Multiple regulation involved in the expression of the uxuR regulatory gene in Escherichia coli K-12

1983 ◽  
Vol 189 (2) ◽  
pp. 351-354 ◽  
Author(s):  
Paul Ritzenthaler ◽  
Mireille Mata-Gilsinger
Keyword(s):  
Escherichia Coli ◽  
Regulatory Gene ◽  
K 12

scholarly journals Enhanced Expression of the Multidrug Efflux Pumps AcrAB and AcrEF Associated with Insertion Element Transposition in Escherichia coli Mutants Selected with a Fluoroquinolone

2001 ◽  
Vol 45 (5) ◽  
pp. 1467-1472 ◽  
Author(s):  
A. S. Jellen-Ritter ◽  
W. V. Kern
Keyword(s):  
Escherichia Coli ◽  
In Vitro Selection ◽  
Regulatory Gene ◽  
Fluoroquinolone Resistance ◽  
Upstream Region ◽  
Single Mutation ◽  
Multidrug Efflux ◽  
E Coli ◽  
Enhanced Expression ◽  
K 12

ABSTRACT The development of fluoroquinolone resistance in Escherichia coli may be associated with mutations in regulatory gene loci such as marRAB that lead to increased multidrug efflux, presumably through activation of expression of the AcrAB multidrug efflux pump. We found that multidrug-resistant (MDR) phenotypes with enhanced efflux can also be selected by fluoroquinolones frommarRAB- or acrAB-inactivated E. coli K-12 strains having a single mutation in the quinolone-resistance-determining region of gyrA. Mutant 3-AG100MKX, obtained from a mar knockout strain after two selection steps, showed enhanced expression of acrB in a reverse transcriptase PCR associated with insertion of IS186 into the AcrAB repressor gene acrR. In vitro selection experiments with acrAB knockout strains yielded MDR mutants after a single step. Enhanced efflux in these mutants was due to increased expression of acrEF and associated with insertion of IS2 into the upstream region ofacrEF, presumably creating a hybrid promoter. These observations confirm the importance of efflux-associated nontarget gene mutations and indicate that transposition of genetic elements may have a role in the development of fluoroquinolone resistance in E. coli.

scholarly journals Characterization of the Detachable Rho-Dependent Transcription Terminator of the fimE Gene in Escherichia coli K-12

2005 ◽  
Vol 187 (24) ◽  
pp. 8256-8266 ◽  
Author(s):  
Paul Hinde ◽  
Padraig Deighan ◽  
Charles J. Dorman
Keyword(s):  
Escherichia Coli ◽  
Regulatory Gene ◽  
Genetic Switch ◽  
Transcription Terminator ◽  
Poor Region ◽  
Gene Switches ◽  
Sequence Elements ◽  
Negative Effect ◽  
K 12 ◽  
G Ratio

ABSTRACT The fim genetic switch in the chromosome of Escherichia coli K-12 is an invertible DNA element that harbors the promoter for transcription of the downstream fim structural genes and a transcription terminator that acts on the upstream fimE regulatory gene. Switches oriented appropriately for structural gene transcription also allow fimE mRNA to read through, whereas those in the opposite orientation terminate the fimE message. We show here that termination is Rho dependent and is suppressed in a rho mutant or by bicyclomycin treatment when fimE mRNA is expressed by the fimE gene, either from a multicopy recombinant plasmid or in its native chromosomal location. Two cis-acting elements within the central portion of the 314-bp invertible DNA switch were identified as contributors to Rho-dependent termination and dissected. These fim sequence elements show similarities to well-characterized Rho utilization (rut) sites and consist of a boxA motif and a C-rich and G-poor region of approximately 40 bp. Deletion of the boxA motif alone had only a subtle negative effect on Rho function. However, when this element was deleted in combination with the C-rich, G-poor region, Rho function was considerably decreased. Altering the C-to-G ratio in favor of G in this portion of the switch also strongly attenuated transcription termination. The implications of the existence of a fimE-specific Rho-dependent terminator within the invertible switch are discussed in the context of the fim regulatory circuit.

scholarly journals NEGATIVE DOMINANT MUTATIONS OF THE uidR GENE IN ESCHERICHIA COLI: GENETIC PROOF FOR A COOPERATIVE REGULATION OF uidA EXPRESSION

Genetics ◽  
1986 ◽  
Vol 112 (2) ◽  
pp. 173-182
Author(s):  
Carlos Blanco ◽  
Paul Ritzenthaler ◽  
Mireille Mata-Gilsinger
Keyword(s):  
Escherichia Coli ◽  
Gene Dosage ◽  
Regulatory Gene ◽  
Active Form ◽  
Point Mutations ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Cooperative Process ◽  
Mutant Phenotypes ◽  
K 12

ABSTRACT The uidA gene is the first gene involved in the hexuronide-hexuronate pathway in Escherichia coli K-12 and is under the dual control of the uidR and uxuR encoded repressors. Point mutations affecting the uidR regulatory gene were sought to investigate the regulation of uidA. When the uidR mutant allele was on a multicopy plasmid and the wild-type allele was on the chromosome, some of the mutant phenotypes were dominant to the wild-type phenotype, indicating that the active form of the UidR repressor is multimeric. We have demonstrated that expression of the mutant phenotype is dependent on gene dosage. The dominance of the uidR allele was also sensitive to the presence of the wild-type uxuR allele in the cell. This behavior probably results from UidR-UxuR repressor interactions. A mechanism is proposed: we suggest that the UidR and UxuR repressors interact after their binding to the operator site of uidA; the binding of one regulatory molecule may facilitate the binding of the other one in a cooperative process.

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