INK4
INK4 is a family of cyclin-dependent kinase inhibitors (CKIs). The members of this family (p16INK4a, p15INK4b, p18INK4c, p19INK4d) are inhibitors of CDK4 (hence their name INhibitors of CDK4), and of CDK6. The other family of CKIs, CIP/KIP proteins are capable of inhibiting all CDKs. Their function, inhibiting CDK4/6, is to block progression of the cell cycle beyond the G1restriction point. In addition, INK4 proteins play roles in cellular senescence, apoptosis and DNA repair.
INK4 proteins are tumor suppressors and loss-of-function mutations lead to carcinogenesis.
INK4 proteins are highly similar in terms of structure and function, with up to 85% amino acid similarity. They contain multiple ankyrin repeats.
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