Small RNA Regulators and the Bacterial Response to Stress

Abstract

Recent studies have uncovered dozens of regulatory small RNAs in bacteria. A large number of these small RNAs act by pairingto their target mRNAs. The outcome of pairing can be either stimulation or inhibition of translation. Pairing in vivo frequentlydepends on the RNA-binding protein Hfq. Synthesis of these small RNAs is tightly regulated at the level oftranscription; many of the well-studied stress response regulons have now been found to include a regulatory RNA.Expression of the small RNA can help the cell cope with environmental stress by redirecting cellular metabolism, exemplifiedby RyhB, a small RNA expressed upon iron starvation. Although small RNAs found in Escherichia coli can usually beidentified by sequence comparison to closely related enterobacteria, other approaches are necessary to find the equivalentRNAs in other bacterial species. Nonetheless, it is becoming increasingly clear that many if not all bacteria encode significantnumbers of these important regulators. Tracing their evolution through bacterial genomes remains a challenge.