Abstract
Heparin is well known to activate RNA synthesis in isolated rat liver nuclei. This effect is not due to inhibition by heparin of RNA degradation but to the enhanced template activity of chromatin for RNA synthesis. The RNA synthesized both in the presence and in the absence of heparin contains poly A segment. Polyacrylamide gel electrophoresis revealed that in the presence of heparin discrete peaks of RNA corresponding to 28 S,70 S, and 100 S and heterogeneous RNA of more than 100 S appear already after 30 min of in vitro labeling and after incubation for 60 min the highest peak shifted from 100 S to 70 S, while in the absence of heparin no peak is detected after incubation for 30 min and only a large 13 S peak is found by incubation for 60 min. These results suggest that biosynthesis and processing of heterogeneous nuclear RNA are at least partially reproduced in vitro by incubating isolated nuclei in the presence of heparin.
