p16ink4a (also known as CDKN2A) is a tumor suppressor protein that plays a crucial role in regulating the cell cycle. It is encoded by the CDKN2A gene located on chromosome 9p21. The protein functions primarily by inhibiting cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6), thereby preventing the phosphorylation of the retinoblastoma protein (RB1).
