Evidence for involvement of UvrB in elicitation of ‘SIR’ phenotype by rpoB87-gyrA87 mutations in lexA3 mutant of Escherichia coli

Shanmughapriya, Vinod; Munavar, M. Hussain

doi:10.1016/j.dnarep.2012.09.005

Cited by 8 publications

(10 citation statements)

References 60 publications

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“…Other studies have shown that out of all the Nucleotide Excision Repair functions (UvrA, UvrB and UvrC/Cho) that take part in repair of MMC induced DNA damage only UvrB is mandatory [19]. Our results which showed that increase in expression of the uvrB gene in a lexA3 strain could increase the MMC resistance correlated well with the above observation [7]. This places UvrB in a prominent role in SIR mediated MMC resistance observed in SOS deficient strains.…”

Section: Resultssupporting

confidence: 89%

“…It was shown that mutations inactivating the uvrB gene abolished this resistance. The study revealed that the rpoB87 mutation carries a C 1565 →T 1565 transition in the 522 nd codon of rpoB [7]. This lesion is the same as reported to be present in rpoB3595 mutant as reported by Jin and Gross [8].…”

Section: Introductionsupporting

confidence: 82%

“…It was shown that the rpoB3595 mutation increases the expression of SOS genes in a strain that is constitutive for SOS [26]. In our previous study, we have shown that this increase in expression of uvrB is seen even in lexA3 strains when the rpoB87/rpoB3595 mutation is coupled with the gyrA87 mutation [7].…”

Section: Discussionmentioning

confidence: 71%

“…The rpoB2, rpoB8 and rpoB111 mutations were introduced into DM49N ( lexA3 gyrA87 ) strain as mentioned in materials and methods. The relative survival of various strains was carried out at 37°C in this study as opposed to the 30°C assays used in the previously published data of MMC survival [7] because during the course of this investigation we found that the resistance to MMC was found to be a little better at higher temperatures compared to 30°C (Shanmughapriya and Munavar, Unpublished data). MMC survival analyses of the relevant strains clearly indicate that none of the other mutations could make the lexA3 strain to survive on 0.5 µg/ml MMC containing plates but the rpoB87-gyrA87 - lexA3 strain could survive well at the same concentration (Fig.…”

Section: Resultsmentioning

confidence: 98%

“…This allele is known to define a fast moving RNA Polymerase. The gyrA87 is a hitherto unreported Nal R allele that carries a G 244 →A 244 transition changing the 82 nd codon of gyrA gene giving rise to a D82N change in the GyrA protein [7]. This defines a novel allele for Nalidixic acid resistance.…”

Section: Introductionmentioning

confidence: 99%

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Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

2014

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Very recently, we have reported about an unconventional mode of elicitation of Mitomycin C (MMC) specific resistance in lexA3 (SOS repair deficient) mutants due to a combination of Rif-Nal mutations (rpoB87-gyrA87). We have clearly shown that UvrB is mandatory for this unconventional MMC resistance in rpoB87-gyrA87-lexA3 strains and uvrB is expressed more even without DNA damage induction from its LexA dependent promoter despite the uncleavable LexA3 repressor. The rpoB87 allele is same as the rpoB3595 which is known to give rise to a fast moving RNA Polymerase and gyrA87 is a hitherto unreported NalR allele. Thus, it is proposed that the RNA Polymerase with higher elongation rate with the mutant DNA Gyrase is able to overcome the repressional hurdle posed by LexA3 to express uvrB. In this study we have systematically analysed the effect of three other rpoB (rif) mutations-two known to give rise to fast moving RNAP (rpoB2 and rpoB111) and one to a slow moving RNAP (rpoB8) and four different alleles of gyrA NalR mutations (gyrA199, gyrA247, gyrA250, gyrA259) isolated spontaneously, on elicitation of MMC resistance in lexA3 strains. Our results indicate that in order to acquire resistance to 0.5 µg/ml MMC cells require both rpoB87 and gyrA87 but resistance to 0.25 µg/ml of MMC can be brought about by either rpoB87, gyrA87, fast moving rpoB mutations or other nal mutations also. We have also depicted increased constitutive uvrB expression in strains carrying fast moving RNAP (rpoB2 and rpoB111) with gyrA87 and another nal mutation with rpoB87 and expression level in these strains is lesser than rpoB87-gyrA87 strain. These results evidently suggest an allele specific role for the rif-nal mutations to acquire MMC resistance in lexA3 strains via increased constitutive uvrB expression and a pivotal role for rpoB87-gyrA87 combination to elicit higher levels of resistance.

