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Query: UMLS:C0034186 (pyelonephritis)
 6,144 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyelonephritis-associated pilus (Pap) expression is regulated by a phase variation control mechanism involving PapB, Papl, catabolite activator protein (CAP), leucine-responsive regulatory protein (Lrp) and deoxyadenosine methylase (Dam). Lrp and Papl bind to a specific non-methylated pap regulatory DNA region containing the sequence 'GATC' and facilitate the formation of an active transcriptional complex. Evidence indicates that binding of Lrp and Papl to this region inhibits methylation of the GATC site by Dam. However, if this GATC site is first methylated by Dam, binding of Lrp and Papl is inhibited. These events lead to the formation of two different pap methylation states characteristic of active (ON) and inactive (OFF) pap transcription states. The fae (K88), daa (F1845) and sfa (S) pilus operons share conserved 'GATC-box' domains with pap and may be subject to a similar regulatory control mechanism involving Lrp and DNA methylation.
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PMID:Evidence for global regulatory control of pilus expression in Escherichia coli by Lrp and DNA methylation: model building based on analysis of pap. 135 27

Transcription of the pyelonephritis-associated pilus (pap) operon of Escherichia coli is subject to regulation by a phase variation control mechanism in which the pap pilin gene alternates between transcriptionally active (phase-on) and inactive (phase-off) states. Pap phase variation appears to involve differential inhibition of deoxyadenosine methylase (Dam) methylation of two pap GATC sites, GATC1028 and GATC1130, located in the regulatory region upstream of the papBA promoter. DNA from phase-on cells contains an unmethylated adenosine in the GATC1028 site, whereas DNA from phase-off cells contains an unmethylated adenosine in the GATC1130 site. papI and papB are two regulatory genes in the pap operon. Analysis of pap deletion mutants suggests that papI is required for methylation inhibition at the GATC1028 site; however, neither papI nor papB is required for inhibition of methylation at the GATC1130 site. We have identified a chromosomal locus, mbf (methylation-blocking factor), that is required for methylation protection of both the pap GATC1028 and GATC1130 sites. The mbf locus was identified after transposon mTn10 mutagenesis and mapped to 19.6 min on the E. coli chromosome. The effect of transposon mutations within mbf on pap pilin transcription was determined by using a papBAp-lac operon fusion which places lacZ under control of the papBA promoter. E. coli containing mbf::mTn10 and phase-off mbf+ E. coli cells both expressed beta-galactosidase levels about 30-fold lower than the beta-galactosidase level measured for phase-on mbf+ E. coli cells. These results indicated that mbf was necessary for pap pilin transcription and were supported by Northern (RNA) blotting and primer extension analyses. Moreover, transposon insertion within mbf greatly reduced Pap pilus expression. The mbf locus was isolated on a low-copy-number cosmid, pMBF1. Complementation analysis indicated that each of seven mbf::mTn10 mutants isolated contained a transposon insertion within the same gene or operon. The identification of the mbf locus, required for pap transcription, supports the hypothesis that pap phase variation is controlled by a mechanism involving alternation between different methylation states.
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PMID:Evidence for a methylation-blocking factor (mbf) locus involved in pap pilus expression and phase variation in Escherichia coli. 167 57

Expression of pyelonephritis-associated pili (Pap) varies between transcriptionally active (ON) and inactive (OFF) phase states. Pap phase variation is controlled by the binding of leucine-responsive regulatory protein (Lrp) to two pap regulatory DNA regions, each containing a deoxyadenosine methylase site and designated GATC-I and GATC-II. Methylation of these GATC sites modulates binding of Lrp and plays an essential role in phase variation. PapI, an 8.8-kDa pap-encoded regulatory protein, plays a key role in the switch between OFF and ON transcription states. In the absence of PapI, Lrp binds to sites overlapping the papBA promoter and inhibits transcription. Addition of PapI results in a translocation of Lrp binding to sites over 100 bp upstream, resulting in the ON transcription state. Gel shift analysis using radiolabeled PapI shows that PapI binds with high specificity to Lrp-pap DNA complexes but binds only weakly to free Lrp. Protein cross-linking studies indicate that Lrp and PapI directly interact with each other. On the basis of these data, we present a hypothesis in which PapI facilitates the transition between OFF and ON transcription states by binding to Lrp and altering Lrp's affinity for the pap GATC-I and GATC-II regions.
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PMID:Specific binding of PapI to Lrp-pap DNA complexes. 759 19

