Protein kinase C phosphorylates leukemia RNA polymerase II.
Purified RNA polymerase II from chicken leukemia cells was found to be an effective substrate for protein kinase C but not cAMP-dependent protein kinase. Protein kinase C catalyzed the incorporation of 1-2 mol of phosphate per mol of polymerase II and the reaction was totally calcium and lipid dependent. Electrophoresis studies revealed a time-dependent increase of phosphate incorporation into RNA polymerase II subunits of 220 KDa, 180 KDa and 150 KDa, with a preferential phosphorylation of the 180 KDa polypeptide. The phosphorylated enzyme has a preference for using single-stranded DNA as the template for transcription, including transcription of the single-stranded myb oncogene sequence. Phosphoamino acid analysis indicated that both serine and threonine residues were phosphorylated at equal amounts. Phosphorylation by protein kinase C increased the affinity of substrate-polymerase binding and the initial rate of RNA synthesis, suggesting a mechanism by which gene expression can be activated by protein kinase C.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002645:Chickens; D007700:Kinetics; D015470:Leukemia, Myeloid, Acute / Q000201:enzymology*; D008970:Molecular Weight; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D012319:RNA Polymerase II / Q000302:isolation & purification / Q000378:metabolism*
D000596:Amino Acids; D011493:Protein Kinase C; D012319:RNA Polymerase II