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Section: Resultssupporting

confidence: 89%

Section: Introductionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

2014

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Glu₅₇₁ of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme

et al. 2018

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As of date the two temperature sensitive mutations isolated in pheST operon include pheS5 (G →A ) and pheT354. Recently, we reported that G of pheS defines a hot spot for intragenic suppressors of pheS5. In this investigation, in 13 independent experiments, a collection of temperature sensitive mutants were isolated by localized mutagenesis. Complementation using clones bearing pheS , pheT , and pheS T indicated that 34 mutants could harbor lesion(s) in pheS and four could be in pheT and one mutant might be a double mutant. Surprisingly, all the 34 pheS mutants harbored the very same (G →A ) transition mutation as present in the classical pheS5 mutant. Most unexpectedly, the four pheT mutants isolated harbored the same G →A transition, a mutation which is hitherto unreported. Since all the four pheT mutants were defined by the same G →A base change, we believe that getting other mutations could be hard hitting and therefore it is proposed that G itself could be a "hot spot" for emergence of Ts mutations in pheT and similarly G itself could be a "hot spot" for Ts lesions in pheS. These results clearly imply a vital role for Glutamic acid (Glu ) of PheT and reinforce criticality of Glycine (Gly ) of PheS in the thermal stability of PheRS enzyme.

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G₆₇₃ could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli

Ponmani

Munavar

2014

MicrobiologyOpen

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The pheS5 Ts mutant of Escherichia coli defined by a G293 → A293 transition, which is responsible for thermosensitive Phenylalanyl-tRNA synthetase has been well studied at both biochemical and molecular level but genetic analyses pertaining to suppressors of pheS5 were hard to come by. Here we have systematically analyzed a spectrum of Temperature-insensitive derivatives isolated from pheS5 Ts mutant and identified two intragenic suppressors affecting the same base pair coordinate G673 (pheS19 defines G673 → T673; Gly225 → Cys225 and pheS28 defines G673 → C673; Gly225 → Arg225). In fact in the third derivative, the intragenic suppressor originally named pheS43 (G673 → C673transversion) is virtually same as pheS28. In the fourth case, the very pheS5 lesion itself has got changed from A293 → T293 (named pheS40). Cloning of pheS+, pheS5, pheS5-pheS19, pheS5-pheS28 alleles into pBR322 and introduction of these clones into pheS5 mutant revealed that excess of double mutant protein is not at all good for the survival of cells at 42°C. These results clearly indicate a pivotal role for Gly225 in the structural/functional integrity of alpha subunit of E. coli PheRS enzyme and it is proposed that G673 might define a hot spot for intragenic suppressors of pheS5.

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Evidence for involvement of UvrB in elicitation of ‘SIR’ phenotype by rpoB87-gyrA87 mutations in lexA3 mutant of Escherichia coli

Cited by 8 publications

References 60 publications

Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

Glu₅₇₁ of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme

G₆₇₃ could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli

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Evidence for involvement of UvrB in elicitation of ‘SIR’ phenotype by rpoB87-gyrA87 mutations in lexA3 mutant of Escherichia coli

Cited by 8 publications

References 60 publications

Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

Selective Alleviation of Mitomycin C Sensitivity in lexA3 Strains of Escherichia coli Demands Allele Specificity of rif-nal Mutations: A Pivotal Role for rpoB87-gyrA87 Mutations

Glu571 of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme

G673 could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli

Contact Info

Product

Resources

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Glu₅₇₁ of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme

G₆₇₃ could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli