RNA thermometers are common in alpha- and gamma-proteobacteria.
Expression of many rhizobial small heat-shock genes is controlled by the ROSE element, a thermoresponsive structure in the 5'-untranslated region of the corresponding mRNAs. Using a bioinformatics approach, we found more than 20 new potential ROSE-like RNA thermometers upstream of small heat-shock genes in a wide variety of alpha- and gamma-proteobacteria. Northern blot analyses revealed heat-inducible transcripts of the representative candidate Caulobacter crescentus CC2258, Escherichia coli ibpA and Salmonella typhimurium ibpA genes. Typical sigma(32)-type promoters were mapped upstream of the potential RNA thermometers by primer extension. Additional translational control was demonstrated in a lacZ reporter system and by site-directed mutagenesis. RNA secondary structure predictions strongly suggest that the Shine-Dalgarno sequence in the RNA thermometers is masked at low temperatures. Combining two regulatory modules, a sigma(32) promoter and a ROSE-type RNA thermometer, provides a novel stringent mechanism to control expression of small heat-shock genes.
Waldminghaus
Torsten
T
Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Fippinger
Anja
A
Alfsmann
Juliane
J
Narberhaus
Franz
F
D020561:Alphaproteobacteria / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D016934:Caulobacter / Q000235:genetics / Q000378:metabolism; D019295:Computational Biology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D020563:Gammaproteobacteria / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics / Q000502:physiology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics / Q000502:physiology; D007763:Lac Operon / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009841:Oligonucleotides / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis; D012313:RNA / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism; D013696:Temperature
D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; C097578:IbpA protein, E coli; D009841:Oligonucleotides; D012313:RNA