Small ribozymes such asOryza sativatwister spontaneously cleave their own RNA when the ribozyme folds into its active conformation. The coupling between twister folding and self-cleavage has been difficult to study, however, because the active ribozyme rapidly converts to product. Here, we describe the synthesis of a photocaged nucleotide that releases guanosine within microseconds upon photosolvolysis with blue light. Application of this tool toO. sativatwister achieved the spatial (75 µm) and temporal (≤30 ms) control required to resolve folding and self-cleavage events when combined with single-molecule fluorescence detection of the ribozyme folding pathway. Real-time observation of single ribozymes after photo-deprotection showed that the precleaved folded state is unstable and quickly unfolds if the RNA does not react. Kinetic analysis showed that Mg2+and Mn2+ions increase ribozyme efficiency by making transitions to the high energy active conformation more probable, rather than by stabilizing the folded ground state or the cleaved product. This tool for light-controlled single RNA folding should offer precise and rapid control of other nucleic acid systems.
Ribosome biogenesis is a complex process that is facilitated by a large number of assembly factors. In this issue, Andrade et al () provide evidence that a widely conserved RNA chaperone, Hfq, acts as a ribosomal assembly factor in bacteria. Hfq is known to support regulation of stress response genes by small RNAs. Andrade et al () show that the absence of Hfq results in higher levels of immature 30S ribosomes and error‐prone translation, suggesting that Hfq globally affects the quality of protein synthesis when bacteria are under stress.
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