title: Analysis of Bacillus subtilis hut operon expression indicates that histidine-dependent induction is mediated primarily by transcriptional antitermination and that amino acid repression is mediated by two mechanisms: regulation of transcription initiation and inhibition of histidine transport.
abstract: Expression of the Bacillus subtilis hut operon is induced by histidine and subject to regulation by carbon catabolite repression and amino acid repression. A set of hut-lacZ transcriptional fusions was constructed and used to identify the cis-acting sites required for histidine induction and amino acid repression. Histidine induction was found to be primarily mediated by transcriptional antitermination at a palindromic sequence located immediately downstream of the first structural gene in the hut operon, hutP. High levels of histidine induction were observed only in hut-lacZ fusions which contained this palindromic sequence. The hutC1 mutation, which results in constitutive expression of the hut operon, was sequenced and found to contain a GC to TA transversion located within the stem-loop structure. Transcription of hut DNA in vitro revealed that the palindromic structure functions as a transcriptional terminator with wild-type hut DNA but not with hutC1 DNA. Two sites were found to be involved in amino acid repression of hut expression: (i) an operator, hutOA, which lies downstream of the hut promoter, and (ii) the hut terminator. The rate of [14C]histidine uptake in amino acid-grown cells was sixfold lower than that seen in cells grown without amino acids. Thus, inhibition of histidine transport in amino acid-grown cells indirectly regulates hut expression by interfering with histidine induction at the hut terminator.
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Massachusetts 02118.
authors.forename: L V
authors.initials: LV
authors.lastname: Wray
authors.forename: S H
authors.initials: SH
authors.lastname: Fisher
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006639:Histidine / Q000378:metabolism* / Q000494:pharmacology; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D011993:Recombinant Fusion Proteins; D006639:Histidine; D001616:beta-Galactosidase