TI  - The <prot>p21</prot> Cdk-interacting protein <prot>Cip1</prot> is a potent inhibitor of G1
      cyclin-dependent kinases.
PG  - 805-16
AB  - The    cyclin-dependent kinase <prot>Cdk2</prot>    associates with  <prot>cyclins A</prot> ,  D , and  E  and
      has been implicated in the control of the G1 to S phase transition in
      mammals. To identify potential <prot>Cdk2</prot> regulators, we have employed an
      improved two-hybrid system to isolate human genes encoding Cdk-interacting
      proteins (Cips). <prot>CIP1</prot> encodes a novel 21 kd protein that is found in
       <prot>cyclin A</prot> ,  <prot>cyclin D1</prot> ,  <prot>cyclin E</prot> , and <prot>Cdk2</prot> immunoprecipitates.  <prot>p21CIP1</prot>  is a
      potent, tight-binding inhibitor of  Cdks  and can inhibit the
      phosphorylation of    <prot>Rb</prot>    by  <prot>cyclin A</prot>-<prot>Cdk2</prot> ,  <prot>cyclin E</prot>-<prot>Cdk2</prot> ,  <prot>cyclin D1</prot>-<prot>Cdk4</prot> , and
       <prot>cyclin D2</prot> - <prot>Cdk4</prot>  complexes. Cotransfection experiments indicate that <prot>CIP1</prot>
      and <prot>SV40 T antigen</prot> function in a mutually antagonistic manner to control
      cell cycle progression.
AD  - Verna and Marrs McLean Department of Biochemistry, Baylor College of
