PMID:20233923

Citation	Kasari, V, Kurg, K, Margus, T, Tenson, T and Kaldalu, N (2010) The Escherichia coli mqsR and ygiT genes encode a new toxin-antitoxin pair. J. Bacteriol. 192:2908-19
Abstract	Toxin-antitoxin (TA) systems are plasmid- or chromosome-encoded protein complexes composed of a stable toxin and a short-lived inhibitor of the toxin. In cultures of Escherichia coli, transcription of toxin-antitoxin genes was induced in a nondividing subpopulation of bacteria that was tolerant to bactericidal antibiotics. Along with transcription of known toxin-antitoxin operons, transcription of mqsR and ygiT, two adjacent genes with multiple TA-like features, was induced in this cell population. Here we show that mqsR and ygiT encode a toxin-antitoxin system belonging to a completely new family which is represented in several groups of bacteria. The mqsR gene encodes a toxin, and ectopic expression of this gene inhibits growth and induces rapid shutdown of protein synthesis in vivo. ygiT encodes an antitoxin, which protects cells from the effects of MqsR. These two genes constitute a single operon which is transcriptionally repressed by the product of ygiT. We confirmed that transcription of this operon is induced in the ampicillin-tolerant fraction of a growing population of E. coli and in response to activation of the HipA toxin. Expression of the MqsR toxin does not kill bacteria but causes reversible growth inhibition and elongation of cells.
Links	PubMed PMC2876487 Online version:10.1128/JB.01266-09
Keywords	Antitoxins/classification; Antitoxins/genetics; Antitoxins/metabolism; Bacterial Toxins/classification; Bacterial Toxins/genetics; Bacterial Toxins/metabolism; Biofilms/growth & development; Blotting, Northern; Escherichia coli/genetics; Escherichia coli/growth & development; Escherichia coli/metabolism; Escherichia coli Proteins/classification; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Flow Cytometry; Microscopy, Fluorescence; Nucleic Acid Amplification Techniques; Phylogeny
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:MQSR		GO:0017148: negative regulation of translation	ECO:0000315:		P		Fig 4A	complete
ECOD1:C9QYZ0		GO:0032582: chromatin silencing	IMP: Inferred from Mutant Phenotype:	P	Fig 3D	complete
ECOLI:MQSA		GO:0045892: negative regulation of transcription, DNA-dependent	ECO:0000314:		P		Fig. 3D: MqsA (YgiT) acts as a transcriptional repressor of the mqsR-ygiT operon, counteracting the effects of the MqsR toxin.	complete

References

See Help:References for how to manage references in GONUTS.