Transcriptional coordination of the genes encoding catalytic (CK2alpha) and regulatory (CK2beta) subunits of human protein kinase CK2.

Little is known of how protein kinase CK2 genes are regulated, and it is unclear whether there are mechanisms of transcriptional coordination. Response elements present in the promoter sequences of the human catalytic (CK2alpha) and regulatory (CK2beta) subunit genes have been examined for the significance in transcriptional control using reporter gene assays, electrophoretic mobility shift assays, site-directed mutagenesis, ectopic protein expressions, and transcript assessments. Most strikingly, in both promoters the regions of highest transcriptional activity contain two adjoining, completely identical and conserved Ets1 response elements, and both the mutation of motifs and the overexpression of Ets1 affect significantly transcriptional activity. Also in common are Sp1 response elements that cooperate with Ets1, and Sp1 is phosphorylatable by CK2 holoenzyme but not by individual CK2alpha, the phosphorylation negatively affecting DNA binding. CK2alpha and CK2beta transcript levels and stoichiometries of mRNA species turned out quite constant in cultured cells despite progressing through various stages of proliferation and differentiation. The data seem to indicate transcriptional coordination of the human genes encoding CK2alpha and CK2beta based on an Ets1 double motif common to both genes cooperating with Sp1 motifs and amenable to negative feedback control by the gene products which, following complexation into CK2 holoenzyme, could phosphorylate Sp1 (and Ets1?) and thus downregulate transcription and contribute to the observed constant cellular CK2alpha and CK2beta transcripts situation.