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P Quillardet

Publications and source records attributed to P Quillardet.

At least 19 recordsLinked to original sources
PubMed2000

Mutagenic properties of a nitrofuran, 7-methoxy-2-nitronaphtho[2, 1-b]furan (R7000), in lacI transgenic mice.

The in vivo mutagenic properties of a 5-nitrofuran, the 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), already well known in bacteria, was evaluated in lacI transgenic mice (Big Blue). The mutation frequency was determined in various organs of i.p. - treated mice and the nature of induced mutations was determined for the target organs in which mutation induction was significant. It was found that R7000 is mutagenic in mice, although, on the basis of the number of induced mutants per unit mass in comparison with other known mutagenic chemicals, R7000 appears to be considerably less mutagenic in mice than in bacteria. The most affected organs, small intestine, caecum and colon organs belong to the digestive apparatus. The distribution of R7000-induced mutations in the lacI gene recovered from small intestine of transgenic mice was very similar to that which had been found in E. coli. The difference between mouse and E. coli in the R7000 induced mutational spectra are mainly in the proportion of single base frameshifts versus base substitutions. Since R7000 induced mutations seemed to arise in the population of stem cells and that the stem cells are important for carcinogenesis, our results are compatible with a possible carcinogenic effect of R7000 and other nitrofurans.

Animals↗
PubMed1998

DNA damage induced in vivo by 7-methoxy-2-nitronaphtho[2,1-b]-furan (R7000) in the lacI gene of Escherichia coli.

DNA adducts that block replication, induced in vivo by the 5-nitrofuran derivative R7000 (7-methoxy-2-nitronaphtho[2, 1-b]-furan) were mapped, at nucleotide resolution, in a region of the lacI gene of Escherichia coli, using a reiterative primer extension assay [D. Chandrasekhar, B. Van Houten, High resolution mapping of UV-induced photoproducts in the Escherichia coli lacI gene: inefficient repair of the non-transcribed strand correlates with high mutation frequency, J. Mol. Biol., 1994, Vol. 238, pp. 319-332]. It was found that R7000 induced a broad spectrum of low frequency replication blocks rather than particular hot spots in a limited number of particular targets. Most of these replication blocks were observed at G nucleotides, and most of G nucleotides present in the DNA sequence, if not all, constituted a possible target for the chemical attack of the compound. In addition, a large part of replication blocks observed at A, C or T could also reflect a replication block at the 3' or 5' nucleotide flanking a guanosine-DNA adduct. Only a very small number of replication blocks could be observed at A, C or T nucleotides non-adjacent to a G. These results show that, guanosine-DNA adducts are the main DNA lesions that block replication induced by R7000 in E. coli and suggests a strong reactivity of the genotoxic species generated in vivo by R7000 with the G nucleotidic targets. From 26 R7000-induced mutations previously mapped in this region [E. Touati, E. Krin, P. Quillardet, M. Hofnung, 7-methoxy-2-nitronaphto[2,1-b]furan (R7000)-induced mutation spectrum in the lacI gene of Escherichia coli: influence of SOS mutagenesis, Carcinogenesis, 1996, Vol. 17, pp. 2543-2550.], 22 (85%) occurred at GC base pairs at which termination products were observed. The other mutagenic events involved AT base pairs adjacent to a G nucleotide forming a replication block. Thus all mutagenic events occurred at, or adjacent to, a G nucleotide forming a replication block. Although it could not be excluded that some mutagenic events are due to undetected DNA lesions that do not block replication, these results strongly suggest that guanosine-DNA adducts that block DNA replication are responsive for a large part of the mutagenic events generated by R7000. The powerful capacity of R7000 to form adducts at most of the guanosine residues in a DNA sequence may account for at least part of its very potent genotoxic properties.

Bacterial Proteins↗
PubMed1996

Influence of the uvr-dependent nucleotide excision repair on DNA adducts formation and mutagenic spectrum of a potent genotoxic agent: 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000).

