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Computational Studies of Aflatoxin B 1 (AFB 1): A Review. Toxins (Basel) 2023; 15:toxins15020135. [PMID: 36828449 PMCID: PMC9967988 DOI: 10.3390/toxins15020135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/25/2023] [Accepted: 02/03/2023] [Indexed: 02/11/2023] Open
Abstract
Aflatoxin B1 (AFB1) exhibits the most potent mutagenic and carcinogenic activity among aflatoxins. For this reason, AFB1 is recognized as a human group 1 carcinogen by the International Agency of Research on Cancer. Consequently, it is essential to determine its properties and behavior in different chemical systems. The chemical properties of AFB1 can be explored using computational chemistry, which has been employed complementarily to experimental investigations. The present review includes in silico studies (semiempirical, Hartree-Fock, DFT, molecular docking, and molecular dynamics) conducted from the first computational study in 1974 to the present (2022). This work was performed, considering the following groups: (a) molecular properties of AFB1 (structural, energy, solvent effects, ground and the excited state, atomic charges, among others); (b) theoretical investigations of AFB1 (degradation, quantification, reactivity, among others); (c) molecular interactions with inorganic compounds (Ag+, Zn2+, and Mg2+); (d) molecular interactions with environmentally compounds (clays); and (e) molecular interactions with biological compounds (DNA, enzymes, cyclodextrins, glucans, among others). Accordingly, in this work, we provide to the stakeholder the knowledge of toxicity of types of AFB1-derivatives, the structure-activity relationships manifested by the bonds between AFB1 and DNA or proteins, and the types of strategies that have been employed to quantify, detect, and eliminate the AFB1 molecule.
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Güç İ, Yalçin E, Çavuşoğlu K, Acar A. Toxicity mechanisms of aflatoxin M 1 assisted with molecular docking and the toxicity-limiting role of trans-resveratrol. Sci Rep 2022; 12:14471. [PMID: 36008536 PMCID: PMC9411558 DOI: 10.1038/s41598-022-18791-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/19/2022] [Indexed: 11/30/2022] Open
Abstract
In this study, AFM1 toxicity and the protective role of trans-resveratrol (t-rsv) against this toxicity were investigated with the help of multiple parameters in albino mice. As a result, AFM1 (16 mg/kg b.w) administration caused a decrease in body, kidney and liver weights. This reduction was associated with a decrease in feed consumption. AFM1 induced an increase in AST and ALT enzyme parameters and BUN, creatinine and MDA levels and a decrease in GSH levels. These increases have been associated with liver and kidney cell damage. AFM1 decreased MI and encouraged increases in MN and CAs numbers. The decrease in MI was correlated with AFM1-tubulin and the increase in CAs was associated with the AFM1-DNA interaction, which was demonstrated by molecular docking and spectral shifting. Besides, the decrease in DNA damage and amount was demonstrated by the comet assay technique. Administration of t-rsv (10 and 20 mg/kg b.w) reduced the toxic effects of AFM1 and caused a dose-dependent improvement in all physiological, biochemical and cytogenetic parameter values studied. For this reason, foods containing t-rsv or food supplements should be consumed in the daily diet to reduce the effect of toxic agents.
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Affiliation(s)
- İlknur Güç
- Department of Biology, Faculty of Science and Art, Giresun University, Giresun, Turkey
| | - Emine Yalçin
- Department of Biology, Faculty of Science and Art, Giresun University, Giresun, Turkey
| | - Kültiğin Çavuşoğlu
- Department of Biology, Faculty of Science and Art, Giresun University, Giresun, Turkey.
