CDKN1A encodes a potent cyclin-dependent kinase inhibitor. Cyclin dependent kinase inhibitor 1A binds to and inhibits the activity of cyclin-cyclin-dependent kinase2 or -cyclin-dependent kinase4 complexes, and thus functions as a regulator of cell cycle progression at G1. The expression of CDKN1A is tightly controlled by the tumor suppressor protein p53, through which cyclin dependent kinase inhibitor 1A