Noncoding RNA control of the making and breaking of sugars

Noncoding RNA regulators have been implicated in almost all imaginable cellular processes. Here we review how regulatory small RNAs such as Spot42, SgrS, GlmY, and GlmZ and a cis-encoded ribozyme in glmS mRNA control sugar metabolism. Besides discussing the physiological implications, we show how the study of these molecules contributed to our understanding of the mechanisms and of general principles of RNA-based regulation. These include the post-transcriptional repression or activation of gene expression within polycistronic mRNAs; novel ribonucleoprotein complexes composed of small RNA, Hfq, and/or RNase E; and the hierarchical action of regulatory RNAs.