Reprograming of sRNA target specificity by the leader peptide peTrpL in response to antibiotic exposure.

Trans-acting regulatory RNAs have the capacity to base pair with more mRNAs than generally detected under defined conditions, raising the possibility that sRNA target specificities vary depending on the specific metabolic or environmental conditions. In Sinorhizobium meliloti, the sRNA rnTrpL is derived from a tryptophan (Trp) transcription attenuator located upstream of the Trp biosynthesis gene trpE(G). The sRNA rnTrpL contains a small ORF, trpL, encoding the 14-aa leader peptide peTrpL.

Transcription attenuation-derived small RNA rnTrpL regulates tryptophan biosynthesis gene expression in trans.

Ribosome-mediated transcription attenuation is a basic posttranscriptional regulation mechanism in bacteria. Liberated attenuator RNAs arising in this process are generally considered nonfunctional. In Sinorhizobium meliloti, the tryptophan (Trp) biosynthesis genes are organized into three operons, trpE(G), ppiD-trpDC-moaC-moeA, and trpFBA-accD-folC, of which only the first one, trpE(G), contains a short ORF (trpL) in the 5'-UTR and is regulated by transcription attenuation.

The essential nature of YqfG, a YbeY homologue required for 3' maturation of Bacillus subtilis 16S ribosomal RNA is suppressed by deletion of RNase R.

Ribosomal RNAs are processed from primary transcripts containing 16S, 23S and 5S rRNAs in most bacteria. Maturation generally occurs in a two-step process, consisting of a first crude separation of the major species by RNase III during transcription, followed by precise trimming of 5' and 3' extensions on each species upon accurate completion of subunit assembly. The various endo- and exoribonucleases involved in the final processing reactions are strikingly different in Escherichia coli and Bacillus subtilis, the two best studied representatives of Gram-negative and Gram-positive bacteria, respectively.

RNase E and RNase J are needed for S-adenosylmethionine homeostasis in Sinorhizobium meliloti.

The ribonucleases (RNases) E and J play major roles in E. coli and Bacillus subtilis, respectively, and co-exist in Sinorhizobium meliloti. We analysed S.

The stress-related, rhizobial small RNA RcsR1 destabilizes the autoinducer synthase encoding mRNA sinI in Sinorhizobium meliloti.

Quorum sensing is a cell density-dependent communication system of bacteria relying on autoinducer molecules. During the analysis of the post-transcriptional regulation of quorum sensing in the nitrogen fixing plant symbiont Sinorhizobium meliloti, we predicted and verified a direct interaction between the 5'-UTR of sinI mRNA encoding the autoinducer synthase and a small RNA (sRNA), which we named RcsR1. In vitro, RcsR1 prevented cleavage in the 5'-UTR of sinI by RNase E and impaired sinI translation.

RNase E affects the expression of the acyl-homoserine lactone synthase gene sinI in Sinorhizobium meliloti.

Quorum sensing of Sinorhizobium meliloti relies on N-acyl-homoserine lactones (AHLs) as autoinducers. AHL production increases at high population density, and this depends on the AHL synthase SinI and two transcriptional regulators, SinR and ExpR. Our study demonstrates that ectopic expression of the gene rne, coding for RNase E, an endoribonuclease that is probably essential for growth, prevents the accumulation of AHLs at detectable levels.