title: Expression of the aminoacyl-tRNA synthetase complex in cultured Chinese hamster ovary cells. Specific depression of the methionyl-tRNA synthetase component upon methionine restriction.
abstract: Cultured Chinese hamster ovary cells were subjected to amino acid restriction to examine its effects on the level of expression of the nine aminoacyl-tRNA synthetase components of the multienzyme complex which was previously characterized (Mirande, M., Le Corre, D., and Waller, J.-P. (1985) Eur. J. Biochem. 147, 281-289). Lowering the methionine concentration in the medium from 100 to 1 microM led to growth arrest, rapid deacylation of tRNAMet, and progressive 2-fold elevation of the methionyl-tRNA synthetase level, as assessed by specific activity measurements and immunotitration. The levels of the other eight aminoacyl-tRNA synthetases were not affected. Total methionine deprivation led to the additional derepression of the leucyl- and isoleucyl-tRNA synthetase components, whereas the corresponding tRNAs remained fully acylated. These pleiotropic responses to total methionine restriction were abolished in the presence of 2 mM methioninol, suggesting that amino acid transport systems may play a role in the regulation of aminoacyl-tRNA synthetase expression. The effect of total deprivation of arginine, glutamine, isoleucine, leucine, lysine, or proline from the culture medium on the level of expression of the corresponding aminoacyl-tRNA synthetases was also examined. In all cases, no elevation of the level of the corresponding synthetase was observed. The behavior of methionyl-tRNA synthetase from Chinese hamster ovary cells displaying a 2-fold increased level of the enzyme due to methionine restriction was examined in detail. Failure to detect a free form of the enzyme by gel filtration, as well as the finding that the isolated complex displayed twice the amount of methionyl-tRNA synthetase relative to the other components, indicates that this multienzyme structure can accommodate at least one additional copy of one of its components.
mesh_terms: D000215:Acylation; D000596:Amino Acids / Q000502:physiology; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D005260:Female; D007700:Kinetics; D008715:Methionine / Q000502:physiology*; D008718:Methionine-tRNA Ligase / Q000378:metabolism*; D008970:Molecular Weight; D010053:Ovary; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism
chemical_list: D000596:Amino Acids; D012346:RNA, Transfer, Amino Acyl; C026464:tRNA(m)(Met), methionine-; D008715:Methionine; D000604:Amino Acyl-tRNA Synthetases; D008718:Methionine-tRNA Ligase