title: Mechanism of positive regulation by DsrA and RprA small noncoding RNAs: pairing increases translation and protects rpoS mRNA from degradation.
abstract: Small noncoding RNAs (sRNAs) regulate gene expression in Escherichia coli by base pairing with mRNAs and modulating translation and mRNA stability. The sRNAs DsrA and RprA stimulate the translation of the stress response transcription factor RpoS by base pairing with the 5' untranslated region of the rpoS mRNA. In the present study, we found that the rpoS mRNA was unstable in the absence of DsrA and RprA and that expression of these sRNAs increased both the accumulation and the half-life of the rpoS mRNA. Mutations in dsrA, rprA, or rpoS that disrupt the predicted pairing sequences and reduce translation of RpoS also destabilize the rpoS mRNA. We found that the rpoS mRNA accumulates in an RNase E mutant strain in the absence of sRNA expression and, therefore, is degraded by an RNase E-mediated mechanism. DsrA expression is required, however, for maximal translation even when rpoS mRNA is abundant. This suggests that DsrA protects rpoS mRNA from degradation by RNase E and that DsrA has a further activity in stimulating RpoS protein synthesis. rpoS mRNA is subject to degradation by an additional pathway, mediated by RNase III, which, in contrast to the RNase E-mediated pathway, occurs in the presence and absence of DsrA or RprA. rpoS mRNA and RpoS protein levels are increased in an RNase III mutant strain with or without the sRNAs, suggesting that the role of RNase III in this context is to reduce the translation of RpoS even when the sRNAs are acting to stimulate translation.
authors.affiliation: Laboratory of Molecular Biology, Bldg. 37, Room 5132, National Institutes of Health, Bethesda, MD 20892-4255, USA.
authors.forename: Colleen A
authors.initials: CA
authors.lastname: McCullen
authors.forename: Jihane N
authors.initials: JN
authors.lastname: Benhammou
authors.forename: Nadim
authors.initials: N
authors.lastname: Majdalani
authors.forename: Susan
authors.initials: S
authors.lastname: Gottesman
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006358:Hot Temperature; D014176:Protein Biosynthesis / Q000502:physiology; D020871:RNA Stability; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D058727:RNA, Small Untranslated; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism*; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D018076:DNA, Complementary; C405431:DsrA RNA, E coli; D012329:RNA, Bacterial; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D022661:RNA, Untranslated; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D004722:Endoribonucleases; D043244:Ribonuclease III; C022537:ribonuclease E
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