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

Changes of post-transcriptional modification of wye base in tumor-specific tRNAPhe

Nucleotide sequences of normal mouse liver tRNAPhe and tumor-specific tRNAPhes isolated from Ehrlich ascites tumor and neuroblastoma cells were examined by post-labeling techniques. The results showed that their sequences are identical, except for changes in post-transcriptional modifications that are located in the anticodon region. Normal mouse liver tRNAPhe contained Cm32, Gm34 and YOH37. On the other hand, tumor-specific tRNAPhes were found in one of two possible configurations: 1) Cm32, Gm34 and Y*OH37 (under-modified YOH) or 2) C32, G34 and m1G37. The ratio of the two forms of tRNAPhes differed in different tumor cells; Ehrlich ascites tumor tRNAPhe had mainly Y*OH-containing tRNAPhe whereas neuroblastoma tRNAPhe has predominantly m1G-containing tRNAPhe. It was concluded that tumor-specific tRNAPhes are products of different extents of modification, rather than of new tRNA transcription.

Transfer ribonucleic acids from eleven immunoglobulin-secreting mouse plasmacytomas. Constant and variable chromatographic profiles compared with the myeloma protein sequences

In order to test the concepts that aminoacyl-tRNAs in plasmacytomas may on the one hand modulate the protein synthesized or on the other hand reflect the structure of the synthesized protein, the RPC-5 chromatographic profiles of aminoacyl-tRNAs for all 20 amino acids were studied in tRNA prepared from normal mouse liver and 11 plasmacytomas. The patterns of isoaccepting tRNA were compared with the structure of the myeloma protein being synthesized. The elution profiles of aminoacyl-tRNAs for nine of the amino acids were constant, i.e. they were the same for liver and all plasmacytomas. Significant variability was observed in the profiles of the other 11 families of aminoacyl-tRNAs: asparagine, serine and tryptophan, had peaks of isoaccepting tRNAs found in tumors and not in liver; glutamic acid, histidine and lysine, had different patterns of aminoacyl-tRNAs in plasmacytomas which could be distinguished from the elution profile of liver; and isoleucine, proline, threonine and tyrosine, showed pattern variability in only a few of the tumors. Valyl-tRNA uniquely had one isoacceptor present in liver but absent in the tumors. This variability is thought to be associated with different posttranscriptional modification of the tRNAs rather than regulation of individual tRNA genes in response to particular amino acid sequences in secreted myeloma proteins. Similarily, the lack of correlation of isoacceptors with sequence differences makes the modulation of protein fine structure by tRNA availability unlikely.