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Mutagenesis by simian virus 40. II. Changes in substrate affinities in mutant hypoxanthine-guanine phosphoribosyl
Abstract:
A number of 8-azaguanine-resistant clones selected from Chinese hamster cells infected with SV 40, and supposed to originate by virus infection was investigated to demonstrate and analyze genetic alterations occurring in the cells after infection. All resistant clones tested showed reduced but detectable activity levels of the enzyme hypoxanthine-guanine phosphoribosyltransferase. The extent of reduction in the activity was not identical for different substrates. In all the clones tested, spontaneous mutants included, the pH optimum for the enzymic reaction with guanine was shifted to lower values. The reduced enzymic activities of resistant clones correlated with their colony-forming ability in corresponding selective media. The results support the suggestion that SV 40 is able to induce gene mutations.
Insights
SV40 virus infection induced genetic alterations in Chinese hamster cells, leading to reduced enzyme activity and altered pH optima for hypoxanthine-guanine phosphoribosyltransferase. These changes correlate with cell survival, suggesting SV40 causes gene mutations.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- SV40 virus is known to infect various cell types.
- Investigating virus-induced cellular changes is crucial for understanding viral pathogenesis.
- Gene mutations can lead to altered enzyme function and cellular phenotypes.
Purpose of the Study:
- To analyze genetic alterations in Chinese hamster cells post-SV40 infection.
- To investigate the impact of SV40 on hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity.
- To determine if SV40 infection induces gene mutations.
Main Methods:
- Selection of 8-azaguanine-resistant clones from SV40-infected Chinese hamster cells.
- Assay of HGPRT enzyme activity in resistant clones.
- Analysis of enzyme kinetics, including pH optima.
- Correlation of enzyme activity with colony-forming ability.
Main Results:
- All resistant clones exhibited reduced HGPRT activity.
- The reduction in HGPRT activity varied with different substrates.
- A shift in the pH optimum for guanine metabolism was observed in all clones.
- Reduced enzyme activity correlated with colony-forming ability in selective media.
Conclusions:
- SV40 infection leads to detectable genetic alterations in host cells.
- The observed changes in HGPRT activity and kinetics support the induction of gene mutations by SV40.
- SV40's ability to induce mutations has implications for understanding its oncogenic potential.