 The other family of CKIs, CIP/KIP proteins are capable of inhibiting all CDKs.Enforced expression of INK4 proteins can lead to G1 arrest by promoting redistribution of Cip/Kip proteins and blocking cyclin E-CDK2 activity.In cycling cells, there is a resassortment of Cip/Kip proteins between CDK4/5 and CDK2 as cells progress through G1.