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ParB spreading requires DNA bridging

Thomas G W Graham1, Xindan Wang2, Dan Song3

  • 1Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA;

Genes & Development
|May 16, 2014
PubMed

Insights

The bacterial ParABS system uses ParB protein to spread along DNA, trapping loops. This DNA bridging mechanism explains how ParB spreads and recruits SMC complexes for chromosome segregation.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • The ParABS system is crucial for bacterial plasmid partitioning and chromosome segregation.
  • ParB protein binds parS sites and spreads over adjacent DNA, but the spreading mechanism is unclear.

Purpose of the Study:

  • To investigate the mechanism of ParB spreading and its role in recruiting SMC complexes.
  • To understand how ParB spreads over large DNA regions from parS sites.

Main Methods:

  • Single-molecule approaches were used to study Bacillus subtilis ParB (Spo0J).
  • Analysis of point mutants in Spo0J affecting DNA bridging.

Main Results:

  • Spo0J was found to trap DNA loops, a process dependent on DNA bridging.
  • Mutants defective in DNA bridging showed impaired spreading and SMC complex recruitment in vivo.
  • DNA bridging explains the extensive spread of limited Spo0J molecules.

Conclusions:

  • DNA bridging is a key mechanism for ParB spreading and SMC complex recruitment.
  • This DNA bridging property is conserved across diverse ParB homologs, indicating evolutionary significance.
Keywords:
ParBSpo0Jbacterial chromosome segregationsingle-molecule fluorescence

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