Expression of pyelonephritis-associated pili (Pap) in Escherichia coli is under a phase-variation control mechanism in which individual cells alternate between pili+ (ON) and pili- (OFF) states through a process involving DNA methylation by deoxyadenosine methylase (Dam). Methylation of two GATC sites (GATC1028 and GATC1130) within the pap regulatory region is differentially inhibited in phase ON and phase OFF cells. The GATC1028 site of phase ON cells is non-methylated and the GATC1130 site is fully methylated. Conversely, in phase OFF cells the GATC1028 site is fully methylated whereas the GATC1130 site is non-methylated. Two transcriptional activators, PapI and Lrp (leucine-responsive regulatory protein), are required for this specific methylation inhibition. DNA footprint analysis using non-methylated pap DNAs indicates that Lrp binds to a region surrounding the GATC1130 site, whereas PapI does not appear to bind to pap regulatory DNA. However, addition of Lrp and PapI together results in an additional DNaseI footprint around the GATC1028 site. Moreover, Dam methylation inhibits binding of Lrp/PapI near the GATC1028 site and alters binding of Lrp at the GATC1130 site. Our results support a model in which Dam and Lrp/PapI compete for binding near the GATC1028 site, regulating the methylation state of this GATC site and, consequently, the pap transcription state.
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PMID:Regulation of pyelonephritis-associated pili phase-variation in Escherichia coli: binding of the PapI and the Lrp regulatory proteins is controlled by DNA methylation. 809 19

Pyelonephritis-associated pili (Pap) expression in Escherichia coli is subject to a phase variation control mechanism that is regulated by the leucine-responsive regulatory protein (Lrp), PapI, and deoxyadenosine methylase (Dam). In previous work, we found that the differential Dam methylation of two target sites in pap regulatory DNA, GATC-I and GATC II, is essential for the transition between active and inactive pap transcriptional states. Here, we identify six Lrp binding sites within the pap regulatory DNA, each separated by about three helical turns. Lrp binds with highest affinity to three sites (1, 2 and 3) proximal to the papBAp promoter. A mutational analysis indicates that the binding of Lrp to sites 2 and 3 inhibits pap transcription, which is consistent with the fact that Lrp binding site 3 is located between the --35 and --10 RNA polymerase binding region of papBAp. The addition of PapI decreases the affinity of Lrp for sites 1, 2 and 3 and increases its affinity for the distal Lrp binding sites 4 and 5. Mutations within Lrp binding sites 4 and 5 shut off pap transcription, indicating that the binding of Lrp to this pap region activates pap transcription. The pap GATC-I and GATC-II methylation sites are located within Lrp binding sites 5 and 2, respectively, providing a mechanism by which Dam controls Lrp binding and Pap phase variation.
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PMID:Differential binding of Lrp to two sets of pap DNA binding sites mediated by Pap I regulates Pap phase variation in Escherichia coli. 884 72

Most of the adenine residues in GATC sequences in the Escherichia coli chromosome are methylated by the enzyme deoxyadenosine methyltransferase (Dam). However, at least 20 GATC sequences remain nonmethylated throughout the cell cycle. Here we examined how the DNA methylation patterns of GATC sequences within the regulatory regions of the pyelonephritis-associated pilus (pap) operon and the glucitol utilization (gut) operon were formed. The results obtained with an in vitro methylation protection assay showed that the addition of the leucine-responsive regulatory protein (Lrp) to pap DNA was sufficient to protect the two GATC sequences in the pap regulatory region, GATC-I and GATC-II, from methylation by Dam. This finding was consistent with previously published data showing that Lrp was essential for methylation protection of these DNA sites in vivo. Methylation protection also occurred at a GATC site (GATC-44. 5) centered 44.5 bp upstream of the transcription start site of the gutABD operon. Two proteins, GutR and the catabolite gene activator protein (CAP), bound to DNA sites overlapping the GATC-44. 5-containing region of the gutABD operon. GutR, an operon-specific repressor, was essential for methylation protection in vivo, and binding of GutR protected GATC-44.5 from methylation in vitro. In contrast, binding of CAP at a site overlapping GATC-44.5 did not protect this site from methylation. Mutational analyses indicated that gutABD gene regulation was not controlled by methylation of GATC-44.5, in contrast to regulation of Pap pilus expression, which is directly controlled by methylation of the pap GATC-I and GATC-II sites.
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PMID:Formation of DNA methylation patterns: nonmethylated GATC sequences in gut and pap operons. 981 49

Pap pili play an important role in the pathogenesis of upper urinary tract infections by enabling uropathogenic Escherichia coli to adhere to host epithelial cells. Pap pili are coded for by the pyelonephritis-associated pili (pap) operon, which consists of 11 genes required for the expression and assembly of Pap pili. Expression of Pap pili is regulated by a phase variation mechanism in which the pili expression state of the bacterial population is skewed between phase-on (expression positive) and phase-off (expression negative) states. Pap phase variation is controlled by the cooperative binding of leucine-responsive regulatory protein (Lrp) to two sets of Lrp binding sites in the upstream regulatory region of the pap operon. A single GATC sequence, which is the target site for deoxyadenosine methylase (Dam), is centrally located within each Lrp binding region. Dam plays a critical role in the expression of Pap pili via the formation of DNA methylation patterns. Methylation of GATC-I reduced the affinity of Lrp for pap DNA by about twofold. Conversely, Lrp specifically blocked methylation of pap GATC-I in vitro. These data support the hypothesis that Lrp and Dam compete for binding to GATC-I, and are consistent with previous results indicating that methylation of GATC-I is important for stability of the phase-off state.
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PMID:Regulation of uropathogenic Escherichia coli adhesin expression by DNA methylation. 985 83

