Intracistronic transcription termination in polysialyltransferase gene (<i>siaD</i> ) affects phase variation in <i>Neisseria meningitidis</i>

Lavitola, Alfredo; Bucci, Cecilia; Salvatore, Paola; Maresca, Gabriella; Bruni, Carmelo B.; Alifano, Pietro

doi:10.1046/j.1365-2958.1999.01454.x

Cited by 30 publications

(31 citation statements)

References 55 publications

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“…The phase-variable expression of capsular polysaccharide in Neisseria meningitidis is modulated by premature transcription termination at a cryptic Rho-dependent site in the siaD gene coding for polysialyltransferase (29), and the E. coli clpP-clpX operon expresses transcripts of different lengths FIG. 6.…”

Section: Discussionmentioning

confidence: 99%

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

2005

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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.Escherichia coli and other bacteria end the process of transcript elongation by employing one of the following two types of transcription terminator: intrinsic terminators and factor-dependent terminators (36,40,43,58). Intrinsic terminators typically consist of an approximately 20-bp stretch of DNA that is composed of a GϩC region of hyphenated dyad symmetry followed by a run of T residues. This specifies in the RNA transcript a stable stem-loop structure that is followed by up to eight U residues (8, 31, 50). These U residues base pair weakly with the corresponding A residues in the template DNA strand, and in combination with the formation of the RNA stem-loop structure, lead to destabilization of the RNA polymerase-template-transcript elongation complex and the consequent termination event (43, 61).Factor-dependent terminators utilize the hexameric ringshaped Rho protein to facilitate transcript release from regions of the template that are not characterized by intrinsic RNA-DNA hybrid helix instability (5,7,37,40,47). Rho-dependent terminators lack the obvious structural features that are associated with intrinsic terminators (7). In general, they consist of a bipartite structure that extends for up to 150 bp of DNA and have a high proportion of C relative to G residues (2,14,20,33,39,44,60,62). The Rho utilization (rut) site of a Rho-dependent terminator is a site on the RNA transcript which generally has little secondary structure and is recognized by the RNAbinding Rho factor, while the transcription stop point (tsp) is th...

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Section: Discussionmentioning

confidence: 99%

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

2005

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“…N. meningitidis strains have been reported previously (2,6,16,25,31,32). In particular, the origin, genotype, and phenotype of B1940 and its derivatives, the B1940 cps mutant, the B1940 siaD(ϪC) mutant, and the B1940 siaD(ϩC) mutant (where ϪC and ϩC indicate the deletion and insertion of a cytosine in a polycytidine repeat in the coding region of siaD, respectively), have been described previously (6,10).…”

Section: Methodsmentioning

confidence: 99%

TheNeisseria meningitidisCapsule Is Important for Intracellular Survival in Human Cells

et al. 2007

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While much data exist in the literature about how Neisseria meningitidis adheres to and invades human cells, its behavior inside the host cell is largely unknown. One of the essential meningococcal attributes for pathogenesis is the polysaccharide capsule, which has been shown to be important for bacterial survival in extracellular fluids. To investigate the role of the meningococcal capsule in intracellular survival, we used B1940, a serogroup B strain, and its isogenic derivatives, which lack either the capsule or both the capsule and the lipooligosaccharide outer core, to infect human phagocytic and nonphagocytic cells and monitor invasion and intracellular growth. Our data indicate that the capsule, which negatively affects bacterial adhesion and, consequently, entry, is, in contrast, fundamental for the intracellular survival of this microorganism. The results of in vitro assays suggest that an increased resistance to cationic antimicrobial peptides (CAMPs), important components of the host innate defense system against microbial infections, is a possible mechanism by which the capsule protects the meningococci in the intracellular environment. Indeed, unencapsulated bacteria were more susceptible than encapsulated bacteria to defensins, cathelicidins, protegrins, and polymyxin B, which has long been used as a model compound to define the mechanism of action of CAMPs. We also demonstrate that both the capsular genes (siaD and lipA) and those encoding an efflux pump involved in resistance to CAMPs (mtrCDE) were up-regulated during the intracellular phase of the infectious cycle.