The influence of the uvr-dependent excision repair system on the lethal action, mutagenic specificity, SOS induction and DNA adducts formation of 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), a potent genotoxic nitrofuran, were examined in Escherichia coli. Binding measurements of 3H-labelled R7000 to DNA indicated that R7000-DNA adducts can be removed by excision repair soon after the action of the chemical: 50% of the DNA adducts were removed within 10 min of treatment. After 1 h of incubation the level of excision reached 70%. This result was confirmed using the postlabelling technique. We found that R7000 yielded at least 10 different DNA adducts. Each of the adducts detected could be removed by excision repair. The rates of excision appeared different from one to the other. In addition, using a lacZ reversion system that is able to detect each type of base substitution mutations [1], we found that in uvrA bacteria deficient in excision repair, R7000 can induce 5 out of the 6 possible mutational events: GC-->TA, AT-->TA, GC-->CG, AT-->CG and GC-->AT. The transition AT-->GC was not observed. Only 3 transversions: GC-->TA, AT-->TA and GC-->CG could be detected in repair proficient uvr+ bacteria. The differences between the mutagenic spectra obtained in either uvr+ bacteria or uvrA mutants indicate that some potentially mutagenic DNA adducts induced by R7000 can be removed by excision repair, thus lowering the mutagenic potency of the chemical and modifying the mutagenic spectrum detected.

Bacterial Proteins↗
PubMed1996

Global response of Escherichia coli cells to a treatment with 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), an extremely potent mutagen.

We have studied the global changes which are induced in exponentially growing cultures of Escherichia coli during treatment with 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), a very potent mutagen and inducer of the SOS response. A two-dimensional analysis of the proteins synthesized in the presence of this agent was performed. In a strain deficient in SOS induction, the expression of 24 polypeptides was found to be affected by this treatment: 14 corresponded to proteins known to be implicated in different stress responses, particularly chaperones such as DnaK and GroEL. The variation of another protein was detected for the first time in this study: transketolase I, an enzyme of intermediary metabolism which was characterized in the present work by microsequencing. In parallel, the expression of 9 other proteins, still unidentified, was modified by this nitrofuran. They represent potential candidates involved in metabolic and DNA lesions repair specific of R7000 action.

Bacterial Proteins↗
PubMed1996

7-Methoxy-2-nitronaphtho[2,1-b]furan (R7000)-induced mutation spectrum in the lacI gene of Escherichia coli: influence of SOS mutagenesis.

The mutagenic specificity of 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), a very potent genotoxic 2-nitrofuran, was investigated in the lacI gene of E.coli. To analyze the influence of SOS-mutagenesis on R7000-induced mutations, 86 and 84 LacI- mutants were respectively isolated from umuC+ and umuC strains. Treatment of bacteria with increasing concentrations of R7000, affected 2-4 times more the survival rate in the umuC context, as compared to umuC+. 80% of all mutations occurred primarily at G:C base pairs and were substitution events and single-base frameshifts (-1) in the same proportions. The six possible substitution events were observed in both strains. In the umuC+ context, they were dominated by G:C-->T:A transversions. 38% of substitutions at G:C base pairs occurred in the consensus sequence 5'TGGCG3' or 5'TGGC3' where the G was mutated. When umuC was deficient G:C-->C:G transversions were mainly observed. The proportions of substitution mutations were very similar to those that have been reported for apurinic (AP) sites, suggesting strongly that one mechanism for R7000-induced mutations is the formation of intermediate abasic sites that serve as a substrate for error-prone repair. Single frameshift events consisted essentially of deletions of one (G:C) base pair in runs of contiguous G or C residues. Frameshift frequency increased with the length of the reiterated sequence, suggesting a strand-slippage process. Other mutational classes were recovered to a lower extent, including double-base frameshifts and large deletions. In addition, 10% of the mutants presented two proximate mutations. Comparison of the mutations induced by R7000 in the umuC+/umuC backgrounds suggests an influence of the umuC product on strand specificity of R7000-induced mutations, particularly in the case of frameshift events.

