p21WAF1CIP1

p21WAF1CIP1, also known as cyclin-dependent kinase inhibitor 1 (CDKN1A), is a protein encoded by the CDKN1A gene. It plays a crucial role in cell cycle regulation and DNA repair. This protein acts as a universal inhibitor of cyclin-dependent kinases (CDKs), which are essential for the progression of the cell cycle. By binding to and inactivating CDK complexes, p21WAF1CIP1 effectively halts the cell cycle, typically at the G1 or G2 phase.

The expression of p21WAF1CIP1 is primarily induced by the tumor suppressor protein p53 in response to DNA damage. This induction mechanism is a critical component of the cellular response to genotoxic stress, allowing time for DNA repair before replication or mitosis. If the damage is too severe to repair, p21WAF1CIP1 can also contribute to programmed cell death, or apoptosis.

Beyond its role in cell cycle arrest, p21WAF1CIP1 has also been implicated in other cellular processes, including differentiation and senescence. Its involvement in these diverse functions highlights its multifaceted nature within the cell. Dysregulation of p21WAF1CIP1 expression or function has been observed in various cancers, where it can either promote or inhibit tumor progression depending on the cellular context. Therefore, p21WAF1CIP1 is considered a significant target in cancer research and therapy.