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Six complementation classes of conditionally lethal protein synthesis mutants of CHO cells selected by 3H-amino acid
Abstract:
Using a tritiated amino acid suicide procedure designed specifically to select conditional protein synthesis mutants, we have isolated and characterized a large number of such mutants of Chinese hamster ovary cells. All of the mutants are genetically stable and behave as recessives in somatic cell hybrids. Most of the new mutants are phenotypically dependent on the concentration of a specific amino acid as well as on temperature. In addition to identifying many additional leucyl- and asparagyl-tRNA synthetase mutants, complementation analysis has distinguished four new genetic classes representing methionine-, glutamine-, histidine-, and arginine-dependent mutants. Biochemical characterization of representative mutants from each of these six classes has identified the primary lesions as being defective aminoacyl-tRNA synthetases. Our selection results further demonstrate the high specificity of the 3H-amino acid procedure for isolating protein synthesis mutants. Reconstruction experiments performed with two representative mutants indicated a selection efficiency of approximately 10% under standard conditions.
Insights
Researchers isolated conditional protein synthesis mutants in Chinese hamster ovary cells using a novel tritiated amino acid suicide method. This technique efficiently identified multiple aminoacyl-tRNA synthetase defects, advancing our understanding of cellular protein synthesis.
Area of Science:
- Cell Biology
- Molecular Genetics
- Biochemistry
Background:
- Conditional protein synthesis mutants are crucial for studying cellular processes.
- Existing methods for isolating such mutants have limitations.
- A specific tritiated amino acid suicide procedure was developed to overcome these limitations.
Purpose of the Study:
- To isolate and characterize conditional protein synthesis mutants in Chinese hamster ovary (CHO) cells.
- To identify new genetic classes of amino acid-dependent mutants.
- To validate the efficacy of the tritiated amino acid suicide selection method.
Main Methods:
- Application of a tritiated amino acid suicide procedure for mutant selection.
- Genetic analysis including somatic cell hybridization and complementation analysis.
- Biochemical characterization of identified mutants to pinpoint primary lesions.
Main Results:
- Isolation and characterization of a large number of genetically stable, recessive conditional protein synthesis mutants.
- Identification of mutants dependent on specific amino acids (leucine, asparagine, methionine, glutamine, histidine, arginine) and temperature.
- Complementation analysis distinguished six genetic classes, with biochemical studies confirming defects in aminoacyl-tRNA synthetases.
Conclusions:
- The tritiated amino acid suicide procedure is highly specific and efficient for isolating protein synthesis mutants.
- The study identified novel mutants with defects in various aminoacyl-tRNA synthetases.
- This work provides valuable tools and insights into the regulation of protein synthesis in eukaryotic cells.