Bacterial Proteins↗
PubMed1994

A role for residue 151 of LamB in bacteriophage lambda adsorption: possible steric effect of amino acid substitutions.

LamB is the cell surface receptor for bacteriophage lambda. LamB missense mutations yielding resistance to lambda have been previously grouped in two classes. Class I mutants block growth of lambda with wild-type host range (lambda h+) but support growth of one-step extended-host-range mutants (lambda h). Class II mutants block lambda h but support growth of two-step extended host range mutants (lambda hh*). While Class I mutations occur at 11 different amino acid sites, in five distinct portions of LamB, all the Class II mutations analyzed previously correspond to the same G-to-D change at amino acid 151. We generated by in vitro mutagenesis four different new substitutions at site 151 (to S, V, R, and C). Two of the mutants (G-151-->V [G151V] and G151R) were of Class II, while the two others (G151S and G151C) were of Class I, demonstrating that not only the site but also the nature of the substitutions at residue 151 was critical for the phage sensitivity phenotypes. The introduction of a negatively charged, a positively charged, or an aliphatic nonpolar residue at site 151 of LamB prevented both lambda h+ and lambda h adsorption, indicating that the block is not due to a charge effect. In contrast to G151D, which was sensitive to all the lambda hh* phages, G151V and G151R conferred sensitivity to only four of the five lambda hh* phages. Thus, G151V and G151R represent a new subclass of Class II LamB mutations that is more restrictive with respect to the growth of lambda hh*. Our results agree with the hypothesis that residue 151 belongs to an accessibility gate controlling the access to the phage tight-binding site and that substitutions at this residue affect the access of the phage to the binding site in relation to the size of the substitute side chain (surface area): the most restrictive changes are G151V and G151R, followed to a lesser extent by G151D and they by G151S and G151C.

Bacterial Outer Membrane Proteins↗
PubMed1993

The SOS chromotest: a review.

The SOS chromotest is reviewed through over 100 publications corresponding to the testing of 751 chemicals. 404 (54%) of these chemicals present a genotoxic activity detectable in the SOS chromotest. Their SOS inducing potencies span more than 8 orders of magnitude. For 452 compounds, the results obtained in the SOS chromotest could be compared to those obtained in the Ames test. It was found that 373 (82%) of these compounds give similar responses in both tests (236 positive and 137 negative responses). Thus the discrepancies between both tests concern 79 compounds (18%). A case by case analysis shows that many of these compounds are at the same time very weak SOS inducers and very weak mutagens. Thus we think that, most of the time, the discrepancies between the two tests may be accounted for by differences in the interpretation of the results rather than by the experimental results themselves. However, there are some compounds which are clearly SOS inducers but devoid of mutagenic activity in the Ames test (such as quinoline-1-oxide) and to a larger extent, clearly mutagenic compounds which do not induce the SOS response in the SOS chromotest (such as benzidine, cyclophosphamide, acridines, ethidium bromide). We also analyzed the correlation between SOS induction, mutagenesis and carcinogenesis according to the classification of Lewis. For 65 confirmed carcinogens (class 1), the sensitivity, i.e., the capacity to identify carcinogens, was 62% with the SOS chromotest and 77% with the Ames test. For 44 suspected carcinogens (class 2), the sensitivity was 66% with the SOS chromotest and 68% with the Ames test. Thus, we confirmed previous observations made on 83 compounds that there is a close correlation between the results given by both bacterial tests. The capacity of the Ames test to identify carcinogens is higher than that of the SOS chromotest. However, because the number of false positive compounds was lower in the SOS chromotest, the specificity, i.e., the capacity to discriminate between carcinogens and non-carcinogens of the SOS chromotest, appeared higher than that of the Ames test. Thus, the results of the SOS chromotest and of the Ames test can complement each other. The SOS chromotest is one of the most rapid and simple short-term test for genotoxins and is easily adaptable to various conditions, so that it could be used as an early--perhaps the earliest--test in a battery.

