Sie sind hier: UHH > Chemie > Institute und Abteilungen > Organische Chemie > Prof. Dr. C. Meier > Research > DNA Damage by Aromatic Amines
Inhalt:
Exposure to carcinogens can occur from environmental or work conditions, diet, smoking and endogenous processes. Poly- and monocyclic aromatic amines, e.g. aniline 1, p-toluidine 2, 4-aminobiphenyl 4 and 2-aminofluorene 6 (Figure 1), belong to the class of chemical carcinogens that form covalently bound adducts to the DNA double helix. Covalent damage of DNA (by electrophiles) may be one reason for the induction of chemical carcinogenesis because if these DNA damages are not repaired, they might compromise the fidelity of DNA replication which finally leads to mutations and possibly cancer.
Aromatic amines belong to the group of indirect carcinogens because they require a metabolic activation leading to the so-called ultimate carcinogen (Scheme 1). The initial step is an oxidation catalyzed by cytochrome P450 of the arylamine to the corresponding N-hydroxylamine, followed by esterification into an N-acetoxyarylamine by N-acetyl transferase (NAT) or into a sulfate by a sulfotransferase (ST) to give the ultimate carcinogens.
DNA Damage by Aromatic Amines – Are Arylamine Adducts responsible for the Induction of the Chemical Carcinogenesis?
Exposure to carcinogens can occur from environmental or work conditions, diet, smoking and endogenous processes. Poly- and monocyclic aromatic amines, e.g. aniline 1, p-toluidine 2, 4-aminobiphenyl 4 and 2-aminofluorene 6 (Figure 1), belong to the class of chemical carcinogens that form covalently bound adducts to the DNA double helix. Covalent damage of DNA (by electrophiles) may be one reason for the induction of chemical carcinogenesis because if these DNA damages are not repaired, they might compromise the fidelity of DNA replication which finally leads to mutations and possibly cancer.
Aromatic amines belong to the group of indirect carcinogens because they require a metabolic activation leading to the so-called ultimate carcinogen (Scheme 1). The initial step is an oxidation catalyzed by cytochrome P450 of the arylamine to the corresponding N-hydroxylamine, followed by esterification into an N-acetoxyarylamine by N-acetyl transferase (NAT) or into a sulfate by a sulfotransferase (ST) to give the ultimate carcinogens.
Figure 1. Borderline carcinogens and carcinogenic aromatic
amines.
Scheme 1. Metabolism of arylamines and resulting
adducts.
The predominant reaction of the
arylnitrenium ion occurs at the C8-position of 2’-deoxyguanosine (dG) and,
although to a smaller amount, 2’-deoxyadenosine (dA), leading to C8-adducts 7, 8 and 9, 10. Moreover, N2-adducts
of dG 11, 13 and N6-ortho-arylamine adducts
of dA 12 have been identified as
minor products.
We are working on synthetic
approaches to such nucleobase adducts using not only the borderline
carcinogens, but also poly- and heterocyclic aromatic amines.
Key
step in the chemical synthesis for most of these DNA adducts is a Pd-catalyzed
C-N-bond formation reaction. Subsequently, these adducts were converted into
the corresponding phosphoramidites.
Figure 2. Key steps in the investigation of arylamine modified oligonucleotides
Primer-extension assays
DNA polymerase enzymes employ a number of innate fidelity mechanisms to ensure the faithful replication of the genome. However, when confronted with DNA damage, their fidelity mechanisms can be evaded, resulting in a mutation that may contribute to the carcinogenic process.
Figure 3. Effect of C8-arylamine-adducts on DNA polymerases
EcoRI-Restriction assay
Primer-extension assays
DNA polymerase enzymes employ a number of innate fidelity mechanisms to ensure the faithful replication of the genome. However, when confronted with DNA damage, their fidelity mechanisms can be evaded, resulting in a mutation that may contribute to the carcinogenic process.
Figure 3. Effect of C8-arylamine-adducts on DNA polymerases
EcoRI-Restriction assay
To investigate the impact on
enzyme recognition of arylamine damaged oligonucleotides by an endonuclease,
the EcoRI restriction enzyme was chosen.
Figure 5: HPLC chromatogram of EcoRI restriction
Crystals
In collaboration with the DESY (german electron-synchrotron) we investigate the crystallographic structure of our modified oligonucleotides on the basis of improvement of the buffer, pH-value and different counterions.
Figure 5: HPLC chromatogram of EcoRI restriction
Crystals
In collaboration with the DESY (german electron-synchrotron) we investigate the crystallographic structure of our modified oligonucleotides on the basis of improvement of the buffer, pH-value and different counterions.
- C. Meier, S. Gräsl, Synlett 2002, 802-804.
- C. Meier, S. Gräsl, I. Detmer
- N. Böge, S. Gräsl, C. Meier, J. Org. Chem. 2006, 71, 9728-9738.
- M. I. Jacobsen, C. Meier, Synlett 2006, 2411-2414.
- N. Böge, Z. Szombati, C. Meier, Nucleosides, Nucleotides Nucleic Acids 2007, 26, 705-708.
- N. Böge, S. Krüger, M. Schröder, C. Meier, Synthesis 2007, 24, 3907-3914.
- M. I. Jacobsen, C. Meier, Nucleosides, Nucleotides Nucleic Acids 2007, 26, 11217-1220.
- N. Böge, M. Schröder, C. Meier, Synlett 2008, 1066-1070
- N. Böge, M. I. Jacobsen, Z. Szombati, S. Baerns, F. Di Pasquale, A. Marx, C. Meier, Chem. Eur. J. 2008, 14, 11194-11208.
- Z. Szombati, S. Baerns, A. Marx, C. Meier, ChemBioChem 2012, 13, 700-712.
