Characterization of chlamydial Rho and the role of Rho-mediated transcriptional polarity during interferon gamma-mediated tryptophan limitation

Scot P. Ouellette, Parker R. Messerli, Nicholas A. Wood, Heather Hajovsky

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

As an obligate intracellular, developmentally regulated bacterium, Chlamydia is sensitive to amino acid fluctuations within its host cell. When human epithelial cells are treated with the cytokine interferon gamma (IFN-γ), the tryptophan (Trp)-degrading enzyme, indoleamine-2,3-dioxygenase, is induced. Chlamydiae within such cells are starved for Trp and enter a state of so-called persistence. Chlamydia lacks the stringent response used by many eubacteria to respond to this stress. Unusually, chlamydial transcription is globally elevated during Trp starvation with transcripts for Trp codon-containing genes disproportionately increased. Yet, the presence of Trp codons destabilized 3' ends of transcripts in operons or large genes. We initially hypothesized that ribosome stalling on Trp codons rendered the 3' ends sensitive to RNase activity. The half-life of chlamydial transcripts containing different numbers of Trp codons was thus measured in untreated and IFN-γ-treated infected cells to determine whether Trp codons influenced the stability of transcripts. However, no effect of Trp codon content was detected. Therefore, we investigated whether Rho-dependent transcription termination could play a role in mediating transcript instability. Rho is expressed as a midcycle gene product, interacts with itself as predicted, and is present in all chlamydial species. Inhibition of Rho via the Rho-specific antibiotic, bicyclomycin, and overexpression of Rho are detrimental to chlamydiae. Finally, when we measured transcript abundance 3' to Trp codons in the presence of bicyclomycin, we observed that transcript abundance increased. These data are the first to demonstrate the importance of Rho in Chlamydia and the role of Rho-dependent transcription polarity during persistence.

Original languageEnglish (US)
Article numbere00240-18
JournalInfection and immunity
Volume86
Issue number7
DOIs
StatePublished - Jul 1 2018

Fingerprint

Tryptophan
Interferon-gamma
Codon
Chlamydia
Indoleamine-Pyrrole 2,3,-Dioxygenase
Genes
Bacteria
Operon
Ribonucleases
Starvation
Ribosomes
Half-Life
Epithelial Cells
Cytokines
Anti-Bacterial Agents
Amino Acids
Enzymes

Keywords

  • Chlamydia
  • Interferon gamma
  • Persistence
  • Rho
  • Stringent response
  • Transcription termination

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

Cite this

Characterization of chlamydial Rho and the role of Rho-mediated transcriptional polarity during interferon gamma-mediated tryptophan limitation. / Ouellette, Scot P.; Messerli, Parker R.; Wood, Nicholas A.; Hajovsky, Heather.

In: Infection and immunity, Vol. 86, No. 7, e00240-18, 01.07.2018.

Research output: Contribution to journalArticle

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