The <i>Escherichia coli</i> UVM response is accompanied by an SOS‐independent error‐prone DNA replication activity demonstrable <i>in vitro</i>

Mamun, Abu Amar M. Al; Yadava, Ramesh S.; Ren, Li; Humayun, M. Zafri

doi:10.1046/j.1365-2958.2000.02136.x

Cited by 10 publications

(7 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the numerical values were higher than those obtained with the arrays, which is probably a result of the higher efficiency of the RT step (no cyanine dye incorporation) and the higher sensitivity of the real-time PCR. The same is true for stx 1 . Whereas the ratios for the stx 1 genes were close to being below the threshold values for regulation on the array (1.8 for stxA 1 ) and 1.5 (stxB 1 ), real-time PCR indicated upregulation, with higher ratios of 7.0 (stxA 1 ) and 5.9 (stxB 1 ).…”

Section: Resultsmentioning

confidence: 54%

“…However, a low concentration of norfloxacin could probably switch on alternate DNA repair pathways. E. coli possesses multiple inducible DNA repair pathways; among these are recA-independent pathways, such as the UVM response (1,17). However, the most plausible explanation would be that the low norfloxacin concentration is not able to fully induce the SOS regulon genes.…”

Section: Discussionmentioning

confidence: 99%

“…To obtain a standard curve, real-time reverse transcription (RT)-PCR was performed for serC, stxA 2 , stxB 2, stxA 1 , stxB 1 , and recA with serial dilutions of the cDNA (Table 2). We defined a copy number for each dilution.…”

Section: Herold Et Al Antimicrob Agents Chemothermentioning

confidence: 99%

See 2 more Smart Citations

Global Expression of Prophage Genes in Escherichia coli O157:H7 Strain EDL933 in Response to Norfloxacin

Herold

Siebert²,

Huber³

et al. 2005

Antimicrob Agents Chemother

View full text Add to dashboard Cite

We investigated the influence of a low concentration of the gyrase inhibitor norfloxacin on the transcriptome of enterohemorrhagic Escherichia coli O157:H7 strain EDL933. For this purpose, we used a commercial DNA microarray containing oligonucleotides specific for E. coli O157:H7 strains EDL933 and RIMD0509952 and E. coli K-12 strain MG1655. Under the conditions applied, 5,963 spots (94% of all spots) could be analyzed. Among these, 118 spots (P < 0.05) indicated transcriptional upregulation and 122 spots (P < 0.05) indicated transcriptional downregulation of the E. coli genes present on the array. Eighty-five upregulated EDL933 genes were phage borne. Fifty-two of them could be ascribed to the Shiga toxin-encoding phages (Stx phages) BP-933W and CP-933V; the other 33 genes belonged to non-Stx prophage elements in the EDL933 genome. Genes present in the BP-933W prophage genome were induced most strongly up to 158-fold in the case of stxA 2 upon induction with norfloxacin. Twenty-two additional upregulated genes appeared to be E. coli O157:H7 strain RIMD0509952-specific phage elements, and the remaining 11 genes were related mainly to recombination and stress functions. Downregulation was indicated predominantly for genes responsible for bacterial primary metabolism, such as energy production, cell division, and amino acid biosynthesis. Interestingly, some genes present in the locus of enterocyte effacement appeared to be downregulated. The results of the study have shown that a low concentration of norfloxacin has profound effects on the transcriptome of E. coli O157:H7.

show abstract

Section: Resultsmentioning

confidence: 54%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Global Expression of Prophage Genes in Escherichia coli O157:H7 Strain EDL933 in Response to Norfloxacin

Herold

Siebert²,

Huber³

et al. 2005

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…Analysis of in Vitro Mutation Fixation at ⑀C-Replication reactions were carried out as described above, and the newly synthesized minus strand was selectively amplified by ligation-mediated PCR (LM-PCR) following the procedures described in detail by Al Mamun et al (10,55). The resulting gel-purified 309-bp DNA fragment was subjected to multiplex sequencing reactions as described by Al Mamun et al (10) The elongation products were electrophoresed on 16% polyacrylamide, 8 M urea gels, and the autoradiograms were analyzed by densitometry as described previously (49).…”

Section: Fidelity Of Pol III From E Coli Muta Cellsmentioning

confidence: 99%

DNA Polymerase III from Escherichia coliCells Expressing mutA Mistranslator tRNA Is Error-prone

