Encyclopedia of Cancer

Living Edition
| Editors: Manfred Schwab


  • Axel H. SchönthalEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27841-9_4327-7



Traditionally, the p21 protein has been defined as an inhibitor of cyclin-dependent kinases (CDKs). Inhibition of this group of enzymes by p21 leads to the cessation of cell proliferation. Additionally, p21 binds to and inhibits the activity of PCNA (proliferating cell nuclear antigen, a subunit of DNA polymerase), which results in the termination of DNA replication. Because both of these functions lead to cell cycle arrest, p21 is also called an inhibitor of the cell cycle.

Additional functions of p21 were discovered that are unrelated to its ability to inhibit cell proliferation. For example, p21 can regulate transcription; restrain apoptosis; impose on cytoskeletal dynamics and cell motility; interfere with cellular differentiation, senescence, and aging; act as cytoplasmic regulator of nuclear import; impinge on DNA repair; and affect the generation of induced pluripotent stem cells...


Actin Stress Fiber Formation Adenomatosis Polyposis Coli Cyclin Subunit Proliferation Inhibitory Signaling 
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© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.University of Southern California, Keck School of MedicineLos AngelesUSA