Abstract
The uptake of exogenous nucleoside tracers into RNA proceeds without equilibration of the tracer with the cellular ribonucleotide triphosphate pools. Kinetic analysis of the tracer progression into RNA suggests that the functional nucleotide RNA-precursor pool is very small, so that simple compartmentation into nuclear and cytoplasmic pools fails to account for these results. We have tested the hypothesis that RNA synthesis is dependent on a multienzyme complex (similar to the proposed "DNA replitase") that functions as a metabolic channel. Nuclear lysates of mouse lymphoma S49 cells and human HL-60 promyelocytic leukemia cells were separated on sucrose gradients (20-60%) and fractions analyzed for RNA polymerase and nucleotide kinase activities. At least three fractions with high molecular weights (> 106 Daltons) were identified that were capable of incorporating mono-, di- and triphosphates (U+C+A+G) into acid-insoluble macromolecules. The mono- and diphosphates did not seem to equilibrate with the triphosphate pools in the medium, which suggests metabolic channeling. Tracer incorporation was dependent on the presence of all four bases as their nucleotides in the medium, while DNA template was not required in these fractions. These results provide first evidence for the existence of multienzyme RNA synthetase complexes that preferentially accept distant precursors, i.e. nucleotide mono- and diphosphates. Supported by CA 34304.
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Lawi-Berger, C., Sadée, W. MULTIENZYME RNA SYNTHETASE COMPLEXES: METABOLIC CHANNELLING OF NUCLEOTIDE MONO- AND DIPHOSPHATE PRECURSORS INTO RNA: 110. Pediatr Res 19, 762 (1985). https://doi.org/10.1203/00006450-198507000-00130
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DOI: https://doi.org/10.1203/00006450-198507000-00130