Isoproterenol-induced selective phosphorylation invivo of the 214,000 dalton subunit of rat C6 glioma cell RNA polymerase II

Abstract The phosphorylation in vivo of RNA polymerase II after isoproterenol stimulation of confluent rat C6 glioma cell cultures has been investigated. Glioma cells were incubated in the presence of Na 2 H 32 PO 4 and stimulated for 1 hour with the β-adrenergic agonist isoproterenol. The phosphorylation pattern was analyzed after purification of RNA polymerase II by immunoprecipitation, SDS-polyacrylamide gel electrophoresis and autoradiography. Isoproterenol markedly increased [ 32 P]phosphate incorporation into the 214,000 dalton RNA polymerase subunit. Analysis of the phosphate acceptor amino acid revealed the presence of only [ 32 P]phosphoserine. The data demonstrates an isoproterenol-induced structural modification of RNA polymerase II.