Mamun

Marians

Humayun

2002

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Translational stress-induced mutagenesis (TSM) refers to the elevated mutagenesis observed in Escherichia coli cells in which mistranslation has been increased as a result of mutations in tRNA genes (such as mutA) or by exposure to streptomycin. TSM does not require lexA-regulated SOS functions but is suppressed in cells defective for homologous recombination genes. Crude cell-free extracts from TSM-induced E. coli strains express an error-prone DNA polymerase. To determine whether DNA polymerase III is involved in the TSM phenotype, we first asked if the phenotype is expressed in cells defective for all four of the non-replicative DNA polymerases, namely polymerase I, II, IV, and V. By using a colony papillation assay based on the reversion of a lacZ mutant, we show that the TSM phenotype is expressed in such cells. Second, we asked if pol III from TSM-induced cells is error-prone. By purifying DNA polymerase III* from TSM-induced and control cells, and by testing its fidelity on templates bearing 3,N 4 -ethenocytosine (a mutagenic DNA lesion), as well as on undamaged DNA templates, we show here that polymerase III* purified from mutA cells is error-prone as compared with that from control cells. These findings suggest that DNA polymerase III is modified in TSMinduced cells.Autonomous organisms normally replicate its DNA accurately, but the fidelity of replication can be transiently decreased in response to environmental and physiological stimuli through a number of pathways (1). Although the Escherichia coli SOS response represents the best-described transient mutator response (2), emerging evidence indicates the existence of multiple inducible mutagenic pathways in E. coli (3). One especially intriguing pathway is provoked by increased translational errors resulting from mutations in tRNA genes (4, 5), in genes specifying tRNA-modification enzymes (6), or from exposure to streptomycin, an antibiotic that promotes mistranslation (7). This pathway, dubbed translational stress-induced mutagenesis (TSM) 1 (3), does not require the induction of lexA/ recA-regulated SOS genes and is suppressed in cells defective for RecABC/RuvABC-dependent homologous recombination (5, 7-9). Available genetic (5, 7-9) and biochemical (10) evidence suggests that the TSM phenotype results from error-prone DNA replication rather than from defective DNA repair. On the basis of the effect of elimination of individual genes encoding "non-replicative" polymerases, we previously proposed that either DNA polymerase III or an unidentified new DNA polymerase is responsible for error-prone replication in TSM-induced cells. DNA polymerase III holoenzyme (pol III HE) accounts for more than 90% of cellular DNA synthesis (11, 12) and is also required for the major post-replicative mismatch correction pathway (13, 14). pol III HE was shown to effectively carry out translesion DNA synthesis past abasic sites, mostly producing Ϫ1-bp deletions (15), as contrasted to translesion synthesis carried out by pol V, which mostly yields base substitutions at a...

show abstract

“…The lspA gene, encoding SPase II from R. typhi and E. coli, was cloned by PCR into expression vector pMW119 under a lac promoter (2). Primers used in PCR are shown in Table 1 and were designed based on the genome sequences available in the GenBank database (www.ncbi.nlm.nih.gov).…”

Section: Methodsmentioning

confidence: 99%

The lspA Gene, Encoding the Type II Signal Peptidase of Rickettsia typhi : Transcriptional and Functional Analysis

et al. 2007

View full text Add to dashboard Cite

Lipoprotein processing by the type II signal peptidase (SPase II) is known to be critical for intracellular growth and virulence for many bacteria, but its role in rickettsiae is unknown. Here, we describe the analysis of lspA, encoding a putative SPase II, an essential component of lipoprotein processing in gram-negative bacteria, from Rickettsia typhi. Alignment of deduced amino acid sequences shows the presence of highly conserved residues and domains that are essential for SPase II activity in lipoprotein processing. The transcription of lspA, lgt (encoding prolipoprotein transferase), and lepB (encoding type I signal peptidase), monitored by real-time quantitative reverse transcription-PCR, reveals a differential expression pattern during various stages of rickettsial intracellular growth. The higher transcriptional level of all three genes at the preinfection time point indicates that only live and metabolically active rickettsiae are capable of infection and inducing host cell phagocytosis. lspA and lgt, which are involved in lipoprotein processing, show similar levels of expression. However, lepB, which is involved in nonlipoprotein secretion, shows a higher level of expression, suggesting that LepB is the major signal peptidase for protein secretion and supporting our in silico prediction that out of 89 secretory proteins, only 14 are lipoproteins. Overexpression of R. typhi lspA in Escherichia coli confers increased globomycin resistance, indicating its function as SPase II. In genetic complementation, recombinant lspA from R. typhi significantly restores the growth of temperature-sensitive E. coli Y815 at the nonpermissive temperature, supporting its biological activity as SPase II in prolipoprotein processing.

show abstract

The Escherichia coli UVM response is accompanied by an SOS‐independent error‐prone DNA replication activity demonstrable in vitro

Cited by 10 publications

References 50 publications

Global Expression of Prophage Genes in Escherichia coli O157:H7 Strain EDL933 in Response to Norfloxacin

Global Expression of Prophage Genes in Escherichia coli O157:H7 Strain EDL933 in Response to Norfloxacin

DNA Polymerase III from Escherichia coliCells Expressing mutA Mistranslator tRNA Is Error-prone

The lspA Gene, Encoding the Type II Signal Peptidase of Rickettsia typhi : Transcriptional and Functional Analysis

Contact Info

Product

Resources

About