Regulating Bacterial Transcription with Small RNAs

Abstract

In recent years, the combinations of computational and molecular approaches have led to the identification of an increasing numberof small, noncoding RNAs encoded by bacteria and their plasmids and phages. Most of the characterized small RNAs havebeen shown to operate at a posttranscriptional level, modulating mRNA stability or translation by base-pairing with the 5′ regionsof the target mRNAs. However, a subset of small RNAs has been found to regulate transcription. One example is the abundant6S RNA that has been proposed to compete for DNA binding of RNA polymerase by mimicking the open conformation of promoterDNA. Other small RNAs affect transcription termination via base-pairing interactions with sequences in the mRNA. Here,we discuss current understanding and questions regarding the roles of small RNAs in regulating transcription.