Animals↗
PubMed1993

Determination of target nucleotides involved in 7-methoxy-2-nitro-naphtho[2,1-b]furan (R7000)-DNA adduct formation.

The characterization of target nucleotides involved in the binding to DNA of 7-methoxy-2-nitro-naphtho[2,1-b]furan (R7000), a very potent genotoxic nitrofuran derivative, was investigated. Since R7000 undergoes metabolic activation prior to interacting with DNA, plasmids containing AT-rich and GC-rich sequences were devised and treated by R7000 in bacterial cells presenting nitroreductase activity. The nucleotide modifications to these homogeneous fragments that resulted from R7000 treatment were analyzed using the 'postlabeling' method. A preferential binding to the GC segment was demonstrated. Using a modification of the Maxam-Gilbert sequencing technique, it was demonstrated that activated R7000 creates alkali-labile phosphodiester bonds at the positions of guanines. In addition, the analysis of DNA replication-blocking properties of R7000 lesions was performed using avian myeloblastosis virus (AMV) reverse transcriptase as DNA polymerase. The termination of DNA replication occurred preferentially at the sites of guanine residues in the template strand, indicating that one nucleotide was inserted opposite a lesion. All these results indicate that guanine residues are the preferential sites of formation of R7000-DNA adducts.

Adenosine Triphosphate↗
PubMed1991

First characterization of the mutagenic specificity of 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000) in Salmonella typhimurium.

In order to investigate the mutational events induced by the very potent genotoxic agent 7-methoxy-2-nitronaphtho[2,1-b]furan (R7000), we evaluated its mutagenic potency in a battery of his- mutants of Salmonella typhimurium designed to study mutagenic specificity (Levin and Ames, 1986). Using this system we could show that R7000 is able to induce base-pair substitutions, mainly GC----TA transversions and, perhaps to a lower extent, AT----TA transversions. In addition, our results suggest that this chemical may be a very efficient inducer of base-pair deletions/insertions resulting in frameshifts. Whereas the induction of base-pair substitutions by R7000 is dependent on the presence of plasmid pKM101 carrying the mucA,B operon, the induction of base-pair deletions/insertions is independent of the presence of the plasmid.

Alanine↗
PubMed1989

Detection of ionizing radiations with the SOS Chromotest, a bacterial short-term test for genotoxic agents.

The effects of 3 types of ionizing radiation, gamma-rays, neutrons and accelerated alpha-particles, were examined using the SOS Chromotest, a bacterial colorimetric assay for genotoxic agents based on the measurement of the SOS response in Escherichia coli. The SOS Chromotest appeared to be a sensitive and simple assay to detect quantitatively these radiations as well as their biological effects. The range of adsorbed doses for which induction was observed was similar for the 3 types of radiation, the minimum inducing doses being in the order of 2.5-5 Gy. We discuss the possible use of these observations to study the molecular action of radiations and to compare their genotoxic effects with those of chemicals.

DNA Repair↗
PubMed1989

DNA adduct formation by 7-methoxy-2-nitro-naphtho[2,1-b]furan (R7000), an extremely potent mutagen.

The effects on DNA, in bacteria, of 7-methoxy-2-nitro-naphtho[2,1-b]furan (R7000), a very potent genotoxic product from the 2-nitronaphthofuran series, were investigated with two different approaches: (i) measurement of the binding of the radiolabelled mutagen to DNA and (ii) detection by the '32P-postlabelling' method of DNA adducts following treatment with unlabelled mutagens. The covalent binding of R7000 to DNA in Escherichia coli was demonstrated by both methods, and in the latter case it was found to involve the formation of nine different adducts. Formation of adducts by R7000 was shown to require metabolic activation of the compound.

Chromatography, Thin Layer↗
PubMed1989

Induction of the SOS response by hydrogen peroxide in various Escherichia coli mutants with altered protection against oxidative DNA damage.

