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Error-prone replication of ultraviolet-irradiated simian virus 40 in carcinogen-treated monkey kidney cells
Abstract:
To analyze the molecular mechanism of mutagenesis in carcinogen-treated mammalian cells, we developed a model system composed of various simian virus 40 (SV40) mutants as a biological probe to detect inducible DNA repair and mutagenesis in carcinogen-treated monkey kidney cells (CV1-P). Results have shown that treatment of cells with UV-light, acetoxy-acetyl-aminofluorene, or mitomycin C, increases the mutagenesis of UV-irradiated SV40 ts mutant measured as a reversion frequency from a thermosensitive phenotype toward a thermoresistant phenotype. This increased mutagenesis is not observed in the case of undamaged virus indicating that we are looking at targeted mutagenesis. The molecular analysis of several revertant genomes indicates that some DNA rearrangements may occur in the revertant genomes but in some cases the reversion site is a single basepair substitution located at positions different from the original thermosensitive mutation, which is still present. The general interpretation of our results leads to the conclusion that carcinogen treatment of monkey cells activates some kind of error-prone replication mode able to better replicate UV-damaged templates but leading to a higher level of mutagenesis. This activity may represent a SOS-like function in mammalian cells.
Insights
Carcinogen exposure in mammalian cells triggers an error-prone DNA replication mode, increasing mutagenesis. This suggests a potential SOS-like DNA repair response in monkey kidney cells.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Understanding mutagenesis mechanisms in carcinogen-exposed cells is crucial for cancer research.
- Mammalian cells possess complex DNA repair and mutagenesis pathways.
- Simian virus 40 (SV40) mutants offer a sensitive probe for studying these processes.
Purpose of the Study:
- To investigate the molecular mechanisms underlying mutagenesis in mammalian cells following carcinogen treatment.
- To characterize inducible DNA repair and mutagenesis pathways activated by carcinogens.
- To utilize SV40 mutants as biological probes in carcinogen-treated monkey kidney cells (CV1-P).
Main Methods:
- Development of a model system using SV40 mutants.
- Treatment of CV1-P cells with UV-light, acetoxy-acetyl-aminofluorene, and mitomycin C.
- Analysis of mutagenesis frequency in UV-irradiated SV40 ts mutants.
- Molecular analysis of revertant viral genomes.
Main Results:
- Carcinogen treatment significantly increased mutagenesis of UV-irradiated SV40 ts mutants.
- This mutagenesis increase was specific to damaged viral DNA, indicating targeted mutagenesis.
- Molecular analysis revealed single base-pair substitutions and some DNA rearrangements in revertant genomes.
- The original thermosensitive mutation often remained present alongside new mutations.
Conclusions:
- Carcinogen treatment activates an error-prone replication mode in mammalian cells.
- This mode enhances replication of damaged DNA templates at the cost of increased mutagenesis.
- The observed phenomenon suggests the presence of a SOS-like DNA repair function in mammalian cells.