Fractionation of amino acyl-acceptor RNA on a methylated albumin column

Purification, properties and comparative specificities of the enzyme prolyl-transfer ribonucleic acid synthetase from Phaseolus aureus and Polygonatum multiflorum

1. A prolyl-s-RNA synthetase (prolyl-transfer RNA synthetase) has been purified about 250-fold from seed of Phaseolus aureus (mung bean), a species not producing azetidine-2-carboxylic acid, and more than 10-fold from rhizome apices of Polygonatum multiflorum, a liliaceous species containing azetidine-2-carboxylic acid. The latter enzyme was unstable during ammonium sulphate fractionation. 2. The enzymes exhibited different substrate specificities towards the analogue. That from Phaseolus, when assayed by the ATP-PP(i) exchange, showed azetidine-2-carboxylic acid activation at about one-third the rate with proline. Both labelled imino acids gave rise to a labelled aminoacyl-s-RNA. The enzyme from Polygonatum, however, activated only proline. 3. The enzyme from Polygonatum also formed a labelled prolyl-s-RNA with Phaseolus s-RNA but at a lower rate than when the Phaseolus enzyme was used. No reaction occurred when the Phaseolus enzyme was coupled with Polygonatum s-RNA, and only a very slight one was observed when both enzyme and s-RNA came from Polygonatum. 4. Protein preparations from seeds of Pisum sativum, another species not producing azetidine-2-carboxylic acid, also activated the analogue in addition to proline, whereas those from rhizome and seeds of Convallaria, the species from which the analogue was originally isolated, failed to activate it. However, a liliaceous species not producing the analogue, Asparagus officinalis, activated it. 5. Of the other proline analogues investigated, only 3,4-dehydro-dl-proline and l-thiazolidine-4-carboxylic acid were active with the enzyme preparation from Phaseolus. 6. pH optima of 7.9 and 8.4 were established for the enzymes from Phaseolus and Polygonatum respectively. 7. The Phaseolus enzyme was specific for ATP and PP(i). Mn(2+) partially replaced the requirement for Mg(2+) as cofactor. Preincubation with p-chloromercuribenzoate at a concentration of 0.5mm or higher produced over 99% inhibition of the Phaseolus enzyme. One-half the enzymic activity was destroyed by preheating for 5min. at 62 degrees in tris-hydrochloric acid buffer, pH7.9. 8. All experimental evidence supports the hypothesis that azetidine-2-carboxylic acid and proline are activated by the same enzyme in Phaseolus preparations, whereas the analogue was inactive in all Polygonatum preparations. The possible nature of this different substrate behaviour is discussed.

Altered or increased transfer-RNA methylation in the course of Interferon action on cells in culture?

The induction of the antiviral state by Interferon might reflect the decrease of the rate of biosynthesis, the degradation or the alteration of one or several tRNAs. This could result in rate-limiting concentrations for codons common in viral RNA but rare in host mRNA. Altered methylation of tRNA could be the basis of such a phenomenon. However, we could not find an altered extent of methylation of total tRNA or an altered pattern of methylation, if mixed tRNAs were chromatographed on MAK- or BD-cellulose columns, despite a large range of conditions of pretreatment of chick embryo fibroblast cultures with interferon.

Separation of transfer ribonucleic acid by sepharose chromatography using reverse salt gradients

The transfer ribonucleic acids of Escherichia coli bind to unsubstituted Sepharose in the presence of high concentrations of ammonium sulfate at pH 4.5. Transfer RNA species are eluted individually from the Sepharose by a gradient from high to low concentrations of ammonium sulfate; leucine tRNA is fractionated into five isoaccepting species. The order of elution of these isoaccepting species differs from that seen with reverse phase chromatography. By means of only these two procedures, one isoaccepting species of leucine tRNA can be purified to apparent homogeneity. Isoaccepting tRNA species for 9 amino acids have been resolved. This established the general utility of this chromatographic system for the separation and purification of specific isoaccepting transfer RNAs.

Localization of 5S RNA genes on Drosophila chromosomes by RNA-DNA hybridization

[(3)H]RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [(3)H]uridine. Purified tritiated 5S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [(3)H]RNA and DNA was confined to the 56E-F segment.

Transfer ribonucleic acid in KB cells infected with adenovirus type 2

Populations of transfer ribonucleic acid (tRNA) extracted from control and type 2 adenovirus (Ad2)-infected KB cells were compared. No consistent differences in acceptor activity for 11 amino acids were observed. Comparison of methylated albumin-kieselguhr (MAK) elution profiles of arginyl-tRNA from control and infected cells revealed a minor modification in that the proportion of arginyl-tRNA eluting at high salt concentration was somewhat greater in infected cells. No similar differences were observed in MAK elution profiles of aspartyl-, isoleucyl-, leucyl-, phenylalanyl-, seryl-, tyrosyl-, and valyl-tRNA. Hybridization of 4S RNA from infected cells labeled by incorporation of (3)H-uridine with Ad2 deoxyribonucleic acid revealed the presence of a complementary species of RNA in this preparation. Hybridization of (3)H-arginyl-tRNA and of (3)H-aminoacyl-tRNA labeled by charging with (3)H-arginine or a (3)H-mixture of amino acids, respectively, failed to detect the presence of virus-specific tRNA in Ad2-infected cells.

