Alterations in Post-Transcriptional Modification of the Y Base in Phenylalanine tRNA from Tumor Cells

In the search for a possible role of tRNA in regulatory processes in higher organisms, a number of studies have compared chromatographic profiles of tRNA from different tissues, organs, tumors, and cell cultures (Nishimura 1978). These studies have revealed that tumor cells frequently contain tRNA species which differ in their chromatographic mobility from the corresponding tRNAs present in normal adult tissues. However, in only a few cases have structural studies on these tRNAs been carried out to clarify whether the isoaccepting species are due to a new transcript of a gene or to a different degree of modification (Shindo-Okada et al. 1981; Raba et al. 1979; Roe et al. 1979; Randerath et al. 1981). The primary transcripts of tRNA genes are known to undergo several processing steps prior to their emergence as mature functional tRNA molecules (Altman 1978). In addition to cleavage of the precursor molecules, the formation of modified nucleosides occurs post-transcriptionally (Nishimura 1978).