Induction of a new species of phenylalanine transfer RNA during lens cell differentiation

Abstract

The two major species of phenylalanine transfer RNA (tRNA) of lens cortex have been isolated using BD cellulose and reversed-phase chromatography. Specific activities of 1200 and 1500 pmol of phenylalanine accepted per A 260 of tRNA were obtained for phe-tRNA 1 and phe-tRNA 2 respectively. The fluorescence emission spectra of both phe-tRNAs were identical, with a fluorescence maximum around 420 nm. These measurements, along with chromatographic data, confirm the presence of the Y base in both tRNAs. Nucleotide analysis was carried out on the purified phe-tRNAs. The composition of phe-tRNA 2 was almost identical to the phe-tRNA of rabbit liver. Phe-tRNA 1, however, had a markedly different major base composition. Phe-tRNA 1 therefore, represents a different gene product than phe-tRNA 2. This was confirmed by the fact that phe-tRNA 1, and phe-tRNA 2 chromatograph as separate peaks on a reversed-phase column in the presence of 8·0 m-urea. Therefore the differentiation of a lens epithelial cell into a lens fiber cell is accompanied by a doubling of phe-tRNA as a result of the activation of a new phe-tRNA gene.