The pyelonephritis-associated pili (pap) operon in Escherichia coli is regulated by an epigenetic mechanism involving the formation of specific DNA methylation patterns characteristic of transcriptionally active (phase ON) and inactive (phase OFF) cells. The formation of pap DNA methylation patterns in vivo was previously shown to require the leucine-responsive regulatory protein (Lrp) and DNA adenine methylase (Dam). To monitor the binding of Lrp to pap DNA, an in vitro methylation protection assay was developed. Binding of Lrp to a Dam target site proximal to the papBA promoter (designated GATC(prox)) blocked methylation of this site and specifically repressed transcription. The DNA methylation pattern and transcription state are identical to those observed in vivo in phase OFF cells. To determine if binding of Lrp at GATC(prox) was necessary for repression of papBA transcription, we analyzed a pap mutation (pap-13) that reduced the affinity of Lrp for the GATC(prox) region. Binding of Lrp to pap-13 DNA was shifted to a promoter distal Dam target site (designated GATC(dist)). Lrp blocked methylation of GATC(dist) in the pap-13 mutant, but did not repress papBA transcription. Together, these results show that binding of Lrp to the GATC(prox) region is sufficient for the establishment of the phase OFF DNA methylation pattern and repression of papBA transcription.
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PMID:Regulation of Pap phase variation. Lrp is sufficient for the establishment of the phase off pap DNA methylation pattern and repression of pap transcription in vitro. 1065 4

Plasmid-encoded fimbriae (Pef) expressed by Salmonella typhimurium mediate adhesion to mouse intestinal epithelium. The pef operon shares features with the Escherichia coli pyelonephritis-associated pilus (pap) operon, which is under methylation-dependent transcriptional regulation. These features include conserved DNA GATC box sites in the upstream regulatory region as well as homologues of the PapI and PapB regulatory proteins. Unlike Pap fimbriae, which are expressed in a variety of laboratory media, Pef fimbriae were expressed only in acidic, rich broth under standing culture conditions. Analysis of S. typhimurium grown under these conditions indicated that Pef production was regulated by a phase variation mechanism, in which the bacterial population was skewed between fimbrial expression (phase ON) and non-expression (phase OFF) states. Leucine-responsive regulatory protein (Lrp) and DNA adenine methylase (Dam) were required for pef transcription. In contrast, the histone-like protein (H-NS) and the stationary-phase sigma factor (RpoS) repressed pef transcription. Methylation of the pef GATC II site appeared to be required for pef fimbrial expression based on analysis of a GCTC II mutant that did not express Pef fimbriae. Analysis of the DNA methylation states of pef GATC sites indicated that, under acidic growth conditions, which induced Pef production, most GATC I sites were non-methylated, whereas GATC II and GATC X were predominantly methylated. The methylation protection at GATC I and GATC II was dependent upon Lrp and was modulated by PefI. Together, these results indicate that Pef production is regulated by DNA methylation, which is the first example of methylation-dependent gene regulation outside of E. coli.
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PMID:DNA methylation-dependent regulation of pef expression in Salmonella typhimurium. 1069 51

The ability of bacterial pathogens to bind to the host mucosa is a critical step in the pathogenesis of many bacterial infections and, for Escherichia coli, a large number of different fimbrial adhesins have been implicated as virulence factors. In this chapter, our current understanding of the regulatory mechanisms that control the expression of two of the best characterized fimbrial adhesins, pyelonephritis-associated pilus (encoded by pap) and the type 1 fimbria (encoded by fim), will be described. The expression of both fimbrial adhesins is controlled by phase variation (the reversible and apparently random switching between expressing ('on') and non-expressing ('off') states), and is regulated in response to environmental conditions. The phase variation of pap (and of some other fimbriae in Escherichia coli) is determined by the formation of alternative nucleoprotein complexes that either activate (phase 'on') or suppress (phase 'off') transcription of the fimbria genes. Formation of each complex protects a single Dam methylation site (5' GATC) from modification (GATCdist in phase 'on' cells and GATCprox in phase 'off' cells). Furthermore, complex formation is inhibited by methylation of the two 5' GATC sites. Both the phase variation of pap and the transcription of the pap genes in phase 'on' cells, are regulated and expression is subject to both positive and negative feedback control. In contrast to pap, the phase variation of fim is determined by the site-specific inversion of a short element of DNA (the fim switch). In phase 'on' cells, a promoter within the invertible element directs the transcription of the fim structural genes, whereas in phase 'off' cells transcription of the fimbrial genes is silenced. Despite the very different molecular mechanisms controlling the expression of pap and fim, the two systems share many features in common and have probably evolved to fulfill the same function. In addition to details about the molecular mechanisms that control pap and fim, the possible physiological significance of the observed regulation will be discussed.
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PMID:The regulation of pap and type 1 fimbriation in Escherichia coli. 1145 Jan 7


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