ANALYTICAL STUDIES ON NUCLEAR RIBONUCLEIC ACID USING POLYACRYLAMIDE GEL ELECTROPHORESIS

Rat liver nuclear and cytoplasmic ribonucleic acids (RNAs) have been analyzed by electrophoresis on polyacrylamide and mixed polyacrylamide- agarose gels. Many species of nuclear RNA were found which are not detected in the cytoplasm. On the lower molecular weight side, the nucleus contained, in addition to a distinct 18S RNA species, several species with mobilities somewhat slower than 4S transfer ribonucleic acid (tRNA) and without detectable amino acid acceptor activity. On the high molecular weight side, there were several species of nuclear RNA, with mobilities slower than 30S RNA, which labeled rapidly, unlike cytoplasmic RNA. Newly synthesized 30S RNA and 18 S were found to appear in the cytoplasm at the same time, in contrast to results of studies by others. These results also suggested that “35S” and “45S” nuclear RNAs, as defined by sucrose gradient analysis, were not single species, but rather are composed of many components of different molecular weights. This highly complex nature of nuclear RNA makes it difficult to define precursor-product relationships between nuclear and cytoplasmic RNAs. However, these studies indicate that polyacrylamide gel electrophoresis offers a more discriminating technique for the study of nuclear RNA function and metabolism. © 1968, American Chemical Society. All rights reserved.