Evidence for structural gene alterations affecting aminoacyl-tRNA synthetases in CHO cell mutants and revertants
Aminoacyl-tRNA synthetase (aaRS) activities in extracts of mutant strains of the Chinese hamster ovary line (CHO) were examined for alterations in thermal stability. Mutants having low activity for MetRS, AsnRS, or GlnRS contained aaRSs that were inactivated much more rapidly upon heating than those from wild-type cells. Revertant lines, isolated from cultures of these mutants (Asn-5, Met-2, and Gln-2) after treatment with nitrosoguanidine or ethyl methanesulfonate, had thermolabilities intermediate between mutant and wild-type, and consistently had higher activities than the mutants. With a modified in vivo aminoacylation procedure, two previously exceptional mutants, Arg-l and His-l, showed pronounced reductions in the amount of arginyl-tRNA or histidyl-tRNA, respectively, under restrictive conditions, compared to wild type. Revertants of Arg-l (like the mutant itself) had no measurable ArgRS in vitro activity (< 0.4% of wild type) although in vivo aminoacylation in the one revertant tested was partially restored. These data provide evidence that the forward mutations have occurred in the structural genes of the aaRSs and that most of the reversions are probably the result of second-site point mutations in the aaRS genes.
- Research Organization:
- Univ. of California, Livermore
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5611942
- Journal Information:
- Somatic Cell Genet.; (United States), Vol. 4:4
- Country of Publication:
- United States
- Language:
- English
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CELL CULTURES
GENE MUTATIONS
TRANSFER RNA
LIGASES
ARGININE
EMS
HAMSTERS
HISTIDINE
MUTANTS
NITROSO COMPOUNDS
OVARIES
TEMPERATURE DEPENDENCE
AMINO ACIDS
ANIMALS
AZOLES
BODY
CARBOXYLIC ACIDS
ENZYMES
ESTERS
FEMALE GENITALS
GONADS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
MAMMALS
MUTAGENS
MUTATIONS
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
RNA
RODENTS
SULFONIC ACID ESTERS
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