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Analysis of the pSK1 replicon, a prototype from the staphylococcal multiresistance plasmid family

Stephen M Kwong1, Ricky Lim1, Rebecca J LeBard1

  • 1School of Biological Sciences, University of Sydney, New South Wales 2006, Australia.

Microbiology (Reading, England)
|October 4, 2008
PubMed

Insights

This study identifies essential elements for multidrug-resistant staphylococcal plasmid replication, revealing a conserved mechanism for controlling plasmid copy number via antisense RNA. This is crucial for understanding antimicrobial resistance.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Multidrug-resistant staphylococci harbor plasmids encoding antimicrobial resistance genes.
  • Many of these plasmids utilize a conserved theta-type replication system, exemplified by pSK1.
  • Understanding plasmid replication is key to combating antimicrobial resistance.

Purpose of the Study:

  • To identify essential replication elements of the pSK1 multidrug-resistance plasmid.
  • To investigate the role of the Rep protein and its binding sites.
  • To elucidate the copy number control mechanism.

Main Methods:

  • Cloning of pSK1 replication region segments.
  • Testing plasmid replication proficiency.
  • Overexpression and in vitro binding assays of the Rep protein.
  • Analysis of promoter inactivation effects on plasmid copy number.

Main Results:

  • An iterated region within 'rep' and upstream DNA are essential for origin activity.
  • The Rep protein binds to specific 'Rep boxes' within the 'rep' gene.
  • Inactivation of the P(rnaI) promoter increases plasmid copy number.
  • A conserved genetic organization and antisense RNA regulation are suggested for staphylococcal plasmids.

Conclusions:

  • Essential pSK1 replication elements include an iterated region within 'rep' and upstream DNA.
  • The Rep protein directly interacts with Rep boxes to regulate replication.
  • Antisense RNA likely controls plasmid copy number in staphylococcal multidrug-resistance plasmids.
  • These findings provide insights into the replication and regulation of key resistance plasmids.

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