title: Heat-shock sigma factor RpoH from Geobacter sulfurreducens.
abstract: Recent studies with Myxococcus xanthus have suggested that homologues of the Escherichia coli heat-shock sigma factor, RpoH, may not be involved in the heat-shock response in this delta-proteobacterium. The genome of another delta-proteobacterium, Geobacter sulfurreducens, which is considered to be a representative of the Fe(III)-reducing Geobacteraceae that predominate in a diversity of subsurface environments, contains an rpoH homologue. Characterization of the G. sulfurreducens rpoH homologue revealed that it was induced by a temperature shift from 30 degrees C to 42 degrees C and that an rpoH-deficient mutant was unable to grow at 42 degrees C. The predicted heat-shock genes, hrcA, grpE, dnaK, groES and htpG, were heat-shock inducible in an rpoH-dependent manner, and comparison of promoter regions of these genes identified the consensus sequences for the -10 and -35 promoter elements. In addition, DNA elements identical to the CIRCE consensus sequence were found in promoters of rpoH, hrcA and groES, suggesting that these genes are regulated by a homologue of the repressor HrcA, which is known to bind the CIRCE element. These results suggest that the G. sulfurreducens RpoH homologue is the heat-shock sigma factor and that heat-shock response in G. sulfurreducens is regulated positively by RpoH as well as negatively by the HrcA/CIRCE system.
authors.affiliation: Department of Microbiology, Morrill Science Center IV North, University of Massachusetts Amherst, 639 North Pleasant Street, Amherst, MA 01003-9298, USA.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ueki
authors.affiliation: Department of Microbiology, Morrill Science Center IV North, University of Massachusetts Amherst, 639 North Pleasant Street, Amherst, MA 01003-9298, USA.
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
mesh_terms: D000222:Adaptation, Physiological; D001483:Base Sequence; D001665:Binding Sites; D016384:Consensus Sequence / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D045302:Geobacter / Q000235:genetics* / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D012808:Sigma Factor / Q000096:biosynthesis* / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D006360:Heat-Shock Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; C069774:heat-shock sigma factor 32