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2000
Obrecht-Pflumio S., Dirheimer G.
In vitro DNA and dGMP adducts formation caused by ochratoxin A Journal Article
In: Chem Biol Interact, vol. 127, no. 1, pp. 29-44, 2000, (0009-2797 Journal Article).
Abstract | BibTeX | Tags: Acid/metabolism, Adducts/*metabolism, Agents/pharmacology, Animals, Arachidonic, Carcinogens/pharmacology, Chelating, Chromatography, Deferoxamine/pharmacology, Deoxyguanine, DNA, Female, Kidney/ultrastructure, Liver/metabolism, Male, Mice, Microsomes, Microsomes/metabolism, Mycotoxins/pharmacology, NADP/metabolism, Nucleotides/*metabolism, Nucleotides/metabolism, Ochratoxins/*pharmacology, Peroxidase/metabolism, Rabbits, Spectrophotometry
@article{,
title = {In vitro DNA and dGMP adducts formation caused by ochratoxin A},
author = { S. Obrecht-Pflumio and G. Dirheimer},
year = {2000},
date = {2000-01-01},
journal = {Chem Biol Interact},
volume = {127},
number = {1},
pages = {29-44},
abstract = {Ochratoxin A (OTA), a nephrotoxic and nephrocarcinogenic mycotoxin, leads to the formation of DNA adducts after administration to animals. This could be due to an epigenetic effect. In vitro assays can exclude an indirect effect, where the xenobiotic can generate, in vivo, endogenous reactive compounds which give adducts on DNA. Microsomes prepared from mice or rabbit kidney and liver, used as metabolic activators, were incubated in the presence of commercial salmon testes DNA and OTA, with NADPH or arachidonic acid used as cofactors. Upto 126 DNA adducts for 10(9) nucleotides were detected using the 32P postlabeling method after incubation with the mouse kidney system. Similar results were obtained with rabbit kidney microsomes. Using liver microsomes, the number of DNA adducts detected was much lower. When NADPH was used as a cosubstrate (to explore the cytochrome P450 metabolic pathways), with mice kidney microsomes, the adduct level was only 44% of the one obtained with arachidonic acid. These results lend support to the hypothesis of the preferential activation of OTA by the peroxidase activity of prostaglandin synthases and/or lipoxygenases to direct genotoxic metabolites, and are in agreement with the previously obtained results after in vivo treatment of mice. In order to identify the nucleotides of DNA modified by the OTA metabolites, dAMP, dGMP, dTMP and dCMP were used as substrates under the same conditions as with DNA. The adducts were found only on dGMP. The total adduct level was of 344 adducts per 10(9) nucleotides with the appearance of three major adducts in the presence of arachidonic acid. With NADPH, 271 adducts were obtained per 10(9) nucleotides, with again three major adducts, but only two of them were similar to two adducts obtained in the presence of arachidonic acid. Desferal (desferrioxamine B methanesulphonate), at a 50 microM concentration, did not reduce the adduct level. Adducts were also obtained when polydG, polydC and dG-p-dG were used as alternative substrates, whereas no adducts were obtained with polydA, polydT and polydC. The major adduct obtained after incubation of DNA with OTA, comigrated with the major adduct obtained with dGMP, in two chromatographic solvents. These results show that OTA is metabolized to genotoxic metabolite(s) which interact with the guanine residues of DNA.},
note = {0009-2797
Journal Article},
keywords = {Acid/metabolism, Adducts/*metabolism, Agents/pharmacology, Animals, Arachidonic, Carcinogens/pharmacology, Chelating, Chromatography, Deferoxamine/pharmacology, Deoxyguanine, DNA, Female, Kidney/ultrastructure, Liver/metabolism, Male, Mice, Microsomes, Microsomes/metabolism, Mycotoxins/pharmacology, NADP/metabolism, Nucleotides/*metabolism, Nucleotides/metabolism, Ochratoxins/*pharmacology, Peroxidase/metabolism, Rabbits, Spectrophotometry},
pubstate = {published},
tppubtype = {article}
}
Ochratoxin A (OTA), a nephrotoxic and nephrocarcinogenic mycotoxin, leads to the formation of DNA adducts after administration to animals. This could be due to an epigenetic effect. In vitro assays can exclude an indirect effect, where the xenobiotic can generate, in vivo, endogenous reactive compounds which give adducts on DNA. Microsomes prepared from mice or rabbit kidney and liver, used as metabolic activators, were incubated in the presence of commercial salmon testes DNA and OTA, with NADPH or arachidonic acid used as cofactors. Upto 126 DNA adducts for 10(9) nucleotides were detected using the 32P postlabeling method after incubation with the mouse kidney system. Similar results were obtained with rabbit kidney microsomes. Using liver microsomes, the number of DNA adducts detected was much lower. When NADPH was used as a cosubstrate (to explore the cytochrome P450 metabolic pathways), with mice kidney microsomes, the adduct level was only 44% of the one obtained with arachidonic acid. These results lend support to the hypothesis of the preferential activation of OTA by the peroxidase activity of prostaglandin synthases and/or lipoxygenases to direct genotoxic metabolites, and are in agreement with the previously obtained results after in vivo treatment of mice. In order to identify the nucleotides of DNA modified by the OTA metabolites, dAMP, dGMP, dTMP and dCMP were used as substrates under the same conditions as with DNA. The adducts were found only on dGMP. The total adduct level was of 344 adducts per 10(9) nucleotides with the appearance of three major adducts in the presence of arachidonic acid. With NADPH, 271 adducts were obtained per 10(9) nucleotides, with again three major adducts, but only two of them were similar to two adducts obtained in the presence of arachidonic acid. Desferal (desferrioxamine B methanesulphonate), at a 50 microM concentration, did not reduce the adduct level. Adducts were also obtained when polydG, polydC and dG-p-dG were used as alternative substrates, whereas no adducts were obtained with polydA, polydT and polydC. The major adduct obtained after incubation of DNA with OTA, comigrated with the major adduct obtained with dGMP, in two chromatographic solvents. These results show that OTA is metabolized to genotoxic metabolite(s) which interact with the guanine residues of DNA.
