Nuclear matrix (NM) association of protein kinase CK2 under different conditions of overexpression

Protein kinase CK2 (formerly called casein kinase 2 or II) is a serine/threonine protein kinase that has been implicated in cell growth and proliferation. It is preferentially associated with nuclear structures such as NM in response to growth stimuli (Tawfic. Faust, Gapany, Ahmed: J. Cell. Biochem. 61: 1-7, 1996). Here, we describe the effects of transient overexpression of CK2 on its association with the NM, and the mechanism of CK2 anchoring with the NM. Expression plasmids pCI-a and pCI- containing full length cDNAs encoding the a and subunits of CK2 were employed to transiently transfert a human prostate epithelial cell line (BPH-1). Cytosol from cells transfected with the plasmids containing a, or , or both, demonstrated an increase in CK2 activity of about 30, 20, and 30 %, respectively, compared with that from cells transfected with the pCI vector. However, CK2 activity in the NM fraction demonstrated an increase of about 260, 40, and 260 %, respectively, suggesting that transient overexpression of CK2 in BPH-1 cells resulted in a differential increase in its activity in the NM fraction. Further, investigation of the nature of CK2 association with the NM has revealed that sulfhydryl interactions between CK2 and the NM proteins are involved in this process.