Intracellular location and molecular characteristics of tumour cell transfer RNA precursors

Abstract

A 3H-labelled cytoplasmic RNA fraction which behaves as a precursor of transfer RNA has been partially purified from Krebs 2 ascites tumour cells incubated with [ 3H]guanosine using a cold phenol extraction technique followed by gel filtration on Sephadex G100. Heat treatment of the precursor tRNA molecules, at 60 °C in the presence of Mg 2+ at pH 7.8, served to increase their retention by the gel, suggesting that precursor tRNA molecules might have a molecular conformation different from that of mature tRNA molecules. However their behaviour on Sephadex G100 before and after formaldehyde treatment suggested the further possibility that they are somewhat longer than mature tRNA molecules. Examination of labelled RNA from various cytoplasmic fractions indicated that although precursor tRNA molecules are found in the soluble portion of the cytoplasm (cell sap) rather than associated with mitochondrial or microsomal components, there was no obvious intimate association with any soluble cell sap proteins.