Antagonistic functions between the RNA chaperone Hfq and an sRNA regulate sensitivity to the antibiotic colicin.
The RNA chaperone Hfq is a key regulator of the function of small RNAs (sRNAs). Hfq has been shown to facilitate sRNAs binding to target mRNAs and to directly regulate translation through the action of sRNAs. Here, we present evidence that Hfq acts as the repressor of cirA mRNA translation in the absence of sRNA. Hfq binding to cirA prevents translation initiation, which correlates with cirA mRNA instability. In contrast, RyhB pairing to cirA mRNA promotes changes in RNA structure that displace Hfq, thereby allowing efficient translation as well as mRNA stabilization. Because CirA is a receptor for the antibiotic colicin Ia, in addition to acting as an Fur (Ferric Uptake Regulator)-regulated siderophore transporter, translational activation of cirA mRNA by RyhB promotes colicin sensitivity under conditions of iron starvation. Altogether, these results indicate that Fur and RyhB modulate an unexpected feed-forward loop mechanism related to iron physiology and colicin sensitivity.
Department of Biochemistry, RNA Group, University of Sherbrooke, Sherbrooke, Quebec, Canada.
Hubert
H
Salvail
Marie-Pier
MP
Caron
Justine
J
Bélanger
Eric
E
Massé
D001483:Base Sequence; D003087:Colicins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein / Q000037:antagonists & inhibitors / Q000502:physiology*; D007501:Iron / Q000378:metabolism; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000502:physiology*; D008969:Molecular Sequence Data; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000235:genetics; D012329:RNA, Bacterial / Q000037:antagonists & inhibitors / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism; D054680:Ribosome Subunits, Small, Bacterial / Q000378:metabolism; D015533:Transcriptional Activation
D003087:Colicins; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D018832:Molecular Chaperones; D012329:RNA, Bacterial; D011956:Receptors, Cell Surface; C028593:colicin receptor, E coli; D007501:Iron