Cell-cycle inhibition by independent CDK and PCNA binding domains in p21Cip1

Nature. 1995 May 11;375(6527):159-61. doi: 10.1038/375159a0.


Mammalian cell-cycle control by antimitogenic signals involves p21Cip1/WAF1 (refs 1-4), p27Kip1 (refs 5, 6) and p57Kip2 (refs 7, 8), a family of proteins that bind to and inhibit cyclin-dependent kinases (CDKs) required for initiation of S phase. The protein p21 also binds to the DNA polymerase delta processivity factor, proliferating-cell nuclear antigen (PCNA), and inhibits in vitro PCNA-dependent DNA replication. The CDK and PCNA inhibitory activities of p21 are shown here to be functionally independent and to reside in separate protein domains. The PCNA binding and inhibitory activities, which are not observed with p27 or p57, reside in the C-terminal domain of p21, whereas the CDK inhibitory activity resides in the conserved N-terminal domains of these proteins. When separately overexpressed in mammalian cells, the CDK and PCNA inhibitory domains prevent DNA replication, demonstrating a dual function of p21 as a cell-cycle inhibitor in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • CDC2-CDC28 Kinases*
  • Cell Cycle / physiology*
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinases / antagonists & inhibitors
  • Cyclin-Dependent Kinases / metabolism*
  • Cyclins / antagonists & inhibitors
  • Cyclins / metabolism*
  • DNA / metabolism
  • Humans
  • Mice
  • Molecular Sequence Data
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Recombinant Fusion Proteins / metabolism


  • CDKN1A protein, human
  • Cdkn1a protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Proliferating Cell Nuclear Antigen
  • Recombinant Fusion Proteins
  • DNA
  • Protein-Serine-Threonine Kinases
  • CDC2-CDC28 Kinases
  • CDK2 protein, human
  • Cdk2 protein, mouse
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases