Cyclin-binding motifs are essential for the function of p21CIP1.

Journal Article (Journal Article)

The cyclin-dependent kinase (Cdk) inhibitor p21 is induced by the tumor suppressor p53 and is required for the G1-S block in cells with DNA damage. We report that there are two copies of a cyclin-binding motif in p21, Cy1 and Cy2, which interact with the cyclins independently of Cdk2. The cyclin-binding motifs of p21 are required for optimum inhibition of cyclin-Cdk kinases in vitro and for growth suppression in vivo. Peptides containing only the Cy1 or Cy2 motif partially inhibit cyclin-Cdk kinase activity in vitro and DNA replication in Xenopus egg extracts. A monoclonal antibody which recognizes the Cy1 site of p21 specifically disrupts the association of p21 with cyclin E-Cdk2 and with cyclin D1-Cdk4 in cell extracts. Taken together, these observations suggest that the cyclin-binding motif of p21 is important for kinase inhibition and for formation of p21-cyclin-Cdk complexes in the cell. Finally, we show that the cyclin-Cdk complex is partially active if associated with only the cyclin-binding motif of p21, providing an explanation for how p21 is found associated with active cyclin-Cdk complexes in vivo. The Cy sequences may be general motifs used by Cdk inhibitors or substrates to interact with the cyclin in a cyclin-Cdk complex.

Full Text

Duke Authors

Cited Authors

  • Chen, J; Saha, P; Kornbluth, S; Dynlacht, BD; Dutta, A

Published Date

  • September 1996

Published In

Volume / Issue

  • 16 / 9

Start / End Page

  • 4673 - 4682

PubMed ID

  • 8756624

Pubmed Central ID

  • PMC231467

Electronic International Standard Serial Number (EISSN)

  • 1098-5549

International Standard Serial Number (ISSN)

  • 0270-7306

Digital Object Identifier (DOI)

  • 10.1128/mcb.16.9.4673


  • eng