1998
Dumortier H, Gunnewiek J Klein, Roussel J P, van Aarssen Y, Briand J P, van Venrooij W J, Muller S
In: Nucleic Acids Research, vol. 26, no. 23, pp. 5486–5491, 1998, ISSN: 0305-1048.
Abstract | Links | BibTeX | Tags: Amino Acid Sequence, Animals, Dumortier, HeLa Cells, Humans, I2CT, Molecular Sequence Data, Peptide Fragments, Protein Binding, Rabbits, Ribonucleoprotein, Ribonucleoproteins, Small Nuclear, Solutions, Spliceosomes, Team-Dumortier, U1 Small Nuclear, Zinc, Zinc Fingers
@article{dumortier_at_1998,
title = {At least three linear regions but not the zinc-finger domain of U1C protein are exposed at the surface of the protein in solution and on the human spliceosomal U1 snRNP particle},
author = {H Dumortier and J Klein Gunnewiek and J P Roussel and Y van Aarssen and J P Briand and W J van Venrooij and S Muller},
doi = {10.1093/nar/26.23.5486},
issn = {0305-1048},
year = {1998},
date = {1998-12-01},
journal = {Nucleic Acids Research},
volume = {26},
number = {23},
pages = {5486--5491},
abstract = {No structural information on U1C protein either in its free state or bound to the spliceosomal U1 small nuclear ribonucleoprotein (snRNP) particle is currently available. Using rabbit antibodies raised against a complete set of 15 U1C overlapping synthetic peptides (16-30 residues long) in different immunochemical tests, linear regions exposed at the surface of free and U1 snRNP-bound U1C were identified. Epitopes within at least three regions spanning residues 31-62, 85-103 and 116-159 were recognized on free and plastic-immobilized recombinant human U1C expressed in Escherichia coli, on in vitro translated U1C protein and on U1C bound to the U1 snRNP particle present in HeLa S100 extract. Using a zinc affinity labeling method, we further showed that the N-terminal U1C peptide containing a zinc-finger motif (peptide 5-34) effectively binds65Zn2+. The N-terminal region of U1C, which is functional in U1 snRNP assembly, is apparently not located at the surface of the U1 snRNP particle.},
keywords = {Amino Acid Sequence, Animals, Dumortier, HeLa Cells, Humans, I2CT, Molecular Sequence Data, Peptide Fragments, Protein Binding, Rabbits, Ribonucleoprotein, Ribonucleoproteins, Small Nuclear, Solutions, Spliceosomes, Team-Dumortier, U1 Small Nuclear, Zinc, Zinc Fingers},
pubstate = {published},
tppubtype = {article}
}
No structural information on U1C protein either in its free state or bound to the spliceosomal U1 small nuclear ribonucleoprotein (snRNP) particle is currently available. Using rabbit antibodies raised against a complete set of 15 U1C overlapping synthetic peptides (16-30 residues long) in different immunochemical tests, linear regions exposed at the surface of free and U1 snRNP-bound U1C were identified. Epitopes within at least three regions spanning residues 31-62, 85-103 and 116-159 were recognized on free and plastic-immobilized recombinant human U1C expressed in Escherichia coli, on in vitro translated U1C protein and on U1C bound to the U1 snRNP particle present in HeLa S100 extract. Using a zinc affinity labeling method, we further showed that the N-terminal U1C peptide containing a zinc-finger motif (peptide 5-34) effectively binds65Zn2+. The N-terminal region of U1C, which is functional in U1 snRNP assembly, is apparently not located at the surface of the U1 snRNP particle.
