p21Cip1 (alternatively p21Waf1), also known as cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1, is a cyclin-dependent kinase inhibitor (CKI) that is capable of inhibiting all cyclin/CDK complexes,[5] though is primarily associated with inhibition of CDK2.[6][7] p21 represents a major target of p53 activity and thus is associated with linking DNA damage to cell cycle arrest.[8][9][10] This protein is encoded by the CDKN1Agene located on chromosome 6 (6p21.2) in humans.[11]
^Waldman, Todd, Kenneth W. Kinzler, and Bert Vogelstein. "p21 is necessary for the p53-mediated G1 arrest in human cancer cells." Cancer research 55.22 (1995): 5187-5190.