A shuttle vector plasmid for studying carcinogen-induced point mutations in mammalian cells

Area of Science:

• Molecular Biology
• Mammalian Cell Culture
• Genetic Engineering

Background:

• Studying mutagenesis in mammalian cells requires efficient and stable vectors.
• Existing shuttle vectors can suffer from high frequencies of spontaneous deletion mutations.
• SV40-permissive cell lines offer a suitable environment for studying plasmid replication and mutagenesis.

Purpose of the Study:

• To construct and characterize a novel shuttle vector plasmid for mutagenesis studies in mammalian cells.
• To assess the replication efficiency and mutation frequency of the new vector in comparison to existing ones.
• To evaluate the utility of the plasmid as a mutagenesis marker using UV radiation.

Main Methods:

• Construction of a shuttle vector plasmid designed for replication in both Escherichia coli and SV40-permissive mammalian cell lines (CV1).
• Inclusion of a bacterial suppressor tRNA gene (supF) as a mutagenesis reporter.
• Assessment of plasmid replication efficiency relative to SV40 virus.
• Quantification of spontaneous and UV-induced mutation frequencies after passage in CV1 cells.

Main Results:

• The constructed shuttle vector plasmid replicates efficiently in CV1 cells, comparable to SV40 virus.
• The plasmid demonstrates a substantially lower frequency of spontaneous deletion mutations compared to previously described vectors.
• UV irradiation of the plasmid DNA prior to cell passage resulted in a ~20-fold increase in mutation frequency above the spontaneous background.

Conclusions:

• The novel shuttle vector plasmid is a robust tool for studying mutagenesis in mammalian cells.
• Its design minimizes spontaneous deletion mutations, enhancing the reliability of mutagenesis studies.
• The plasmid effectively serves as a reporter system for DNA damage-induced mutagenesis.