Differential targeting of protein kinase CK2 to the nuclear matrix upon transient overexpression of its subunits.

Modest dysregulation of CK2 has been shown to enhance the oncogenic potential in transgenic models of cancer. Since nuclear matrix serves as an anchor for CK2 and plays a key role in growth-related activities, we examined the effects of CK2 overexpression on its signaling to the nuclear matrix. Expression plasmids pCI-CK2alpha, pCI-CK2beta, and the bicistronic pCI-CK2alphabeta containing full length cDNAs encoding the various subunits were employed to transiently transfect two cell lines, BPH-1 and COS-1. Cytosol from transfected BPH-1 cells containing alpha or beta or alpha + beta or alphabeta showed a modest increase in CK2 activity by 26%, 1%, 20%, and 17%, respectively, over that in the controls transfected with pCI vector. However, the corresponding increase in CK2 activity in the NM fraction was 156%, 8%, 147%, and 152%, respectively. Immunoblot analysis of the CK2 in the NM accorded with these data. Similar results were obtained with COS-1 cells or other expression vectors. The results suggest that moderate overexpression of CK2 in the cells evokes a differential several-fold enhancement in NM associated CK2 relative to that in the cytosol. This process may have a bearing on the functional signaling of this kinase in relation to its possible role in oncogenesis.