Transcription of the ibpB heat-shock gene is under control of sigma(32)- and sigma(54)-promoters, a third regulon of heat-shock response.
The expression of the ibpAibpB heat-shock operon of Escherichia coli was found previously not to conform to the known pattern of expression of the sigma(32)-regulated operons because the rpoH gene mutation inactivating the sigma(32) protein did not abolish the ibp induction. We show here that this effect can depend partly on the sigma(54)-promoter that is inducible by heat shock, located upstream of the ibpB, the distal gene of the operon. It may also depend on a metabolic signal, postulated by others, and possibly required for the expression of the ibpAB genes. Thus, the ibpB gene can be translated from the transcript covering the whole operon starting from the sigma(32)-promoter and from the ibpB gene transcript starting from the sigma(54)-promoter. These results indicate that the ibpB gene is a second member of the sigma(54)-heat-shock regulon in E. coli besides pspA-E operon. Thus, heat-shock response involves three regulons controlled by sigma(32), sigma(24), and sigma(54) RNA polymerase subunits.
Kuczyńska-Wisńik
D
D
Department of Biochemistry, University of Gdańsk, Kladki 24, Gdańsk, 80 822, Poland.
Laskowska
E
E
Taylor
A
A
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D051877:RNA Polymerase Sigma 54; D012333:RNA, Messenger / Q000378:metabolism; D018085:Regulon / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; C097578:IbpA protein, E coli; C097579:IbpB protein, E coli; D012333:RNA, Messenger; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; C497751:rpoN protein, E coli; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54