Increased DNA associated with rat liver nucleoli when isolated with spermidine

Summary When rat liver nucleoli were isolated in the presence of 5 mM spermidine rather than 5 mM magnesium, the nucleolar-associated RNA polymerase activity was found to increase some 10-fold. The spermidine-isolated nucleoli contained more than twice the amount of DNA found in magnesiumisolated nucleoli. The protein concentrations and RNA content were similar. These findings suggest that spermidine stimulation of nucleolar DNA-dependent RNA polymerase may be due to its capacity to increase the amount of DNA available as template for the enzyme.