Molecular assembly and functional modulation of Escherichia coli RNA polymerase

Ishihama, Akira

doi:10.1016/0065-227x(90)90005-e

Cited by 257 publications

(425 citation statements)

References 28 publications

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“…Regulation of the hdeAB operon. The figure has been produced using data from the literature (8,13,16,20,22,24,26,27,30,33,37,39,42,43,44,46) as well as the results obtained in this study. Thick arrows represent genes.…”

Section: Resultsmentioning

confidence: 99%

Role of the Multidrug Resistance Regulator MarA in Global Regulation of the hdeAB Acid Resistance Operon in Escherichia coli

2008

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MarA, a transcriptional regulator in Escherichia coli, affects functions such as multiple-antibiotic resistance (Mar) and virulence. Usually an activator, MarA is a repressor of hdeAB and other acid resistance genes. We found that, in wild-type cells grown in LB medium at pH 7.0 or pH 5.5, repression of hdeAB by MarA occurred only in stationary phase and was reduced in the absence of H-NS and GadE, the main regulators of hdeAB. Moreover, repression of hdeAB by MarA was greater in the absence of GadX or Lrp in exponential phase at pH 7.0 and in the absence of GadW or RpoS in stationary phase at pH 5.5. In turn, MarA enhanced repression of hdeAB by H-NS and hindered activation by GadE in stationary phase and also reduced the activity of GadX, GadW, RpoS, and Lrp on hdeAB under some conditions. As a result of its direct and indirect effects, overexpression of MarA prevented most of the induction of hdeAB expression as cells entered stationary phase and made the cells sevenfold more sensitive to acid challenge at pH 2.5. These findings show that repression of hdeAB by MarA depends on pH, growth phase, and other regulators of hdeAB and is associated with reduced resistance to acid conditions.

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Section: Resultsmentioning

confidence: 99%

Role of the Multidrug Resistance Regulator MarA in Global Regulation of the hdeAB Acid Resistance Operon in Escherichia coli

2008

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“…As in the case of H-NS, the HU protein affects the global pattern of gene transcription by modulating the conformation of genome DNA. IHF was ®rst identi®ed as a host factor for the integrative recombination of phage l (Craig & Nash 1984), but it is now recognized as a factor of global regulation in the transcription of many genes (Ishihama 1997a(Ishihama , 2000. For transcription regulation, IHF appears to make a direct contact with the RNA polymerase as well as modulation of DNA conformation.…”

Section: Intracellular Distribution Of E Coli Nucleoid Proteinsmentioning

confidence: 99%

Two types of localization of the DNA‐binding proteins within the Escherichia coli nucleoid

2000

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Background: The genome DNA of Escherichia coli is folded into the nucleosome-like structure, often called a nucleoid, by the binding of several DNAbinding proteins. We previously determined the speci®city and af®nity of DNA-binding for 12 species of the E. coli DNA-binding protein, and their intracellular concentrations at various growth phases. The intracellular localization of these proteins in E. coli could be predicted from these data, but no attempt has been made thus far to directly observe the intracellular distribution of the DNA-binding proteins.

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“…s 70 , the exponential-phase s factor, is responsible for the transcription of housekeeping genes involved in cell maintenance and growth. As the culture approaches stationary phase, s 38 increases in concentration and competes with s 70 for binding with the core polymerase (Ishihama, 2000). This leads to competing priorities for bacteria: regulation via s 38 provides protection against multiple stresses, particularly low pH (Farrell and Finkel, 2003;King et al, 2006), whereas regulation via s 70 provides improved nutrient scavenging (Notley-McRobb et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Evolutionary loss of the rdar morphotype in Salmonella as a result of high mutation rates during laboratory passage

2008

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Rapid evolution of microbes under laboratory conditions can lead to domestication of environmental or clinical strains. In this work, we show that domestication due to laboratory passage in rich medium is extremely rapid. Passaging of wild-type Salmonella in rich medium led to diversification of genotypes contributing to the loss of a spatial phenotype, called the rdar morphotype, within days. Gene expression analysis of the rdar regulatory network demonstrated that mutations were primarily within rpoS, indicating that the selection pressure for scavenging during stationary phase had the secondary effect of impairing this highly conserved phenotype. If stationary phase was omitted from the experiment, radiation of genotypes and loss of the rdar morphotype was also demonstrated, but due to mutations within the cellulose biosynthesis pathway and also in an unknown upstream regulator. Thus regardless of the selection pressure, rapid regulatory changes can be observed on laboratory timescales. The speed of accumulation of rpoS mutations during daily passaging could not be explained by measured fitness and mutation rates. A model of mutation accumulation suggests that to generate the observed accumulation of r 38 mutations, this locus must experience a mutation rate of approximately 10 À4 mutations/gene/generation. Sequencing and gene expression of population isolates indicated that there were a wide variety of r 38 phenotypes within each population. This suggests that the rpoS locus is highly mutable by an unknown pathway, and that these mutations accumulate rapidly under common laboratory conditions.

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Molecular assembly and functional modulation of Escherichia coli RNA polymerase

Cited by 257 publications

References 28 publications

Role of the Multidrug Resistance Regulator MarA in Global Regulation of the hdeAB Acid Resistance Operon in Escherichia coli

Role of the Multidrug Resistance Regulator MarA in Global Regulation of the hdeAB Acid Resistance Operon in Escherichia coli

Two types of localization of the DNA‐binding proteins within the Escherichia coli nucleoid

Evolutionary loss of the rdar morphotype in Salmonella as a result of high mutation rates during laboratory passage

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