Posttranscriptional Regulation by Copper with a New Upstream Open Reading Frame

Area of Science:

• Microbiology and Molecular Biology
• Bacterial Physiology and Regulation
• Host-Pathogen Interactions

Background:

• Copper is essential but toxic, requiring tight bacterial homeostasis.
• Existing copper regulation mechanisms are primarily transcriptional.
• Posttranscriptional regulatory mechanisms for copper remain largely uncharacterized.

Purpose of the Study:

• To identify and characterize novel posttranscriptional regulatory mechanisms of copper homeostasis in bacteria.
• To investigate the function of the DUF2946 protein family in copper regulation.
• To elucidate the role of the bp2923-bfrG-bp2921 operon in Bordetella pertussis.

Main Methods:

• Identification of a copper-downregulated operon (bp2923-bfrG-bp2921) in Bordetella pertussis.
• Characterization of the upstream gene product (Bp2923) as a novel upstream Open Reading Frame (uORF).
• Analysis of Rho-dependent transcription termination triggered by copper perception via a CXXC motif and relieved translation arrest on a RAPP motif.

Main Results:

• Bp2923, named CruR (copper-responsive upstream regulator), acts as a posttranscriptional regulator.
• Copper binding to CruR's CXXC motif induces Rho-dependent transcription termination.
• This mechanism downregulates downstream copper uptake genes, limiting copper import.

Conclusions:

• A novel mode of posttranscriptional gene regulation by a transition metal (copper) has been discovered.
• CruR represents a new class of bacterial regulatory proteins controlling copper homeostasis.
• The identified regulatory mechanism is conserved and likely widespread in bacteria.