Hepatoma--foetal Phe-tRNA also present in normal rat liver

Aminoacyl-transfer RNA populations in mammalian cells chromatographic profiles and patterns of codon recognition

The chromatographic profiles of 20 aminoacyl-tRNAs from rabbit liver were compared to those of rabbit reticulocytes by reverse phase chromatography and the chromatographic profiles of 20-aminoacyl-tRNAs from bovine liver were compared to those of bovine brain. The two rabbit tissues showed significant differences in the elution profiles of most aminoacyl-tRNAs, while the elution profiles of the aminoacyl-tRNAs from the bovine tissues showed fewer differences. The patterns of codon recognition of several aminoacyl-tRNAs fractionated from rabbit reticulocytes have also been compared to those fractionated from rabbit liver.

Multiple chromatographic peaks of phenylalanyl-tRNA associated with spontaneous hydrolysis of Y base during isolation

In contrast to the single phenylalanyl-tRNA found in normal cells, some tumours are known to have more than one phenylalanine isoacceptor. However, during certain steps in tRNA isolation from normal or tumour tissue, additional chromatographic peaks can be artificially produced which may be confused with the tumour-specific Phe-tRNA. Such procedures as extraction with unbuffered phenol and unbuffered gel filtration chromatography appear to produce adventitious isoacceptors by hydrolysis of Y base.

Biochemical research on oogenesis. Comparison between transfer RNAs from somatic cells and from oocytes in Xenopus laevis

The properties of tRNA from oocytes of Xenopus laevis were compared with those of tRNA from somatic cells of the same species. Both types of tRNAs were found to have the same average length and to contain an equal variety of modified nucleotides. However, tRNA from small oocytes differed from somatic tRNA by its chromatographic behavior on methylated-albumin kieselguhr columns. The elution profiles from reversed-phase chromatography 5 columns of several aminoacyl tRNAs were compared after charging somatic and oocyte tRNSs with 3H or 14C-labelled amino acids. Striking differences in peak position were observed when tRNA from small oocytes was mixed and co-chromatographed with somatic tRNA. The differences were less important when tRNAs from large oocytes and from somatic cells were compared. Mixtures of egg and somatic tRNAs gave completely or almost completely coincident elution profiles. Only one isoacceptor, tNRA1Met (initiator tRNA) had the same position in all reversed-phase chromatography 5 chromatograms. The results are discussed in terms of possible post-transcriptional modifications of tRNA in the course of oogenesis. An alternative explanation resorting to changes in the tRNA population of the growing oocyte is also envisaged.

Studies on human tRNA. I. The rapid, large scale isolation and partial fractionation of placenta and liver tRNA

A procedure for the large scale isolation of mammalian tRNA has been applied to the isolation of several grams of human liver, human placenta, rabbit liver and rat liver tRNA. This procedure entails an initial grinding of the tissue in phenol-sodium acetate at acidic pH, followed by DEAE cellulose chromatography. Procedures are also described for analysis of the purified tRNA on the basis of size, using controlled pore glass bean columns. In addition, the acceptor activity of isolated tRNAs has been determined using both the heterologous and homologous synthetases. The chromatographic profile of individual isoaccepting species using BD cellulose chromatography is shown and the 3' terminal nucleoside content was also determined. The methods described now make it feasible for large scale studies of mammalian tRNA enabling us to better understand the relationships between the structure of mammalian tRNA and its many diversified functions.

Isolation and chromatographic behaviour of phenylalanine tRNA from barley embryos

Two fractions of phenylalanine tRNA (tRNA(Phe) (1) and tRNA(Phe) (2)) were purified by BD-cellulose and RPC-5 chromatography of crude tRNA isolated from barley embryos. Successive RPC-5 rechromatography runs of tRNA(Phe) (2) showed its conversion into more stable tRNA(Phe) (1), suggesting that the two fractions have essentially the same primary structure. Both tRNA(Phe) (1) and tRNA(Phe) (2) had about the same acceptor activity, but tRNA(Phe) (2) was aminoacylated much faster than tRNA(Phe) (1). RPC-5 chromatography of crude aminoacylated tRNA showed higher contents of phe-tRNA(Phe) (2) than of phe-tRNA(Phe) (1) but the ratio of these two fractions estimated by relative fluorescence intensity was about 1. Fluorescence spectra of tRNA(Phe) from barley embryos suggest that it contains Y base similar to Y(w) from wheat tRNA(Phe).