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At least 19 recordsLinked to original sources
PubMed1976

Transfer RNA and transfer RNA methylase activity in spleens of patients with Hodgkin's disease and histiocytic lymphoma.

tRNA levels, base composition, and tRNA methylase activities of normal and tumor tissue from the spleens of 24 patients (18 with Hodgkin's disease and 6 with histiocytic lymphoma) were studied. There were no significant differences in major base composition of normal and tumor tissue. Methylated guanosine was increased in tumor tissue of some patients, and tRNA methylase activities were increased in extracts from the tumors.

Hodgkin Disease↗
PubMed1976

Chloroplast DNA codes for transfer RNA.

Transfer RNA's were isolated from Euglena gracilis. Chloroplast cistrons for tRNA were quantitated by hybridizing tRNA to ct DNA. Species of tRNA hybridizing to ct DNA were partially purified by hybridization-chromatography. The tRNA's hybridizing to ct DNA and nuclear DNA appear to be different. Total cellular tRNA was hybridized to ct DNA to an equivalent of approximately 25 cistrons. The total cellular tRNA was also separated into 2 fractions by chromatography on dihydroxyboryl substituted amino ethyl cellulose. Fraction I hybridized to both nuclear and ct DNA. Hybridizations to ct DNA indicated approximately 18 cistrons. Fraction II-tRNA hybridized only to ct DNA, saturating at a level of approximately 7 cistrons. The tRNA from isolated chloroplasts hybridized to both chloroplast and nuclear DNA. The level of hybridization to ct DNA indicated approximately 18 cistrons. Fraction II-type tRNA could not be detected in the isolated chloroplasts.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Transfer RNA and aminoacyl transfer RNA in developing rats.

The total transfer RNA (tRNA) level in the liver, kidney, skeletal muscle and heart muscle of developing rats was determined by purification using (3H)tRNA as an internal standard. Liver and kidney contained almost twice as much tRNA per gram tissue as heart and skeletal muscle. There were no apparent differences between the sexes. The aminoacylation capacities of six tRNA species (alanyl, aspartyl, leucyl, methionyl, phenylalanyl, and tryptophanyl) from rat liver were not different during 3 developmental stages (suckling, weaning and young adult), and there were also no differences noted between males females. The in vivo percent aminoacylation of 4 tRNAs (aspartyl, leucyl, methionyl, and phenylalanyl) was lower during the newborn and suckling periods than in weaning and young adult rat livers. The tRNA of young adults was almost completely aminoacylated in vivo with the exception of alanyl-tRNA.

Acylation↗
PubMed1975

Equilibrium measurements of cognate and noncognate interactions between aminoacyl transfer RNA synthetases and transfer RNA.

The interaction of Escherichia coli isoleucyl-tRNA synthetase with its cognate and five noncognate tRNAs, and of yeast valyl-tRNA synthetase with its cognate and four noncognate tRNAs, has been measured directly by fluorescence quenching. The cognate associations are strongest (association constant of 10(8) M-1 or more at pH 5.5, 17 degrees). A wide variation is found in the strengths of the noncognate interactions; these have association constants smaller than that of these cognate association by a factor of less than 10 to over 10(4), depending on the enzyme-t-RNA pair. A more detailed study of the cognate isoleucyl-tRNA synthetase-tRNAIle association suggests that the strength of the interaction is markedly sensitive to a pH-dependent transition in the enzyme centered at pH 6 on the other hand, Mg2+-induced structural changes in tRNAIle at 17 degrees in low salt do not greatly affect the availability of the nucleic acid's receptor sites for enzyme...

Amino Acyl-tRNA Synthetases↗
PubMed1976

Aminoacyl transfer RNA formation. Binding of cations to transfer RNA and its role in aminoacyl transfer RNA formation.

The role of cations (polyamines and Mg2+) in isoleucyl-tRNA formation catalyzed by purified isolecuyl-tRNA synthetase [EC 6.1.1.5] from Escherichia coli was studied. It was found that spermine, spermidine, and Mg2+ bind to tRNA and that when bound to these cations, tRNA acts as substrate of aminoacylation without requiring further cations. These findings suggest that the primary function of cations in aminoacyl-tRNA formation is to bind to tRNA to stabilize its structure, not to bind to the enzyme to activate it.

Binding Sites↗
PubMed1978

The genes for 5 S ribosomal RNA and transfer RNA in Tetrahymena pyriformis.

In the present communication a characterization of the 5 S rRNA genes and the tRNA genes of Tetrahymena pyriformis has been performed. The number of 5 S rRNA and tRNA genes in the macromolecular DNA has been established. Furthermore no sequence homology is observed for these genes. The number of both types of genes does not change significantly under starvation conditions. The genomic organization of the 5 S rRNA and tRNA genes has been investigated. From in vivo replication studies it is concluded, that replication of both 5 S rRNA and tRNA genes takes place throughout the whole S-period.

