Functional analysis of the <i>Enterococcus faecalis</i> plasmid pAD1‐encoded stability determinant <i>par</i>

Weaver, Keith E.; Jensen, Kristi D.; Colwell, A; Sriram, Saileela

doi:10.1111/j.1365-2958.1996.tb02488.x

Cited by 74 publications

(65 citation statements)

References 54 publications

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“…It was subsequently shown that the arrangement of genes was very similar to that for Hok-Sok (20), with srnB and pndA encoding toxin proteins containing single transmembrane domains and srnC and pndB encoding small antisense RNAs (36). RNAI-RNAII encoded on the pAD1 plasmid of Enterococcus faecalis, the first type I toxinantitoxin pair found for a gram-positive bacterium, was identified on the basis of a postsegregational killing phenotype (54,55). For this pair, RNAI encodes the small Fst (E. faecalis plasmid-stabilizing toxin), protein while RNAII functions as the regulatory sRNA (24).…”

Section: Plasmid-encoded Type I Toxin-antitoxinmentioning

confidence: 99%

Small Toxic Proteins and the Antisense RNAs That Repress Them

Fozo

Hemm

Storz

2008

Microbiol Mol Biol Rev

220

235

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SUMMARY There has been a great expansion in the number of small regulatory RNAs identified in bacteria. Some of these small RNAs repress the synthesis of potentially toxic proteins. Generally the toxin proteins are hydrophobic and less than 60 amino acids in length, and the corresponding antitoxin small RNA genes are antisense to the toxin genes or share long stretches of complementarity with the target mRNAs. Given their short length, only a limited number of these type I toxin-antitoxin loci have been identified, but it is predicted that many remain to be found. Already their characterization has given insights into regulation by small RNAs, has suggested functions for the small toxic proteins at the cell membrane, and has led to practical applications for some of the type I toxin-antitoxin loci.

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Section: Plasmid-encoded Type I Toxin-antitoxinmentioning

confidence: 99%

Small Toxic Proteins and the Antisense RNAs That Repress Them

Fozo

Hemm

Storz

2008

Microbiol Mol Biol Rev

220

235

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“…Synthetic Fst (United Biochemical Research) was prepared with the predicted sequence MK DLMSLVIAPIFVGLVLEMISRVLDEEDDSRK derived from the par DNA sequence (42). Synthetic Fst was used at a final concentration of 200 g/ml from a 20-mg/ml stock in dimethyl formamide.…”

Section: Strains and Plasmidsmentioning

confidence: 99%

“…The third antisense-regulated toxin-antitoxin system is the par system encoded by the pAD1 plasmid of Enterococcus faecalis (42). pAD1 is the prototype of a family of plasmids whose conjugative systems are induced by peptide sex pheromones secreted by potential recipients (8,12).…”

mentioning

confidence: 99%

Enterococcus faecalisPlasmid pAD1-Encoded Fst Toxin Affects Membrane Permeability and Alters Cellular Responses to Lantibiotics