| | - Ali Acar
- Department of Medical Services and Techniques, Vocational School of Health Services, Giresun University, Giresun, Turkey
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Fedeles BI, Essigmann JM. Impact of DNA lesion repair, replication and formation on the mutational spectra of environmental carcinogens: Aflatoxin B 1 as a case study. DNA Repair (Amst) 2018; 71:12-22. [PMID: 30309820 DOI: 10.1016/j.dnarep.2018.08.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In a multicellular organism, somatic mutations represent a permanent record of the past chemical and biochemical perturbations experienced by a cell in its local microenvironment. Akin to a perpetual recording device, with every replication, genomic DNA accumulates mutations in patterns that reflect: i) the sequence context-dependent formation of DNA damage, due to environmental or endogenous reactive species, including spontaneous processes; ii) the activity of DNA repair pathways, which, depending on the type of lesion, can erase, ignore or exacerbate the mutagenic consequences of that DNA damage; and iii) the choice of replication machinery that synthesizes the nascent genomic copy. These three factors result in a richly contoured sequence context-dependent mutational spectrum that, from appearances, is distinct for most individual forms of DNA damage. Such a mutagenic legacy, if appropriately decoded, can reveal the local history of genome-altering events such as chemical or pathogen exposures, metabolic stress, and inflammation, which in turn can provide an indication of the underlying causes and mechanisms of genetic disease. Modern tools have positioned us to develop a deep mechanistic understanding of the cellular factors and pathways that modulate a mutational process and, in turn, provide opportunities for better diagnostic and prognostic biomarkers, better exposure risk assessment and even actionable therapeutic targets. The goal of this Perspective is to present a bottom-up, lesion-centric framework of mutagenesis that integrates the contributions of lesion replication, lesion repair and lesion formation to explain the complex mutational spectra that emerge in the genome following exposure to mutagens. The mutational spectra of the well-studied hepatocarcinogen aflatoxin B1 are showcased here as specific examples, but the implications are meant to be generalizable.
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Affiliation(s)
- Bogdan I Fedeles
- Departments of Biological Engineering, Chemistry and The Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - John M Essigmann
- Departments of Biological Engineering, Chemistry and The Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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Mutational spectra of aflatoxin B 1 in vivo establish biomarkers of exposure for human hepatocellular carcinoma. Proc Natl Acad Sci U S A 2017; 114:E3101-E3109. [PMID: 28351974 DOI: 10.1073/pnas.1700759114] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Aflatoxin B1 (AFB1) and/or hepatitis B and C viruses are risk factors for human hepatocellular carcinoma (HCC). Available evidence supports the interpretation that formation of AFB1-DNA adducts in hepatocytes seeds a population of mutations, mainly G:C→T:A, and viral processes synergize to accelerate tumorigenesis, perhaps via inflammation. Responding to a need for early-onset evidence predicting disease development, highly accurate duplex sequencing was used to monitor acquisition of high-resolution mutational spectra (HRMS) during the process of hepatocarcinogenesis. Four-day-old male mice were treated with AFB1 using a regimen that induced HCC within 72 wk. For analysis, livers were separated into tumor and adjacent cellular fractions. HRMS of cells surrounding the tumors revealed predominantly G:C→T:A mutations characteristic of AFB1 exposure. Importantly, 25% of all mutations were G→T in one trinucleotide context (CGC; the underlined G is the position of the mutation), which is also a hotspot mutation in human liver tumors whose incidence correlates with AFB1 exposure. The technology proved sufficiently sensitive that the same distinctive spectrum was detected as early as 10 wk after dosing, well before evidence of neoplasia. Additionally, analysis of tumor tissue revealed a more complex pattern than observed in surrounding hepatocytes; tumor HRMS were a composite of the 10-wk spectrum and a more heterogeneous set of mutations that emerged during tumor outgrowth. We propose that the 10-wk HRMS reflects a short-term mutational response to AFB1, and, as such, is an early detection metric for AFB1-induced liver cancer in this mouse model that will be a useful tool to reconstruct the molecular etiology of human hepatocarcinogenesis.
