The interdependence of RNA transport and the metabolism of nucleotide additives was investigated. Rat-liver RNA was radioactively labeled in vivo for 45 min before isolation of liver nuclei, and the concentration dependence of RNA transport on nucleotide additives was determined. In a parallel investigation, using nucleotide additives labeled in the base moiety, the distributions of label in the tri-, di-, and monophosphate forms were examined after various intervals of incubation. Analysis of results revealed that RNA transport was linearly related to the decline in energy charge of nucleotide additives, with high statistical correlation. Kinetic analysis of labeled-nucleotide metabolism led to a simple schematic model for pathways for the utilization of high-energy phosphate bonds, and predictions of the scheme were confirmed by studies examining the effects of nucleotide analogues upon RNA transport. Data concerning inhibitors and chelators intimated that multiple avenues of inhibition and stimulation may potentially influence RNA transport. On the basis of previous data and the results presented in this communication, we conclude that nucleocytoplasmic RNA transport is dependent upon high-energy phosphate-bond hydrolysis and that nucleotides do not stimulate RNA transport via a simple chelation mechanism.
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