Pheromone cCF10 and plasmid pCF10‐encoded regulatory molecules act post‐transcriptionally to activate expression of downstream conjugation functions

Bensing, Barbara A.; Manias, Dawn A.; Dunny, Gary M.

doi:10.1046/j.1365-2958.1997.3301710.x

Cited by 47 publications

(37 citation statements)

References 23 publications

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“…The amino acid sequence of iCF10 is encoded by the last 7 amino acids of the prgQ gene product on pCF10, preceded by a regular signal sequence. Cells unable to produce iCF10 show a slight increase in expression of Asc10, as would be expected with autoinduction by cCF10 (4). In addition, the cell wall of E. faecalis contains a considerable amount of cCF10 activity (5).…”

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confidence: 65%

In Vivo Induction of Virulence and Antibiotic Resistance Transfer in Enterococcus faecalis Mediated by the Sex Pheromone-Sensing System of pCF10

2002

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Enterococcus faecalis has become one of the most notable nosocomial pathogens in the last decade. Aggregation substance (AS) on the sex pheromone plasmids of E. faecalis has been implicated as a virulence factor in several model systems. We investigated the AS-encoding plasmid pCF10 for its ability to increase virulence in a rabbit endocarditis model. Cells containing pCF10 increased the virulence in the model significantly, as assessed by an increase in aortic valve vegetation size. The results confirmed in vivo induction of the normally tightly controlled AS. In addition to the expression of AS when E. faecalis cells were in contact with plasma, plasmid transfer of the tetracycline resistance-carrying plasmid was also activated in vitro and in vivo. In vivo, plasmid transfer reached remarkable frequencies of 8 ؋ 10 ؊2 to 9 ؋ 10 ؊2 . These values are comparable to the highest frequencies ever observed in vitro. Cells harboring pCF10 had a significant survival advantage over plasmid-free cells indicated by pCF10 present in two-thirds of the recipient population. Plasma induction was dependent on the presence of the plasmid-encoded PrgZ protein, indicating the requirement of the pheromonesensing system in the induction process. The data suggested that the mechanism of in vivo induction may involve interference of plasma with the normal function of the pheromone peptide and its inhibitor. Aggregation substance (AS) is a 137-kDa surface protein encoded on sex pheromone plasmids of Enterococcus faecalis.This protein mediates strong binding between E. faecalis cells as manifested by the formation of visible cell aggregates preceding the conjugative transfer of a sex pheromone plasmid (14). The plasmid transfer response is initiated by 7-to 8-amino-acid-long hydrophobic peptides secreted by potential recipient cells (16,32). These peptides are part of signal sequences of chromosomally encoded lipoproteins (10) and lead to induction of AS expression.Asc10, the AS of the sex pheromone plasmid pCF10 (encoding tetracycline resistance) (17), is induced by the 7-aminoacid peptide cCF10 (32) encoded by the ccfA gene. The donor cell binds the peptide (37), employing a specific plasmid-encoded receptor, PrgZ, an OppA homologue (Fig. 1). The peptide is then transported into the cell via the oligopeptide permease system (29), leading to the expression of AS and subsequent plasmid transfer. Since expression of AS and the other plasmid transfer machinery is presumably a very energyconsuming process, it is not surprising that expression of AS is tightly regulated. This ensures that the nonmotile enterococcal cells expressing transfer functions are in close proximity for cell contact to occur between mating partners. pCF10 donor cells are faced with the dilemma that they secrete unaltered amounts of cCF10 (33), necessitating a complex scheme to prevent autoinduction by their own pheromones. A schematic overview of the events controlling AS expression is given in Fig. 1. Secreted cCF10 may accumulate to approximately 8 pg/ml (33). To...

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confidence: 65%

In Vivo Induction of Virulence and Antibiotic Resistance Transfer in Enterococcus faecalis Mediated by the Sex Pheromone-Sensing System of pCF10

2002

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“…PrgS may stabilize the association of QL with whole ribosomes, with the small subunit, or with some other complex of r-proteins and translation factors, and the modified recognition complex supports translation of the prgB message. The significance of finding prgS-region RNA associated with ribosomes translating the prgB::lacZ fusions is addressed in the accompanying paper (Bensing et al, 1997), and will not be discussed further here.…”

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confidence: 99%

Pheromone‐inducible expression of an aggregation protein in Enterococcus faecalis requires interaction of a plasmid‐encoded RNA with components of the ribosome

Bensing

Dunny

1997

Molecular Microbiology

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SummaryTransfer of the conjugative plasmid pCF10 from Enterococcus faecalis donor strains is induced by a peptide pheromone (cCF10) secreted by recipient cells. Highefficiency transfer requires expression of an aggregation protein (Asc10) encoded by the prgB gene and positively regulated by genes in a region 3-5 kb upstream, containing prgQ-R-S. Transcriptional fusion data reported here support the results of recent molecular analysis of the 5Ј ends of prgB transcripts which indicated that prgB transcription occurs by readthrough from the prgQ promoter. A 530-nucleotide prgQ-encoded RNA molecule (QL ) with rRNA-like domains is required for Asc10 production. QL and cCF10 were found to interact with the L6 and S5 ribosomal proteins, respectively. Mutational analysis of QL indicates that this RNA may also directly interact with 16S RNA. QL is present in ribosomes translating the prgB message, and pheromone cCF10 may affect the association of this RNA with translation complexes. Results suggest that the positive regulatory molecules act post-transcriptionally on the polycistronic message and modify a ribosome population to enhance pheromone-induced translation of prgB.

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“…At the same time, the low levels of cCF10 production could make it easier to control the response to endogenous pheromone in donor cells. Interestingly, the levels of induction of pCF10 transfer genes observed in donor cells at physiologically relevant cCF10 concentrations are relatively modest (5-to 50-fold) and probably transient (6,25,29), but these are obviously sufficient to promote frequent transfer of the plasmid under favorable conditions, i.e., availability of recipient cells. When considered as autonomous ("selfish") DNA elements, the pheromone plasmids seem to have adapted an economical evolutionary strategy to optimize their dissemination while minimizing their metabolic burden on the host cell.…”

Section: Discussionmentioning

confidence: 99%

ccfA , the Genetic Determinant for the cCF10 Peptide Pheromone in Enterococcus faecalis OG1RF

Antiporta

Dunny

2002

J Bacteriol

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Pheromone cCF10 and plasmid pCF10‐encoded regulatory molecules act post‐transcriptionally to activate expression of downstream conjugation functions

Cited by 47 publications

References 23 publications

In Vivo Induction of Virulence and Antibiotic Resistance Transfer in Enterococcus faecalis Mediated by the Sex Pheromone-Sensing System of pCF10

In Vivo Induction of Virulence and Antibiotic Resistance Transfer in Enterococcus faecalis Mediated by the Sex Pheromone-Sensing System of pCF10

Pheromone‐inducible expression of an aggregation protein in Enterococcus faecalis requires interaction of a plasmid‐encoded RNA with components of the ribosome

ccfA , the Genetic Determinant for the cCF10 Peptide Pheromone in Enterococcus faecalis OG1RF

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