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Nakatani K, Matsuno T, Adachi K, Hagihara S, Saito I. Selective intercalation of charge neutral intercalators into GG and CG steps: implication of HOMO-LUMO interaction for sequence-selective drug intercalation into DNA. J Am Chem Soc 2001; 123:5695-702. [PMID: 11403601 DOI: 10.1021/ja003956i] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have synthesized naphthopyranone epoxide 4 from D-isoascorbic acid together with its three diastereoisomers. DNA alkylation of ODNs containing 5'XGT3' and 5'TGY3' by 4 (11R, 13R), where X and Y are any nucleotide bases, occurred at all G residues except at G of the 5'TGC3' sequence. In contrast, the three other diastereoisomers of 4 showed only weak G alkylation activity. Differential (1)H NMR NOE of the 4-G adduct confirmed the G-N7 alkylation at the epoxide carbon of 4 with concomitant S(N)2 ring opening of the epoxide. Quantitative HPLC analysis of G alkylation efficiency for 4 showed the order of G alkylation susceptibility as TGGT approximately CGT >> TGA > AGT > TGT >> TGC. The order was fully consistent with those reported for aflatoxin B(1) oxide and kapurimycin A(3), suggesting that the sequence selectivity observed for these DNA alkylating agents is not structure dependent but most likely due to the intrinsic property of DNA sequences. We found that the order of G alkylation susceptibility obtained for 4 completely matched the calculated HOMO energy level of G-containing sequences. These results underscore that 4 is a unique molecular probe for ranking the HOMO level of G-containing sequences by well-known G alkylation chemistry and suggests that the intercalation of charge neutral intercalators is a HOMO-controlled process.
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Affiliation(s)
- K Nakatani
- Department of Synthetic Chemistry and Biological Chemistry, Faculty of Engineering, Kyoto University, CREST, Japan Science and Technology Corporation (JST), Kyoto 606-8501, Japan
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6
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Guengerich FP, Johnson WW, Shimada T, Ueng YF, Yamazaki H, Langouët S. Activation and detoxication of aflatoxin B1. Mutat Res 1998; 402:121-8. [PMID: 9675258 DOI: 10.1016/s0027-5107(97)00289-3] [Citation(s) in RCA: 210] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Aflatoxin B1 (AFB1) is a potent hepatocarcinogen in experimental animals and a hazard to human health in several parts of the world. Implementation of rational intervention plans requires understanding of aspects of the roles of individual chemical steps involved in its disposition. AFB1 is activated to AFB1 exo-8,9-epoxide primarily by cytochrome P450 (P450) enzymes, particularly P450 3A4. However, P450 3A4 and other P450s also oxidize AFB1 to less dangerous products. The exo-epoxide is unstable in H2O (t1/2 1 s at 25 degreesC, k=0.6 s-1) and the diol product undergoes base-catalyzed rearrangement to a dialdehyde that reacts with protein lysine residues. AFB1 exo-8, 9-epoxide reacts with DNA to give adducts in high yield (>98%). This interaction is characterized by a Kd of approximately 1.4 mM, intercalation between base pairs, and rapid reaction with the guanyl N7 atom (k approximately 40 s-1). A proton field on the periphery of DNA is postulated to catalyze hydrolysis and also conjugation. Rat and especially human epoxide hydrolase show very little rate acceleration of hydrolysis of AFB1 exo- or endo-8,9-epoxide. However, glutathione transferases (GSTs) can catalyze AFB1 exo-8,9-epoxide conjugation. Kinetic analysis indicates a range of ratios of kcat/Kd varying from 10 to 1700 s-1 M-1, with the polymorphic GST M1-1 having the highest activity of the human GSTs. Studies with human hepatocytes indicate a major role for GST M1-1 in AFB1 conjugation and that the model chemoprotective agent oltipraz can act by both inducing GSTs and inhibiting P450s.