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Updated: Aug 17, 2026
Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency
Published on: June 16, 2011
Abstract:
Variants resistant to canavanine, an arginine analogue, have been isolated from two long-term human lymphoblastoid cell lines. They are 20-fold more resistant to canavanine than the parental lines and this phenotype is stable in the absence of canavanine for more than 100 generations. The specific activity of argininosuccinate synthetase, the first of two enzymes necessary for the conversion of citrulline to arginine, is elevated in variants from both cell lines. Furthermore, this enzyme activity is refractory to the repression caused by arginine in normal lymphoblasts. The specific activity of argininosuccinate lyase, the second enzyme in the pathway from citrulline to arginine, is not appreciably changed. Arginine uptake appears normal in the variants since they grow as well as the parental lines in media containing a wide range of arginine concentrations. Arginyl-tRNA synthetase activity is also unchanged. Thus the canavanine-resistant variants have altered control of at least one urea cycle enzyme and appear to be regulatory mutants of human cells.
Insights
Human cell lines resistant to canavanine, an arginine analogue, were developed. These variants show altered control of urea cycle enzymes, indicating they are regulatory mutants.
Area of Science:
- Biochemistry
- Cell Biology
- Genetics
Background:
- Canavanine is an arginine analogue that inhibits cell growth.
- Human lymphoblastoid cell lines are used to study cellular resistance mechanisms.
- Understanding urea cycle enzyme regulation is crucial for metabolic studies.
Purpose of the Study:
- To isolate and characterize human cell variants resistant to canavanine.
- To investigate the underlying biochemical mechanisms of canavanine resistance.
- To identify potential regulatory mutations in human cells.
Main Methods:
- Isolation of canavanine-resistant variants from long-term human lymphoblastoid cell lines.
- Measurement of argininosuccinate synthetase and argininosuccinate lyase enzyme activities.
- Assessment of arginine uptake and arginyl-tRNA synthetase activity.
- Evaluation of phenotypic stability in the absence of canavanine.
Main Results:
- Canavanine-resistant variants exhibited a 20-fold increase in resistance compared to parental lines.
- Elevated argininosuccinate synthetase activity was observed in resistant variants.
- This enzyme activity was refractory to arginine-mediated repression.
- Arginine uptake and arginyl-tRNA synthetase activity remained unchanged.
- The resistant phenotype was stable for over 100 generations.
Conclusions:
- Canavanine resistance in these variants is linked to altered urea cycle enzyme regulation.
- The findings suggest the presence of regulatory mutations affecting argininosuccinate synthetase.
- These cell lines serve as models for studying human metabolic regulation and drug resistance.
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