Purification and properties of a nuclear protein kinase associated with ribonucleic acid polymerase I.
A cyclic AMP-dependent nuclear protein kinase was found to be closely associated with rat liver nucleolar RNA polymerase I throughout most of its purification. This protein kinase was purified to near homogeneity. It exhibits a number of unusual catalytic properties, including the inability to utilize Mn2+ when RNA polymerase is the substrate and the ability to phosphorylate both acidic and basic substrates. Phosphorylation of RNA polymerase I by this protein kinase results in the formation of phosphoester bonds characteristic of phosphoserine and phosphothreonine. Radioautography of polyacrylamide-gel electrophoretograms of the phosphorylated RNA polymerase I revealed that the 32P was located primarily on enzyme subunits SA1, SA3, SA5, and SA6 [nomenclature of Kedinger, Gissinger & Chambon (1974) Eur. J. Biochem, 44, 421-436].
D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D002499:Centrifugation, Density Gradient; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008099:Liver / Q000201:enzymology; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D012318:RNA Polymerase I / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
D011494:Protein Kinases; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I