RNA thermosensors: how might animals exploit their regulatory potential?

The secondary and tertiary orders of RNA structure are crucial for a suite of RNA-related functions, including regulation of translation, gene expression and RNA turnover. The temperature sensitivity of RNA secondary and tertiary structures is exploited by bacteria to fabricate RNA thermosensing systems that allow a rapid adaptive response to temperature change. RNA thermometers (RNATs) present in non-coding regions of certain mRNAs of pathogenic bacteria enable rapid upregulation of translation of virulence proteins when the temperature of the bacterium rises after entering a mammalian host. Rapid upregulation of translation of bacterial heat-shock proteins likewise is governed in part by RNATs. Turnover of mRNA may be regulated by temperature-sensitive RNA structures. Whereas the roles of temperature-sensitive RNA structures similar to RNATs in Eukarya and Archaea are largely unknown, there would appear to be a potential for all taxa to adaptively regulate their thermal physiology through exploitation of RNA-based thermosensory responses akin to those of bacteria. In animals, these responses might include regulation of translation of stress-induced proteins, alternative splicing of messenger RNA precursors, differential expression of allelic proteins, modulation of activities of small non-coding RNAs, regulation of mRNA turnover and control of RNA editing. New methods for predicting, detecting and experimentally modifying RNA secondary structure offer promising windows into these fascinating aspects of RNA biochemistry. Elucidating whether animals too have exploited the types of RNA thermosensing tools that are used so effectively by bacteria seems likely to provide exciting new insights into the mechanisms of evolutionary adaptation and acclimatization to temperature.