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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McGuire SM, Silva JC, Casillas EG, Townsend CA. Purification and characterization of versicolorin B synthase from Aspergillus parasiticus. Catalysis of the stereodifferentiating cyclization in aflatoxin biosynthesis essential to DNA interaction. Biochemistry 1996; 35:11470-86. [PMID: 8784203 DOI: 10.1021/bi960924s] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The absolute configuration of the dihydrobisfuran ring system characteristic of aflatoxin B1 is essential to the covalent reaction of its metabolically activated form with double-stranded DNA. The biosynthesis of this potent mycotoxin proceeds through three configurationally labile intermediates to racemic versiconal hemiacetal. Subsequent enzymatic cyclization establishes the stereochemistry of this, critical ring fusion in (-)-versicolorin B and is catalyzed by versicolorin B synthase (VBS). The isolation and purification of VBS from Aspergillus parasiticus (SU-1, ATCC 56775) and its kinetic characterization and attempted inactivation are described. Initial purification trials were plagued both by a chromophoric impurity which was difficult to remove and by low recoveries of active protein. The discovery of a remarkably broad pH range of enzyme stability and catalytic activity led to an efficient procedure involving preparative isoelectric focusing and ion exchange FPLC chromatography. The enzyme behaved as a dimer upon gel filtration and migrated with M(r) 78000 Da during denaturing gel electrophoresis. The UV spectrum of pure VBS gave no evidence of a bound chromophore. Detailed kinetic analysis of VBS revealed that this protein selects from two equilibrating enantiomers of versiconal hemiacetal to cyclize the appropriate antipode to optically pure versicolorin B. By varying the amount of enzyme to a fixed concentration of substrate, the rate of enzymic cyclization could be limited by the intrinsic rate of enantiomerization of the substrate under the conditions of reaction. It was possible to quantitate the dynamics of this substrate enantiomerization/cyclization process, to establish the role played by VBS, and to evaluate the significance of each to the overall biosynthesis of aflatoxin. The potential role of an acidic residue of the enzyme in catalysis was supported by analysis of the pH-rate profile of VBS and chemical labeling studies. Successful demonstration of competitive inhibition of VBS by a simple substrate analogue led to the design and synthesis of a potential mechanism-based inactivator of the protein.
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Affiliation(s)
- S M McGuire
- Department of Chemistry, John Hopkins University, Baltimore, Maryland 21218, USA
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Silva JC, Minto RE, Barry CE, Holland KA, Townsend CA. Isolation and characterization of the versicolorin B synthase gene from Aspergillus parasiticus. Expansion of the aflatoxin b1 biosynthetic gene cluster. J Biol Chem 1996; 271:13600-8. [PMID: 8662689 DOI: 10.1074/jbc.271.23.13600] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Versicolorin B synthase catalyzes the side chain cyclization of racemic versiconal hemiacetal to the bisfuran ring system of(-)-versicolorin B, an essential transformation in the aflatoxin biosynthetic pathway of Aspergillus parasiticus. The dihydrobisfuran is key to the mutagenic nature of aflatoxin B1. The protein, which shows 58% similarity and 38% identity with glucose oxidase from Aspergillus niger, possesses an amino-terminal sequence homologous to the ADP-binding region of other flavoenzymes. However, this enzyme does not require flavin or nicotinamide cofactors for its cyclase activity. The 643-amino acid native enzyme contains three potential sites for N-linked glycosylation, Asn-Xaa-Thr or Asn-Xaa-Ser. The cDNA and genomic clones of versicolorin B synthase were isolated by screening the respective libraries with random-primed DNA probes generated from an exact copy of an internal vbs sequence. This probe was created through polymerase chain reaction by using nondegenerate polymerase chain reaction primers derived from the amino acid sequences of peptide fragments of the enzyme. The 1985-base genomic vbs DNA sequence is interrupted by one intron of 53 nucleotides. Southern blotting, nucleotide sequencing, and detailed restriction mapping of the vbs-containing genomic clones revealed the presence of omtA, a methyltransferase active in the biosynthesis, 3.3 kilobases upstream of vbs and oriented in the opposite direction from vbs. The presence of omtA in close proximity to vbs supports the theory that the genes encoding the aflatoxin biosynthetic enzymes in A. parasiticus are clustered.
