Casein kinase type II is involved in the inhibition by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole of specific RNA polymerase II transcription

Abstract

We have described a HeLa protein kinase whose activity is inhibited by the nucleotide analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) at concentrations similar to those required to inhibit in vivo and in vitro specific transcription (Zandomeni, R., and Weinmann, R. (1984) J. Biol. Chem. 259, 14804-14822). We have now detected an analogous DRB-sensitive kinase from calf thymus and purified it to homogeneity. Based on the subunit composition of the enzyme and other common biochemical and chromatographic properties, we identified it as casein kinase II. The extent of DRB inhibition of the purified calf thymus enzyme is indistinguishable from that observed for inhibition of in vitro transcription with the HeLa cell extract. The DRB bromo- derivative, 5,6-dibromo-1-beta-D-ribofuranosylbenzimidazole is a more potent inhibitor of in vivo transcription and inhibits purified casein kinase II activity and specific in vitro transcription at 6-10 times lower concentrations than DRB. Moreover, addition of an excess of the purified calf thymus casein kinase II enzyme to a HeLa in vitro transcription reaction inhibited by DRB partially overcomes this inhibition. Thus, we conclude that casein kinase II is involved directly or indirectly in the inhibition by DRB of specific RNA polymerase II-mediated transcription. This demonstrates the participation of a protein kinase in a eukaryotic RNA polymerase II-specific transcription system.