Cyclin-Dependent Kinase Inhibitor 1 (CDKN1A) is a member of the CDI family. CDKN1A is widely expressed in all adult tissues, but low expressed in the brain tissue. CDKN1A can be induced by p53/TP53, mezerein and IFNB1, repressed by HDAC1. CDKN1A may be an important intermediate, by which p53/TP53 mediates its role as an inhibitor of cellular proliferation in response to DNA damage, CDKN1A can bind to and inhibit cyclin-dependent kinase activity, preventing phosphorylation of critical cyclin-dependent kinase substrates and blocking cell cycle progression.