The iron-sensing aconitase B binds its own mRNA to prevent sRNA-induced mRNA cleavage.
Bottom Line: 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.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.
Affiliation: Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada.Show MeSH
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Mentions: Low intracellular iron conditions favor the switch of enzymatic (holo) AcnB to its RNA-binding (apo) conformation. We asked whether citrate, the substrate of AcnB, could interfere with this switch. To answer this question, EM1238 (ΔryhB) cells were used to monitor the effect of apo-AcnB alone on acnB mRNA. Thus, cells were grown in iron-rich LB medium until mid-log phase, at which point Dip or a combination of Dip and citrate were added, followed by rifampicin to assess acnB mRNA stability. Densitometry analysis indicated that acnB mRNA half-life was slightly stabilized in the presence of Dip, which correlated with the switch of holo- to apo-AcnB RNA under low iron (Figure 7, top and middle panels). In contrast, the addition of citrate decreased the stability of acnB in a way similar to growth conditions in medium alone (Figure 7). These data were consistent with the interpretation that the presence of citrate prevented the switch of holo- to apo-AcnB even under low Fe conditions.
Affiliation: Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada.