Tn5 transposition in Escherichia coli is repressed by Hfq and activated by over-expression of the small non-coding RNA SgrS

Abstract

BackgroundHfq functions in post-transcriptional gene regulation in a wide range of bacteria, usually by promoting base pairing of mRNAs with trans-encoded sRNAs. It was previously shown that Hfq down-regulates Tn10 transposition by inhibiting IS10 transposase expression at the post-transcriptional level. This provided the first example of Hfq playing a role in DNA transposition and led us to ask if a related transposon, Tn5, is similarly regulated.ResultsWe show that Hfq strongly suppresses Tn5 transposition in Escherichia coli by inhibiting IS50 transposase expression. However, in contrast to the situation for Tn10, Hfq primarily inhibits IS50 transposase transcription. As Hfq does not typically function directly in transcription, we searched for a transcription factor that also down-regulated IS50 transposase transcription and is itself under Hfq control. We show that Crp (cyclic AMP receptor protein) fits these criteria as: (1) disruption of the crp gene led to an increase in IS50 transposase expression and the magnitude of this increase was comparable to that observed for an hfq disruption; and (2) Crp expression decreased in hfq−. We also demonstrate that IS50 transposase expression and Tn5 transposition are induced by over-expression of the sRNA SgrS and link this response to glucose limitation.ConclusionsTn5 transposition is negatively regulated by Hfq primarily through inhibition of IS50 transposase transcription. Preliminary results support the possibility that this regulation is mediated through Crp. We also provide evidence that glucose limitation activates IS50 transposase transcription and transposition.Electronic supplementary materialThe online version of this article (doi:10.1186/s13100-014-0027-z) contains supplementary material, which is available to authorized users.

Acis-encoded sRNA, Hfq and mRNA secondary structure act independently to suppress IS200transposition

“…Notably, the number of events was considerably higher than in a control where the tnpA gene contained a mutation in the catalytic tyrosine (construct (ii)). We confirmed that these were authentic transposition events by mapping two independent hops from construct (i) using ST-PCR ( 36 , 49 ) (Supplementary Figure S6A). We therefore conclude that the IS 200 TnpA protein from Salmonella is active for transposition in E. coli .…”

“…All Miller assays and related RNA analyses were performed in E. coli K-12 derivatives DBH323 (MC4100 Δ recA774::kan ) or DBH326 (DBH323 hfq-1::cat ) ( 36 ). Salmonella enterica subsp.…”

Escherichia coli as a host for metabolic engineering

“…However, the physiological effect was demonstrated in E. coli B, but not in K-12, during growth on high levels of glucose (Negrete et al, 2010). As expected, overexpression of SgrS in a K-12 strain was demonstrated to reduce the growth rate and acetate secretion during growth on glucose (Negrete et al, 2013;Ross et al, 2014). Extensive studies have been conducted to characterize SgrS and its role in regulating "glucose-phosphate stress response" (Vanderpool and Gottesman, 2007).…”

The Escherichia Coli Hfq Protein: An Unattended DNA-Transactions Regulator

“…Hfq-mediated regulation of transcription of the gene coding for the IS50 transposase might also explain the inhibition of Tn5 transposition (see Transcription; Haniford and Ellis, 2015 ). Moreover, Crp (cyclic AMP receptor protein) was proposed to mediate Hfq effect on Tn5 transposition (Ross et al, 2014 ). This, together with the known role of Hfq in stress response processes, supports the hypothesis of linking of transposition to the physiological status of the cell.…”