Cyclin Dependent Kinase Inhibitor 1B (CDKN1B)

Cyclin-dependent kinase inhibitor 1B is a protein which belongs to the Cip/Kip family of cyclin dependent kinase (Cdk) inhibitor proteins. The encoded protein binds to and prevents the activation of cyclin E-CDK2 or cyclin D-CDK4 complexes, and thus controls the cell cycle progression at G1. It is often referred to as a cell cycle inhibitor protein because its major function is to stop or slow down the cell division cycle.

The p27^Kip1 gene has a DNA sequence similar to other members of the "Cip/Kip" family which include the p21^Cip1/Waf1 and p57^Kip2 genes. In addition to this structural similarity the "Cip/Kip" proteins share the functional characteristic of being able to bind several different classes of Cyclin and Cdk molecules.