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Affiliation(s)
- J C Silva
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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9
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Gopalakrishnan S, Liu X, Patel DJ. Solution structure of the covalent sterigmatocystin-DNA adduct. Biochemistry 1992; 31:10790-801. [PMID: 1329956 DOI: 10.1021/bi00159a021] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Sterigmatocystin and aflatoxin are potent mutagens that contaminate foodstuffs stored under conditions that permit fungal growth. These food mycotoxins can be metabolically activated to their epoxides, which subsequently form covalent adducts with DNA and can eventually induce tumor development. We have generated the sterigmatocystin-d(A1-A2-T3-G4-C5-A6-T7-T8) covalent adduct (two sterigmatocystins per duplex) by reacting sterigmatocystin-1,2-epoxide with the self-complementary d(A-A-T-G-C-A-T-T) duplex and determined its solution structure by the combined application of two-dimensional NMR experiments and molecular dynamics calculations. The self-complementary duplex retains its 2-fold symmetry following covalent adduct formation of sterigmatocystin at the N7 position of G4 residues on each strand of the duplex. The H8 proton of [ST]G4 exchanges rapidly with water and resonates at 9.58 ppm due to the presence of the positive charge on the guanine ring following adduct formation. We have assigned the exchangeable and nonexchangeable proton resonances of sterigmatocystin and the duplex in the covalent adduct and identified the intermolecular proton-proton NOEs that define the orientation and mode of binding of the mutagen to duplex DNA. The analysis was aided by intermolecular NOEs between the sterigmatocystin protons with both the major groove and minor groove protons of the DNA. The molecular dynamics calculations were aided by 180 intramolecular nucleic acid constraints, 16 intramolecular sterigmatocystin constraints, and 56 intermolecular distance constraints between sterigmatocystin and the nucleic acid protons in the adduct. The sterigmatocystin chromophore intercalates between the [ST]G4.C5 and T3.A6 base pairs and stacks predominantly over the modified guanine ring in the adduct duplex. The overall conformation of the DNA remains right-handed on adduct formation with unwinding of the helix, as well as widening of the minor groove. Parallel NMR studies on the sterigmatocystin-d(A1-A2-A3-G4-C5-T6-T7-T8) covalent adduct (two sterigmatocystins per duplex) provide supportive evidence that the mutagen covalently adducts the N7 position of G4 and its chromophore intercalates to the 5' side of the guanine and stacks over it. The present NMR-molecular dynamics studies that define a detailed structure for the sterigmatocystin-DNA adduct support key structural conclusions proposed previously on the basis of a qualitative analysis of NMR parameters for the adduct formed by the related food mutagen aflatoxin B1 and DNA [Gopalakrishnan, S., Harris, T. M., & Stone, M. P. (1990) Biochemistry 29, 10438-10448].
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Affiliation(s)
- S Gopalakrishnan
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University New York, New York 10032
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Buetler TM, Slone D, Eaton DL. Comparison of the aflatoxin B1-8,9-epoxide conjugating activities of two bacterially expressed alpha class glutathione S-transferase isozymes from mouse and rat. Biochem Biophys Res Commun 1992; 188:597-603. [PMID: 1445304 DOI: 10.1016/0006-291x(92)91098-b] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The complementary DNAs of rat glutathione S-transferase (GST, EC 2.5.1.18) Yc1 and of mouse Yc were expressed from a prokaryotic expression vector in E. coli. The purified proteins were analyzed for their activity toward aflatoxin B1-8,9-epoxide (AFBO), the reactive intermediate of the fungal mycotoxin aflatoxin B1 (AFB). The mouse Yc isozyme had about 50-fold higher conjugating activity toward AFBO than the rat Yc1 isozyme (144 nmol/mg/min versus 3.3 nmol/mg/min). The rat Yc1 isozyme had specific activities toward 1-chloro-2,4-dinitrobenzene, cumene hydroperoxide and ethacrynic acid of 10.7, 0.98 and 0.92 mumol/mg/min, respectively, whereas the mouse Yc isozyme had specific activities of 5.7, 2.1 and 0.1 mumol/mg/min for these substrates, respectively. These data provide further support for the hypothesis that the constitutive presence of the alpha class GST Yc isozyme in mouse liver protects mice from the hepatocarcinogenic effects of aflatoxin B1.
