Relation of cell type and cell density to the degree of post-transcriptional modification of tRNALys and tRNAPhe.

An examination of the reversed-phase chromatographic profiles of tRNALys and tRNAPhe from SV40-transformed BALB/3T3 cells grown to different cell densities, untransformed BALB/3T3 cells grown to confluency and BALB/c mouse liver indicates that with increasing cell density in culture the degree of the peroxy-Y modification in tRNAPhe and an undetermined modification in tRNALys become more like that of differentiated tissue (liver). Because precursor/product relationships appear to exist among the unmodified and modified forms of the isoaccepting species for each of these tRNAs, the present findings support the view that the often reported differences in tRNA isoaccepting spectra result primarily from differences in post-transcriptional modifications, rather than from different tRNA transcripts.