Disease relevance of rpoS

• The rpoS-encoded sigma(S) subunit of RNA polymerase in Escherichia coli is a global regulatory factor involved in several stress responses [1].
• The RNA-binding protein HF-I, known as a host factor for phage Qbeta RNA replication, is essential for rpoS translation in Escherichia coli [1].
• Mutations that increase expression of the rpoS gene and decrease its dependence on hfq function in Salmonella typhimurium [2].
• Control of rpoS transcription in Escherichia coli and Pseudomonas: why so different [3]?
• The rpoS gene from Yersinia enterocolitica and its influence on expression of virulence factors [4].

High impact information on rpoS

• Using a combination of gene fusion analysis and pulse-chase experiments, we demonstrate that the hfq mutant is specifically impaired in rpoS translation [1].
• Our analysis also indicates that at least five different signals [cAMP, a growth rate-related signal (ppGpp?), a cell density signal, an osmotic signal, and a starvation signal] are involved in the control of all these processes that regulate rpoS/sigma S expression [5].
• The Escherichia coli host factor I, Hfq, binds to many small regulatory RNAs and is required for OxyS RNA repression of fhlA and rpoS mRNA translation [6].
• The OxyS regulatory RNA represses rpoS translation and binds the Hfq (HF-I) protein [7].
• The katF gene product, a stationary phase-specific sigma factor, was not required for the expression of rmf [8].

Chemical compound and disease context of rpoS

• For E. coli CFT073, introduction of an rpoS deletion impaired trehalose accumulation, osmotolerance and stationary-phase thermotolerance [9].
• Mutation of the phoP gene rendered Salmonella as sensitive to hydrogen peroxide as an rpoS mutant after growth in low Mg(2+) [10].
• We compared the viabilities (direct viable counts) and culturabilities (colony counts) in seawater of Escherichia coli and Salmonella typhimurium strains and those in which rpoS was deleted or which were deficient in guanosine 3',5'-bispyrophosphate (ppGpp) synthesis (relA spoT) [11].
• The E. coli parental strains reached the non-culturable state in 33 days when the plate counts were evaluated on Luria-Bertani agar containing sodium pyruvate, whereas cells of the rpoS mutants lost their culturability in only 21 days [12].
• When tetracycline was present, tetA(C) reduced acid tolerance, suppressed rpoS expression, and increased the concentration of total soluble proteins in stationary-phase Escherichia coli [13].

Biological context of rpoS

• The rpoS gene of Escherichia coli encodes a putative RNA polymerase sigma factor that is considered to be the central regulator of gene expression in stationary phase [14].
• In stationary phase, a mutation in rpoS, which controls the expression of starvation genes including those which protect against oxidative stress, renders the cells hypersensitive to killing by HOCl [15].
• DNA sequence analysis of the mutants suggests a model in which the RNA secondary structure near the ribosome binding site of the rpoS mRNA plays an important role in limiting expression in the wild type [2].
• In this study, the role of HF-I was explored by isolating suppressor mutations that map to the region directly upstream of rpoS [2].
• To clarify that these three proteins are strongly involved in cell viability, the rmf, rpoS (encoding sigma(38)), and ompC genes were disrupted [16].

Anatomical context of rpoS

• The heterogeneity of rpoS-dependent phenotypes observed for stress-related phenotypes was also evident in the Caco-2 cell adherence assay [17].

Associations of rpoS with chemical compounds

• Inasmuch as this inhibition by poly(P)ase did not affect the levels of the stringent-response guanosine nucleotides (pppGpp and ppGpp) and in view of the capacity of additional rpoS expression to suppress the poly(P)ase inhibition of katE expression, a role is proposed for poly(P) in inducing the expression of rpoS [18].
• In stark contrast, the inactivation of both oxyR and rpoS genes dramatically decreased the viability of glucose-starved cells [19].
• Indeed, the rpoS mutant strain shows severely impaired growth on some sugars such as fructose and N-acetylglucosamine [20].
• The rpoS gene controls the production of indole, which acts as a signal molecule in stationary-phase cells, via regulation of the tnaA-encoded tryptophanase enzyme [20].
• The rpoS gene product (sigma 38) was rapidly degraded after addition of chloramphenicol to cultures in the exponential, but not the stationary phase [21].

Regulatory relationships of rpoS

• We found that a crl null allele influences expression of RpoS-regulated genes in a fashion similar to an rpoS null allele [22].

Other interactions of rpoS

• Mutations in rprA and compensating mutations in the rpoS leader demonstrate that RprA interacts with the same region of the RpoS leader as DsrA [23].
• However, a mutation in rpoS did not prevent an increase in hmp expression by paraquat in exponentially growing cells [24].
• With the exception of the dksA mutant, which had a modest defect in Luria-Bertani medium, none of these mutants was defective for rpoS stationary-phase induction [25].
• Evolution of multi-gene segments in the mutS-rpoS intergenic region of Salmonella enterica serovar Typhimurium LT2 [26].
• However, the genetic elimination of the rpoS, whose product is an alternative sigma factor (RpoS), derepressed the tktA gene expression in the stationary growth phase, indicating that the RpoS sigma factor negatively regulates the tktA gene expression in the stationary growth phase [27].

Analytical, diagnostic and therapeutic context of rpoS

• Co-immunoprecipitation and gel mobility shift experiments revealed that the OxyS RNA binds Hfq, suggesting that OxyS represses rpoS translation by altering Hfq activity [7].
• As demonstrated by two dimensional gel electrophoresis, this induction of the RelA protein resulted in global alterations in gene expression including increased synthesis of some rpoS-dependent proteins [28].
• Transcription levels of the two divergently transcribed agf operons required for biogenesis of thin aggregative fimbriae by Northern blot analysis with gene probes for agfA and agfD as well as expression levels of AgfA by Western blotting were compared in the wild type, the constitutive mutants and their respective ompR and rpoS- derivatives [29].
• Gel mobility shift assays show that HU is able to bind specifically an RNA fragment containing the translational initiation region of rpoS mRNA 1000-fold more strongly than double-stranded DNA [30].
• Sequence analysis of the complementing clone revealed an 1.008-bp open reading frame which is predicted to encode a 336-amino-acid protein with 71 to 63% overall identity to other reported rpoS gene products [31].

References