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Affiliation(s)
- T M Buetler
- Dept. of Environmental Health, University of Washington, Seattle 98195
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Hsieh DP, Atkinson DN. Bisfuranoid mycotoxins: their genotoxicity and carcinogenicity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 283:525-32. [PMID: 1906226 DOI: 10.1007/978-1-4684-5877-0_69] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Based on the mode of action of AFB1 and the activities of its biologically active intermediates, one may conclude that: 1. The mode of toxic action of the bisfuranoid mycotoxin is through epoxidation of the vinyl ether double bond of their dihydrobisfuran functionality. 2. The DNA and plasma albumin adducts formed in vivo may be useful in the molecular dosimetry of these environmental carcinogens. 3. There appears to be a linear correlation between the steady state levels of AFB1-FAPy-DNA adducts and the carcinogenicity of AFB1. Elucidation of the molecular basis of this correlation may shed light on the mechanism of AFB1-induced carcinogenesis. 4. Consistent appearance of AFB1-DNA adducts in the livers of liver cancer patients tested is supportive of the IARC conclusion that AFB1 is a human carcinogen involved in human primary liver cancer.
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Affiliation(s)
- D P Hsieh
- Department of Environmental Toxicology, University of California, Davis 95616
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Loechler EL. Molecular modeling studies of O2-alkylthymines and O4-alkylthymines in DNA: structures that may be pertinent to the incorporation of the corresponding dAlkTTP into DNA by DNA polymerases in vitro. Mutat Res 1990; 233:39-44. [PMID: 2233811 DOI: 10.1016/0027-5107(90)90149-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- E L Loechler
- Department of Biology, Boston University, MA 02215
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14
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Carvajal M, Mulholland F, Carner RC. Comparison of the EASI-EXTRACT immunoaffinity concentration procedure with the AOAC CB method for the extraction and quantitation of aflatoxin B1 in raw ground unskinned peanuts. J Chromatogr A 1990; 511:379-83. [PMID: 2120278 DOI: 10.1016/s0021-9673(01)93302-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- M Carvajal
- Department of Biology, University of York, Heslington, U.K
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Aflatoxin-DNA Binding and the Characterization of Aflatoxin B1-Oligodeoxynucleotide Adducts by 1H NMR Spectroscopy. ACTA ACUST UNITED AC 1990. [DOI: 10.1007/978-94-011-3728-7_30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Loechler EL. Adduct-induced base-shifts: a mechanism by which the adducts of bulky carcinogens might induce mutations. Biopolymers 1989; 28:909-27. [PMID: 2742984 DOI: 10.1002/bip.360280502] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Most carcinogens have been shown to be mutagens, and DNA adducts are formed when mutagenic/carcinogenic substances react with DNA. It is generally believed these adducts (or their derivatives) induce misreplication events that result in mutations. Many of the more potently mutagenic substances are bulky and three-dimensionally complex, such as the polycyclic aromatic hydrocarbons, aromatic amines, and aflatoxins; little is known about the mechanisms by which they induce mutations. Several theories exist and herein an additional mechanism is proposed by which bulky adducts might induce mutations at GC base pairs. Molecular modeling in conjunction with molecular mechanical calculation is used to assess if the mutagen/carcinogen moiety of the adduct might be able to shift the position of the base moiety of the adduct in such a way that misreplication events might be facilitated. This mechanism is referred to as adduct-induced base-shift, and two classes appeared possible; adduct-induced base-wobble and adduct-induced base-rotation. The latter has been proposed previously. By adduct-induced, base-wobble, the mutagen/carcinogen moiety of the adduct induces a shift in the position of the base moiety of the adduct with respect to the helix axis, which might facilitate mispairing events that are reminisent of non-Watson/Crick pairing that occurs at the wobble base of tRNA during translation. For example, in some guanine adducts, the guanine appears more thymine-like, which might facilitate G.A mispairing and thereby ultimately GC to TA transversion mutations. Adduct-induced base-rotation involves the rotation of the adducted base from the anti to the syn conformation and a variety of mispairing events might result.
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