Biochemistry 1995 Jan 10;341:122-7.

DNA inhibits the catalytic activity of the alpha subunit of protein kinase CK2.

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The recombinant alpha subunit of protein kinase CK2 (casein kinase 2) from Xenopus laevis is inhibited by the addition of single stranded or double stranded DNA. This inhibition is competitive with the casein substrate, having an apparent Ki of 160 nM for an 86 bp DNA fragment. Assays with a fragment containing the putative promoter of the human CK2 beta gene indicated that the affinity of CK2 for this fragment was not greater than that of other unrelated DNA. The inhibitory capacity of DNA toward the protein phosphorylating activity of CK2 alpha is greatly reduced by the presence of the beta subunit which can completely reverse the inhibition. The interaction of CK2 alpha with DNA can also be assayed by the nitrocellulose filter binding assay. This assay demonstrates that the interaction of CK2 alpha with the tested DNAs is not sequence specific and that the beta subunit can also greatly diminish the binding of CK2 alpha to DNA. Casein at substrate concentrations also is inhibitory to CK2 alpha DNA binding. Likewise, polyanionic inhibitors of the CK2 catalytic activity, such as heparin, poly(U), and copoly(Glu:Tyr) polypeptides, can compete for and inhibit the binding of DNA to CK2 alpha. However, quercetin, which also inhibits CK2 phosphorylation activity, and ATP do not affect DNA binding. A mutant CK2 alpha in which glutamic acids replace two lysine residues in positions 75 and 76 of the alpha peptide chain is less susceptible to DNA inhibition, indicating that this basic region of the molecule is involved in its interaction with DNA.

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Species referenced: Xenopus laevis
Genes referenced: csnk2b