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Temperature-controlled structural alterations of an RNA thermometer.
Saheli Chowdhury1, Curdin Ragaz, Emma Kreuger
1Institut of Microbiology, Eidgenössische Technische Hochschule, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland.
The Journal of Biological Chemistry
|September 10, 2003
Summary
ROSE elements in mRNA act as thermometers, controlling gene expression in response to temperature changes. These RNA structures sense temperature shifts between 30-40°C, crucial for bacterial heat shock responses.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Thermoresponsive structures in mRNA's 5'-untranslated region regulate gene translation.
- The ROSE (repression of heat shock gene expression) element controls rhizobial heat shock genes.
- ROSE is hypothesized to block ribosome access at low temperatures via secondary structure.
Purpose of the Study:
- To investigate the ROSE element as a temperature-sensitive RNA thermometer.
- To determine the temperature range and mechanism of ROSE-mediated translational control.
Main Methods:
- In vivo and in vitro experiments.
- Site-directed mutagenesis of the ROSE element.
- UV and Circular Dichroism (CD) spectroscopy.
- RNase H susceptibility assays with complementary oligonucleotides.
Main Results:
- ROSE functions as a thermometer between 30-40°C.
- Mutations disrupting base pairing increased expression at 30°C; compensatory mutations restored repression.
- A 5'-truncated ROSE variant showed moderate inducibility, suggesting coordinated stem loop interactions.
- Subtle structural changes, not major rearrangements, involving the Shine-Dalgarno sequence mediate translational control.
Conclusions:
- The ROSE element is a sensitive RNA thermometer crucial for regulating heat shock gene expression.
- Temperature sensing by ROSE is an ordered process, likely independent of accessory factors.
- The secondary structure of ROSE, particularly stem loop interactions, is vital for its thermosensing function.