title: Identification of LexA regulated promoters in Escherichia coli O157:H7.
abstract: In Escherichia coli (E. coli), most DNA damage-inducible (din) genes belong to the LexA regulon, whose products are related to functions such as DNA repair and induced mutagenesis. The E. coli K-12 cells have about 30 operons that are known to be members of the LexA regulon. LexA acts as a transcriptional repressor of these unlinked genes by binding to the specific DNA sequences located within the promoter regions. We developed a genetic screening method to isolate LexA dependent promoters. By using an applied whole-genome shotgun method with a lac-operon system, we isolated promoter candidates of din genes from the E. coli O157:H7 genome. We found that transcriptional repression from most of these promoters was dependent on lexA and purified LexA protein bound directly to the DNA fragments carrying them. Finally, we identified 16 and 5 promoters that regulated expression of previously known and novel LexA dependent genes, respectively. In addition to them, we also identified 2 antisense promoters which were considered to regulate expression of antisense RNAs for mRNAs of the ecs1779 and ecs2988 genes. All newly identified promoter regions contained DNA sequences similar to the consensus LexA binding sequence.
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Yokosuka, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yaguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Mikami
authors.forename: Kazuki
authors.initials: K
authors.lastname: Igari
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Katsushi
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Kozo
authors.initials: K
authors.lastname: Makino
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D019453:Escherichia coli O157 / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D015698:Genomic Library; D007763:Lac Operon / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D018085:Regulon / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein