Energy-dependent mitochondrial mutagenicity of antibacterial ofloxacin and its recombinogenic activity in yeast

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Ofloxacin is a known inhibitor of bacterial topoisomerase II.
• This enzyme is crucial for DNA replication and repair in various organisms.
• Ofloxacin has demonstrated effects on yeast cell growth and mutation induction.

Purpose of the Study:

• To investigate the mechanisms underlying ofloxacin's effects on yeast (Saccharomyces cerevisiae).
• To determine the role of mitochondrial ATP and DNA repair pathways in ofloxacin-induced mutagenesis.
• To elucidate the specific molecular targets and consequences of ofloxacin activity in yeast.

Main Methods:

• Assessing ofloxacin's impact on yeast cell growth and petite mutant frequency under varying ATP levels.
• Evaluating the induction of mitotic recombination and reverse mutation in diploid yeast strains.
• Comparing the sensitivity of wild-type and DNA repair-deficient yeast strains (e.g., rad52 mutants) to ofloxacin.

Main Results:

• Ofloxacin-induced petite mutant frequency was significantly reduced in ATP-depleted yeast cells.
• The drug induced mitotic recombination and reverse mutation but did not eliminate killer plasmids or 2-micron DNA.
• Yeast strains deficient in DNA strand-break repair (rad52) exhibited higher sensitivity to ofloxacin compared to wild-type strains.

Conclusions:

• Ofloxacin's cytotoxic and genetic activities in yeast are likely due to the inhibition of topoisomerase II's DNA ligation function.
• This inhibition leads to DNA breaks that are primarily repaired via the recombination repair pathway.
• The findings highlight the importance of DNA repair mechanisms in mediating the genotoxicity of fluoroquinolones in eukaryotic cells.