title: The rpoH gene encoding heat shock sigma factor sigma32 of psychrophilic bacterium Colwellia maris.
abstract: The rpoH gene encoding a heat shock sigma factor, sigma(32), was cloned from the psychrophilic bacterium Colwellia maris. The deduced amino acid sequence of sigma(32) from C. maris is more than 60% homologous to that of sigma(32) from mesophilic bacteria. The RpoH box, a 9-amino-acid sequence region (QRKLFFNLR) specific to sigma(32), and two downstream box sequences complementary to a part of 16S rRNA were identified. Primer extension analysis showed that the C. maris rpoH is expressed from only one sigma(70)-type promoter. Northern blot analysis showed that the level of rpoH mRNA was clearly increased at 20 degrees C, a temperature that induces heat shock in this organism. In the presence of an inhibitor of transcriptional initiation, the degradation of rpoH mRNA was much slower at 20 degrees C than at 10 degrees C. Thus, increased stability of the rpoH mRNA might be responsible for the rpoH mRNA accumulation. The predicted secondary structure of the 5'-region of C. maris rpoH mRNA was different from the conserved patterns reported for most mesophilic bacteria, and the base pairing of the downstream boxes appeared to be less stable than that of Escherichia coli rpoH mRNA. Thus, essential features that ensure the HSP expression at a relatively low temperature are embedded in the rpoH gene of psychrophiles.
authors.affiliation: Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamauchi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Okuyama
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hayashi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D020563:Gammaproteobacteria / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D012329:RNA, Bacterial / Q000737:chemistry; D012333:RNA, Messenger / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000235:genetics*
chemical_list: D006360:Heat-Shock Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; C069774:heat-shock sigma factor 32