Abstract
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-1 and His-1, showed pronounced reductions in the amount of arginyl-tRNA or histidyl-tRNA, respectively, under restrictive conditions, compared to wild type. Revertants of Arg-1 (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.
Similar content being viewed by others
Literature cited
Adair, G. M., Thompson, L. H., and Lindl, P. A. (1978).Somat. Cell Genet. 4:27–44.
Thompson, L. H., Lofgren, D. J., and Adair, G. M. (1977).Cell 11:157–168.
Taylor, R., and Hanna, L. C. (1977).Arch. Biochem. Biophys. 181:331–344.
Andrulis, I. L., Chiang, C. S., Arfin, S. M., Miner, T. A., and Hatfield, G. W. (1978).J. Biol. Chem. 253:58–62.
Thompson, L. H., Harkins, J. L., and Stanners, C. P. (1973).Proc. Natl. Acad. Sci. U.S.A. 70:3094–3098.
Farber, R. A., and Deutscher, M. P. (1976).Somat. Cell Genet. 2:509–520.
Thompson, L. H., Stanners, C. P., and Siminovitch, L. (1975).Somat. Cell Genet. 1:187–208.
Haars, L., Hampel, A., and Thompson, L. H. (1976).Biochim. Biophys. Acta 454:493–503.
Hankinson, O. (1976).Somat. Cell Genet. 2:497–507.
Wasmuth, J. J., and Caskey, C. T. (1976).Cell 9:655.
Sato, K. (1975).Nature 257:813.
Lofgren, D.J., and Thompson, L. H. (1978). Submitted.
Molnar, S. J., Thompson, L. H., Lofgren, D. J., and Rauth, A. M. (1978). Submitted toJ. Cell Physiol.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Thompson, L.H., Lofgren, D.J. & Adair, G.M. Evidence for structural gene alterations affecting aminoacyl-tRNA synthetases in CHO cell mutants and revertants. Somat Cell Mol Genet 4, 423–435 (1978). https://doi.org/10.1007/BF01538864
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF01538864