Phosphorylation of Escherichia coli RNA polymerase by rabbit skeletal muscle protein kinase

Effect of protein phosphorylation on the activity of RNA polymerase in streptomycetes

RNA polymerase was isolated from Streptomyces granaticolor and protein kinase was partially purified from Streptomyces albus. When RNA polymerase was treated with protein kinase in vitro the activity of RNA polymerase was markedly enhanced. Furthermore, a protein of M = 65 kDa was isolated which, after being phosphorylated, stimulated RNA polymerase activity in vitro. Because neither the beta-subunits nor the alpha-subunits of RNA polymerase were phosphorylated it is assumed that phosphorylation of the 65 kDa protein may regulate the activity of RNA polymerase in streptomycetes.

Phosphorylation of calf thymus RNA polymerase II by nuclear cyclic 3',5'-AMP-independent protein kinase

Nucleoplasmic RNA polymerase II (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) from calfthymus is phosphorylated by homologous cyclic AMP-independent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37). Polyacrylamide gel electrophoresis of the 32P-labeled RNA polymerase II under non-denaturing conditions revealed that both forms of the enzyme were phosphorylated. Polyacrylamide gel electrophoresis of the 32P-labeled RNA polymerase II under denaturing conditions showed that the 25 000 dalton subunit was the phosphate acceptor subunit. Partial acid hydrolysis of the 32P-labeled RNA polymerase II followed by ion-exchange chromatography revealed serine and threonine as the [32P]phosphate acceptor amino acids. Phosphorylation of the RNA polymerase II was accompanied by a stimulation of enzymatic activity and was dependent upon the presence of ATP.

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].