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XB-ART-17802
Mol Cell Biol 1996 Sep 01;169:4673-82. doi: 10.1128/MCB.16.9.4673.
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Cyclin-binding motifs are essential for the function of p21CIP1.

Chen J , Saha P , Kornbluth S , Dynlacht BD , Dutta A .


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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.

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Species referenced: Xenopus laevis
Genes referenced: cdk2 cdk4 cdkn1a tp53

References [+] :
Brugarolas, Radiation-induced cell cycle arrest compromised by p21 deficiency. 1995, Pubmed