The iron-sensing aconitase B binds its own mRNA to prevent sRNA-induced mRNA cleavage

作者：Benjamin Julie Anna M; Masse Eric^*

来源：Nucleic Acids Research, 2014, 42(15): 10023-10036.

DOI：10.1093/nar/gku649

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%26apos;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%26apos;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.

• 出版日期2014