Cyclin B regulates the activation, subcellular localization, and substrate specificity of cdk1, and destruction of cyclin B is necessary for mitotic exit.

In addition to acting as a master regulator of mitosis, recent evidence has indicated that Cdk1/cyclin B1 plays a key role in regulation of cell death during mitotic arrest and directly phosphorylates several apoptotic regulatory proteins including antiapoptotic Bcl-2 proteins (8–11), caspase-9 (20), caspase-2 (21), ...

Cyclins are the regulatory subunits of holoenzyme CDK complexes that control progression through cell-cycle checkpoints by phosphorylating and inactivating target substrates. The cyclins associate with different CDKs to provide specificity of function at different times during the cell cycle (see Fig. 9-2).

Cyclin D1 is an important regulator of cell cycle progression and can function as a transcriptionl co-regulator. The overexpression of cyclin D1 has been linked to the development and progression of cancer.