METABOLISM OF SMALL MOLECULAR WEIGHT MONODISPERSE NUCLEAR RNA

The small molecular weight, nuclear monodisperse RNA (snRNA) species of HeLa cells have been further characterized. 1. 1. In addition to the six species previously reported, three additional ones are now described. 2. 2. Several monodisperse, metabolically unstable RNA species are found in the cytoplasmic supernatant. They appear to be unrelated to the nuclear snRNA species. 3. 3. The snRNA of the nucleoplasm is more weakly bound to the chromatin than the nucleoplasmic, heterogeneous RNA. Some of the snRNA may exist in a soluble form in vivo in the nucleoplasm. 4. 4. Several of the snRNA species are metabolically as stable as ribosomes, while others have half-lives of about one day. 5. 5. The synthesis of snRNA does not appear to be co-ordinated with the replication of DNA in S phase. 6. 6. The breakdown of snRNA does not appear to occur during passage of the cells through mitosis. 7. 7. The synthesis of snRNA is strongly affected by several of the inhibitors of nucleolar RNA synthesis. © 1969.