The role of RNA localization in controlling gene expression and RNA stability in eukaryotes has been well established, but until recently there were no bacterial RNAs known to localize to specific subcellular sites. Studies in Caulobacter crescentus and Escherichia coli have now demonstrated that both regulatory RNAs and mRNAs can be concentrated at fixed positions in bacterial cells. tmRNA, a regulatory RNA involved in trans-translation, is localized to a helical structure in C. crescentus, and some mRNAs are localized to discrete spots in C. crescentus and E. coli. Given that bacteria also localize proteins, plasmids, and regions of the chromosome, the localization of RNA may not be particularly surprising. Nonetheless, the possibility that RNA activity and abundance can be controlled by subcellular localization represents a new paradigm for regulation of RNA, and suggests that many new discoveries of bacterial RNA localization lie ahead. Why are RNAs localized, and how is RNA localization achieved? Our understanding is far from complete because these questions are just beginning to be addressed, yet it is now reasonable to review what is known about the mechanisms and physiological rationales for localization of RNAs in bacteria, and to speculate about what additional pathways remain to be discovered.
RNA localization in bacteria. Curr Opin Microbiol. 2011 14(2):155-159
Bacteria localize proteins and DNA regions to specific subcellular sites, and several recent publications show that RNAs are localized within the cell as well. Localization of tmRNA and some mRNAs indicates that RNAs can be sequestered at specific sites by RNA binding proteins, or can be trapped at the location where they are transcribed. Although the functions of RNA localization are not yet completely understood, it appears that one function of RNA localization is to regulate RNA abundance by controlling access to nucleases. New techniques for visualizing RNAs will likely lead to increased examination of spatial control of RNAs and the role this control plays in the regulation of gene expression and bacterial physiology.