title: In vivo transcription of nrdAB operon and of grxA and fpg genes is triggered in Escherichia coli lacking both thioredoxin and glutaredoxin 1 or thioredoxin and glutathione, respectively.
abstract: We have previously described () that Escherichia coli maintains a balanced supply of deoxyribonucleotides by a regulatory mechanism that up-regulates the levels of ribonucleotide reductase with the lack of its main hydrogen donors thioredoxin, glutaredoxin 1, and glutathione (GSH). By using a semi-quantitative reverse transcription/multiplex polymerase chain reaction fluorescent procedure that enables simultaneous analysis of up to seven mRNA species, we now demonstrate that regulation operates at the transcriptional level. Double mutant cells lacking both thioredoxin and glutaredoxin 1 had increased transcription of the nrdAB operon, as compared with the corresponding wild type parent (maximal induction of 10- and 9-fold for mRNA of nrdA and nrdB genes, respectively). Likewise, a dramatic increase of 36-fold in grxA mRNA was observed in bacteria simultaneously deficient in thioredoxin and GSH (the physiological reductant of all glutaredoxins). The increased expression of the grxA gene in trxA gshA double mutant bacteria was mimicked in trxA single mutant cells by depletion of GSH with diethylmaleate (DEM). This induction of grxA transcription was rapid since maximal increase was detected upon 10 min of DEM exposure. Like grxA expression, the basal level of fpg mRNA, encoding formamidopyrimidine-DNA glycosylase, was increased (about 4-fold) in a trxA gshA double mutant strain; this expression was also induced upon exposure to DEM (11-fold maximal induction). These results suggest that transcription of grxA might share common redox regulatory mechanism(s) with that of the fpg gene, involved in the repair of 8-oxoguanine in DNA.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, 14071-Córdoba, España.
authors.forename: R
authors.initials: R
authors.lastname: Gallardo-Madueño
authors.forename: J F
authors.initials: JF
authors.lastname: Leal
authors.forename: G
authors.initials: G
authors.lastname: Dorado
authors.forename: A
authors.initials: A
authors.lastname: Holmgren
authors.forename: J
authors.initials: J
authors.lastname: López-Barea
authors.forename: C
authors.initials: C
authors.lastname: Pueyo
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D054477:Glutaredoxins; D005978:Glutathione / Q000235:genetics* / Q000502:physiology; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000378:metabolism; D009876:Operon; D010088:Oxidoreductases; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics* / Q000502:physiology; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D013879:Thioredoxins / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D054477:Glutaredoxins; D011506:Proteins; D013879:Thioredoxins; D010088:Oxidoreductases; D012264:Ribonucleotide Reductases; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D005978:Glutathione