CEBPA binds CDK4, inhibits the kinase activity of CDK4, and enhances the proteasomal degradation of CDK4 (Wang et al. 2001, Wang et al. 2002). These mechanisms may contribute to the inhibition of cell proliferation observed in response to CEBPA. CEBPA interacts with the T loop region of CDK4. In mouse liver cells, 5%-10% of Cdk4 is associated with Cebpa (Wang et al. 2001).