Messenger RNA Translation in the Presence of Homologous and Heterologous tRNA

Abstract

The effect of tRNA distribution in the cell on the rate of specific protein synthesis has been investigated. A tRNA-dependent cell-free protein-synthesizing system derived from Krebs-11 ascites cells has been worked out. In this system it is possible to synthesize specific proteins (egg-white proteins or globin) by the translation of oviduct or reticulocyte messenger RNA in the presence of tRNA from homologous or heterologous tissues. The rate of translation of a given messenger RNA is optimal in the presence of tRNA from the homologous tissue. The lower level of protein synthesis obtained with an excess of heterologous tRNA can be overcome by adding the homologous tRNA. Nevertheless homologous isoaccepting species partly purified by a reversed-phase chromatography or a benzoylated DEAE-cellulose column cannot fully restore the optimal synthesis, eliminating the hypothesis according to which a particular tRNA species is involved in this phenomenon. The correct distribution of tRNA is necessary for optimal translation of a messenger RNA.In birds estrogens control the synthesis of eggwhite and yolk proteins [1,2]. Palmiter [3] has shown an increase of the initiation and elongation rates of ovalbumin synthesis under estrogen stimulation which suggests that hormonal control occurs not only at transcription but also at the level of the translation of messenger RNAs into proteins. Our previous work [4,5] indicated that there is a low probability of regulation by the aminoacyl-tRNA synthetases. For example, the seryl-tRNA synthetases prepared either from laying hen liver (estrogen stimulation) or from rooster liver (control) showed the same chromatographic and electrophoretic properties. This enzyme also had the same kinetic constants for the four serylisoaccepting tRNAs either from hens or from other animals such as rabbits or rats. Nevertheless, we have found significant quantitative differences in the distribution of the tRNA isoaccepting species from liver and oviduct (two target organs for estrogens in hens). This observation suggests that a functional adaptation of the tRNA population might exist in response to the requirements of the proteins synthesized in the cell. In order to verify if the tRNA distribution has an influence on the protein synthesis, we developed a tRNA-dependent cell-free system derived from Krebs-I1 ascites cells. In this system we have characterized specific proteins synthesized by translation of Definition. A260 unit, the quantity of material contained in 1 ml of a solution which has an absorbance of 1 at 260 nm, when measured in a I-cm pathlength cell.

Starvation phase of Physarum polycephalum: characterization of transfer ribonucleic acid.

“…Our results are, however, consistent with several recent reports (10,(22)(23)(24)26) which have associated specific protein synthetic efficiency with the overall quantitative distribution of tRNA populations and not with the presence or absence of specific isoacceptors. Whether evidence can be obtained to suggest that the starvation-phase tRNA population of Physarum has undergone a "functional or quantitative adapation" (6) to specifically acommodate the synthesis of starvation-phase specific proteins remains to be determined.…”

Analysis of Messenger RNA Coding for S100 Protein in the Mammalian Brain

“…Induction of SlOO protein differs in this respect from the induction of a number of other tissue-specific proteins. In other systems the capacity of the tissue for protein synthesis increases and the distribution of isoacceptor species of transfer RNA favors the translation of the mRNA for the induced proteins (Palmiter, 1975;LeMeur et al, 1976). These adaptive mechanisms amplify the induction by promoting a more efficient translation of the induced mRNA.…”

Protein folding and tRNA biology

“…This was the case for isoacceptor tRNA-Ala and tRNA-Ser species present in the posterior gland of the silkworm Bombyx mori and the aminoacyl-tRNA population of human reticulocytes (Garel et al 1976;Sprague et al 1977;Hentzen et al 1981;Hatfield et al 1982). Other observations, using cell-free protein synthesis systems, stressed that the rate of translation of a given mRNA was optimal in the presence of tRNA from the homologous tissue (Le Meur et al 1976;Sharma and Beezley 1976). It is worth mentioning early works emphasizing the biological importance of posttranscriptional modifications of tRNA (Björk and Neidhardt 1975;Ny and Björk 1977;Labuda et al 1982;Vacher et al 1984;Meier et al 1985;Grosjean et al 1995).…”