Weaver

Wells

et al. 2003

J Bacteriol

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Fst is a peptide toxin encoded by the par toxin-antitoxin stability determinant of Enterococcus faecalis plasmid pAD1. Intracellular overproduction of Fst resulted in simultaneous inhibition of all cellular macromolecular synthesis concomitant with cell growth inhibition and compromised the integrity of the cell membrane. Cells did not lyse or noticeably leak intracellular contents but had specific defects in chromosome partitioning and cell division. Extracellular addition of synthetic Fst had no effect on cell growth. Spontaneous Fst-resistant mutants had a phenotype consistent with changes in membrane composition. Interestingly, overproduction of Fst sensitized cells to the lantibiotic nisin, and Fst-resistant mutants were cross-resistant to nisin and the pAD1-encoded cytolysin.Postsegregational killing or addiction systems were originally identified as determinants ensuring proper segregational stability of bacterial plasmids (19). In this context, they function by programming any daughter cell that loses the plasmid for death. Postsegregational killing systems are ubiquitous on low-copy bacterial plasmids and have been identified on plasmids native to both gram-negative and gram-positive species. They uniformly encode at least two components, a stable toxin and an unstable antitoxin. As long as the plasmid is present, the antitoxin prevents postsegregational killing toxicity. If the plasmid is lost, the antitoxin is rapidly degraded and the toxin kills the cell (for comprehensive reviews, see references 17 and 27).The discovery that restriction-modification systems can perform a postsegregational killing function when present on plasmids (32) and the observation that postsegregational killing homologs are widespread among bacterial chromosomes (15) have forced a reexamination of the roles that such systems play in the bacterial cell. Obviously, chromosomally located postsegregational killing-like systems would not be useful for postsegregational killing. Potential roles in genome shuffling (30), an expanded stringent response (6, 33), and bacterial apoptosis (1) have been proposed for these loci. Since toxin-antitoxin pairs clearly play roles in addition to postsegregational killing, a more general designation as toxin-antitoxin modules (15) is probably more appropriate.The targets for toxins of toxin-antitoxin modules vary widely, and many remain undefined. The first clearly defined target was that of the CcdB toxin of the F-encoded ccd locus. CcdB targets the GyrA subunit of DNA gyrase and appears to poison a gyrase-DNA complex, trapping it as a DNA-cleaved intermediate. Quinolone antibiotics function in a similar manner, but CcdB binds to a different GyrA site, and mutations resulting in resistance to CcdB and the quinolones map to different locations on GyrA (3). Recently, the ParE toxin of the parDE toxin-antitoxin system of RK2 has also been shown to target DNA gyrase (28). The Kid toxin of the R1-encoded Kis/Kid locus inhibits DnaB-dependent initiation of DNA replication (34). The RelE protein of the...

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“…pAD1 is the prototype of a family of plasmids whose conjugative systems are induced by peptide sex pheromones secreted by potential recipients (10). par is a self-contained PSK locus less than 400 bp in size encoding two small RNAs, the ϳ70-nucleotide regulatory RNA, RNA II, and the ϳ215-nucleotide toxin-encoding RNA, RNA I (37,38). Unlike most plasmidencoded RNA-regulated systems, the two RNAs are transcribed convergently, overlapping only at a bidirectional intrinsic terminator.…”

mentioning

confidence: 99%

Addiction Toxin Fst Has Unique Effects on Chromosome Segregation and Cell Division inEnterococcus faecalisandBacillussubtilis

Patel

Weaver

2006

J Bacteriol

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The Fst toxin of the Enterococcus faecalis pAD1-encoded par addiction module functions intracellularly to kill plasmid-free segregants. Previous results had shown that Fst induction results in membrane permeabilization and cessation of macromolecular synthesis, but only after 45 min. Electron micrographs of toxin-induced cells showed no obvious membrane abnormalities but did reveal defects in nucleoid segregation and cell division, begging the question of which is the primary effect of Fst. To distinguish the possibilities, division septae and nucleoids were visualized simultaneously with fluorescent vancomycin and a variety of DNA stains. Results showed that division and segregation defects occurred in some cells within 15 min after induction. At these early time points, affected cells remained resistant to membrane-impermeant DNA stains, suggesting that loss of membrane integrity is a secondary effect caused by ongoing division and/or segregation defects. Fst-resistant mutants showed greater variability in cell length and formed multiple septal rings even in the absence of Fst. Fst induction was also toxic to Bacillus subtilis. In this species, Fst induction caused only minor division abnormalities, but all cells showed a condensation of the nucleoid, suggesting that effects on the structure of the chromosomal DNA might be paramount.

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Functional analysis of the Enterococcus faecalis plasmid pAD1‐encoded stability determinant par

Cited by 74 publications

References 54 publications

Small Toxic Proteins and the Antisense RNAs That Repress Them

Small Toxic Proteins and the Antisense RNAs That Repress Them

Enterococcus faecalisPlasmid pAD1-Encoded Fst Toxin Affects Membrane Permeability and Alters Cellular Responses to Lantibiotics

Addiction Toxin Fst Has Unique Effects on Chromosome Segregation and Cell Division inEnterococcus faecalisandBacillussubtilis

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