title: ToxR (RegA) activates Escherichia coli RNA polymerase to initiate transcription of Pseudomonas aeruginosa toxA.
abstract: The Pseudomonas aeruginosa (Pa) structural gene (toxA), which encodes the exotoxin A protein has been shown to be regulated at the transcriptional level by a protein designated ToxR (also known as RegA). We have previously reported that ToxR directly enhances toxA transcription in vitro; however, in the absence of ToxR, Pa RNA polymerase (RNAP) transcribes toxA with low efficiency. In the present study, we have examined the ability of ToxR to initiate toxA transcription using the heterologous Escherichia coli (Ec) RNAP and found that ToxR can function with Ec RNAP to efficiently transcribe toxA both in vitro and in vivo. Antibodies produced against the sigma 70 subunit of Ec RNAP inhibit ToxR-mediated enhancement of toxA transcription, suggesting that the RNAP holoenzyme (E sigma 70) is required for transcriptional activation of toxA. We further demonstrate that ToxR is required for open-complex formation at the toxA promoter. By selectively deleting toxA upstream sequences, we have localized at 214-bp region containing both the toxA promoter and a putative ToxR-binding site sufficient for ToxR-mediated transcription of toxA.
authors.affiliation: Department of Microbiology, Ohio State University, Columbus 43210-1292.
authors.forename: S L
authors.initials: SL
authors.lastname: Walker
authors.forename: L S
authors.initials: LS
authors.lastname: Hiremath
authors.forename: D R
authors.initials: DR
authors.lastname: Galloway
mesh_terms: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins / Q000502:physiology*; D001427:Bacterial Toxins; D001483:Base Sequence; D002474:Cell-Free System; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D005098:Exotoxins / Q000096:biosynthesis / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006493:Heparin / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D012318:RNA Polymerase I / Q000378:metabolism*; D012808:Sigma Factor / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases; D005098:Exotoxins; D006493:Heparin; D012318:RNA Polymerase I; D012808:Sigma Factor; D014157:Transcription Factors; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C066719:toxR protein, bacteria; C081775:RNA polymerase sigma 70