title: A large family of antivirulence regulators modulates the effects of transcriptional activators in Gram-negative pathogenic bacteria.
abstract: We have reported that transcription of a hypothetical small open reading frame (orf60) in enteroaggregative E. coli (EAEC) strain 042 is impaired after mutation of aggR, which encodes a global virulence activator. We have also reported that the cryptic orf60 locus was linked to protection against EAEC diarrhea in two epidemiologic studies. Here, we report that the orf60 product acts as a negative regulator of aggR itself. The orf60 protein product lacks homology to known repressors, but displays 44-100% similarity to at least fifty previously undescribed small (<10 kDa) hypothetical proteins found in many gram negative pathogen genomes. Expression of orf60 homologs from enterotoxigenic E. coli (ETEC) repressed the expression of the AraC-transcriptional ETEC regulator CfaD/Rns and its regulon in ETEC strain H10407. Complementation in trans of EAEC 042orf60 by orf60 homologs from ETEC and the mouse pathogen Citrobacter rodentium resulted in dramatic suppression of aggR. A C. rodentium orf60 homolog mutant showed increased levels of activator RegA and increased colonization of the adult mouse. We propose the name Aar (AggR-activated regulator) for the clinically and epidemiologically important orf60 product in EAEC, and postulate the existence of a large family of homologs among pathogenic Enterobacteriaceae and Pasteurellaceae. We propose the name ANR (AraC Negative Regulators) for this family.
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America.
authors.forename: Araceli E
authors.initials: AE
authors.lastname: Santiago
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America.
authors.forename: Fernando
authors.initials: F
authors.lastname: Ruiz-Perez
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America.
authors.forename: Noah Y
authors.initials: NY
authors.lastname: Jo
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America; Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Vidhya
authors.initials: V
authors.lastname: Vijayakumar
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America.
authors.forename: Mei Q
authors.initials: MQ
authors.lastname: Gong
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, Virginia, United States of America.
authors.forename: James P
authors.initials: JP
authors.lastname: Nataro
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism*; D044082:Citrobacter rodentium / Q000235:genetics / Q000276:immunology*; D003967:Diarrhea / Q000382:microbiology; D004756:Enterobacteriaceae Infections / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000472:pathogenicity*; D015964:Gene Expression Regulation, Bacterial / Q000276:immunology; D051379:Mice; D015534:Trans-Activators / Q000378:metabolism*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D015534:Trans-Activators