title: LasR of Pseudomonas aeruginosa is a transcriptional activator of the alkaline protease gene (apr) and an enhancer of exotoxin A expression.
abstract: The lasR gene of Pseudomonas aeruginosa is required for transcription of the genes for elastase (lasB) and LasA protease (lasA), two proteases associated with virulence. We report here that the alkaline protease gene (apr) also requires the lasR gene for transcription. Alkaline protease mRNA was absent in the lasR mutant PAO-R1 and present when an intact lasR gene was supplied in trans as determined by Northern (RNA) analysis. The lasR gene also enhances exotoxin A production. Exotoxin A activity in supernatants of PAO-R1 were 30% less than in supernatants of the parental strain, PAO-SR. Multiple copies of lasR in trans in PAO-R1 in increased toxin A activity to twice the parental levels. Analysis of PAO-R1 containing the toxA promoter fused to beta-galactosidase suggests that LasR acts at the toxA promoter or at upstream toxA mRNA sequences. beta-Galactosidase activity was approximately 40% lower in PAO-R1 than in the parental strain, PAO-SR. Furthermore, the effect of LasR on the toxA promoter is not due to the stimulation of transcription of regA, a transcriptional activator of toxA. No difference in chloramphenicol acetyltransferase (CAT) activity was noted between PAO-SR and PAO-R1 containing transcriptional regA promoter-CAT gene fusions. These results broaden the regulatory dominion of lasR and suggest that the lasR gene plays a global role in P. aeruginosa pathogenesis.
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642.
authors.forename: M J
authors.initials: MJ
authors.lastname: Gambello
authors.forename: S
authors.initials: S
authors.lastname: Kaye
authors.forename: B H
authors.initials: BH
authors.lastname: Iglewski
mesh_terms: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D001483:Base Sequence; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D010450:Endopeptidases / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D005098:Exotoxins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D012697:Serine Endopeptidases / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics*; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004268:DNA-Binding Proteins; D010450:Endopeptidases; D005098:Exotoxins; D011065:Poly(ADP-ribose) Polymerases; D012697:Serine Endopeptidases; D015534:Trans-Activators; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C080365:LasR protein, Pseudomonas aeruginosa; C032923:microbial serine proteinases