Figure 3
From: JNKs function as CDK4-activating kinases by phosphorylating CDK4 and p21
Mutations of p21 phosphorylation sites do not impair the phosphorylation of CDK4 by JNKs in vitro. Extracts of CHO cells transfected with vectors encoding cyclin D1, CDK4 and wild -type (wt) p21 or the indicated phosphorylation mutants of p21 were Ip with cyclin D1 antibody (Ip cyclin D1), and incubated with recombinant JNK1 or JNK2 and ATP. Next, they were separated by 2D-gel electrophoresis followed by immunodetection of CDK4 and p21. Colored arrows indicate phosphorylated forms of p21, black arrows indicate the enhanced abundance of the phosphorylated form of CDK4. This experiment was reproduced with identical results using cyclin D3-CDK4-p21 complexes and incubation with JNK1 or JNK2.
