title: Targeted decay of a regulatory small RNA by an adaptor protein for RNase E and counteraction by an anti-adaptor RNA.
abstract: Bacterial small RNAs (sRNAs) are well established to regulate diverse cellular processes, but how they themselves are regulated is less understood. Recently, we identified a regulatory circuit wherein the GlmY and GlmZ sRNAs of Escherichia coli act hierarchically to activate mRNA glmS, which encodes glucosamine-6-phosphate (GlcN6P) synthase. Although the two sRNAs are highly similar, only GlmZ is a direct activator that base-pairs with the glmS mRNA, aided by protein Hfq. GlmY, however, does not bind Hfq and activates glmS indirectly by protecting GlmZ from RNA cleavage. This complex regulation feedback controls the levels of GlmS protein in response to its product, GlcN6P, a key metabolite in cell wall biosynthesis. Here, we reveal the molecular basis for the regulated turnover of GlmZ, identifying RapZ (RNase adaptor protein for sRNA GlmZ; formerly YhbJ) as a novel type of RNA-binding protein that recruits the major endoribonuclease RNase E to GlmZ. This involves direct interaction of RapZ with the catalytic domain of RNase E. GlmY binds RapZ through a secondary structure shared by both sRNAs and therefore acts by molecular mimicry as a specific decoy for RapZ. Thus, in analogy to regulated proteolysis, RapZ is an adaptor, and GlmY is an anti-adaptor in regulated turnover of a regulatory small RNA.
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August-University, D-37077 Göttingen, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Göpel
authors.forename: Kai
authors.initials: K
authors.lastname: Papenfort
authors.forename: Birte
authors.initials: B
authors.lastname: Reichenbach
authors.forename: Jörg
authors.initials: J
authors.lastname: Vogel
authors.forename: Boris
authors.initials: B
authors.lastname: Görke
mesh_terms: D000595:Amino Acid Sequence; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020871:RNA Stability; D012329:RNA, Bacterial / Q000378:metabolism*; D016601:RNA-Binding Proteins; D016415:Sequence Alignment
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; C524677:YhbJ protein, E coli; D004722:Endoribonucleases; C022537:ribonuclease E