CDKN1A A gene on chromosome 6p21.2 that encodes a cyclin-dependent kinase inhibitor, which binds to and inhibits the activity of cyclin-CDK2 or -CDK4 complexes, thus acting as a regulator of cell cycle progression at G1. CDKN1A expression is controlled by p53, a tumour suppressor that mediates p53-dependent cell cycle G1-phase arrest in response to various stress stimuli. CDKN1A is specifically cleaved by CASP3-like caspases, activating CDK2 and possibly also the apoptosis pathway.
p21 Also known as p53 protein, an anticancer protein of the class of cyclin-dependent kinase inhibitors. Cyclin-dependent kinases are enzymes that have been described by Elizabeth Finkel as ‘the engines that drive the cell-cycle past its various control checkpoints.’ Inhibition of these enzymes provides a way of controlling rapidly-reproducing cells such as cancer cells. High levels of p21 are found in ageing cells. p21 protein is dysfunctional in most human cancers.