title: Escherichia coli toxin/antitoxin pair MqsR/MqsA regulate toxin CspD.
abstract: Previously we identified that the Escherichia coli protein MqsR (YgiU) functions as a toxin and that it is involved in the regulation of motility by quorum sensing signal autoinducer-2 (AI-2). Furthermore, MqsR is directly associated with biofilm development and is linked to the development of persister cells. Here we show that MqsR and MqsA (YgiT) are a toxin/antitoxin (TA) pair, which, in significant difference to other TA pairs, regulates additional loci besides its own. We have recently identified that MqsR functions as an RNase. However, using three sets of whole-transcriptome studies and two nickel-enrichment DNA binding microarrays coupled with cell survival studies in which MqsR was overproduced in isogenic mutants, we identified eight genes (cspD, clpX, clpP, lon, yfjZ, relB, relE and hokA) that are involved in a mode of MqsR toxicity in addition to its RNase activity. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) showed that (i) the MqsR/MqsA complex (and MqsA alone) represses the toxin gene cspD, (ii) MqsR overproduction induces cspD, (iii) stress induces cspD, and (iv) stress fails to induce cspD when MqsR/MqsA are overproduced or when mqsRA is deleted. Electrophoretic mobility shift assays show that the MqsA/MqsR complex binds the promoter of cspD. In addition, proteases Lon and ClpXP are necessary for MqsR toxicity. Together, these results indicate the MqsR/MqsA complex represses cspD which may be derepressed by titrating MqsA with MqsR or by degrading MqsA via stress conditions through proteases Lon and ClpXP. Hence, we demonstrate that the MqsR/MqsA TA system controls cell physiology via its own toxicity as well as through its regulation of another toxin, CspD.
authors.affiliation: Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA.
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Kim
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Wang
authors.forename: Xue-Song
authors.initials: XS
authors.lastname: Zhang
authors.forename: Simina
authors.initials: S
authors.lastname: Grigoriu
authors.forename: Rebecca
authors.initials: R
authors.lastname: Page
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Peti
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Wood
mesh_terms: D000992:Antitoxins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D049071:Endopeptidase Clp / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D049070:Protease La / Q000235:genetics / Q000378:metabolism; D053038:Quorum Sensing / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D000992:Antitoxins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; C508571:MqsR protein, E coli; C490240:cspH protein, E coli; D049070:Protease La; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp