Structure, molecular mechanism and biotechnological application of RNA thermometers

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Direct sensing of environmental cues has only recently been recognized as an intrinsic property of certain mRNAs. Conformational changes in the 5`-untranslated region (5`-UTR) of sensory RNA molecules are predicted to control either transcription or translation of downstream genes. We are currently studying the RNA thermometer ROSE (Repression Of heat Shock gene Expression) which presumably detects temperature changes via reversible RNA folding and unfolding. According to our model, translation initiation signals are masked at low temperatures, whereas melting of the RNA structure at elevated temperatures alleviates repression by allowing ribosome entry too the Shine-Dalgarno region. Computer-based structural predictions og the sensory RNA are supported by mutational analyses and will now be testet by various techniques, including chemical and enzymatic probing experiments. Toe-printing analyses will be used to examine the temperature effect on ribosome binding to the sensory RNA. Completed microbial genome sequences will be searched for other RNA thermometers which will then be studied by a complementary set of in vivo an in vitro techniques. Finally, RNA thermosensors will be exploited for biotechnological purposes by the construction of temperature-controllable expression vectors.