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Escherichia coli YafP protein modulates DNA damaging property of the nitroaromatic compounds.

Gutierrez A, Elez M, Clermont O, Denamur E, Matic I - Nucleic Acids Res. (2011)

Bottom Line: Using a murine septicaemia model, we showed that YafP activity reduced the bacterial fitness in the absence of PolIV.The YafP antimutator activity was independent of the PolIV activity.Given that YafP was annotated as a putative acetyltransferase, it could be that YafP participates in the metabolic transformation of genotoxic compounds, hence modulating the balance between their mutagenicity and cytotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine Paris Descartes, Inserm U1001, Université Paris Descartes, Paris, France.

ABSTRACT
Escherichia coli SOS functions constitute a multifaceted response to DNA damage. We undertook to study the role of yafP, a SOS gene with unknown function. yafP is part of an operon also containing the dinB gene coding for DNA Polymerase IV (PolIV). Our phylogenetic analysis showed that the gene content of this operon is variable but that the dinB and the yafP genes are conserved in the majority of E. coli natural isolates. Therefore, we studied if these proteins are functionally linked. Using a murine septicaemia model, we showed that YafP activity reduced the bacterial fitness in the absence of PolIV. Similarly, YafP increased cytotoxicity of two DNA damaging nitroaromatic compounds, 4-nitroquinoline-1-oxide (NQO) and nitrofurazone, in the absence of PolIV. The fact that PolIV counterbalances YafP-induced cytotoxicity could explain why these two genes are transcriptionally linked. We also studied the involvement of YafP in genotoxic-stress induced mutagenesis and found that PolIV and YafP reduced NQO-induced mutagenicity. The YafP antimutator activity was independent of the PolIV activity. Given that YafP was annotated as a putative acetyltransferase, it could be that YafP participates in the metabolic transformation of genotoxic compounds, hence modulating the balance between their mutagenicity and cytotoxicity.

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Effect of Pol IV and YafP on NQO-induced mutagenesis. Frequency of spontaneous (A) and NQO-induced (B) rifampicin resistant (RifR) mutants in WT, dinB, yafP and dinB yafP strains. Each point represents the mean (±SE) values from at least five replicates in three independent experiments. The median values for WT, dinB, yafP, dinB yafP RifR frequency mutants are respectively: 3.30 × 10−8, 3.04 × 10−8, 2.71 × 10−8, 4.21 × 10−8 in LB and 2.86 × 10−7, 1.74 × 10−6, 2.54 × 10−6, 4.74 × 10−6 in LB with 10 μM NQO.
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Figure 5: Effect of Pol IV and YafP on NQO-induced mutagenesis. Frequency of spontaneous (A) and NQO-induced (B) rifampicin resistant (RifR) mutants in WT, dinB, yafP and dinB yafP strains. Each point represents the mean (±SE) values from at least five replicates in three independent experiments. The median values for WT, dinB, yafP, dinB yafP RifR frequency mutants are respectively: 3.30 × 10−8, 3.04 × 10−8, 2.71 × 10−8, 4.21 × 10−8 in LB and 2.86 × 10−7, 1.74 × 10−6, 2.54 × 10−6, 4.74 × 10−6 in LB with 10 μM NQO.

Mentions: NQO is a DNA damaging agent that reacts with DNA only after metabolic activation (6). Because acetylation changes the reactivity of NQO with DNA (24), and because YafP is a putative N-acetyltransferase, we tested whether YafP plays a role in NQO mutagenicity (Figure 5). It was previously shown that the inactivation of the dinB gene increases NQO-induced mutagenesis (6), but the role of YafP was not tested. Strains were treated with 10 µM NQO. Mutagenic effect was estimated by scoring of rifampicin resistant (RifR) mutants. While the RifR mutant frequency was identical for all strains in the absence of the NQO treatment, all tested strains showed significant NQO-induced mutagenesis (Figure 5). The ratio of median values of NQO-induced RifR mutant frequencies and RifR mutant frequencies of untreated controls were: 9-, 57-, 94- and 113-fold for parental, dinB, yafP and dinB yafP strains, respectively. dinB, yafP and dinB yafP strains had significantly higher NQO-induced mutant frequency relative to the WT strain (Mann–Whitney P < 0.05). dinB yafP strain had significantly higher RifR mutant frequency compared to the dinB strain. yafP strain did not show significantly different RifR mutant frequency compared to either dinB or dinB yafP strain. In conclusion, these data show an epistatic effect of Pol IV and YafP proteins on reduction of NQO mutagenicity.Figure 5.


