MW: 8,731 Da. Purity >95% as determined by SDS-PAGE Analysis. p16-INK4a is a nuclear protein that regulates the cell cycle by inhibiting cyclin dependent kinase-4 (CDK4) and CDK6. p16-INK4a inhibits CDK activity by binding to the CDK molecules in a manner that interferes with their ability to interact with cyclin D. This activity has the effect of suppressing tumor formation and growth, and of inducing replicative senescence in various normal cells, including stem cells. The expression of p16-IN