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Genome-wide identification and characterization of transcripts translationally regulated by bacterial

Hiroshi Kitamura1, Masatoshi Ito, Tomoko Yuasa

  • 1Laboratories for Immunogenomics, RIKEN Research Center for Allergy and Immunology, Yokohama, Japan. ktmr@rcai.riken.jp

Physiological Genomics
|January 31, 2008
PubMed

Insights

Escherichia coli lipopolysaccharide (LPS) alters gene expression at the translational level in macrophages. LPS stimulation translationally downregulates mitochondrial respiratory chain genes, impacting oxidative phosphorylation independently of nitric oxide.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cellular Biology

Background:

  • Escherichia coli lipopolysaccharide (LPS) is a potent activator of macrophage inflammatory responses.
  • The genome-wide impact of LPS on mRNA translational states in macrophages remains largely unexplored.
  • Understanding translational regulation provides deeper insight into LPS-mediated cellular responses.

Purpose of the Study:

  • To investigate the genome-wide translational regulation of transcripts in macrophages stimulated with LPS.
  • To identify specific genes and pathways affected at the translational level by LPS.
  • To elucidate the role of translational control in LPS-induced changes in mitochondrial function.

Main Methods:

  • Utilized Affymetrix Mouse Genome 430 2.0 GeneChips to analyze mRNA profiles.
  • Compared mRNA abundance in total cellular, polysomal, and free messenger ribonucleoprotein particle (mRNP) fractions of J774.1 cells.
  • Stimulated cells with LPS (100 ng/ml) for 1, 2, or 4 hours.
  • Performed gene ontology-based analysis to identify affected pathways.

Main Results:

  • Identified 115 upregulated and 418 downregulated transcripts at the translational level after LPS stimulation.
  • Translationally downregulated genes were enriched for mitochondrial respiratory chain components (complexes I, IV, V).
  • LPS stimulation led to decreased protein levels of cytochrome oxidase subunit Va without altering its total mRNA levels.
  • Total amounts and activities of mitochondrial complexes I and IV were attenuated by LPS, independent of nitric oxide.

Conclusions:

  • LPS modulates macrophage gene expression through translational control.
  • Translational suppression of mitochondrial respiratory chain genes contributes to LPS-mediated attenuation of oxidative phosphorylation.
  • This regulatory mechanism operates independently of nitric oxide production.

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