title: The iron-sensing aconitase B binds its own mRNA to prevent sRNA-induced mRNA cleavage.
abstract: Aconitase is an iron-sulfur protein and a major enzyme of the TCA cycle that catalyzes the conversion of citrate to isocitrate under iron-rich conditions. In Escherichia coli, aconitase B (AcnB) is a typical moonlighting protein that can switch to its apo form (apo-AcnB) which favors binding its own mRNA 3'UTR and stabilize it when intracellular iron become scarce. The small regulatory RNA (sRNA) RyhB has previously been shown to promote RNase E-dependent degradation of acnB mRNA when it was expressed from an ectopic arabinose-dependent promoter, independently of intracellular iron levels. In marked contrast, we report here that expression of RyhB under low-iron conditions did not result in acnB mRNA degradation even when RyhB was bound to acnB ribosome binding site (RBS). Genetic and biochemical evidence suggested that, under low-iron conditions, apo-AcnB bound to acnB 3'UTR close to a RNase E cleavage site that is essential for RyhB-induced acnB mRNA degradation. Whereas RyhB can block acnB translation initiation, RNase E-dependent degradation of acnB was prevented by apo-AcnB binding close to the cleavage site. This previously uncharacterized regulation suggests an intricate post-transcriptional mechanism that represses protein expression while insuring mRNA stability.
authors.affiliation: Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada.
authors.forename: Julie-Anna M
authors.initials: JA
authors.lastname: Benjamin
authors.affiliation: Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada eric.masse@usherbrooke.ca.
authors.forename: Eric
authors.initials: E
authors.lastname: Massé
mesh_terms: D020413:3' Untranslated Regions; D000154:Aconitate Hydratase / Q000235:genetics* / Q000378:metabolism; D001051:Apoenzymes / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism; D059367:RNA Cleavage; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D058727:RNA, Small Untranslated / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D001051:Apoenzymes; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D019343:Citric Acid; D007501:Iron; D000154:Aconitate Hydratase
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