3'-UTRs as a source of regulatory RNAs in bacteria

Abstract

Bacterial small non-coding RNAs, sRNAs, have up to now been identified primarily in intergenic regions. Chao et al reveal that the 3'-region of mRNAs is another rich reservoir of sRNAs.

Figure 1

sRNA DapZ is transcribed from an internal promoter in the 3′ region of the lysine biosynthesis gene dapB (relative lengths of dapB-coding region and 3′-UTR not drawn to scale). DapZ expression is dependent on the HilD transcription factor that is the major regulator of Salmonella invasion genes. The Hfq protein hexamer binds and stabilizes DapZ and mediates its interaction with the translation-intitiation region (target) of mRNAs oppA and dppA to repress their translation. This results in inhibition of cellular peptide uptake during activation of invasion genes; sRNA DapZ binds to its target regions via a G/U-rich R1 sequence element that resembles a corresponding element in another sRNA, GcvB. DapZ and GcvB target sites in oppA and dppA overlap; oppA and dppA are the first cistrons of polycistronic operons.