CK2 is a protein kinase responsible for phosphorylation of substrates in various pathways within a cell; ATP or GTP can be used as phosphate source. CK2 has a dual functionality with involvement in cell growth/proliferation and suppression of apoptosis. CK2s anti-apoptotic function is in the continuation of the cell cycle; from G1 to S phase and G2 to M phase checkpoints. This function is achieved by protecting proteins from caspase-mediated apoptosis via phosphorylation of sites adjacent to the caspase cleavage site, blocking the activity of caspase proteins. CK2 also protects from drug-induced apoptosis via similar methods but it is not as well understood. Knockdown studies of both α and α’ sub-units have been used to verify this anti-apoptotic function.
Important phosphorylation events also regulated by CK2 are found in DNA damage repair pathways, and multiple stress-signaling pathways. Examples are phosphorylation of p53 or MAPK, which both regulate many interactions within their respective cellular pathways.
Another indication of separate function of α subunits is that mice that lack CK2α’ have a defect in the morphology of developing sperm.