DNA repair and sequence context affect (1)O(2)-induced mutagenesis in bacteria

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Singlet oxygen ((1)O(2)), an electronically excited form of molecular oxygen, is a known mutagen.
• DNA damage induced by (1)O(2) can lead to mutations, impacting cellular processes.
• Understanding the repair mechanisms and mutagenic outcomes of (1)O(2) damage is crucial for cellular health.

Purpose of the Study:

• To investigate the mutagenicity of (1)O(2)-induced DNA damage in Escherichia coli.
• To determine the role of nucleotide and base excision repair pathways in modulating (1)O(2) mutagenesis.
• To identify specific mutation types and their dependence on DNA repair deficiencies and sequence context.

Main Methods:

• A plasmid containing a (1)O(2)-damaged oligonucleotide was transfected into various E. coli repair-deficient mutants.
• Mutations were screened using hybridization with the original DNA sequence.
• Mutation frequencies and types (G-->T, G-->C transversions) were analyzed in different repair-deficient strains.

Main Results:

• Mutagenesis was observed in all tested E. coli strains.
• Mutagenesis was particularly high in strains deficient in fpg, mutY, and uvrC repair pathways.
• The fpg mutY double mutant showed higher mutagenesis than the fpg mutY uvrC triple mutant, suggesting UvrABC excinuclease activity can influence mutagenesis.
• Mutation types were dependent on guanine position and host bacterial repair status.

Conclusions:

• The mutagenicity of (1)O(2)-induced DNA damage is significantly influenced by bacterial DNA repair pathways.
• Specific repair deficiencies, such as in fpg and mutY, enhance (1)O(2) mutagenesis.
• The interplay between DNA repair, sequence context, and (1)O(2) damage dictates the resulting mutation spectrum.