Post-Translational Modification of RNA Polymerase I by Protein Kinase NII and Some Novel Immunological Aspects of the Two Enzymes
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Protein kinase NII from a rat tumor, Morris hepatoma 3924A, was purified essentially to homogeneity. It had a molecular weight of 110,000 and consisted of two subunits of molecular weights 42,000 and 25.000. A protein kinase with characteristics similar to protein kinase Nil was associated with RNA polymerase I purified to homogeneity from the hepatoma. Based on several physiochemical criteria, the 42 and 25 kilodalton polypeptides of RNA polymerase I appear to correspond to the protein kinase Nil. These two subunits were present in stoichiometric amounts in RNA polymerase I from the tumor and its proportion in the enzyme molecule was related to the RNA polymerase I activity. The protein kinase autophosphorylated its 25 kilodalton polypeptide as well as the 120, 65, 25 and 19.5 kilodalton polypeptides of RNA polymerase I. Polyamines, at physiological concentrations, augmented the phosphorylation reaction several fold, which resulted from phosphorylation at additional sites in the enzyme molecule. Phosphorylation of RNA polymerase I resulted in its activation and prevented premature termination of RNA chains.
KeywordsSystemic Lupus Erythematosus Systemic Lupus Erythematosus Patient Mixed Connective Tissue Disease Rheumatic Autoimmune Disease Morris Hepatoma
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