Isolation and properties of poly(A)-containing RNA from the cytoplasm of rat liver cells.

1. The described technique for preparative isolation of poly(A)-containing RNA by complexing with poly(U)-cellulose and elution at 45 degrees C, is simple, reproducible, and the poly(U)-cellulose preparation is suitable for repeated use. 2. The poly(A)-containing RNA isolated from the poly(U)-cellulose complex is still contaminated by ribosomal RNA which can be removed by recomplexing. The purified preparation is heterogeneous on polyacrylamide-gel electrophoresis and is located over the region from 5-6S to 28S. Poly(A) segments of cytoplasmic RNA show heterogeneous size distribution. 3. In acidic medium, the poly(A) segments form ordered double-stranded structure. 4. The rapid labelling of rat liver and fibroblast cytoplasmic poly(A)-containing RNAs and their base composition resemble closely the corresponding properties of mRNA.