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“…68, 2004 SIALIC ACID SYNTHESIS, CATABOLISM, AND GLOBAL SIGNALING 147 lated by transcriptional mechanisms, the availability of CMPSia or sialylated glycoconjugate donors is probably the crucial feature determining the extent of cell surface decoration in these organisms. In contrast, meningococci and H. influenzae are known to phase vary between sialylated and unsialylated states (17,59,78,134), whereas in E. coli K1 sialic acid is the inducer of its own catabolic system, creating the potential for a futile cycle in which the obligate PSA precursor is degraded by an inducible catabolic pathway (103). Similarly, H. influenzae is faced with the metabolic decision to degrade any scavenged sialic acid for nutrition or activate it for cell surface sialylation (149).…”

Section: Regulation Of Cell Surface Sialylationmentioning

confidence: 99%

“…One mechanism controlling this phase variation is transposition of an insertion element into the genes for PSA expression (58). However, a more common mechanism appears to be slipped-strand mispairing in a poly(dC) tract of the capsule polymerase gene, siaD, causing premature translational arrest coupled with Rho-dependent termination (78). Evidence from the effects of the Rho inhibitor bicyclomycin on phase variation of a siaD reporter fusion expressed in a mismatch-defective E. coli host suggested coupling between transcriptional termination and the cell's mismatch repair system.…”

Section: Meningococcal Psa Phase Variation and Los Sialylationmentioning

confidence: 99%

“…Evidence from the effects of the Rho inhibitor bicyclomycin on phase variation of a siaD reporter fusion expressed in a mismatch-defective E. coli host suggested coupling between transcriptional termination and the cell's mismatch repair system. This coupling between transcriptional termination and the mutator phenotype was suggested to account for the greater frequency of capsule switching from off to on than from on to off rate (78).…”

Section: Meningococcal Psa Phase Variation and Los Sialylationmentioning

confidence: 99%

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Diversity of Microbial Sialic Acid Metabolism

Vimr

Kalivoda

Deszo

et al. 2004

Microbiol Mol Biol Rev

516

663

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Sialic acids are structurally unique nine-carbon keto sugars occupying the interface between the host and commensal or pathogenic microorganisms. An important function of host sialic acid is to regulate innate immunity, and microbes have evolved various strategies for subverting this process by decorating their surfaces with sialylated oligosaccharides that mimic those of the host. These subversive strategies include a de novo synthetic pathway and at least two truncated pathways that depend on scavenging host-derived intermediates. A fourth strategy involves modification of sialidases so that instead of transferring sialic acid to water (hydrolysis), a second active site is created for binding alternative acceptors. Sialic acids also are excellent sources of carbon, nitrogen, energy, and precursors of cell wall biosynthesis. The catabolic strategies for exploiting host sialic acids as nutritional sources are as diverse as the biosynthetic mechanisms, including examples of horizontal gene transfer and multiple transport systems. Finally, as compounds coating the surfaces of virtually every vertebrate cell, sialic acids provide information about the host environment that, at least in Escherichia coli, is interpreted by the global regulator encoded by nanR. In addition to regulating the catabolism of sialic acids through the nan operon, NanR controls at least two other operons of unknown function and appears to participate in the regulation of type 1 fimbrial phase variation. Sialic acid is, therefore, a host molecule to be copied (molecular mimicry), eaten (nutrition), and interpreted (cell signaling) by diverse metabolic machinery in all major groups of mammalian pathogens and commensals

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Intracistronic transcription termination in polysialyltransferase gene (siaD ) affects phase variation in Neisseria meningitidis

Cited by 30 publications

References 55 publications

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

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

TheNeisseria meningitidisCapsule Is Important for Intracellular Survival in Human Cells

Diversity of Microbial Sialic Acid Metabolism

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