Nucleic acid homologies among species of Saccharomyces

Evolutionary divergence among species of the yeast genus Saccharomyces was estimated from measurements of deoxyribonucleic acid (DNA)/DNA and ribosomal ribonucleic acid (RNA)/DNA homology. Much diversity was found in the DNA base sequences with several species showing little or no homology to the three reference species, S. cerevisiae, S. lactis, and S. fragilis. These three reference species also showed little or no homology to each other. On the other hand the diversity among ribosomal RNA base sequences was small since most species showed a high degree of homology to the reference species. The arrangement of species based on ribosomal RNA homologies agrees in most cases with current taxonomic groupings. A yeast hybrid (S. fragilis x S. lactis) was shown to contain two nonhomologous genomes. A minimum genome size of 9.2 x 10(9) daltons for S. cerevisiae was calculated from the rate of DNA renaturation.

Inhibition of host cell ribosomal ribonucleic acid methylation by foot-and-mouth disease virus

A study of protein and ribonucleic acid (RNA) synthesis in cells infected by foot-and-mouth disease virus has indicated possible mechanisms of viral control over host cell metabolism. Foot-and-mouth disease virus infection of baby hamster kidney cells resulted in 50% inhibition of host cell protein synthesis at 180 min postinfection. A viral-induced interference with host cell RNA methylation was observed to be more rapidly inhibited than protein synthesis. To determine the nature of methylation inhibition, the kinetics of several host cell methylated RNA species were examined subsequent to virus infection. Data from sucrose zonal centrifugation and methylated albumin kieselguhr chromatography showed that methylation of nuclear RNA was inhibited 50% at 60 min postinfection. Inhibition of nuclear ribosomal RNA precursors and formation of nascent ribosomes correlated with inhibition kinetics of nuclear RNA methylation. It is suggested that the viral interference with the host nuclear RNA methylation is directly responsible for the observed loss of nascent ribosome formation. Moreover, early in the infectious cycle, methylation inhibition of host cell RNA could, in part, account for the cessation of host protein synthesis.

Presence and function of sulur-containing transfer ribonucleic acid of Bacillus subtilis

Bacillus subtilis transfer ribonucleic acid (tRNA) was analyzed for the occurrence of thionucleotides by in vivo labeling with (35)S and fractionation by methylated albumin kieselguhr column chromatography. Alkaline hydrolysates of tRNA were also examined by column chromatography and paper electrophoresis, and the amino acid-accepting ability of thionucleotide-containing tRNA was tested after iodine oxidation. The results showed that B. subtilis tRNA contains 4-thiouridylate, a second nucleotide with properties similar to 2-thiopyrimidine, and a third unidentified thionucleotide. The amino acid-accepting ability for serine, tyrosine, lysine, and glutamic acid was markedly inhibited after oxidation of the tRNA with iodine, suggesting the presence of thionucleotides in these tRNA species. This inhibition could be reversed by thiosulfate reduction. The iodine treatment totally inactivated all lysine tRNA species, partially inactivated the serine tRNA species, and did not affect the accepting ability for valine. A comparison of tRNA from cells in the log and stationary phases and from spores revealed similar iodine inactivation patterns in all cases. The thionucleotide content in B. subtilis tRNA differed from that in Escherichia coli, both in extent and in distribution. A possible function of the thionucleotides in tRNA is discussed.

Chloroplast and cytoplasmic low-molecular-weight ribonucleic acid components of the leaf of Vicia faba L

1. A method for the extraction of plant nucleic acids and their separation on methylated-serum-albumin-kieselguhr columns is described. It is demonstrated that the characteristics of the elution profiles of material from the same source are consistently reproducible. 2. Major dissimilarities were found in the elution profiles of nucleic acids from root and from leaves of Vicia faba L. These dissimilarities were confirmed by polyacrylamide-gel electrophoresis. 3. Four distinct types of low-molecular-weight RNA were demonstrated to be present in leaves, clearly distinguished by their behaviour when chromatographed on methylated-serum-albumin-kieselguhr columns. (a) Both cytoplasmic and chloroplast ribosomes contained a low-molecular-weight RNA, and these components were distinct from each other. (b) The chloroplast possessed a unique ;soluble' RNA (i.e. RNA that is not precipitated by centrifugal forces that sediment ribosomes) which was not present in the rest of the cell. (c) A soluble component, probably transfer RNA, was found in both the chloroplasts and in the cytoplasm. 4. The components distinguishable by methylated-serum-albumin-kieselguhr column chromatography could not be distinguished by sucrose-density-gradient centrifugation.