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Repair of topoisomerase-mediated DNA damage in bacteriophage T4

B A Stohr1, K N Kreuzer

  • 1Departments of Microbiology and Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.

Genetics
|May 3, 2001
PubMed

Insights

Type II topoisomerase inhibitors like m-AMSA stimulate recombinational repair of DNA damage. Bacteriophage T4 assays reveal specific gene dependencies for this repair pathway, similar to double-strand break repair.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Type II topoisomerase inhibitors are crucial in cancer and bacterial infection treatments.
  • These drugs induce lethal DNA damage by stabilizing DNA-topoisomerase cleavage complexes.
  • Recombinational repair pathways can reduce sensitivity to these agents, indicating DNA damage repairability.

Purpose of the Study:

  • To develop a novel in vivo plasmid-based assay for analyzing topoisomerase-mediated DNA repair products.
  • To investigate the role of the antitumor agent m-AMSA in stimulating recombinational repair.
  • To elucidate the genetic requirements for repairing topoisomerase-induced DNA damage.

Main Methods:

  • Utilized a bacteriophage T4 model system with a plasmid-based assay.
  • Physically analyzed repair products at a specific topoisomerase cleavage site.
  • Performed genetic analyses to determine gene dependencies for repair product formation.

Main Results:

  • The antitumor agent m-AMSA stabilizes T4 type II topoisomerase, stimulating recombinational repair at a specific plasmid site.
  • m-AMSA-dependent repair products require functional topoisomerase and are observed with a drug-hypersensitive mutant.
  • Repair product formation necessitates a T4 origin of replication and shows specific dependencies on T4 genes (32, 46, uvsX, uvsY, 49).

Conclusions:

  • Recombinational repair is stimulated by type II topoisomerase inhibitors like m-AMSA.
  • The identified genetic requirements for repairing topoisomerase-induced DNA damage are similar to those for repairing endonuclease-generated double-strand breaks.
  • This suggests a mechanistic overlap between these DNA repair pathways.

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