Apurinic sites cause mutations in simian virus 40

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• SV40 serves as a molecular probe for studying DNA damage in mammalian cells.
• Apurinic sites (Ap) are common DNA lesions that can arise from various damaging agents.

Purpose of the Study:

• To investigate the mutagenicity of apurinic sites (Ap) in mammalian cells using SV40 as a molecular probe.
• To determine the impact of Ap sites on SV40 virus survival and mutation frequency.

Main Methods:

• Monkey kidney cells were transfected with depurinated SV40 DNA (tsB201 mutant).
• Apurinic sites were introduced into SV40 DNA by heating at 70°C under acidic conditions (pH 4.8).
• Mutation frequency was assessed by screening for phenotypic revertants at the restrictive temperature (41°C).

Main Results:

• Apurinic sites significantly reduced SV40 virus survival, with approximately 3 Ap lesions per genome causing lethality.
• Apurinic sites generated by heating were found to be highly mutagenic in animal cells.
• UV irradiation of host cells prior to transfection did not alter the mutation frequency in the viral progeny.

Conclusions:

• Apurinic sites are a significant source of mutations in mammalian cells.
• The study provides the first evidence for the high mutagenicity of heat-induced apurinic sites in animal cells.
• Host cell UV irradiation does not influence the mutagenic potential of apurinic sites in this experimental system.