Replicon-specific regulation of small heat shock genes in Agrobacterium tumefaciens.
Four genes coding for small heat shock proteins (sHsps) were identified in the genome sequence of Agrobacterium tumefaciens, one on the circular chromosome (hspC), one on the linear chromosome (hspL), and two on the pAT plasmid (hspAT1 and hspAT2). Induction of sHsps at elevated temperatures was revealed by immunoblot analyses. Primer extension experiments and translational lacZ fusions demonstrated that expression of the pAT-derived genes and hspL is controlled by temperature in a regulon-specific manner. While the sHsp gene on the linear chromosome turned out to be regulated by RpoH (sigma32), both copies on pAT were under the control of highly conserved ROSE (named for repression of heat shock gene expression) sequences in their 5' untranslated region. Secondary structure predictions of the corresponding mRNA strongly suggest that it represses translation at low temperatures by masking the Shine-Dalgarno sequence. The hspC gene was barely expressed (if at all) and not temperature responsive.
Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Zürich, Switzerland.
Sylvia
S
Balsiger
Curdin
C
Ragaz
Christian
C
Baron
Franz
F
Narberhaus
D020121:5' Untranslated Regions / Q000235:genetics; D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response; D006358:Hot Temperature; D008969:Molecular Sequence Data; D012093:Replicon; D020218:Response Elements / Q000235:genetics* / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D012808:Sigma Factor; C069774:heat-shock sigma factor 32