Escherichia coli YafP protein modulates DNA damaging property of the nitroaromatic compounds.

Gutierrez A, Elez M, Clermont O, Denamur E, Matic I - Nucleic Acids Res. (2011)

Effect of Pol IV and YafP on NQO-induced mutagenesis. Frequency of spontaneous (A) and NQO-induced (B) rifampicin resistant (RifR) mutants in WT, dinB, yafP and dinB yafP strains. Each point represents the mean (±SE) values from at least five replicates in three independent experiments. The median values for WT, dinB, yafP, dinB yafP RifR frequency mutants are respectively: 3.30 × 10−8, 3.04 × 10−8, 2.71 × 10−8, 4.21 × 10−8 in LB and 2.86 × 10−7, 1.74 × 10−6, 2.54 × 10−6, 4.74 × 10−6 in LB with 10 μM NQO.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3105422&req=5

Figure 5: Effect of Pol IV and YafP on NQO-induced mutagenesis. Frequency of spontaneous (A) and NQO-induced (B) rifampicin resistant (RifR) mutants in WT, dinB, yafP and dinB yafP strains. Each point represents the mean (±SE) values from at least five replicates in three independent experiments. The median values for WT, dinB, yafP, dinB yafP RifR frequency mutants are respectively: 3.30 × 10−8, 3.04 × 10−8, 2.71 × 10−8, 4.21 × 10−8 in LB and 2.86 × 10−7, 1.74 × 10−6, 2.54 × 10−6, 4.74 × 10−6 in LB with 10 μM NQO.
Mentions: NQO is a DNA damaging agent that reacts with DNA only after metabolic activation (6). Because acetylation changes the reactivity of NQO with DNA (24), and because YafP is a putative N-acetyltransferase, we tested whether YafP plays a role in NQO mutagenicity (Figure 5). It was previously shown that the inactivation of the dinB gene increases NQO-induced mutagenesis (6), but the role of YafP was not tested. Strains were treated with 10 µM NQO. Mutagenic effect was estimated by scoring of rifampicin resistant (RifR) mutants. While the RifR mutant frequency was identical for all strains in the absence of the NQO treatment, all tested strains showed significant NQO-induced mutagenesis (Figure 5). The ratio of median values of NQO-induced RifR mutant frequencies and RifR mutant frequencies of untreated controls were: 9-, 57-, 94- and 113-fold for parental, dinB, yafP and dinB yafP strains, respectively. dinB, yafP and dinB yafP strains had significantly higher NQO-induced mutant frequency relative to the WT strain (Mann–Whitney P < 0.05). dinB yafP strain had significantly higher RifR mutant frequency compared to the dinB strain. yafP strain did not show significantly different RifR mutant frequency compared to either dinB or dinB yafP strain. In conclusion, these data show an epistatic effect of Pol IV and YafP proteins on reduction of NQO mutagenicity.Figure 5.

Bottom Line: Using a murine septicaemia model, we showed that YafP activity reduced the bacterial fitness in the absence of PolIV.The YafP antimutator activity was independent of the PolIV activity.Given that YafP was annotated as a putative acetyltransferase, it could be that YafP participates in the metabolic transformation of genotoxic compounds, hence modulating the balance between their mutagenicity and cytotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine Paris Descartes, Inserm U1001, Université Paris Descartes, Paris, France.

ABSTRACT
Escherichia coli SOS functions constitute a multifaceted response to DNA damage. We undertook to study the role of yafP, a SOS gene with unknown function. yafP is part of an operon also containing the dinB gene coding for DNA Polymerase IV (PolIV). Our phylogenetic analysis showed that the gene content of this operon is variable but that the dinB and the yafP genes are conserved in the majority of E. coli natural isolates. Therefore, we studied if these proteins are functionally linked. Using a murine septicaemia model, we showed that YafP activity reduced the bacterial fitness in the absence of PolIV. Similarly, YafP increased cytotoxicity of two DNA damaging nitroaromatic compounds, 4-nitroquinoline-1-oxide (NQO) and nitrofurazone, in the absence of PolIV. The fact that PolIV counterbalances YafP-induced cytotoxicity could explain why these two genes are transcriptionally linked. We also studied the involvement of YafP in genotoxic-stress induced mutagenesis and found that PolIV and YafP reduced NQO-induced mutagenicity. The YafP antimutator activity was independent of the PolIV activity. Given that YafP was annotated as a putative acetyltransferase, it could be that YafP participates in the metabolic transformation of genotoxic compounds, hence modulating the balance between their mutagenicity and cytotoxicity.

Show MeSH
Related in: MedlinePlus