A small RNA regulates multiple ABC transporter mRNAs by targeting C/A-rich elements inside and upstream of ribosome-binding sites.
The interactions of numerous regulatory small RNAs (sRNAs) with target mRNAs have been characterized, but how sRNAs can regulate multiple, structurally unrelated mRNAs is less understood. Here we show that Salmonella GcvB sRNA directly acts on seven target mRNAs that commonly encode periplasmic substrate-binding proteins of ABC uptake systems for amino acids and peptides. Alignment of GcvB homologs of distantly related bacteria revealed a conserved G/U-rich element that is strictly required for GcvB target recognition. Analysis of target gene fusion regulation in vivo, and in vitro structure probing and translation assays showed that GcvB represses its target mRNAs by binding to extended C/A-rich regions, which may also serve as translational enhancer elements. In some cases (oppA, dppA), GcvB repression can be explained by masking the ribosome-binding site (RBS) to prevent 30S subunit binding. However, GcvB can also effectively repress translation by binding to target mRNAs at upstream sites, outside the RBS. Specifically, GcvB represses gltI mRNA translation at the C/A-rich target site located at positions -57 to -45 relative to the start codon. Taken together, our study suggests highly conserved regions in sRNAs and mRNA regions distant from Shine-Dalgarno sequences as important elements for the identification of sRNA targets.
Sharma
Cynthia M
CM
RNA Biology Group, Max Planck Institute for Infection Biology, 10117 Berlin, Germany.
Darfeuille
Fabien
F
Plantinga
Titia H
TH
Vogel
Jörg
J
D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D035683:MicroRNAs / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D033902:Periplasmic Binding Proteins / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D050436:Regulatory Elements, Transcriptional / Q000502:physiology; D012270:Ribosomes / Q000378:metabolism*; D012475:Salmonella / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D035683:MicroRNAs; D033902:Periplasmic Binding Proteins; D012333:RNA, Messenger