Animals↗
PubMed1976

Isotope labeling of free and aminoacyl transfer RNA synthetase-bound transfer RNA.

The structural organization of the complex of Escherichia coli Ile-tRNA synthetase and tRNA Ile has been studied by isotope labeling of purine units in the tRNA. Free or bound tRNA is incubated in tritiated water for 5 to 15 h at 37 degrees in order to incorporate tritium into the C-8 positions of purine units. (Previous work has shown that the labeling rate of a purine is very sensitive to its microenvironment.) Under conditions where exchange-out does not occur, the nucleic acid is digested with nucleases and purines are subsequently isolated from known locations in the structure. Four purines are substantially perturbed by bound Ile-tRNA synthetase; in each case, the rate of labeling is retarded in the presence of the synthetase. The four purines occur at or near the 3' terminus and at the interface of the dihydrouridine stem and loop. These bases occur in segments of the tRNA that previous photochemical cross-linking studies have identified as important for synthetase-tRNA interactions. It appears that the effects observed on these sites are caused by their direct interaction with or shielding by the bound synthetase. In addition, two other sites, one in the anticodon and one in the amino acid acceptor-T psi C helix, appear to be perturbed (retarded labeling rates) by the bound enzyme. The data also suggest there is no significant conformational change in the tRNA upon binding to the synthetase.

Adenine Nucleotides↗
PubMed1979

Regulation of biosynthesis of aminoacyl-transfer RNA synthetases and of transfer-RNA in Escherichia coli.

We have isolated temperature resistant revertants from temperature sensitive E. coli strains containing either a thermolabile glutaminyl-tRNA synthetase or leucyl-tRNA synthetase. Among the revertants which still contained the thermolabile leucyl-tRNA synthetase we found two classes of regulatory mutants (leuX and leu Y) which have elevated levels of this enzyme. The leuX mutation specifies an operator-promoter region adjacent to the structural gene (leuS) for the enzyme. The leuY gene maps away from the leuS gene and codes for a protein. Using these mutants we demonstrated that the levels of leucyl-tRNA are related to the derepression of the leucine and isoleucine-valine operons. Among the revertants which still contained the thermolabile glutaminyl-tRNA synthetase were characterized three classes of mutants, glnT, glnU, and glnR. The glnT and glnU mutants contain elevated levels of tRNAgln, while the glnR mutant possesses elevated levels of glutaminyl-tRNA synthetase. The level of glutamine synthetase, the enzyme responsible for the formation of glutamine, is also derepressed in the glnT and glnR mutants.

Amino Acyl-tRNA Synthetases↗
PubMed1978

Photobinding of 8-methoxypsoralen to transfer RNA and 5-fluorouracil-enriched transfer RNA.

The photobinding of [3H]8MOP to tRNA upon irradiation at 365 nm in the absence of O2 was determined by gel filtration. The maximum photobinding was found to be ca. 4 mol of 8MOP er mol of tRNA and 5FU-tRNA, with an overall quantum yield of 2.3 X 10(-3). The photobinding kinetics for 8MOP-tRNA showed an apparent induction period or sigmoidal kinetic curve, indicating a specific initial photobinding site on tRNA which was identified as 4-thiouridine at position 8 from the 5'-end of Escherichia coli tRNA. Photobinding of 8MOP to 5FU-tRNA proceeded without an apparent induction period. 8MOP-tRNA and 8MOP-5FU-tRNA adducts were characterized by absorption, fluorescence, and CD spectroscopy. A modified procedure was also developed to analyze the nucleoside composition in modified 8MOP-tRNA and 8MOP-5FU-tRNA. The results showed that 8MOP photochemically added mainly to pyrimidine bases. The photobinding of 8MOP changed the conformation (secondary in particular) of tRNA and inhibited aminoacyl-tRNA synthetase activity.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Biosynthesis of mammalian transfer RNA. Evidence for regulation by deacylated transfer RNA.

The rate of tRNA synthesis in cultured Friend leukemia cells has been examined as a function of the variation in polyribosome structure produced by treatment with a variety of inhibitors of protein synthesis. The results indicate, in contrast to the conclusions of Bölcsföldi (Bölcsföldi, G. (1974) Exp. Cell Res., 88, 231--240), that no necessary relationship exists between the ribosome distribution and the rate of tRNA synthesis. Alternatively, it is observed that inhibitors of tRNA aminoacylation cause, in all cases, a decrease in the rate of tRNA synthesis whereas drugs which may stimulate the aminoacylation of tRNA cause, in all cases, an elevation of the rate of tRNA synthesis. It is concluded that tRNA synthesis in mammalian cells may be regulated by the relative levels of acylated and deacylated tRNA.

Animals↗