Protein kinase CK2 in DNA damage and repair

Protein kinase CK2, formerly known as casein kinase 2, is a ubiquitously expressed serine/threonine kinase, which is absolutely required for cell viability of eukaryotic cells. The kinase occurs predominantly as a tetrameric holoenzyme composed of two regulatory a or alpha' subunits and two non-catalytic beta subunits. It is highly expressed and highly active in many tumour cells. The proliferation promoting as well as the anti-apoptotic functions have made CK2 an interesting target for cancer therapy. It phosphorylates numerous substrates in eukaryotic cells thereby regulating a variety of different cellular processes or signalling pathways. Here, I describe the role of CK2 in DNA damage recognition followed by cell cycle regulation and DNA repair. It turns out that CK2 phosphorylates a number of different proteins thereby regulating their enzymatic activity or platform proteins which are required for recruiting proteins for DNA repair. In addition, the individual subunits bind to various proteins, which may help to target the kinase to places of DNA damage and repair. Recently developed pharmacological inhibitors of the kinase activity are potent regulators of the CK2 activity in DNA repair processes. Since DNA damaging agents are used in cancer therapy the knowledge of CK2 functions in DNA repair as well as the use of specific inhibitors of CK2 may improve cancer treatment in the future.