows the base 5′ to the adduct to serve as the template, resulting in a −1 frameshift. Subsequent strand realignment produces a mismatched base opposite the lesion. These structural observations, in combination with replication and mutagenesis data, suggest a model in which the additional substrate-binding site stabilizes the extrahelical nucleotide for lesion bypass and generation of base substitutions and −1 frameshift mutations.

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Section: Biochemistrymentioning

confidence: 99%

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

Bauer

Xing²,

Yagi³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

139

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“…Reaction of BaP DE-2 with DNA in cells or with nucleic acids in solution occurs mainly by trans and to a lesser extent cis opening of the epoxide ring at C-10 by the exocyclic 2-and 6-amino groups of the guanine and adenine bases, respectively. The trans-opened deoxyguanosine adduct of (+)-(7R,8S,9S,10R)-DE-2 is the major DNA adduct formed from (()-DE-2 in rodent epidermal cells (5) as well as by its reaction with DNA in solution (6).…”

Section: Introductionmentioning

confidence: 99%

3‘-H-Phosphonate Synthesis of Chiral Benzo[a]pyrene Diol Epoxide Adducts at N² of Deoxyguanosine in Oligonucleotides

Iyer

Yagi

Sayer

et al. 2007

Chem. Res. Toxicol.

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A synthetic route to oligonucleotides containing N(2)-deoxyguanosine adducts at C-10 of the enantiomeric 7,8-diol 9,10-epoxides of 7,8,9,10-tetrahydrobenzo[a]pyrene in which the epoxide oxygen and the 7-hydroxyl group are trans is described. The present adducts result from the trans addition of N(2) of deoxyguanosine to the epoxide at C-10. Our synthesis proceeds via preparation of the 3'-H-phosphonate of a suitably protected deoxyguanosine N(2)-adduct. The blocking groups consisted of O(6)-allyl on the deoxyguanosine, acetates on the 7-, 8-, and 9-hydroxyl groups of the hydrocarbon moiety, and dimethoxytrityl on the 5'-hydroxyl group of the sugar. These blocking groups are well suited to oligonucleotide synthesis on solid supports. The free 3'-hydroxyl group of this nucleoside adduct was readily converted to its 3'-H-phosphonate with diphenyl phosphite in pyridine in high yield for both the 10R and 10S isomers. For synthesis of oligonucleotides, the first several nucleotides were incorporated onto the solid support with an automated synthesizer using standard phosphoramidite chemistry. The adducted deoxyguanilic acid residue was introduced as the H-phosphonate in a manual step (80% yield), followed by completion of the sequence on the synthesizer. Although a 10-fold excess of the 3'-H-phosphonate was used in the manual coupling step, as much as 70% of the reactant could be recovered. The 3'-H-phosphonate of the protected 10S nucleoside adduct was converted to the unblocked nucleotide adduct, various salts of which failed to form crystals suitable for X-ray analysis. Although submilligram quantities of this compound have been formed as mixed diastereomers by direct reaction of deoxyguanylic acid with racemic diol epoxide, the present study represents the first actual synthesis of the major DNA adduct formed from benzo[a]pyrene in mammals as its 3'-phosphate.

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“…However, alkylation by chlorohydrins in vitro favors cis adduct formation and increases overall adduct yield. When applied to rodent skin ex vivo, the chlorohydrin of anti-BPDE produces DNA adducts whose cis proportion is 50% or greater (14) (in this situation, adduct yield is low owing to the instability of the chlorohydrin coupled with the requirement for diffusion to the alkylation target). Alkylation of DNA by BPDE chlorohydrin formed in vivo is suggested by the larger than typical proportion of cis adducts (∼16%) generated by BPDE applied to cat salivary cell cultures.…”

Section: Introductionmentioning

confidence: 99%

Benzo[a]pyrene Diol Epoxide Forms Covalent Adducts with Deoxycytidylic Acid by Alkylation at Both Exocyclic Amino N⁴ and Ring Imino N-3 Positions

Wolfe

Smith

Meehan

2004

Chem. Res. Toxicol.

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The carcinogen 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) alkylates DNA at dGuo, dAdo, and dCyd. dCyd adducts, formed in small amounts, elute near the more abundant dGuo adducts. We isolated the dCyd adducts formed with dCMP. Each BPDE enantiomer forms three major adducts with dCMP, two cis and one trans. The trans adduct and one of the cis adducts form by alkylation at exocyclic N(4), while the second cis adduct is a dUrd adduct formed by alkylation at ring N-3 followed by deamination. Epoxide ring-opening geometries were assigned on the basis of halide and temperature effects on adduct yield, the sign of the major CD band, and benzo ring proton NMR coupling constants. One of each set of cis adducts is fluorescent (FL), and the other is nonfluorescent (NF). The trans and FL cis adducts have fluorescence quantum yields 40-50% of that of the BPDE hydrolysis product. The long wavelength UV maxima of the FL and NF cis adducts are red-shifted 1 and 3 nm relative to the trans adduct. (1)H NMR deuterium exchange experiments indicate that in the trans and FL cis adducts N(4)-H is coupled to C10-H. Adduct formation experiments with methyl-protected Cyd derivatives show that NF cis adducts result from alkylation at N-3. MS results, pK(a) measurements, and dUrd alkylation experiments indicate that the N-3 dCyd adducts spontaneously deaminate to dUrd adducts. NMR coupling constants show that in the NF cis adduct the C7 and C8 substituents are quasi equatorial and the C9 substituent is quasi axial, unlike in other cis BPDE adducts. (1)H NOESY spectra of the (-)-BPDE NF cis adduct reveal that it exists in two conformers. Molecular modeling shows that the conformers result from two low-energy conformations of very similar energies with the pyrimidine in opposite orientations, separated by significant barriers to rotation of the uracil moiety.

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Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin

Cited by 8 publications

References 15 publications

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

3‘-H-Phosphonate Synthesis of Chiral Benzo[a]pyrene Diol Epoxide Adducts at N² of Deoxyguanosine in Oligonucleotides

Benzo[a]pyrene Diol Epoxide Forms Covalent Adducts with Deoxycytidylic Acid by Alkylation at Both Exocyclic Amino N⁴ and Ring Imino N-3 Positions

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Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin

Cited by 8 publications

References 15 publications

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

A structural gap in Dpo4 supports mutagenic bypass of a major benzo[ a ]pyrene dG adduct in DNA through template misalignment

3‘-H-Phosphonate Synthesis of Chiral Benzo[a]pyrene Diol Epoxide Adducts at N2 of Deoxyguanosine in Oligonucleotides

Benzo[a]pyrene Diol Epoxide Forms Covalent Adducts with Deoxycytidylic Acid by Alkylation at Both Exocyclic Amino N4 and Ring Imino N-3 Positions

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Product

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About

3‘-H-Phosphonate Synthesis of Chiral Benzo[a]pyrene Diol Epoxide Adducts at N² of Deoxyguanosine in Oligonucleotides

Benzo[a]pyrene Diol Epoxide Forms Covalent Adducts with Deoxycytidylic Acid by Alkylation at Both Exocyclic Amino N⁴ and Ring Imino N-3 Positions