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Singlet oxygen mutagenicity induced in the lac operon
Archives Internationales De Physiologie Et De Biochimie
|December 1, 1986
Summary
Singlet oxygen (1O2) causes DNA mutations in M13 mp 19 phage, primarily single-base substitutions. Oxidized guanine is misread as thymine by DNA polymerase, leading to specific G-to-T and C-to-A transversions.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Singlet oxygen (1O2) is a reactive oxygen species implicated in oxidative DNA damage.
- Understanding mutagenesis mechanisms is crucial for assessing DNA damage and repair.
- M13 mp 19 hybrid phage is a suitable model for studying mutagenesis in single-stranded DNA.
Purpose of the Study:
- To investigate the mutagenic specificity of singlet oxygen (1O2) in M13 mp 19 phage.
- To characterize the types and frequencies of mutations induced by 1O2.
- To elucidate the DNA polymerase reading errors responsible for 1O2-induced mutations.
Main Methods:
- Analysis of 107 lac mutants induced by 1O2 in M13 mp 19 phage.
- Sequencing of mutant DNA to identify base substitutions and deletions.
- Utilizing the replicative form of M13 mp 19 DNA (RFDNA) as a substrate for 1O2 reactions.
Main Results:
- 93% of mutations were single-base substitutions, with 7% being deletions (40-50 bases).
- Major substitutions included G----T (27%) and C----A (54%) transversions.
- Oxidized guanine lesions are responsible for both types of transversions.
Conclusions:
- Singlet oxygen induces specific base substitutions in M13 mp 19 phage DNA.
- E. coli DNA polymerase-I misreads oxidized guanine as thymine, causing G----T and C----A transversions.
- This study clarifies the molecular mechanism of 1O2-induced mutagenesis.