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Mutagen-induced changes in cellular deoxycytidine triphosphate and thymidine triphosphate in Chinese hamster ovary
Abstract:
Deoxynucleoside triphosphate concentrations in Chinese hamster ovary cell lines, CHO-K1 and Mut 8-16, were examined following exposure of cells to UV or dimethylsulfate. Marked decreases in dCTP were observed 2 hr after exposure to both mutagens. In contrast, dTTP concentrations increased with increased cell killing after exposure to UV but not after exposure to dimethylsulfate. Examination of DNA synthesis in permeabilized cells in the presence of excess concentrations of dNTP substrates suggests that excess dCTP enhances replication while excess of dTTP inhibits replication. We therefore ask whether the increase in the dTTP/dCTP ration in mutagenized whole cells either contributes to or prolongs induced inhibition of replication. In addition we proposed that such an induced dNTP imbalance may also contribute to an increase in mutations by enhancing the probability for base-misincorporation.
Insights
Exposure to UV or dimethylsulfate mutagens decreased deoxycytidine triphosphate (dCTP) and increased deoxythymidine triphosphate (dTTP) in Chinese hamster ovary cells. This deoxyribonucleoside triphosphate imbalance may inhibit DNA replication and increase mutations.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Deoxynucleoside triphosphates (dNTPs) are essential building blocks for DNA replication and repair.
- Cellular dNTP pools can be altered by environmental stressors, including DNA damaging agents.
- Imbalances in dNTP concentrations have been linked to genomic instability and mutagenesis.
Purpose of the Study:
- To investigate the impact of UV radiation and dimethylsulfate exposure on dNTP concentrations in Chinese hamster ovary (CHO) cell lines.
- To determine if altered dNTP levels, specifically the dTTP/dCTP ratio, correlate with inhibited DNA replication.
- To explore the potential role of dNTP imbalances in mutagenicity.
Main Methods:
- Quantification of dNTP concentrations (dCTP and dTTP) in CHO-K1 and Mut 8-16 cell lines after exposure to UV or dimethylsulfate.
- Assessment of DNA synthesis rates in permeabilized cells using varying dNTP substrate concentrations.
- Correlation analysis between dNTP pool dynamics, cell killing, and DNA replication inhibition.
Main Results:
- Both UV and dimethylsulfate exposure led to significant decreases in dCTP levels within 2 hours.
- dTTP concentrations increased following UV exposure, correlating with increased cell killing, but not with dimethylsulfate exposure.
- Excess dCTP enhanced DNA replication, while excess dTTP inhibited it in permeabilized cells.
Conclusions:
- Mutagenic treatments induce significant alterations in cellular dNTP pools, characterized by decreased dCTP and variable dTTP changes.
- The observed increase in the dTTP/dCTP ratio may contribute to the inhibition of DNA replication following mutagen exposure.
- Induced dNTP imbalances are hypothesized to increase mutation rates by promoting base-misincorporation during DNA synthesis.