The induction of the SOS response by H2O2 was measured in Escherichia coli by means of a sfiA::lacZ operon fusion. The effects of mutations in genes involved in DNA repair or DNA metabolism on the SOS response were investigated. We found that in an uvrA mutant, H2O2 induced the SOS response at lower concentrations than in the uvr+ parent strain, indicating that some lesions induced by H2O2 may be repaired by the uvrABC-dependent excision repair system. A nth mutation, yielding deficiency in thymine glycol DNA glycosylase, had no detectable effect on SOS induction, indicating that thymine glycol, a DNA lesion expected to be induced by H2O2, does not participate detectably in the induction of the SOS response by this chemical under our conditions. H2O2 still induced the SOS response in a dnaC(Ts) uvrA double mutant under conditions in which no DNA replication proceeds, suggesting that this chemical induces DNA strand breaks. Induction of the SOS response by H2O2 was also assayed in various mutants affected in genes suspected to be important for protection against oxidative stress. Mutations in the catalase genes, katE and katG, had only minor effects. However, in an oxyR deletion mutant, in which the adaptative response to H2O2 does not occur, SOS induction occurred at much lower H2O2 concentrations than in the oxyR+ parent strain. These results indicate that some enzymes regulated by the oxyR gene are, under our conditions, more important than catalase for protection against the H2O2-induced DNA damages which trigger the SOS response.

Chromosome Deletion↗
PubMed1988

Evaluation of the genotoxic activity of 2-nitroanthrafurans.

We measured the genotoxic activities in two bacterial tests, the Salmonella/histidine assay (a reverse mutation assay) and the SOS chromotest (an assay for SOS induction in E. coli), of three 2-nitroanthrafurans: 2-nitroanthra[1,2-b]furan (R-7688), the isomeric compound 2-nitroanthra[2,1-b]furan (R-7686) and its 8-methoxylated derivative (R-7707). Their genotoxic activities were compared to that of 7-methoxy-2-nitronaphtho[2,1-b]furan (R-7000) which has been studied in previous works (Arnaise et al., 1986). We found that: (1) for all three 2-nitroanthrafurans, as generally observed for other 2-nitrofuran derivatives, the responses were correlated in the 2 tests and were decreased in the presence of an 'activating mixture' and in nitroreductase-deficient strains; (2) in contrast to what is usually observed with other 2-nitrofuran derivatives for which methoxylation increases genotoxic activity, the genotoxic activity of the methoxylated 2-nitroanthrafuran (R-7707) was comparable and may be even lower than that of the unsubstituted 2-nitroanthrafuran (R-7686); (3) the addition of a third ring that leads from 2-nitronaphthofurans to 2-nitroanthrafurans increased slightly the genotoxic activity of these compounds; (4) compounds with the oxygen heteroatom outside the 'bay region', R-7686 and R-7707, gave higher responses than their isomers with the oxygen heteroatom within the 'bay region', R-7688.

Animals↗
PubMed1988

Absence of genotoxic activity of refined smoke flavor (RSF) in two bacterial short-term tests.

The genotoxic activities of refined smoke flavor (RSF) produced in Poland and used in food processing were investigated in 2 bacterial short-term tests. Its mutagenic activity was examined in the Salmonella/histidine plate assay and its SOS-inducing capacity in the SOS Chromotest both without and with 'activation' by a rat liver homogenate. No genotoxic activity was detected using these 2 bacterial tests.

Animals↗
PubMed1988

The SOS Chromotest, a colorimetric assay based on the primary cellular responses to genotoxic agents.

The SOS Chromotest is a quantitative bacterial colorimetric assay for genotoxins. Substantial validation is now available. We describe the tester strain as well as results of validation studies. Comparison of the results with those obtained in the Mutatest (the Ames test) showed that most (90 percent) of the mutagenic compounds were also SOS inducers. For these compounds, a quantitative correlation was observed between the mutagenic potency and the SOS-inducing potency (SOSIP). The present data indicate that the SOS Chromotest has many practical advantages and may be used as a primary screening tool or as part of a battery of short-term tests for carcinogens. Theoretical considerations on the relation between the SOSIP and the mutagenic potency are briefly discussed.

Benzo(a)pyrene↗