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Regulatory cross-talk in the double par locus of plasmid pB171

Simon Ringgaard1, Gitte Ebersbach, Jonas Borch

  • 1Department of Biochemistry and Molecular Biology, Campusvej 55, University of Southern Denmark, DK-5230 Odense M, Denmark.

The Journal of Biological Chemistry
|November 10, 2006
PubMed

Insights

The Escherichia coli double par locus involves two systems, par1 and par2, that interact. ParB from par2 surprisingly represses the par1 operon, revealing cross-talk in plasmid partitioning.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • The pB171 plasmid in Escherichia coli harbors a unique double par locus, comprising par1 and par2.
  • par1 encodes ParM (actin ATPase), and par2 encodes ParA (MinD-like ATPase).
  • These loci share cis-acting regions, parC1 and parC2, crucial for their function.

Purpose of the Study:

  • To investigate the interaction and regulatory mechanisms between the par1 and par2 systems.
  • To elucidate the roles of ParR and ParB proteins in DNA binding and transcriptional regulation.
  • To identify novel factors involved in par2-mediated plasmid partitioning.

Main Methods:

  • Electrophoretic mobility shift assays (EMSAs) to study protein-DNA interactions.
  • In vitro and in vivo transcriptional assays to assess promoter activity.
  • Genetic analysis to identify interacting factors.

Main Results:

  • ParR (par1) and ParB (par2) bind cooperatively to distinct DNA repeats within parC1.
  • ParB represses transcription of the noncognate par1 operon, demonstrating cross-talk.
  • The par promoters (P1 and P2) exhibit negative cross-regulation.
  • Integration host factor (IHF) is identified as a novel factor in par2-mediated partitioning.

Conclusions:

  • The double par locus exhibits complex regulatory interactions and cross-talk between par1 and par2 systems.
  • Cooperative DNA binding by ParR and ParB is essential for partitioning and transcriptional control.
  • IHF plays a significant role in par2-mediated plasmid partitioning, highlighting a novel regulatory element.

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