CSNK2A1 encodes the catalytic subunit of casein kinase 2 (CK2), a constitutively active serine/threonine kinase that phosphorylates substrates with acidic residues C-terminal to phosphorylation sites. This kinase regulates multiple cellular processes including cell cycle progression, apoptosis, transcription, and DNA damage response 123. During mitosis, CSNK2A1 functions in the p53-dependent spindle assembly checkpoint, maintaining cyclin-B-CDK1 activity in response to spindle damage 4. Following DNA damage, CSNK2A1 phosphorylates repair proteins (MDC1, MRE11, RAD51, RAD9A), promoting their recruitment to damage sites 567. CSNK2A1 exhibits dual roles in apoptosis: it can phosphorylate p53 at Ser-392 following UV irradiation, promoting apoptosis, but also negatively regulates apoptosis by phosphorylating caspases and protective factors like YY1 189. The kinase regulates transcription through direct phosphorylation of RNA polymerases and numerous transcription factors (NF-κB, STAT1, CREB1, MYC) 3. Disease associations include Okur-Chung neurodevelopmental syndrome and enrichment in developmental disorder mutations 10. CSNK2A1 mutations also associate with adult T cell leukemia and contribute to cancer drug resistance in pancreatic adenocarcinoma and esophageal carcinoma 111213.