title: Global transcriptional upregulation in the absence of increased translation in Chlamydia during IFNgamma-mediated host cell tryptophan starvation.
abstract: The developmentally regulated intracellular pathogen Chlamydia pneumoniae is a natural tryptophan auxotroph. These organisms survive tryptophan starvation induced by host cell activation with IFNgamma by blocking maturation to the infectious form. In most bacteria, the stringent response is induced during amino acid starvation to promote survival. However, the response of obligate intracellular pathogens, which are predicted to lack stringent responses to amino acid starvation, is poorly characterized. Chlamydial transcription and translation were analysed during IFNgamma-mediated tryptophan starvation using genomic normalization methods, and the data revealed the novel findings that: (i) global chlamydial transcription was upregulated; and (ii) protein synthesis was dramatically reduced. These results indicate a dysregulation of developmental gene expression and an uncoupling of transcription from translation. These observations represent an alternative survival strategy for host-adapted obligate intracellular bacterial pathogens that have lost the genes for stringent control during reductive evolution.
authors.affiliation: Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Scot P
authors.initials: SP
authors.lastname: Ouellette
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Hatch
authors.forename: Yasser M
authors.initials: YM
authors.lastname: AbdelRahman
authors.forename: Lorne A
authors.initials: LA
authors.lastname: Rose
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Belland
authors.forename: Gerald I
authors.initials: GI
authors.lastname: Byrne
mesh_terms: D002460:Cell Line; D002690:Chlamydia Infections / Q000235:genetics / Q000378:metabolism; D016993:Chlamydophila pneumoniae / Q000235:genetics / Q000502:physiology*; D007371:Interferon-gamma / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects*; D014364:Tryptophan / Q000172:deficiency*; D015854:Up-Regulation
chemical_list: D011500:Protein Synthesis Inhibitors; D007371:Interferon-gamma; D014364:Tryptophan