Point mutations induced by 1,2-epoxy-3-butene N1 deoxyinosine adducts

Area of Science:

• Toxicology
• Molecular Biology
• Genetics

Background:

• The National Toxicology Program classifies 1,3-butadiene (BD) as a human carcinogen.
• BD is metabolized into genotoxic intermediates, including 1,2-epoxy-3-butene (EB).
• These metabolites are implicated in DNA damage across various species and cell types.

Purpose of the Study:

• To investigate the mutagenic effects of EB-induced N1 deoxyadenosine lesions.
• To characterize the DNA damage and mutation spectrum caused by specific EB stereoisomers.

Main Methods:

• Site-specific incorporation of R and S stereoisomers of N1 deoxyinosine lesions into an 11-mer oligodeoxynucleotide.
• Incorporation into M13mp7L2 single-stranded DNA and transfection into E. coli.
• Assessment of plaque-forming ability and DNA sequence analysis for point mutations.

Main Results:

• Both EB stereoisomers modestly reduced plaque-forming ability, indicating bypassability.
• The N1 adducts were highly mutagenic, with approximately 90% mutation frequency per replication cycle.
• A predominance of adenine to guanine (A --> G) transitions was observed.

Conclusions:

• EB-induced N1 deoxyadenosine lesions are highly mutagenic in E. coli.
• The primary mutation type induced by these lesions is A --> G transition.
• This study elucidates the genotoxic mechanism of a key 1,3-butadiene metabolite.