Transcription of the Escherichia coli osmB gene is induced by several stress conditions. osmB is expressed from two promoters, osmBp1 and osmBp2. The downstream promoter, osmBp2, is induced after osmotic shock or upon entry into stationary phase in a sigma(s)-dependent manner. The upstream promoter, osmBp1, is independent of sigma(s) and is activated by RcsB, the response regulator of the His-Asp phosphorelay signal transduction system RcsCDB. RcsB is responsible for the induction of osmBp1 following treatment with chlorpromazine. Activation of osmBp1 by RcsB requires a sequence upstream of its -35 element similar to the RcsB binding site consensus, suggesting a direct regulatory role. osmB appears as another example of a multistress-responsive gene whose transcription involves both a sigma(s)-dependent promoter and a second one independent of sigma(s) but controlled by stress-specific transcription factors.

ABSTRACT The RcsCDB His-Asp phosphorelay is shown to positively regulate the bdm (biofilm-dependent modulation) and sra (stationary-phase-induced ribosome-associated protein) genes in Escherichia coli. The regulation is direct and requires an RcsB box next to the bdm −35 element. In addition, bdm is shown to be activated by osmotic shock in an Rcs-dependent way.

ABSTRACT Transcription of the Escherichia coli osmC gene is induced by several stress conditions. osmC is expressed from two overlapping promoters, osmCp1 and osmCp2. The proximal promoter, osmCp2, is transcribed at the entry into the stationary phase by the σs sigma factor. The distal promoter, osmCp1, is activated by NhaR and RcsB. NhaR is a positive regulator of the LysR family and is known to be an activator of the nhaA gene encoding an Na+/H+ antiporter. RcsB is the response regulator of the RcsCDB His-Asp phosphorelay signal transduction system. Genetic data indicated that activation of osmCp1 by both NhaR and RcsB requires the same short sequences upstream of the −35 region of the promoter. Accordingly, DNase I footprint analysis indicated that both activators protect an overlapping region close to the −35 box of the promoter and suggested that the regulatory effect is direct. Despite the overlap of the binding sites, each activator acts independent of the other and is specific for a particular stress. NhaR can stimulate osmCp1 in response to an osmotic signal even in the absence of RcsB. RcsB is responsible for the induction of osmCp1 by alteration of the cell envelope, even in the absence of NhaR. osmCp1 as an example of multiple-stress-responsive promoter is discussed in light of a comparison of the NhaR and RcsB target regions in the Enterobacteriaceae.

The genes involved in flagellum synthesis, motility and chemotaxis in Escherichia coli are expressed in a hierarchical fashion. At the top of the hierarchy lies the master regulator FlhDC, required for the expression of the whole set of genes. The operon flhDC is controlled by numerous regulators including H-NS, CRP, EnvZ/OmpR, QseBC and LrhA. In the present work, we report that the flhDC operon is also negatively regulated by the His-Asp phosphorelay system RcsCDB. The regulation is potentiated by the RcsB cofactor RcsA. Genetic analysis indicates that an RcsAB box, located downstream of the promoter, is required for the regulation. The binding of RcsB and RcsA to this site was demonstrated by gel retardation and DNase I protection assays. In addition, mutation analysis suggests that RcsA-specific determinants lie in the right part of the 'RcsAB box'.

ABSTRACT The RcsCB His-Asp phosphorelay system regulates the expression of several genes of Escherichia coli , but the molecular nature of the inducing signal is still unknown. We show here that treatment of an exponentially growing culture of E. coli with the cationic amphipathic compound chlorpromazine (CPZ) stimulates expression of a set of genes positively regulated by the RcsCB system. This induction is abolished in rcsB or rcsC mutant strains. In addition, treatment with CPZ inhibits growth. The wild-type strain is able to recover from this inhibition and resume growth after a period of adaptation. In contrast, strains deficient in the RcsCB His-Asp phosphorelay system are hypersensitive to CPZ. These results suggest that cells must express specific RcsCB-regulated genes in order to cope with the CPZ-induced stress. This is the first report of the essential role of the RcsCB system in a stress situation. These results also strengthen the notion that alterations of the cell envelope induce a signal recognized by the RcsC sensor.

ABSTRACT The Escherichia coli osmC gene encodes an envelope protein of unknown function whose expression depends on osmotic pressure and growth phase. The gene is transcribed from two overlapping promoters, osmCp 1 and osmCp 2 . Several factors regulating these promoters have been reported. The leucine-responsive protein Lrp represses osmCp 1 and activates osmCp 2 , the nucleoid-associated protein H-NS represses both promoters, and the stationary-phase sigma factor ς s specifically recognizes osmCp 2 . This work reports the identification of an additional regulatory element, the two-component system rcsB - rcsC , affecting positively the distal promoter osmCp 1 . The response regulator of the system, RcsB, does not affect expression of the proximal promoter osmCp 2 . Deletion analysis located the site necessary for RcsB activation just upstream of osmCp 1 . In vitro transcription experiments and gel mobility shift assays demonstrated that RcsB stimulates RNA polymerase binding at osmCp 1 .

Genes rcsC and rcsB form a two‐component system in which rcsC encodes the sensor element and rcsB the regulator. In Escherichia coli, the system positively regulates the expression of the capsule operon, cps, and of the cell division gene ftsZ. We report the identification of the promoter and of the sequences required for rcsB‐dependent stimulation of ftsZ expression. The promoter, ftsA1p, located in the ftsQ coding sequence, co‐regulates ftsA and ftsZ. The sequences required for rcsB activity are immediately adjacent to this promoter.

The ratio of the FtsZ to FtsA proteins determines the correct initiation of cell division in Escherichia coli. The genes for these proteins are contiguous on the chromosome. Although both genes are transcribed from common promoters, the presence of ftsZ-specific promoters, along with differences in the efficiency of translation of their respective mRNAs, contribute to the increased relative expression of ftsZ. We report here that the polycistronic ftsA-ftsZ transcripts are cleaved by RNase E and that this cleavage affects the decay of ftsA and ftsZ mRNA. As a consequence of the cleavage, RNase E also contributes to the differential expression of the two genes.

In phage lambda and its relatives most early phage genes are located downstream from transcription termination sites, and full gene expression requires suppression of termination (or antitermination). Phage HK022, a lambda relative, also antiterminates early transcription, but, unlike its relatives, does so in the absence of any active phage gene product. We found no functional equivalent of the lambda N antitermination protein in HK022. In addition, nus mutations, which alter host proteins required for lambda antitermination, have no apparent effect on HK022 early gene expression. We have shown that terminators located several thousand base-pairs from the start point of transcription are suppressed, and that in the left operon suppression requires a short, promoter-proximal segment. A 40 bp region within this segment is repeated in the right operon. The chromosomal locations of these repeated segments resemble those of the nut antitermination sites of other lambdoid phages, but the HK022 sites lack the conserved sequence elements of the nut sites. It appears that HK022 antiterminates early transcription in a novel way.

The pL, pR and pM promoters of lambdoid phages direct the transcription of early phage genes and the prophage repressor gene. We have determined the start points of transcription for these three promoters in the lambdoid phage HK022 and have shown that the HK022 repressor represses the early promoters, pL and pR, and activates the repressor promoter, pM. HK022 resembles other phages of the lambda family in these respects, as it does in the functional organization of most of its early genes and sites. One exception is nun, the first gene of the HK022 pL operon, which is expressed in the presence of prophage repressor and thus differs from its lambda counterpart, gene N. We show that transcription of nun in a lysogen does not initiate at pL but instead starts upstream at the pM promoter. This difference in transcription fits the different roles of Nun and N proteins in the physiology of the two phages: Nun protects HK022 lysogens against superinfection with certain other lambdoid phages, while N promotes the transcription of early lambda genes.

We have established that the long non-coding intercistronic region of the dicB operon of Escherichia coli expresses a trans-acting division inhibitor specified by a region dicF, at most 65 nucleotides-long. The present study deals with the processing of dicBF operon mRNA in vivo, and identifies the dicF gene product as a 53 nucleotide RNA species. A sequence at the end of DicF resembles, and behaves as, a Rho-independent terminator, but further processing of readthrough transcripts, presumably by RNase III, followed by a limited 3' to 5' degradation, appears to generate additional DicF-RNA 3' ends. For the 5' end of DicF-RNA, our results show that a 190 nucleotide precursor DicF-RNA species is formed by cleavage at an RNase III site, while the 53 nucleotide minimal DicF-RNA is generated by further processing requiring the presence of an active form of RNase E in vivo. These data indicate that an untranslated product derived from an operon RNA can have a regulatory activity by affecting cell division.

The dicA1 mutation, located in the replication termination region of Escherichia coli at 34.9 min, confers a temperature-sensitive, division defective phenotype to its hosts. Previous analysis had suggested that dicA codes for a repressor of a nearby division inhibition gene dicB. We show now that gene dicB is part of a complex operon. Five open reading frames (ORFs 1 to 5) preceeded by a promoter sensitive to dicA repression are found within a 1500 bp segment, and are organized into two clusters separated by a long untranslated region. Evidence for expression of these ORFs was obtained from in vitro or in vivo translation of plasmid-coded genes. IPTG-dependent cell filamentation was obtained when either the entire or the C-terminal part of the fourth ORF was placed under control of the lac promoter. In both cases, a 7 KD protein corresponding to translation from an in-frame ATG of ORF4 (dicB) was made. We propose that this C-terminal protein is the division inhibitor synthesized in dicA1 mutants.

A mutation in a gene dicA of Escherichia coli leads to temperature-sensitive cell division, by allowing expression of a nearby division inhibition gene dicB (1). We have now established the sequence of the DicA region and identified DicA as a 15.5 KD protein. A second gene dicC transcribed divergently from dicA and coding for an 8.5 KD protein can also complement mutation dicA1 when provided on a multicopy plasmid.

A mutation in a gene dicA of Escherichia coli leads to temperature-sensitive cell division, by allowing expression of a nearby division inhibition gene dicB (1). We have now established the sequence of the DicA region and identified DicA as a 15.5 KD protein. A second gene dicC transcribed divergently from dicA and coding for an 8.5 KD protein can also complement mutation dicA1 when provided on a multicopy plasmid.